Safety shutoff valves are the last line of defense against a potentially catastrophic incident. When conditions require, they interrupt the flow of fuel to the burner(s) and oven. There are many options when selecting fuel safety shutoff valves for your application. The construction and application of these devices is highly regulated by interlocking standards created by many different organizations. The goal of this article is to clarify how to comply with the most common standard affecting the reader: NFPA 86.
This column appeared in Heat Treat Today’s2021 Trade Show September print edition. John Clarke is the technical director at Helios Electric Corporation and is writing about combustion related topics throughout 2021 for Heat Treat Today.
John B. Clarke Technical Director Helios Electric Corporation Source: Helios Electric Corporation
To start, we must define our terms. The 2019 edition of NFPA 86* defines a safety shutoff valve as a “normally closed valve installed in the piping that closes automatically to shut off the fuel, atmosphere gas, or oxygen in the event of abnormal conditions or during shutdown.”1 A valve is “normally closed” (NC) if it closes automatically when power is removed. A furnace or oven typically has as few as two or more safety shutoff valves. [Author’s note: If the system uses radiant tubes for heating, and all the criteria are met, it may be acceptable to use only one valve in series, but this exception is not recommended by the author and will not be covered in this article.] There are two common arrangements for safety shutoff valve arrays—the Simple Double Block (Illustration 1) and the Double Block and Vent (Illustration 2). While both arrangements are compliant with the current version of NFPA 86, the vent is NOT required. In other words, Illustration 1 and Illustration 2 below are both acceptable.
The simple double block arrangement consists of two automatic, normally closed (NC) valves piped in series. It provides redundancy—both valves must leak for fuel gas to pass to the burner system. A double block and vent has two automatic, NC valves piped in series with a third automatic normally open (NO) valve installed between the NC valves. The purpose of the NO valve is to provide a path for any fuel gas leaking past the first NC valve to move to a safe location. Whether one should deploy a double block and vent approach depends on several considerations: Is the NO valve supervised? Is the selected vent location safe? And how will the system be inspected?
Illustration 1
Illustration 2
To start with, if the NO vent valve’s coil or wiring fails, it will remain open even when the system is operating—venting fuel gas. This is not only expensive, but high concentrations of vented fuel gas are an environmental and safety hazard. The solution to this concern is installing a monitored vent valve that only opens the NC valves after the vent valve is proven to be closed. This is typically accomplished with a proof-of-closure position switch that only closes after the vent valve is fully closed.
The next concern is the location and maintenance of the vent. The vent must terminate at a safe location that can accept the entire flow of fuel gas in the event of a failure. Therefore, hazards such as fresh air intakes and sources of ignition must be avoided at all costs. It is also important to periodically inspect the vent piping to ensure it remains unobstructed—insects and rodents may find the vent line a comfortable place to nest and bring up their young.
The last challenge is the periodic inspection of the vent valve and the vent piping—it is generally a challenge to test whether a vent line meets the design criteria, and leaking fuel gas can be vented without excessive backpressure.
A simple double block provides redundancy without the complexity of the vent. Good design practice, with proper valve selection, combined with proper fuel filtration greatly improves the reliability and longevity of both systems.
Valves used for safety shutoff valve applications must be listed by an approval agency for the service intended.2 Furthermore, depending on the flow rate, the valves must be equipped with either a local indicator showing the valve position and a means to prove the valve is closed.
For fuel gas flows below or equal to 150,000 BTU/hour, two safety shutoff valves in series will suffice. See Illustration 3 below. This is very typical for pilot lines.
Illustration 3
For fuel gas flows greater than 150,000 BTU/hour and less than or equal to 400,000 BTU/hour, two safety shutoff valves in series with local position indication are required. Local indication is generally a window where an operator can see the actual position of the valve—open or closed—without relying on any electrical circuit or pilot light. See Illustration 4 below.
Illustration 4
For fuel gas flows greater than 400,000 BTU/hour, NFPA 86 requires two safety shutoff valves in series with local position indication. One valve must be equipped with a valve closed switch (VCS) that closes after the valve is fully closed, or a valve proving system (VPS) that runs a tightness check which must be utilized. The signal from either this VCS or VPS must be included in the burner management system’s (BMS) purge permissive string to ensure no fuel gas is flowing during the system preignition purge. The VCS must not actuate before the valve is fully closed. This is typically accomplished by using valve overtravel, where the valve closes first, then the mechanism continues to move until the VCS is actuated. This arrangement is depicted in Illustration 5 below.
Illustration 5
For the arrangement depicted in Illustration 5, NFPA only requires one valve be supervised with a VCS—the additional costs of supervising both valves are very low and will enhance safety.
Whatever the method used to shut off the fuel to burners or pilots, the array of valves must be inspected and tested annually or per the manufacturer’s recommendations, whichever period is the shortest. All systems must be designed to be tested—with provision provided to cycle valves in test mode and the ability to measure any potential leakage. We will explore how a fuel train should be “designed to be tested” in an upcoming article.
The one thing to always remember—safety shutoff valves are always deployed to provide redundancy, so that any one component failure will not prevent a safe interruption of fuel gas; but, as with all systems, there may be unforeseen events that can lead to complete failure. Only qualified people should design, operate, and maintain combustion systems.
References
[1] National Fire Protection Association – NFPA 86 Standard for Ovens and Furnaces 2019 Edition (NFPA, Quincy, Massachusetts, May 24, 2018) 3.3.82.2 pp 86-14.
[2] National Fire Protection Association – NFPA 86 Standard for Ovens and Furnaces 2019 Edition (NFPA, Quincy, Massachusetts, May 24, 2018) 13.5.11.1 pp 86-49.
About the Author:
John Clarke, with over 30 years in the heat processing area, is currently the technical director of Helios Electric Corporation. John’s work includes system efficiency analysis, burner design as well as burner management systems. John was a former president of the Industrial Heating Equipment Association and vice president at Maxon Corporation.
In June, we spent a good deal of time discussing a simple pressure switch to emphasize the many considerations that are necessary for proper installation. Now we will expand the discussion to how the switch works and what steps we can take to detect a failure that is likely to occur sometime in the future.
This column appeared in Heat TreatToday’s2021 Automotive August print edition. John Clarke is the technical director at Helios Electric Corporation and is writing about combustion related topics throughout 2021 for Heat TreatToday.
John B. Clarke Technical Director Helios Electric Corporation Source: Helios Electric Corporation
A pressure switch is a Boolean device — it is either on or off — so how can we evaluate its performance in a manner where a potential failure can be detected before it occurs? The simple answer is time — how long does it take for the switch to respond to the condition it is intended to sense? What is the period between starting an air blower and the pressure switch closing? Has this time changed? Is a change in this time period to be expected, or does it portend a future failure?
A simple approach to evaluating this pressure switch’s time is to create predetermined limits — if the switch responds either too rapidly or too slowly — an alarm is set and the operator is alerted. Graph 1 illustrates this approach.
In Graph 1, the black band represents the time between the action (the start of the air blower) and the pressure switch closing. There is a warning band (yellow) — both high and low — that provides the early warning of a system performance problem. There is also a critical band (red) — both high and low — that provides the point at which the feedback for the pressure switch is determined to be unreliable. If the switch is part of a safety critical interlock, the system should be forced to a safe condition (in the case of a combustion system, with the burner off and a post purge being executed) if required.
Graph 1
Graph 2 depicts when a switch closing time exceeds the warning level. It could be the result of a problem with the blower and/or the pressure switch, but the deviation is not sufficiently large as to undermine confidence in the switch’s ultimate function.
Programmatically, if the time exceeds the warning band, and an alarm is registered, the responsible maintenance person is notified. If that is in the warning band, it can be addressed as time allows.
Graph 2
The warning bands give us the crystal ball to potentially see a problem before it causes a shutdown. As it is continuously monitored by the programmable logic controller (PLC), it may provide an increased level of safety, but that is dependent on a number of factors that are beyond the scope of this article.
The switch can be not only too slow to respond: an unusually fast response is a reason to be concerned as well. It could be that the pressure switch setpoint has been set too low — so low that it no longer provides useful feedback. Graph 3 is an example with an unusually fast response.
If the time is less than the “Critical Low” preset value, the switch’s feedback is determined to be unreliable. In this case, the setpoint may have been changed during a maintenance interval or even worse — the switch may be jumpered (this assumes we have an interlock string wired in series). The critical values are NOT intended to provide forward looking estimates of required maintenance — they are simply an enhanced safety measure.
This scenario assumes that the response of a component is consistent. In our example of a pressure switch monitoring an air blower, we can assume the time the blower required to reach full speed, the time for a pressure rise time in the air piping, and the responsiveness of the switch is consistent. These time intervals may not be consistent. The air supplied to the blower could be sourced from outside the building (temperate climate), which could cause air density changes between a cool, dry day and a hot, moist day. In this instance, what can be done to detect a failure?
An approach where we see fluctuations in the timing even in instances where all the components are operating properly would be to run a moving average of the time based on the last n operations. Then we compare the moving average to the last time and confirm that any change falls within a specific range.
Step 1 would be to average the last n values for the time required for the switch to trip. Then compare this value (ta) to the last time and see if the deviation exceeds the preset values. Let us assume if the time varies by more than 20% a warning should be issued to the maintenance staff.
Now this method will accommodate rapid fluctuations – but if the performance of the component degrades in a near linear fashion, this formula will not detect a premature failure.
An alternate approach would be to execute this routine on the first n cycles, as opposed to continuously updating the average. Using this method, the performance of the specific component is captured. Or this averaging can be executed on demand or based on the calendar or Hobbs timer.
These concepts are far from new, and it has only been because of the recent expansion in PLC memory storage capacity and processing power that it has been reasonable to perform this analysis on dozens of components on a furnace or oven. Remember, it is a shame to waste PLC processing time and memory!
One or more of these approaches, or similar approaches analyzing time, can indeed be a crystal ball that gives us warning of any of a number of potential failures — warning before a system shutdown is required.
About the Author:
John Clarke, with over 30 years in the heat processing area, is currently the technical director of Helios Electric Corporation. John’s work includes system efficiency analysis, burner design as well as burner management systems. John was a former president of the Industrial Heating Equipment Association and vice president at Maxon Corporation.
Last month we began the discussion about the relationship between combustion safety and uptime, highlighting how combustion safety, reliability, emissions, and efficiency are inseparable. This month, we will explore the subject in greater detail and outline a path that can both reduce the risk of an incident and protect the bottom line.
This article written by John Clarke, technical director at Helios Electric Corporation, appears in the annual Heat TreatToday 2021 Buyer's Guide June print edition. Return to our digital editions archive on Monday June 21, 2021 to access the entire print edition online!
John B. Clarke Technical Director Helios Electrical Corporation Source: Helios Electrical Corporation
How many times have we heard the tale about the man with the leaky roof? He cannot fix his roof when it is raining, and the roof doesn’t need repaired when it is not. This story is also applicable to heating system maintenance, perhaps more so than other plant maintenance activities because it so seldom “rains.” Ovens and boilers tend to be very reliable. (This statement is true for equipment operating at low or moderate temperatures, less so for equipment operating above 1832°F (1000°C).) It is exactly when the machine is properly producing parts that the planning for combustion safety, availability, and performance must occur.
The first critical step we must take is to understand that combustion safety, routine maintenance, tuning, and calibration are parts of a larger work strategy. To focus solely on the annual inspection of safety components while ignoring system tuning will not only compromise tuning and efficiency, but also the safety. We have seen how managerial reactions to high profile incidents have caused some firms to dispatch teams to annually examine valves and pressure switches. This effort is highly compromised if it does not include all aspects of system maintenance as well as capturing what is learned each time to improve future inspections and equipment designs. There is data beyond pass and fail that is valuable if we wish to optimize the performance of our equipment
Let us assume it is a clear sunny day, and we are ready to invest some time in preparing to improve our combustion system starting with a deep dive examination of two pressure switches: the low fuel gas pressure switch (LFGPS) and high fuel gas pressure switch (HFGPS). These ubiquitous components are present on nearly every fuel train and are vital for safe operation. As their names imply, they monitor the fuel pressure and shut the safety valves if the fuel gas pressure is either too high or too low.
These switches must be listed for the service they provide by an agency independent of the manufacturer – UL, TUV, FM, etc. Simply looking for a stamp may not be enough; take the time to read the file or standard being applied by the agency and determine if it describes the application. Next, ask if the pressure switch carries the basic ratings expected, like the enclosure rating (Nema or IP). Is a Nema 1 switch operating in a Nema 12 area? Temperature ratings must be confirmed. All too often a component rated for 32°F (0°C) is applied in an outdoor environment in cold climates, or one with a maximum rating of 120°F (50°C) is applied next to the hot wall of a furnace. The component may operate out of specified environmental ranges for some time, but to apply a component in this manner is betting against the house – sooner are later we are going to lose. Ask the people of Texas if the bet against sustained cold temperatures in early 2021 was worth it.
"John Clarke, Technical Director, Helios Electrical The first critical step we must take is to understand that combustion safety, routine maintenance, tuning, and calibration are parts of a larger work strategy"
Next, let us look at the contact(s) rating of the switch and how it is applied to the burner management circuit. More often than not, these switches are in control circuits fused for more current than the contact rating. If the switch rating is too low, the electrical designer has an option to use an interposing relay to increase the current carrying capacity to this device. This relay is an added component, and as such, adds yet another possible point of failure. If the relay is interposed, is it dedicated to this one switch? Multiple devices being interposed by a single relay is prohibited by NFPA 86, for good reason. Is the relay designed to fail safely? That is, will a relay coil burn out or wiring fault close the critical safety valves? Is the wire gauge suitable for the current carried and protection device used?
Next, is the switch mounted in a safe location free from possible vibration or the foot of an eager furnace operator? If the switch must be changed, are clearances provided to perform this maintenance? What is the mean time to replace (MTTR) the component? Is the way the device is wired providing a path for combustible gas to enter the control enclosure and cause an explosion? Flexible conduit, without a means to seal the connection, is a very common error. Use a properly specified cord and consider using some type of connector to terminate the wiring at the switch. A simple 7/8-16 or DIN connector not only provides additional protection from combustion gas getting into the electrical conduit but is also a great benefit when changing the component in a rush and helps to isolate the component’s control circuit during testing and calibration.
Is the pressure switch suitably protected from bad “actors” in the fuel gas? Perhaps soot is present that could foul narrow passages or H2S that could result in corrosion. These are rare conditions, but coke oven gas may not be as clean as purchased natural gas. Do we need to specify stainless steel components? Would a filter make sense to protect the switch and increase the intervals between maintenance?
Finally, let’s discuss pressure ratings. Unfortunately, nomenclature varies by manufacturer. What is the maximum pressure the device can sustain and not fail, i.e., leak fuel gas into the environment? Many switches can experience a pressure surge without risk of leakage, but the high-pressure event will damage the switch internally. It is important when determining if this rating is adequate to consider possible failure modes that might expose the pressure switch to excessive pressure. As a rule of thumb, a pressure switch must be able to sustain a surge pressure delivered to the inlet of the pressure reducing regulator immediately upstream of the device. Think of it this way, if the upstream regulator experiences a failure, the full pressure delivered to this regulator will pass to the pressure switch in question.
Other obvious pressure ratings are the maximum and minimum set points. The pressure switch should be set to trip as close to the middle of the range as possible and should never be set close to either the minimum or maximum setpoint. Is the pressure switch manually or automatically reset after a trip? In general, it is best practice that the LFGPS resets automatically, and the HFGPS requires a reset by the operator. This recommendation is because LFGPS trips each time pressure is removed from the system, and it is generally understood that the system needs fuel to operate. On the other hand, a high-pressure event is exceedingly rare, and the operator should be made aware of this unusual event.
This article has discussed a lot about the simple pressure switch. It appears to be a heavy lift to perform this analysis on every pressure switch in a facility, but take comfort, once the exercise has been completed on the first system, it is much easier to replicate what has been learned to properly assess other systems. We should most definitely insist that our OEM provides this data, in detail, when new equipment is supplied. Why did we review all these specifications? Because I have been around for a while and have seen nearly every one of these errors in the application of pressure switches on operating combustion equipment.
Next month, we will expand on the pressure switch discussion to describe the tune/calibration and testing processes. I hope this deep and specific dive has been of value. If you have any questions or comments, please let me know.
About the Author:
John Clarke, with over 30 years in the heat processing area, is currently the technical director of Helios Corporation. John’s work includes system efficiency analysis, burner design as well as burner management systems. John was a former president of the Industrial Heating Equipment Association and vice president at Maxon Corporation.
Heat treaters know the importance of keeping current with advancing technologies when it comes to combustion. But tragedy can strike if the necessary standards and training aren't in place.
Written by Robert Sanderson P.E., director of business development at Rockford Combustion Solutions, Heat Treat Today is pleased to bring this Original Content article to you this Technical Tuesday.
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Robert Sanderson P.E. Director of Business Development Rockford Combustion Solutions (Source: Rockford Combustion Solutions)
When you hear about large-scale combustion explosions and loss of human life, you wonder how such a tragedy could happen. And, yet, the number one cause of industrial fuel and combustion system explosions is human error. Therefore, the most critical element of every combustion safety system is not a pressure gauge or shut-off valve, but rather knowledgeable, well-trained operators.
Case History
On June 18, 2007, one of two boilers at a manufacturing plant in Tennessee exploded, causing extensive damage to the facility and surrounding area, and seriously injuring one employee. The 2000-built high-pressure firetube boiler was operating concurrently with a second high-pressure boiler to handle the steam demand of plant operations.
Tennessee state officials concluded that there were a number of factors that contributed to the accident: lack of standard training and boiler operation procedures, inadequate boiler attendance and record keeping, inadequate and improper boiler maintenance, and inoperative and improper operating controls and safety devices. As part of its recommendations, officials stated, the plant “should develop procedures for the training and certification of all boiler operators.”
National Fire Protection Association Standards
Training is so critical that the National Fire Protection Association (NFPA) requires that “all operating, maintenance, and supervisory personnel shall receive regularly scheduled retraining and testing.”
The NFPA publishes multiple prescriptive sets of standards to help keep your staff and combustion equipment safe, and each of these standards stress the value of operator training. Among these standards are:
NFPA 54 — National Fuel Gas Code
NFPA 85 — Boiler and Combustion Systems Hazards (> 12.5 MMBtu/hr)
NFPA 86 — Standard for Ovens and Furnaces
NFPA standards apply to new installations and modifications of existing equipment, and some insurance underwriters apply the current standards retroactively. Operations that use heat are nearly limitless, but larger, common combustion applications include pulp and paper processing, tempered glass production, tire manufacturing, paint/drywall/shingle manufacturing, power plants, coating operations, ethanol and asphalt production, wastewater and sewage treatment, plastic bottle manufacturing, college campuses and breweries to list just a few. Understanding and enforcing applicable NFPA standards is paramount to the safety of every business using a combustion or heat treatment system.
Each NFPA standard has hundreds of pages covering the necessities for safe design, installation, operations, and maintenance of the respective equipment. This article gives a cursory overview of NFPA 54, 85 and 86, and provides guidelines to obtain safety training. When it comes to fuel-fired equipment operation, training is literally a life and death issue.
Consider this: The National Board of Boiler and Pressure Vessel Inspectors and the NFPA have identified that 83% of boiler/pressure vessel accidents, 69% of injuries and 60% of recorded deaths were a direct result of human oversight or lack of knowledge. Poor training also leads to production outages that cost millions of dollars in business interruption, supply chain delays, lost orders and competitiveness. Many companies only learn the value of combustion system training after an accident or expensive shutdown has occurred.
NFPA 54 — National Fuel Gas Code
Also known as ANSI Z223.1, the NFPA 54 standard details minimum safety requirements for the installation of gas piping systems, appliances and equipment supplied with LP-gas, natural gas or manufactured gas. Basically, NFPA 54 addresses the "how’s" and "why’s" of:
Piping system design, materials, and components
Piping sizing
Installing pipes, outlets, and inside concealed spaces
Inspection, testing and purging procedures
Installation and venting of appliances.
NFPA 54 is specific; it does not apply to natural gas systems operating at pressures above 125 psi, propane systems operating over 50 psi, gas/air mixes within the flammable range at pressures over 10 psi, and several other types of systems.
Checking pressure gauges on combustion equipment. (Source: iStockphotos.com)
NFPA 85 — Boiler and Combustion Systems Hazards
NFPA 85 gives those involved with large boiler installations and combustion systems the information they need for fire safety compliance, from system design and installation to inspection. Specifically, the standard addresses single burner boilers, multiple burner boilers, stokers, and atmospheric fluidized bed boilers with a fuel input rating of 12.5 million Btu/hr or greater. It also covers pulverized fuel systems at any heat input rate, fired or unfired steam generators, and other combustion turbine exhaust systems.
NFPA 85 offers guidelines as to the strength of a structure, operation and maintenance procedures, combustion and draft control equipment, safety interlocks, alarms, trips, and other related controls that are essential to safe equipment operation.
NFPA 86 — Industrial Ovens and Furnaces
NFPA 86 outlines the safe operation of Class A, Class B, Class C and Class D ovens, dryers, furnaces, thermal oxidizers, and many other heated enclosures used for processing materials. NFPA 86 guidelines set standards as to how industrial furnaces and ovens are to be designed and operated in order to promote safety, with each class of operation organized into four main categories: location and construction, heating systems, operational requirements, and safety equipment. Beyond these basic categories, each class may have unique conditions addressed for distinct hazards, such solvents or special atmospheres.
NFPA 86 specifically states that personnel who operate, maintain, or supervise the oven or furnace shall be thoroughly instructed and trained in their job functions, demonstrate an understanding of safe operation procedures, be kept current with changes in the equipment and operating procedures, and shall receive regular refresher training.
Training your staff to understand and comply with NFPA 54, 85 and 86 standards will minimize the risk of a catastrophic event. In addition, training enhances overall productivity and helps cut costs. For example, having in-house staff with the skills to recognize defects will lead to better fuel efficiency, fewer interruptions, and the avoidance of outages and downtime. And of course, training is a compliance requirement to be completed on an annual basis.
There are four common ways for your staff to obtain training, all of which can meet requirements to varying degrees.
First, attend a combustion workshop. Doing so will offer a more in-depth experience for your staff since workshops typically include hands-on training and face-to-face instruction. Also, you’ll be able to network with combustion safety and design engineers during breaks and lunches. Workshops normally award attendees with the documentation needed to supply proof of completion. They are held on-site at a training facility, or the instructor may go to the customer’s site to train staff on the plant’s fuel-fired systems and what ancillary equipment is required to support its operation.
Second, in this age of COVID-19, utilize online or remote training programs for a smart choice. Pre-recorded webinars are available 24/7, so attendees can learn at their own pace and convenience. Remote live workshops can be broadcast on Zoom, Cisco, Webex or other digital platforms. This lets attendees interact with the instructor and participate in simulations, so they’ll be equipped with the knowledge & skills required to operate combustion systems without leaving their office.
Third, take OEM instruction. NFPA 86 requires manufacturers to provide instruction upon installation of new ovens, dryers, thermal oxidizers, furnaces and boilers. However, OEMs are not required to return to installation sites to educate operators on the newest changes in national and international regulations, or in equipment design. While the OEM’s initial training may suffice to get the new equipment up-and-running, it is not enough to guarantee ongoing safety. If process changes have been made after installation, the original OEM training may be out of date.
Fourth, develop your own program. This endeavor entails an investment in time, research, continuous improvement, and the participation of dedicated team leaders. If you take this path, you’ll likely need to hire outside experts to ensure that the training curriculum encompasses all NFPA requirements including general safety, operation of equipment, and the latest code protocols.
Valve Inspection (Source: iStockphotos.com)
Conclusion: Training is Essential
Human error is the largest cause of industrial fuel and combustion system accidents, explosions, fires and outages. Fuel-fired equipment incidents can be extremely dangerous and necessitate special attention, engineering know-how, experience and especially, training. Understanding and complying with national codes, along with establishing a safety culture, will save lives and improve the competitiveness of any company using fuel-fired equipment.
About the Author: Robert Sanderson is the Director of Business Development at Rockford Systems dba Rockford Combustion Solutions and is a registered Professional Engineer with over 25 years of combustion safety industry experience. Mr. Sanderson has expanded the business to provide standard and custom combustion safety solutions, ventless valve trains, safety inspections, and training.
One of the great benefits of a community of heat treaters is the opportunity to challenge old habits and look at new ways of doing things. Heat TreatToday’s101 Heat TreatTipsis another opportunity to learn the tips, tricks, and hacks shared by some of the industry’s foremost experts.
Today’s tips are the 1 – 2 – 3! They come to us from Dry Coolers with a word on cooling system growth capability; Bloom Engineering Company Inc. on the importance of careful spending; and Rick Kaletsky, Safety Consultant about clear content labeling.
Heat TreatTip #1
Buy a Cooling System Capable of Growth
Plan for future growth. It is more cost effective to provide additional capacity while equipment is being installed. Simple planning for the addition of future pumps (e.g. providing extra valved ports on tanks) and space for heat transfer equipment (e.g. pouring a larger pad or adding extra piers) can save considerable money down the road with little upfront expenditure. Consider installing one size larger piping for the main distribution supply and return; if this is not possible, make sure you can add an additional piping run on the hangers you will install now. Above all, be sure to include all necessary drains, vents, isolation valves, and plenty of instrumentation. These items are critical aids in maintenance, troubleshooting, and future system expansion. (Dry Coolers)
Thinking about future growth will help you choose the right cooling system.
Heat TreatTip #2
Never Go Cheap on These Two Things
There are 2 things in life you should never go cheap on: Toilet paper and combustion equipment! When upgrading or looking at new systems, spend the money to do it right. Designing on the cheap will only lead to operational and maintenance headaches. And trying to reuse the ancient artifacts when upgrading just to save a buck will cost you 10x that down the road. You don’t have to break your budget to do a quality job! (Bloom Engineering Co. Inc.)
Heat TreatTip #3
Container Clarity Counts!
Assure that container label wording (specifically for identifying chemical contents) matches the corresponding safety data sheets (SDS). Obvious? I have seen situations where the label wording was legible and accurate and there was a matching safety data sheet for the contents, but there was still a problem. The SDS could not be readily located, as it was filed under a chemical synonym, or it was filed under a chemical name, whereas the container displayed a brand name. A few companies label each container with (for instance) a bold number that is set within a large, colored dot. The number refers to the exact corresponding SDS. (Rick Kaletsky, Safety Consultant)
Unclear labeling of chemical materials creates a hazardous situation.
Welcome to another episode of Heat Treat Radio, a periodic podcast where Heat Treat Radio host, Doug Glenn, discusses cutting-edge topics with industry-leading personalities. Below, you can either listen to the podcast by clicking on the audio play button, or you can read an edited version of the transcript. To see a complete list of other Heat Treat Radio episodes, click here.
In this conversation, Heat Treat Radio host, Doug Glenn, interviews Carl Nicolia, President of PSNergy, to learn about how applying efficient combustion can drastically improve the performance of your machines. Click below to hear about high value solutions and where we stand in the "evolution" of combustive techniques.
The following transcript has been edited for your reading enjoyment.
DougGlenn (DG): Today's topic is combustion. It is not only an important feature, but also the core to heat treat as the key to high value solutions; that is, according to today's guest, Carl Nicolia (CN), the president of PSNergy. Carl wrote an article that appeared in a recent edition of Heat TreatToday entitled, The Science of Combustion in an Era of Uncertainty. Several of the points Carl dealt with in that article, we'll deal with today. Get ready to read why not all fire is created equal and why your company needs to evolve with the times and take advantage of the recent combustion efficiency technologies.
First page of Carl Nicolia's article from the June Automotive Issue, The Science of Combustion in an Era of Uncertainty: Darwin was right...Evolve or Perish.
DG: Carl, tell us about your background.
CN: I had a great career in larger global businesses - folks like GE and Chrysler Corporation. After that run, I had met several very smart people that had been in the combustion industry for some time and they had some unique ideas on how we could really truly help elevate the performance of heat treating operations. After doing some homework on the industry, the technology, and the opportunity there, we started PSNergy in May of 2013. Since then, we have been helping customers, really throughout North America, solve combustion issues and help deliver productivity to combustion operations. We are primarily focused on radiant tube combustion systems. We do some open fire work as well. The team itself brings over 40 years of combustion experience to the table. We were really formed on innovation around the fundamental sciences, mostly physics and heat treat, and with a huge obsession for customer satisfaction. We really like to take the approach of becoming part of the customer's team, not really being considered an outside resource, but more of a team member with them, and really develop and play for the long term. That's the background on how we got into the combustion industry.
DG: The immediate reason for us talking with you today is because in our June 2020 issue, on page 37, we had a very interesting article or column written by yourself entitled The Science of Combustion in an Era of Uncertainty: Darwin was right, Evolve or Perish. That was the name of the column. A little bit provocative and an interesting column. And, for those who might be reading this at a later point, we are on the, I want to say, the tail end of a Covid-19 pandemic, but some people might say we're in the middle of it. Nonetheless, that's why the article says, “in an era of uncertainty.” I want to talk to you a little about that column. You make this comment in there, and there are a couple of comments I want to ask you about, and then we'll move on to the more substantive stuff. You say, “All fire is not created equal.” This is an interesting comment. What did you mean by that?
CN: Our team has been having a lot of fun with the caveman references and the whole concept of evolution and when we thought about it, it really did apply well, especially in today's times. We won't get into whether we're at the beginning, middle or end of the Covid thing, but thinking about going from fire at the end of a club to modern combustion systems is a huge leap forward. It was a good way for us to think about and highlight the concept that all fire is not created equal. Just because the burners are firing and the furnace is hot, doesn't mean that you're burning efficiently. There is a big difference between well-tuned, well-balanced combustion systems, and not well-tuned and well-balanced. So in that reference, we talk about setting combustion appropriately: getting the right air/fuel ratio can mean the difference between, in a heat treater's case, profitability and loss or high quality and scrap. Balancing that combustion across the entire system can mean the difference in getting customers and providing the turnaround times that they need. Getting that combustion system balanced and tuned, and keeping that system balanced and tuned, are really essential to “getting the most out of your fire,” if you will. So we had some fun with that reference. You will see that carry through some our advertising in the months to come, as well.
(photo source: PSNergy)
DG: You make one other reference to Charles Darwin and a quote that he mentioned. The quote is not all that brief, but I wanted you to comment on it, if you could. It says “It is not the strongest of the species that survive, nor the most intelligent that survive. It's the one that is most adaptable to change. Intelligence is based on how efficient a species became at doing the things they need to survive.”
CN: That's a great quote, and again, we're having a little bit of fun with it, but especially in today's world. I know that many of your readers have been in operation for generations and those companies have found a way to get a little better, a little smarter, every day, every year, and have not gone through Covid-19, but I'm sure other different issues. I think having them focus on what's critical, really making smart investments, these are the type of things that help move their operations forward, help evolve their operation. That's the type of evolution we're talking about.
Evolution to us is small, impactful changes that make a big difference. Although today it might be difficult to imagine, end customers in automotive, construction, and off-highway vehicles are going to be back. And there is going to be pent-up demand. Productivity is going to be an issue in the months ahead. Our end customers, as they come back online and look for suppliers that can meet that rate with high quality and responsiveness, that's going to be a differentiator. And so, we think that thinking about that evolution now is really important. Making the changes now while you can and be responsive when the time comes, is the right move for us; that's the evolutionary piece.
DG: PSNergy, as you've already mentioned, really focuses in on combustion, combustion efficiency, furnace efficiency and that type of thing. On the second page of this article (page 38 in the June 2020 issue), you mention a case study in there where your crew went in and helped a contract commercial heat treater to improve some efficiency. Can you run down through that case study quickly and tell us what you guys were able to do to help them adapt and improve the type of fire they had in their organization?
CN: Sure. And this is a great story, but it is not a unique story for us. We have quite a few of these success stories around our products and services. We had a Midwest contract heat treating company that was interested in the ceramic waste heat recovery inserts. These are patented devices that we design here at PSNergy. They go into the exhaust leg of the radiant tube and they capture that energy that is normally lost out the exhaust, keeping that energy inside the furnace. In the process, it balances the tube temperature and really increases the productivity of the process.
[blocktext align="left"]Their recovery cycle was reduced by 25% ... And in that total cycle, they dropped gas consumption 5% which eventually led to an increase in output of that furnace by 10% ... the total cost to implement this was less than $10,000.[/blocktext]So, in this particular example, it was a 9-ft IQ furnace and it had four U-tubes, probably a pretty typical type of furnace that we might see in a lot of the contract heat treating manufacturers, like your audience. What we did was install inserts in the exhaust legs of the four tubes and then balanced and tuned the system. This entire process took less than one 8-hour shift to finish. As you can see, the results were really impressive. I always like to say at this point, this is not our data, this is customer data. Their recovery cycle was reduced by 25%. Now, a recovery cycle is from the time I close the door to the time I start my controlled cycle. 25% reduction. And in that total cycle, they dropped gas consumption 5% which eventually led to an increase in output of that furnace by 10%. What we love about this, and this is kind of the theme of the article really, is that the total cost to implement this was less than $10,000. This is a perfect example of high value solution. I hate to say 'low cost' because cost is relative, but this is high value. If I can deliver 25% improvement with less than $10,000, or if I can deliver 10% double-digit output increases for less than $10,000, that's a high value solution.
DG: At $2500/tube, and you had four tubes you were 'upgrading,' if you will, that's pretty impressive.
CN: The beauty of this was there were no piping changes, no construction, and no long downtime. By using the patented technology, the new technology that's out there, combined with our tech-enabled services (balancing and tuning), again using the latest in sensing technology and cloud computing, this customer was able to achieve significant performance improvement. What's awesome is that this is a pretty common story for us. When we do this, these are the types of numbers we can achieve.
DG: We kind of skimmed over a little bit about the inserts. Let’s take just a minute and make clear what exactly you're providing as far as the inserts primarily, and the services as well.
CN: The radiant tube inserts, we like to call them ceramic waste heat recovery devices or waste heat recovery inserts, are primarily silicon carbide and they are in a patented configuration that provides significant improvement in delivering energy through the tube into the load. And they do that by being the right material, (silicon carbide has a very high emissivity, having the right shape, where we take advantage of radiant energy transfer to the tube because of the shape of the insert, and having a wide open cross-section which does not put a lot of back pressure on the combustion system; we allow the combustion system to breathe. Inserts have been around for a long time. The big technology improvement here is having the right material and having it in the right configuration to maximize the amount of energy that is delivered in a radiant tube and minimize the effect on the combustion system.
DG: And are these inserts only for U-tubes?
CN: No, they can be applied on any radiant tube. We've applied them on straight tubes (or I-tubes), U-tubes, Trident® tubes, and W-tubes.
DG: You talk in the article about combustion efficiency and furnace efficiency. Can you elaborate on that and the difference between the two?
CN: We think about this relatively broadly. Combustion efficiency is getting the most energy out of the fuel you purchase, and ensure that you continue to get that same level of performance. This is happening at the combustion system level, the burners, if you will. This goes back to achieving optimal air/fuel ratios. And it is so important, yet often overlooked by a lot of people. The difference between 7% excess oxygen in the exhaust and 3% excess oxygen is significant. If you're at 7% excess oxygen, you're delivering 20% less energy to the furnace than you are at 3%. 20% is a huge, huge number. Especially when you're talking about the core process for heat treating operations, making heat. I think often times we forget that in heat treating, combustion is the core process. Anytime we're running through a heat treat operation, you have to have optimal combustion. And there are high value, easily implemented solutions out there that help you maintain and achieve the optimum combustion.
When we think about furnace efficiency, furnace efficiency is what our customers get paid for - getting energy from the combustion system to the product. And how well we do that, in our view, is furnace efficiency. Think about it this way: You could have a perfectly balanced and tuned combustion system (those four tubes on our example furnace can be tuned perfectly), but we can let, in that system, 40% of the energy escape out of the exhaust. So combustion efficiency might be high, but furnace efficiency is not optimal. That's where we think about implementing the ceramic waste heat recovery devices, for example. You could talk about textured tubes or bubble tubes as another example to help you get that energy from the combustion system into the load. Getting more of the energy produced in efficient combustion for that product being processed – that's the name of the game, and that's furnace efficiency as we see it.
DG: You and I were talking about a recent report that came out from ArcelorMittal regarding their “green movement.” Can you recap that, and maybe hit on the ability for small companies to also embrace the technology that some of these bigger companies are able to embrace?
CN: We found this very informative. ArcelorMittal issued their 2019 “integrated report,” where they discuss their corporate responsibility and sustainability initiatives in the US. They have ten sustainability development outcomes, and energy management is one of those ten key outcomes. ArcelorMittal highlighted the development of a low-cost oxygen sensor for furnaces that reduce fuel consumption by allowing plants to see that combustion performance and then tune for optimization. This goes back to our discussion: Furnace combustion performance is the core to these operations, and they're highlighting the value of getting combustion balanced and tuned correctly and keeping it correct.
Not everyone listening and reading, I'm sure, has the resources of ArcelorMittal, so luckily, PSNergy has developed this technology for everyday heat treating operations and any one of us can now apply this. In fact, the same leading edge sensing technology and cloud computing technology is what our service team uses to deliver our combustion engineering services, or balance and tuning, and that is also incorporated into our combustion monitoring and alerting system. We like to call that CMA. And installing CMA on your furnace is like having a dedicated technician taking combustion measurements every day. If something is starting to go out of tune, actions can be taken immediately before furnace performance is affected and alerts can be sent through the system. Daily reports are issued on combustion and so you know combustion is running well. And if it's not, you're deploying resources to get that out.
DG: So this combustion monitoring and alerting system is a cloud-based system?
CN: Yes, it is, but fundamentally, it is a sensor. It's oxygen monitoring and pressure monitoring that is installed on each individual tube of the furnace that records excess oxygen in the stack just as if you would stand there as a technician with a handheld meter, but this is all connected through the cloud which allows it to be accessible, which allows it to store the data for future trend analysis. We've been able to use that tool to identify failing motorized control valves, declining performance on combustion air fans, etc. There is so much that you can see over and above when you're starting to look at data over time versus a single point in time and that's where the cloud piece comes in. It starts with pulling the sample from the right spot in situ from the exhaust and having the highest level of sensing technology available on the oxygen side and then sending all of that up to the cloud for the analysis for the reporting. It basically is a tech standing there taking measurements every day and then you're able to then get a report that says this is where our combustion is, and I can take steps to do that.
DG: I've got a question about that. So you've got 24/7, 365 monitoring of the system, cloud-based, the reports are coming back to the people in the company only – and only to those people that need to know. Are these things that you guys are alerted to so that you call if something goes wrong, or is it basically just held in-house?
CN: It can be either. You have the option of adding our team into it and we can provide input. The one thing we have decided though is any time the system is deployed, we never want to see that system not functioning properly. We keep a close eye on it. The combustion measurements are only a small piece. There are also a lot of help measurements around the system itself, so we're able to keep an eye on the system. If something started to go wrong from a system standpoint, we haven't seen that yet, but if it ever does, we're able to send our technicians out to make sure that you don't get a break in that monitoring.
DG: Have you had any issues with companies being concerned about cybersecurity?
[blocktext align="right"]Get it right and keep it right and then get the most out of the gas that you purchase. Stop throwing away energy. [/blocktext]CN: Not yet. We deal with that in two ways. Number one is that the data we're taking is relatively agnostic. I'm going to see basically pressures and excess oxygen readings and it's not really associated with anything else. Typically, when we get an output through the customer's system, that is usually on the other side of their firewall so the system security is in place and we can have a clean channel out to our cloud. When customers are uncomfortable with that, we'll use cell technology to deliver that, so there is no interconnectivity to their system. We have thought that through. Some customers are more uncomfortable than others, but we've done it both ways, where we've connected through a portal in their system to get out to the internet and then we've also connected through cellular.
DG: Is it possible to have a completely contained system where there is no internet connectivity?
CN: No. Because a lot of the calculations and analysis is done in the cloud. It's not to say that we haven't been asked for that, and we are working on local displays for let's say a technician that just wants to walk up to the furnace and see how things are running; we do have provisions for that as well.
DG: “All fire is not created equal” we know that, so it sounds like PSEnergy has got some good options for people to help improve and maintain not only combustion efficiency but also furnace efficiency. The example you had in the article was for a commercial heat treater, but obviously this also applies to anybody who's doing any type of combustion heating, captive heat treaters, manufacturers or commercial.
What exactly would you emphasize to these manufacturers with their own in-house heat treating, or in the commercials, about the importance of combustion in the heat treating process?
CN: Combustion is really the core of their process. If I could leave you with a message that there are high value easily implemented solutions for achieving and maintaining that optimal combustion, then I think we've given the listeners and readers a little bit of value here. Get your combustion right and keep it right, and then look for that technology that is available out there that can help you get the most out of every BTU that you burn.
DG: Exactly. And the payback is almost a no-brainer in a lot of situations. Obviously, each situation is going to be unique, but the example you gave in the article, the payback was enormously good. It's certainly worth investigating.
CN: It is. It's always worth investigating when it's about achieving more output. When you can achieve more output and ring the cash register more and create more opportunities for selling additional product or new product capacity, those are easier ROIs. If we're just looking at wanting to save fuel, well sure, that pencils out in that case, it's just not the same sort of three-month turnaround or as quick.
In our case, we recommend three areas: Get combustion right and keep it right, with a tech-enabled service team and monitoring. I really wanted to point out, and we've heard this a hundred times– if it's not measured, it's not sustained. The core of heat treating is combustion, yet very few of us actually measure the performance of combustion. We might measure the output (temperature), but we don't measure excess oxygen, which is really the necessary metric to achieve the efficiency. The big steel example there kind of guides us. You should never wonder how well your combustion system is running. You should know with data. That's the core of your process.
So, get it right and keep it right and then get the most out of the gas that you purchase. Stop throwing away energy. Utilize these high value, easily implemented solutions and get the most out of it.
And the piece that we really didn't talk about was- train your team. There are combustion trainings out there. Ours is specifically geared towards combustion and really for heat treating operations, but train your team and talk about a common understanding and a common language around combustion. That dispels a lot of myths around combustion and exposes the team to the latest technologies and best practices.
Lastly, keep reading and listening to Heat TreatToday and Heat TreatRadio because that's the best way to stay informed on the latest technologies. You've got to keep up on it. All kidding aside, it is a really great way, the information that you guys provide is significant towards staying up on the technology.
DG: I appreciate that shameless promotion there. ~chuckles~
If someone wanted to get a little more information, what are you comfortable giving out as far as contact information for people to get a hold of you?
Carl Nicolia, President of PSNERGY, LLC (photo source: Carl Nicolia)
“There was a time when the caveman’s torch was the top end of heat treating technology. We have since learned that all fire is not created equal. Heat treat technology has evolved from fire to combustion and from combustion to efficient combustion.”
Join Carl Nicolia, president of PSNERGY, LLC, as he challenges industry leaders to evolve with viable and proven solutions to achieve combustion and furnace efficiency in this original Heat Treat Today article.
This article appears in the June edition of Heat Treat Today’sAutomotive Heat Treating magazine.
As a technical professional, engineer, and self-proclaimed geek, in times of uncertainty I take comfort in going back to fundamentals. Going back to basic concepts defined by fundamental scientific principles of physics and heat transfer brings us to a point where we know what will happen, and this can give us all some comfort in these uncertain times. We can take comfort in knowing that when we combine the right mix of air and fuel with an ignition source, we will get fire! And as the caveman said, “Fire good!”
There was a time when the caveman’s torch was the top end of heat treating technology. We have since learned that all fire is not created equal. Heat treat technology has evolved from fire to combustion and from combustion to efficient combustion. We have learned how to optimize the delivery of energy produced by fire to achieve remarkable results. There is high-value technology available today (i.e. low cost with high impact) that can be quickly and easily implemented on existing furnaces, regardless of size or age.
Businesses are moving through some of the most challenging times in modern history. Even though a few months ago the economy was booming, we are now being pushed to respond in new and unique ways. Many businesses, though, have existed for generations and have overcome other challenging market conditions. How did they survive? They evolved!
Darwin was right; “It is not the strongest of the species that survives, not the most intelligent that survives. It is the one that is most adaptable to change. Intelligence is based on how EFFICIENT (my emphasis) a species became at doing the things they need to survive.”
Industries coming back online after extended down times and lost production days, are driving new customer demands for quality parts produced faster and cheaper. End customers are executing plans to ramp-up their plants to run at maximum efficiency. They are securing additional critical inventory and capacity from their supply chain. The productivity ante has been raised! Have your operations evolved to meet these demands?
Combustion efficiency and furnace efficiency are the heart of all gas-fired heat treating operations. Combustion and furnace efficiency can mean the difference between profit and loss, high quality and scrap, survival and extinction. Now more than ever, finding low-cost, easily-implemented technologies to increase efficiency is critical to your business’s evolution. Good news: Products and services enabled by revolutionary technology exist today and can improve the efficiency of your business. Because the technology is revolutionary, the implementation is simple.
Case Study
To understand the impact of this type of innovative technology, let’s look at an example from a contract heat treating company with a 9’ IQ box furnace. This batch annealing furnace is heated by four 5” ID x 65” U-tubes with bayonet recuperators. The company installed the latest technology of radiant tube inserts (RTI) into the exhaust legs of the radiant tubes. Once the RTI’s were installed, the combustion system was tuned, utilizing the latest sensing technology. The results are impressive:
Recovery cycle time reduced by 25%
Total gas consumption per load reduced by 5%
Furnace output increased by 10%
Total time to implement this solution was one day. Total cost to implement this solution was less than $10,000. Payback on this installation was less than three months!
Combustion Efficiency
Combustion efficiency is getting the most energy out of the gas purchased and ensuring you continue getting that same level of performance. Most talk about the importance of proper tuning, yet how many recognize the likelihood they are not running optimally today and can quantify the impact? A furnace running just two points out of tune at 5% excess oxygen is delivering 8% less energy to the system. Jump that to 7% excess oxygen and you are throwing away over 20% of the energy. Keeping the combustion system in tune is critical (Figure 1).
Figure 1: Impact of proper combustion tuning. (photo source: Carl Nicolia)
Just like the caveman, gone are the days of running through the burners with a handheld meter once a year, making adjustments based on a single point in time. There are combustion engineering service teams utilizing the latest technology to achieve higher levels of system performance. It is no longer acceptable to take a burner view of combustion: It must be at the combustion system level. If your service team is still working with single handheld meters, it is time to evolve. At a minimum, service teams today should be equipped with the latest sensing technology that allows them to view combustion in entire zones, if not entire furnaces, record data over the range of operation, and store this data for trending and preventive maintenance.
Once the combustion system is tuned, it is necessary to ensure the system stays tuned. Technology that monitors combustion across the entire furnace multiple times per day is available. Utilizing the latest sensing equipment, along with leading edge controls and IIOT technology, these systems seamlessly collect, analyze, and store combustion data and provide simple actionable alerts that keep your combustion system operating at maximum efficiency. Utilizing this type of technology allows you to stay ahead of combustion efficiency in real time and prevent your operation from throwing away profits.
Furnace Efficiency
Getting and keeping maximum combustion efficiency is certainly the first step in your evolution; however, the only thing you get paid for is getting that energy to product. How well the energy provided through efficient combustion is transmitted to the product being processed is called furnace efficiency. Again, there is low-cost, high-value technology available to increase furnace efficiency.
Waste heat recovery technology continues to evolve. Recuperators have been a great first step that many in the industry have incorporated into their systems, but there is more that can be done.
Ceramic inserts are waste heat recovery devices that work alone, or in conjunction with recuperators, balancing the energy delivered across the entire length of the radiant tube, significantly improving furnace efficiency as well as increasing radiant tube life. Recent technological advancements in ceramic insert design and material have increased the effectiveness of ceramic inserts. Additionally, alternative radiant tube designs, such as bubble tubes and textured tubes, help deliver more energy to the product.
Don't let your radiant tube furnace be the caveman of your operations. Take comfort in understanding that all fire is not created equal, and many combustion technology advancements are based in fundamental scientific principles. Get more information on these low-cost and easily implemented technologies available to the heat treating industry today. Recognize that utilizing these revolutionary technologies is the key to evolving your business to measurably higher levels of responsiveness and performance and will allow your business to thrive in this environment.
Will you evolve?
About the Author: Carl Nicolia is president of PSNERGY, LLC, which provides modern solutions to combustion problems, improving equipment life, enhancing productivity, and reducing emissions through smart application of proprietary products, services, and technology.
Ernesto Perez, Director of Engineering, Nutec Bickley
In today’s Heat Treat TodayTechnical Tuesday feature, Ernesto Pérez, Director of Engineering, at Nutec Bickley, introduces readers to different options when it comes to furnace temperature control.
The main aim of the temperature control function is to keep a furnace operating within certain predefined values and it is composed of two main parts:
Electronic control element, usually a PID (proportional–integral–derivative) controller
Mechanical components
In this article we will look at the various control modes used in industrial furnaces, and their applications for various heat treatment processes.
Back to the Beginning: “Zero Control” Mode
Figure 1
Before considering the modes currently used, we should briefly mention the “zero control” mode found in earlier furnace models, employed some time back, also known as “atmospheric mode.”
This mode operates by taking air from the environment by means of the venturi effect to perform combustion without controlling the air flow, resulting in an inefficient use of energy. (Figure 1)
Fuel-Only Control System
Figure 2
This operates in a similar way to zero mode, where only the gas is controlled. However, instead of the air being introduced by the venturi effect, there is a turbo fan that provides a constant flow to the process, while the gas is regulated during the different stages of combustion. (Figure 2)
Economic system having a single line of control.
It provides good temperature uniformity in applications where all items being fired in the furnace need to be at the same temperature.
Ideal for low temperature furnaces, kilns for ceramics and applications that require high-level heating homogeneity.
Possible Disadvantages This technique leads to high gas consumption due to the heating of all the air present, irrespective of the size of the load in the furnace.
Proportional Control System
Figure 3
With this control mode, the air and the gas are controlled proportionally. (Figure 3)
The operation starts with a small flame, and as the temperature rises, it grows as the air and gas levels increase.
This system allows you to adjust the amount of gas based on the air present in order to achieve perfect combustion and optimal fuel consumption.
Ideal for any type of furnace, for example for heat treatments such as aging, tempering, forging and normalizing.
Possible Disadvantages At the beginning of the heating process, it can be the case that temperature uniformity across the entire furnace is not so good due to the small flame, so it is not a system recommended for the treatment of very fragile pieces that can break.
Mass Flow Control System
Figure 4
This system controls air/gas in the same as the previously described method, but it also gives allowance to vary the air/gas ratio during combustion process in order to optimize the fuel. (Figure 4)
It enables for the achievement of optimal combustion conditions with less energy input.
If more air is needed in a particular heat treatment stage (usually at the beginning), it can be temporarily increased.
Ideal for any type of furnace, like heat treatments such as aging, tempering, forging, normalizing and applications involving fragile products.
Possible Disadvantages Because of the technology behind the system, it is more expensive.
Pulse Control System
Figure 5
This is one of the most recently introduced methods that provides a fixed air/gas ratio, but unlike the previous mentioned systems, flame velocity for product heating is always high, which generates ideal temperature uniformity right from the beginning of the cycle. (Figure 5)
The burners pulse from high-fire to low-fire, repeating this cycle every 15 to 60 seconds.
It is cheaper to operate than the mass flow system, allowing users to handle the entire range of products with a smaller investment.
It provides greater fuel efficiency by heating the product evenly from the beginning.
Ideal for any furnace, for example for heat treatments such as aging, tempering, forging, normalizing and applications involving fragile ceramic products.
Possible Disadvantages The radiation of the flame can affect certain products; however, by installing an additional instrument it is possible to control this effect and to reduce flame radiation.
Experts in Temperature Control
Nutec Bickley can offer all current systems, advise on the most appropriate choice with the best cost benefits, update old systems with current technology, and provide repair and spare parts services for existing temperature control systems.
About the author: Ernesto has been sharing his expertise at Nutec for 18 years. As an electronic system engineer with a master’s degree in artificial intelligence, the 25-year industry veteran has been focused on the control aspect of software and hardware.
Climate change and fossil fuels are topics that can spur many lively conversations. In today’s Heat Treat TodayTechnical Tuesday feature, explore their connection as it relates to heating industrial furnaces in the future with Dr. Joachim G. Wüenning, president, WS Inc. and an expert in clean efficient combustion.
Many people view climate change as the biggest threat to mankind. Technical and social efforts will be required to meet the goals, formulated in the “Paris Climate Agreement,” to limit global warming to less than 35.6° F (2° C).
Combustion of fossil fuels is by far the largest human contribution to global warming. Fossil fuel-fired power plants and internal combustion engines are already in the public focus. The transformation to alternative drives for vehicles has just started, and the days of coal-fired power plants are numbered.
Combustion of fossil fuels for industrial furnaces is also a large contributor to greenhouse gases and air pollution. The industrial heating sector is not in the public focus yet, but that will change soon; therefore the topic should be addressed proactively.
For mid- to long-term future industrial process heating, there are three main scenarios:
heating with renewable electricity, or
heating with non-fossil fuels, or
a combination of both.
Humans used non-fossil fuels for hundreds of thousands of years and are returning to that habit after a short period of about 250 years where fossil fuels were primarily used.
Reducing CO2 Now and In the Future
Heating a furnace using electricity is locally CO2 free, but an even greater amount of CO2 is emitted at power plants since the majority of electricity is generated by burning fossil fuels. For every kilowatt hour (kWh) produced, roughly one pound (~0.45kg) of CO2 is emitted into the atmosphere [1]. This is true for Germany, and the figures for the United States are in the same range.
Heating an industrial furnace with a typical temperature of around 1832°F (1000°C) with natural gas produces about 0.4kg CO2 for every kWh of available heat for a cold air burner, and less than 0.25kg/kWh CO2 when using a recuperative or regenerative burner where waste heat is recovered using a heat exchanger.
So, the short-term measure to reduce CO2 emissions is to use an efficient burner with heat recovery or to switch from electric to natural gas heating, which can cut CO2 emissions by 50% or more.
For a further reduction, we have to wait until electricity generation becomes predominantly regenerative, or we have to use green, non-fossil fuels. The possible paths to non-fossil heating of industrial furnaces are drafted in Figure 1. It shows that the short-term action should be improving the efficiency of burner systems or a switch from electric to gas heating. In the mid- to long-term future, there should be a healthy competition between non-fossil fuel gas and electricity, driving the prices for non-fossil energy down.
Figure 1
Changing Fuel Compositions
The most relevant characteristic for the interchangeability of fuel gases is the Wobbe Index (Figure 2), with the lower or upper heating value (Hi, Hs), the density of the fuel gas (r) and the density of dry air (r0). Fuel gases with the same temperature, pressure, and the same Wobbe Index will provide the same energy output from a burner. If the Wobbe Index is changing, the flow must be corrected by changing the fuel gas pressure or a flow throttle device to keep the burner power constant.
Figure 2
In most cases, the air does not need to be corrected since the ratio between stoichiometric air ratio and lower heating value is about 0.95 m3/kWh for common hydrocarbons. That means that a burner with a given heating power needs the same amount of air even when different fuel gases are used. A good rule of thumb is that one cubic meter per hour of air is required for every kilowatt of heating power.
If hydrogen is used as a fuel, about 15% less air is required. So, when hydrogen is added to natural gas and the fuel gas flow is corrected but the air flow is left unchanged, the system would be operated with somewhat more excess air, slightly less efficient but safe.
If gas fluctuations will occur in the future, adjusting the burners with more excess air would be an easy measure to ensure safe operation. With an effective heat recovery system and low exhaust gas temperatures, efficiency losses would be minimal.
Fuel Gases With High Hydrogen Content or Pure Hydrogen
The flame speed of hydrogen is much faster compared to hydrocarbons. That can cause some problems, especially in premixed burners where a flashback can occur. Another challenge resulting from faster combustion could be higher flame peak temperature leading to higher thermal NOx emissions. Modern low NOx methods are available to address this problem.
A positive effect of hydrogen can be a more reliable and easier ignition of burner systems. Many industrial burner systems can be operated with high percentages of hydrogen or with pure hydrogen with little or reasonable modifications.
Fuel Gases Containing Fuel Bound Nitrogen
Using ammonia or bio-gases with fuel bound nitrogen will produce excessive amounts of NOx-emissions when burned in most burner systems. There are a number of options to achieve low NOx-combustion with fuel bound nitrogen.
One method is fuel conditioning where fuel bound nitrogen is broken up into molecular nitrogen. This was successfully demonstrated using a stainless steel reactor in combination with a flameless oxidation burner system.[2] Another method would be exhaust gas cleaning by selective (SCR) or non-selective (SNCR) catalytic exhaust gas cleaning. Both processes require large investments and operating costs and should only be used if other options are not available.
The development of combustion systems with integrated treatment of fuel bound nitrogen would be the preferred method and will be an important topic for combustion research in the coming years. One approach is multi-stage flameless oxidation [3].
Fuel Conditioning
Fuel conditioning might be required to keep fuel gas properties within regulated limits inside the gas transport and distribution grid or for certain customers with special requirements. Fuel conditioning can be performed by blending different gases or by changing their compositions by using reformers or gas separation units like pressure swing adsorption (PSA) or membrane technology.
If future regulations propose a certain hydrogen content in the fuel gas grid, strategically placed steam reformers could keep the hydrogen content within certain ranges, even if there is no regenerative electricity available to operate electrolysers.
Reformers could also crack ammonia, ethanol, or methanol before being used as fuel gas to heat processes.
Outlook
There are several options towards non-electric, fossil-free industrial process heating. All these options have to be thoroughly investigated to keep a number of options open for future energy systems. The energy system of the future will be based on regenerative power generation but it will involve additional energy carriers to store and transport the energy. There are some challenges for combustion but there is no doubt that these can be overcome.
A fair and open competition between the different energy options will create the best solutions for society and the planet. A planned economy will not provide the fertile soil for innovations and entrepreneurship necessary to meet the challenges.
References
[1] German Environment Agency, CO2 Grid Emission Factors from 1990 – 2018 for the German Energy Mix, March 2019
[2] Domschke T., Becker C., Wüenning J.G., Thermal Use of Off‐Gases with High Ammonia Content – a Combination of Catalytic Cracking and Combustion, Chem. Eng. Technol., 21: 726-730
About the Author: Joachim G. Wüenning is president of WS Wärmeprozesstechnik GmbH and his area of expertise is in clean efficient combustion, FLOX—flameless oxidation, heat recovery, radiant tubes, and recuperative, regenerative burners. This article originally appeared in Heat Treat Today’sMarch 2020 Aerospace print edition.
This article on the critical role of valve safety trains in the prevention of catastrophic fuel-delivery accidents at heat treating facilities is authored by Robert Sanderson, P.E., Director of Business Development in the Combustion Safety division of Rockford Systems, LLC, based in Rockford, Illinois. Valve safety trains require regular inspections, maintenance, and training.
Heat treating, a thermal process used to alter the physical, and sometimes chemical, properties of a material or coating, is a high-temperature operation that involves the use of heating or chilling, normally to extreme temperatures, to modify a material’s physical properties — making it harder or softer, for example. Applications for heat treating are virtually endless, but at the heart of all thermal processes is the valve safety train.
These fuel-delivery devices maintain consistent conditions of gasses into furnaces, ovens, dryers, and boilers, among others, making them crucial in assuring safe ignition, operation, and shutdown. Equally important, they keep gas out of the system whenever equipment is cycled or shut off.
A valve safety train isn’t a single piece of equipment. Instead, it has many components including regulators, in-line strainers (“sediment traps”), safety shut-off valves (SSOV), manual valves (MV), pressure switches, and test fittings logically linked to a burner management system.
Flame-sensing components make sure that flames are present when they are supposed to be, and not at the wrong time. Other components may consist of leak-test systems, gauges, and pilot gas controls. At a minimum, there are two crucial gas pressure switches in a valve safety train, one for low pressure and one for high pressure. The low gas pressure switch ensures the minimum gas pressure necessary to operate is present. As you would assume, it will shut off fuel to the burner if the gas pressure is below the setpoint. The high gas pressure switch ensures excessive pressure is not present. It too will shut off fuel if the gas pressure is too high. Both switches must be proven safe to permit operation. Additionally, there will be an air pressure switch to ensure sufficient airflow is present to support burner operation.
Some systems have supplementary pressure switches, such as a valve-proving pressure switch. Switches such as these are typically used to enhance safety or provide other safety aspects specific to that application’s needs. A multitude of sensors within the valve safety train — pressure switches, flame detectors, position indicators — and isolation and relief valves work together in concert to prevent accidents.
Valve safety trains must be compliant with all applicable local and national codes, standards, and insurance requirements. The most common of these for North America are NFPA, NEMA, CSA, UL, FM. Annual testing and preventive maintenance are not only an NPFA requirement, but also oftentimes required by insurance agencies, equipment manufacturers, and national standards, including ANSI, ASME, and NEC.
Set Your Trap
The primary function of a valve safety train is to reliably isolate the inlet fuel from the appliance. Safety shut-off valves are purposely selected to do this. To protect these valves, the initial section of a safety train is used to condition the fuel and remove debris that could potentially damage or hinder all downstream safety components.
The first conditioning step is a sediment trap (a.k.a. dirt leg, drip leg). This trap captures large debris and pipe scale and provides a collection well for pipe condensates. The proper orientation of a sediment trap is at the bottom of a vertical feed. This downwards flow arrangement promotes the capture of debris and condensate into the trap. A horizontal feed across a sediment trap is an improper application. The second conditioning step is a flow strainer or filter element. These devices are fine particulate sieves. The removal of fine particulates from the fuel stream further protect the downstream safety devices from particulate erosion and abrasion. Taken together these conditioning steps remove particulates and condensates that might block, hinder, erode, or otherwise compromise the safety features of the downstream devices.
The Explosive Force of a Bomb
Owing to the presence of hazardous vapors and gases, a poorly designed or inadequately maintained safety train can lead to catastrophic accidents, ranging from explosions and fires to employee injuries and death. When this explosive force is unleashed, the shock wave carries equipment, debris, materials, pipes, and burning temperatures in all directions with tremendous force.
The following incidences provide just a few examples of why it is important to purchase the highest quality valve safety train and to keep it professionally maintained, inspected, and tested.
In 2018, a furnace explosion at a Massachusetts vacuum systems plant killed two men and injured firefighters as a result of fuel malfunction.
In Japan, an automobile manufacturer lost tens of millions of dollars when it was forced to shut down production for nearly a month after a gas-fueled furnace exploded due to flammable fumes building up in the tank.
In a Wisconsin bakery, an employee was seriously injured when he ignited an oven’s gas and was struck by a door that was blown off. A malfunctioning valve had allowed natural gas to build up inside the oven.
In 2017, a van-sized boiler exploded at a St. Louis box company, killing three people and injuring four others. The powerful, gas-fueled explosion launched the equipment more than 500 feet into the air.
In 2016, a boiler explosion in a packaging factory in Bangladesh enveloped the five-story building in flames, killing 23 people.
Two Dangers: Valves and Vents
Valves are mechanical devices that rely upon seats and seals to create mechanical barriers to control flow. Over time, these barriers wear out for a variety of
Glassblowing Furnace with Pipes
reasons, whether it is age, abrasion, erosion, chemical attack, fatigue or temperature. Increased wear contributes to leaks, and leaks lead to failures and hazards. Defective valves can allow gas to leak into a furnace even when the furnace is not in operation. Then, when the furnace is later turned on, a destructive explosion could occur.
Testing a valve’s integrity is an evaluation of current barrier conditions and may be used to identify a valve that is wearing out prior to failure. As such, annual valve leakage tests are an important aspect of a safety valve train inspection program. Along with annual testing, valves should be examined during the initial startup of the burner system, or whenever the valve maintenance is performed. Only trained, experienced combustion technicians should conduct these tests.
Improper venting is another danger. Here is the problem: Numerous components in a valve safety train require an atmospheric reference for accurate operation. Many of these devices, however, can fail in modes that permit fuel to escape from these same atmospheric points. Unless these components are listed as “ventless,” vent lines are necessary. Vent lines must be correctly engineered, installed, and routed to appropriate and approved locations. In addition, building penetrations must be sealed, pipes must be supported, and the vent terminations must be protected from the elements and insects. In short, vent lines are another point of potential failure for the system.
Even when vent lines are properly installed, building pressures can vary sufficiently enough that they prevent optimal burner performance. Building pressures often vary with seasonal, daily weather, and manufacturing needs, further complicating matters. Condensate in vent lines can collect and drain to low points or into the devices themselves. Heating, cooling, and building exhausters are known to influence building pressures and device responses, but so can opening and closing of delivery doors for shipping and receiving. Hence a burner once tuned for optimal operation might not be appropriately tuned for the opposite season’s operation.
The smart alternative to traditional vented valve trains is a ventless system that will improve factory safety and enhance burner operation. Ventless systems reference and experience the same room conditions where the burners are located, resulting in more stable year-round operating conditions, regardless of what is happening outside. Additionally, ventless designs typically save on total installation costs, remove leaky building penetrations, eliminate terminations that could be blocked by insects, snow or ice, improve inspection access, and ensure a fail-safe emergency response.
Final Thoughts
Valve safety trains are critical to the operation of combustion systems. Despite being used daily in thousands of industrial facilities, awareness of their purpose and function may be dangerously absent because on-site training is minimal or informal. To many employees on the plant floor, this series of valves, piping, wires, and switches is simply too complex to take the time to understand. What is known can be dangerously misunderstood.
Understanding of fuel-fired equipment, especially the valve safety train, is necessary to prevent explosions, injuries, and property damage. The truth is, although valve safety trains are required to be check regularly, they are rarely inspected, especially when maintenance budgets are cut. And while codes require training, they offer very little in terms of specific directions.
As a safety professional, the onus is on you. You and your staff must have a core level of knowledge regarding safe practices of valve safety trains, even if a contractor will be doing the preventive maintenance work. Most accidents and explosions are due to human error and a lack of training when an unknowing employee, for example, attempts to bypass a safety control. Preventive maintenance is essential to counter equipment deterioration, as is the documentation of annual inspection, recording switch set points, maintaining panel drawings, and verifying purge times. Accidents happen when this type of documentation is not available. Don’t wait for a near-miss or accident to upgrade your valve safety train.
Safety shutoff valves are the last line of defense against a potentially catastrophic incident. When conditions require, they interrupt the flow of fuel to the burner(s) and oven. There are many options when selecting fuel safety shutoff valves for your application. The construction and application of these devices is highly regulated by interlocking standards created by many different organizations. The goal of this article is to clarify how to comply with the most common standard affecting the reader: NFPA 86.
