2016-1-28-fueling-suspicion

Fueling Suspicion: Manufacturer defects in gas appliance fires

DonanEngineering Appliance, Product & Component Failures, Forensic Engineering, Residential & Commercial Structure Fires, Vehicle & Equipment Fires

Fires can be caused by devices that fail due to a manufacturer’s defect.  Quality assurance procedures have gone a long way to eliminate out-of-box failures but manufacturers sometimes bypass quality checks on consumer products for competitive reasons.  Even the most ethical companies are susceptible to human error that can cause an almost imperceptible change in an otherwise flawless manufacturing procedure.

Recently installed equipment or equipment that has not achieved a significant level of historical performance is sometimes the cause of fires, and these fires can be difficult to investigate.  Fire claims that involve the recent installation of gas-fired equipment often require that involved parties have their interests represented by a qualified engineer who knows the total environment at the fire scene.  Important factors in these fire investigations can include all or some of the following: the human actions leading up to the fire, the normal operating procedures for the equipment, the control logic required to appropriately program the system, and the intricate detail of the flame control system.

Installation Safe Guards

The most common fire-related factory defective products are those which use a petroleum product to raise the temperature of water to heat transfer fluid or ambient air.  Qualified contractors often test the products at their facility before final installation at the consumers’ site.  When testing is done by local building inspectors, rigid specifications must be met with regard to the ability of the piping system to contain the fuel in question.  Records of leak tests are kept in local municipality offices, and often allow fire investigators to rule out installation error.  While these efforts provide safe guards against installation errors, these quality assurance procedures fail to protect from factory defective fuel piping systems.

Popularity & Risk of Gas Appliances

fire 2A gas fireplace is a popular feature in homes.  Consumers are familiar with the short laminar blue flames close to the burner tube, and are likely mesmerized by the leaping yellow flames that  cast an illuminated glow to the room.  The current low cost of natural gas and propane has made gas fireplaces and appliances a desirable feature in new construction.  When compared to the cost of electrical heating costs, gas appliances make economic sense and can sometimes alleviate problems associated with power outages.  But self-igniting fireplaces can fail shortly after installation.

And there are still those who prefer the speed and control of cooking with natural gas or fire 3over a propane stove.  These too pose a danger for defects.

Virtually every gas-fired piece of equipment that has been in operation for over 100 hours of runtime without incident will likely run for thousands of hours without a problem.  Though valves used to control the flow of gas or oil in these appliances are electrical, there is also a mechanical element.  The mechanical elements in these valves will only cycle a certain number of times before failure.  It is the nature of mechanical devices to be subject to age and wear, which will eventually affect the ability of the valve to perform correctly.  In most cases these valves are designed ‘Fail Safe’ and will fail in the closed position.

Controlling the Fuel Source

Anyone who has attended to a structure fire knows the chilling effect of the speed and intensity with which a building is engulfed in flames.  But once the fuel feeding the fire is contained, a raging fire is quickly under control.

fire 4Oil and gas engineering professionals know that one of the most crucial devices on an upstream processing site is the emergency shut-down valve (ESDV). The oil or gas piping is almost always schedule 40 or 80 steel pipe that is not susceptible to melting under normal industrial situations.

Whenever oil or gas is present in high concentrations, the equipment is designed to be ignition proof and it has control systems that are capable of automatically sensing the release of flammable liquids or gases and will shut off the fuel source to prevent substantial losses due to inadvertent fires.  Unfortunately, local residential building codes have not been upgraded to take advantage of technological upgrades in control equipment that could be utilized in residential applications at a reasonable price.
fire 5In the industrial world where oil or gas is used to fuel large industrial burners, control systems are designed to provide ‘fail-safe’ protection and
always include the application of a “Flame Safety Valve”.  These valves are the emergency shut-off valves and are strategically placed outside of the location where a flame may exist.  This is true of each individual device. When oil, chemicals, natural gas, or propane are providing fuel to the fire, firemen know how important it is to shut the valves to the pipes feeding the flames.  In industry, these valves are sometimes referred to as “flame safety valves” that are automatically programmed to close under any potential fire event.  In the event that the fire is upstream from these valves, there are strategically located valves that can be electrically initiated, air-operated, and/or manually operated to allow immediate shut off by the personnel attending the fire.

Residential & Commercial Shortfalls

fire 6This is not true of residential and many commercial installations.  Schedule 40 or 80 steel pipe is seldom found in residential gas systems and instead a much more vulnerable tubing system is utilized to convey the natural gas or propane to the fired appliance or device.  When there is a fire in a residence where gas appliances are present, a fast moving fire will melt the pressure regulator and tubing containing the propane or natural gas and turn the tubing into a burner that makes the fire worse than any wood-fueled fire. The absence of a discernible gas pressure regulator in the rubble of a house fire can mean that the gas tubing was turned into a ‘burner’ capable tof producing the high flame temperatures that melt the alloys used to make the pressure regulators.

 

Summary

Whenever a mysterious fire-related loss occurs at a property where natural gas- or propane-fueled devices have been recently installed, investigate the burner system fuel piping as a possible cause.  Look for climatic changes that may have logically contributed to the events leading up to the incident. Inspect the scene for melted and substantially deformed alloyed metals that would not have been destroyed in a wood-fueled fire. And consider supplementing a fire investigator with the services of a technologically astute combustion and control engineer.

 

About the author

In 1977, while working as a research engineer for Cargill,  Lee Dirkzwager, P.E., led the research that resulted in a paper presented at the First International Symposium on Grain Dust Explosions in Kansas City, Missouri.  In 1978, Mr. Dirkzwager moved into management as a Plant Engineer for a lead smelter in Texas and commissioning Project Manager for a lead smelter built in Los Angeles.  After receiving his Professional Engineering license in 1983, Mr. Dirkzwager formed the consulting engineering company, Pyro Engineering, and has served industrial clientele in the areas of combustion, mechanical engineering, electrical controls engineering and automation programming for a variety of industries including chemical production, materials handling, and food processing.  He has focused on the oil, gas and biofuels industries since 2006 and has led the development of over one hundred industrial control systems since 1981.  Mr. Dirkzwager has participated in many fire investigations during his career and now is a part of the Donan Forensic Engineering team.

 

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