The propane tank is a seemingly simple device, most often found in backyards across the country, hooked up to a grill for a barbecue. However, closer inspection reveals that these devices have been engineered to provide consumers with multiple layers of safety. In this article we open a propane tank to show you what is inside, how they have been designed with safety in mind, and why they are sometimes still involved in fires and explosions despite engineering efforts to make them safer.
Propane Tank Fires & Explosions - Expert Article
Even with the various safety features engineered into modern propane tanks, the mechanical engineers at Robson Forensic are frequently retained to investigate fires and explosions involving gas grills, fryers, and other pieces of equipment that rely on propane tanks for fuel. Our investigations have determined many reasons for mishaps, including improper tank usage, re-filling of tanks beyond their certification date, manufacturing defects and the failure of related appurtenances. To understand the causes of these incidents, we’ll first examine the anatomy of a propane tank, and their built-in safety features.
Anatomy and Safety Features of a Propane Tank
Consumer propane cylinders, also called bottles or tanks, have several anatomical features. The cylinder contains a mixture of liquefied gas and vapor in the cylinder, which is the shell of the tank. The cylinder collar at the top of the cylinder protects the gas valve and incorporates carry handles. The cylinder foot is a ring of steel at the bottom of the cylinder which provides a stable base for the cylinder to rest on.
OPD Valve: The Overfilling Prevention Device (OPD) Valve is the most modern and current industry standard gas valve for consumer propane cylinders. The OPD Valve is the result of generational product improvement and has had several safety devices incorporated into it as its design has matured, improving safety. These include the pressure relief valve and a quick closing coupling. The OPD valve gets its name from the Overfilling Protection Device. This is a float which closes off the filling tube when the tank is 80% full. It works just like the float in a toilet cistern. By only allowing the tank to be 80% full, there is adequate room left in the tank, called headspace. The headspace allows the propane to expand and contract with normal temperature changes, without creating excessive pressures. The pressure relief valve built into the OPD valve will relieve pressure in the tank, should excess pressure form. This allows the tank to release pressure in a controlled way, and is intended to prevent catastrophic rupture of the cylinder. The quick closing coupling in the OPD valve shuts off the flow of propane if the gas regulator becomes detached from the tank. Still included is the manually operated hand wheel, giving the user the ability to manually turn the flow of propane on and off
Low BTU Gas Regulator: Most outdoor appliances, such as grills, heaters, and other products which use these types of propane cylinders for fuel consume gas at a rate less than 100,000 BTU per hour, and at a pressure of 11 in. water column, which is about a half a PSI. The bottle regulators which provide this type of gas service are not suitable for use on a whole house type of service, and should not be used for that purpose.
Gas Hose: The gas hose is flexible connection, safely delivering gas from the gas regulator to the appliance. Gas hoses are typically made of rubber, unarmored, and are susceptible to damage and deterioration over time. At least annually (but preferably more frequently), gas hoses should be visually checked for leaks and damage. Dry rotted, cracked, or burned hoses are damaged and should be replaced. All connections and hoses should also be checked with leak detection fluid, which forms bubbles when leaks are present. Leak detection fluid is inexpensive, simple, easy to use, and effective.
Explosions Still Occur
Even with the many safety features built into propane tanks, fires and explosions still occur, resulting in personal injury and damage to property that can be catastrophic. Common causes for these incidents include:
- Leaky supply lines or connections
- Faulty or leaking valves
- Re-use of older tanks that do not include certain modern safety features
- Corroded cylinders
- User error
Propane Tank Explosion Investigations
The experts in the Fire and Explosion practice at Robson Forensic are experienced in performing forensic investigations of propane tank explosions and fires, from minor incidents with minimal damages to serious, sometimes fatal catastrophes. Our Fire and Explosion experts are qualified to investigate matters related to origin and cause of a fire or explosion, fire patterns, fire prevention and building codes, materials flammability, arson, appliance fires, electrical fires, and vehicle fires.
For more information, submit an inquiry or contact the author of this article.
Mechanical Engineer & Building Systems Expert
Stanley Jaworski is a mechanical engineer with a broad base of professional and vocational experience. He earned his Bachelor of Science in Mechanical Engineering Technology and is licensed as a Professional Engineer in multiple states. He is a member of the American Society of Heating, Refrigeration & Air Conditioning (ASHRAE), the American Society of Mechanical Engineers (ASME), and the National Association of Fire Investigators (NAFI). Stanley has more than 10 years of professional experience designing, installing, commissioning, and servicing HVAC and industrial process systems. He has a wide variety of complex building systems expertise involving boilers, chillers, compressors, gas and liquid piping systems, gas fired appliances, hydraulic systems, and fire protection and controls. Stanley’s vocational background has provided the spectrum of experience from welding components into place to designing turnkey systems.