Q & A About Propane Gas OPDís

By Gary Motley

We have received calls from customers asking for more information about the National Fire Protection Associationís (NFPA) requirement for overfill prevention devices (OPDís) on Propane cylinders with capacities from 4lbs to 40lbs. This requirement went into effect on April 1,2002. An exception to the requirement is horizontal cylinders manufactured before October 1,1998. Here is some guidance from the National Propane Gas Association (NPGA) on NFPA 58 (the Propane Gas Code) and the OPD issue:

Q: Why do some propane retail marketers fill cylinders that would normally be required to be requalified and have an OPD installed, whereas other marketers require the OPD to be retrofit on the cylinder before they refill it?

A: Propane marketers of integrity are those that care about the handling and the use of the cylinders that they refill, knowing that the families of consumers deserve the best and the safest service that can be offered. If a propane marketer elects to do otherwise, that choice speaks for itself. Also keep in mind that some states have not adopted the 1998 or later editions of NFPA 58.

New Style OPD with Hose.

This old style POL is no longer legal on vertical cylinders.

Q: If the requirement for a cylinder to be equipped with an OPD is not a law in my state, then how can it be enforced by a propane marketer?

A: The code is not adopted, state-by-state, on a uniform basis. In time, most states, if not all, will move to enforce the OPD criteria.

Q: Is the requirement for OPDís a mercenary ploy by those in the propane industry to take advantage of consumerís pocketbooks?

A: This is a good question and deserves a direct answer which is Ö.no. The OPD was developed to offer the consumer a higher degree of safety and protection. The OPD will not allow the cylinder to fill past 80% full, thus preventing overfilled cylinders. A full cylinder only contains about 80% propane liquid. The 20% space that is left allows room for propane to safely expand as the outside temperature increases. When an overfill container is heated, such as by the sun, the propane expands, causing a pressure increase within the cylinder. To prevent the cylinder from pressure damage, a relief valve in the container is provided. When the pressure gets too high, the relief valve opens and vents directly to the atmosphere. Other safety features provided with the new OPD involve its mating new hose that connects the cylinder to the RVís manifold. This new ACME connection (1 and 5/16 inch ACME thread) on the supply hose has a nut that can be tightened to the OPD cylinder valve by hand, without using a wrench. The new hose nut also includes an internal excess flow valve the prevents full container pressure from being expelled from the cylinder if this supply hose is cut or ruptures. The new OPD also has a back check feature that will not allow propane to flow unless the supply hose mating nut is connected to the cylinder. Finally, there is a bushing behind the mating nut that will melt when exposed to fire with temperatures between 240 and 300 degrees. This melting allows a brass nipple inside the mating nut to move about ľ inch, closing a small piston inside the OPD, totally shutting off the flow of propane. This feature helps to mitigate fires or explosions.

Q: I have a horizontal cylinder on my RV. Are OPDís available for that kind of service?

A: The 2001 edition of NFPA 58 (the propane gas code) recognizes that horizontally oriented cylinders that were manufactured prior to October 1,1998, are unable to be retrofitted with the OPDís. As a result of this fact, the code cow exempts these cylinders from having to be retrofit with OPD valves. Any such cylinder must have a label affixed to it to inform the user and the refiller that an OPD valve is not installed.

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