The Overfilling Prevention Device:
For Propane Marketers

Although broad in scope, these Q&A's will not answer all questions that may arise, but are intended to provide a basic understanding for the application of overfilling prevention devices.

• What is an overfilling prevention device (OPD)?
• What does the Code require?
• How can an OPD be identified when it is installed in a cylinder?
• Is an OPD intended to be an aid in the filling of a cylinder?
• Using a 20 lb. propane gas grill cylinder as an example, how does one know that the cylinder is equipped with an OPD that is operable?
• Is the requirement of OPD's a mercenary ploy by those in the propane industry to take advantage of consumers pocketbooks?
• Am I violating rules by refilling a cylinder that is not equipped with an OPD?
• What about the time it takes to provide the consumer with a replacement cylinder while on my time I schedule the insertion of a new valve.
• Our state has not yet adopted NFPA 58 -1998, so do we still have to abide by the Code?
• The U. S. DOT (DOT) says we don't have to requalify cylinders not used in commerce so how can we enforce OPD requirements?
• What happens when the float breaks off?
• What should we do with the old cylinders that we are accumulating?
• Was the OPD forced upon us by cylinder and valve manufacturers?
• Roofers and other commercial customers are trying to use OPD equipped tanks on torch applications and they are not getting an adequate flow through the valve. What can we do about this?
• I think these OPD valves are unsafe. Why can't we get this reversed like the U. S. Environmental Protection Agency's RMP?
• For more information, please contact Bruce Swiecicki.

Q: What is an overfilling prevention device (OPD)?

A: As defined by the National Fire Protection Association's (NFPA) Pamphlet 58 - LP-Gas Code - 1998 Edition (Code), it is...'A safety device that is designed to provide an automatic means to prevent the filling of a container in excess of the maximum permitted filling limit.'  Typically, the overfilling prevention device will appear as part of a cylinder valve that is installed as a complete unit into the cylinder.  The cylinder valve will have either a CGA 791 (ACME threads) or a CGA 810 (push-pull, quick disconnect) connection device.

Q. What does the Code require?

A: For propane cylinders* in the 4 lb. through 40 lb. propane capacity range, with limited exceptions the Code requires them to be equipped with an OPD, as follows: New cylinders for vapor service which are fabricated after September 30, 1998; as cylinders are requalified after September 30, 1998 through March 31, 2002; effective April 1, 2002, before any cylinder is filled.

*All references to cylinders applies to only those in the 4 lb. through 40 lb. propane capacity range. The exceptions to this rule are: 1) cylinders used in industrial truck service; 2) cylinders identified and used for industrial welding and cutting gases; and 3) as of the 2001 edition of NFPA 58, horizontal cylinders manufactured prior to 10/1/98 for which no OPD is available and which are labeled to indicate that an OPD is not installed. (See the Code for further details.)

Q: How can an OPD be identified when it is installed in a cylinder?

A: Listed (e.g. Underwriters Laboratories) OPD's are easily recognizable by observing their unique trilobular handwheel. The handwheel is connected to the valve stem in a tamperproof manner for the purpose of reducing the possibility of putting a user at risk by attempting to interchange an OPD handwheel on to a conventional non-OPD valve. It should be noted that the valve stems on non-OPD equipped cylinders are not easily matched with the standard trilobular OPD handwheel. Those who fill cylinders should take care in observing whether or not a cylinder that appears to be equipped with an OPD, actually is.

Note - Prior to the Code's requirement for the use of OPD's, early non-uniform valves were introduced into the marketplace. Thousands of these valves had conventional handwheels and were not marked as now required by the UL listing.

While the safety features of these early valves is not being questioned, cylinder refillers should be aware that many are still in service. In time, these valves will decline from use through normal attrition.

Q:Is an OPD intended to be an aid in the filling of a cylinder?

A: The device is designed to only be a backup in the filling a cylinder. With an OPD equipped cylinder, the traditional procedures of filling by the weight or volumetric methods should be followed.

Q: Using a 20 lb. propane gas grill cylinder as an example, how does one know that the cylinder is equipped with an OPD that is operable?

A: Above 40 degrees F, listed OPD's are uniformly designed to prevent the continued filling of a (e.g.) 20# cylinder to a point slightly less than 20#. Correspondingly, at temperatures below 40 degrees F, a listed OPD is designed to allow minimally more than 20# of propane to be placed in the cylinder. Therefore, the integrity of an OPD can be confirmed by a trained operator either through the use of a weight scale or by action of the maximum liquid level gauge which is an integral part of the service valve.

Q:Is the requirement of OPD's a mercenary ploy by those in the propane industry to take advantage of consumers pocketbooks?

A: This is a good question and deserves a direct answer which is......no. Those marketers who fill propane cylinders for customers have had virtually nothing to do with the advent of the OPD. The term 'virtually' is used as there were a few highly concerned and industry active propane marketers who became involved in resolving issues which surrounded the advent of OPD's, including a reasonable time frame for the introduction of these new safety devices into the marketplace.

Q: Am I violating rules by refilling a cylinder that is not equipped with an OPD?

A: The answer to this question depends on whether or not the authority having jurisdiction in your particular state is enforcing the provisions of the Code.

Your attention is drawn to both the OPD state enforcement listing and to the liability comments that accompany this advisory. In compliance with the Code since October 1, 1998, the predominant U.S. manufacturers claim to have fabricated and equipped no cylinders in the 4 lb. to 40 lb. range without OPD's. Eventually, it is expected that the use of these devices will be uniformly accepted.

In the final analysis, the decision to fill a cylinder, regardless of how it is equipped or maintained, is a judgment call of the dispenser operator.

Q: As a propane marketer, I'm frustrated. We're experiencing less than acceptable quality in some of the OPD's, particularly in the lack of adequate flow capacity for purging and use, plus poor handwheel durability. Inasmuch as manufacturers are not offering replacement parts for OPD's, I feel abused even though I may receive a replacement valve for a defective one at no charge, what about the time it takes to provide the consumer with a replacement cylinder while on my time I schedule the insertion of a new valve.

A: Like other things that are newly introduced into commerce, there are times when it appears that field trials are continuing even though the equipment is in the hands of the end-user. This is not good. No evidence has surfaced that propane marketers are being taken advantage of in the application of OPD's. Even so, manufacturers do take serious note of such reports and act accordingly, rather than face interrogation from federal agencies as to their marketing practices.

Q: Our state has not yet adopted NFPA 58 -1998, so do we still have to abide by the Code?

A: Please refer to the information contained in the'The OPD: A Legal Primer.'.

Q: The U. S. DOT (DOT) says we don't have to requalify cylinders not used in commerce so how can we enforce OPD requirements?

A: DOT's requalification jurisdiction applies only to those cylinders in commerce.

For example, cylinders that are privately owned and transported in a non-business mode, are not subject to DOT's rules. However in 1999, NFPA issued a formal interpretation stating that the Code requires cylinders of 4 lb. through 40 lb. propane capacity must be equipped with an OPD as 'they are requalified after September 30, 1998 through march 31, 2002'. In the 2001 edition of NFPA 58, a new requirement states that even those portable cylinders which are not within the jurisdiction of DOT are required to be requalified, which in effect adopts the formal interpretation into the Code. To repeat, effective April 1, 2002, the Code requires all cylinders to be equipped with an OPD before it can be filled.

Q: What happens when the float breaks off?

A: If an OPD is determined to be inoperable, it should be replaced.

Q: What should we do with the old cylinders that we are accumulating?

A: In the future, these cylinders should be treated as they have been in the past. They can either be requalified and put back into service or salvaged-out in a safe manner.

Q: Was the OPD forced upon us by cylinder and valve manufacturers?

A: To confirm that this is not the case, please refer to: 'The OPD: A Short History'.

Q: Roofers and other commercial customers are trying to use OPD equipped tanks on torch applications and they are not getting an adequate flow through the valve. What can we do about this?

A: Some of the early OPD valves had an insufficient flow capacity for certain types of service such as high pressure torch applications. Market competition has resulted in OPD's becoming available that have significantly greater rates of flow.

Q: I think these OPD valves are unsafe. Why can't we get this reversed like the U. S. Environmental Protection Agency's RMP?

A: No sufficient grounds for seeking third party scientific criteria has been developed in order to support an effort that would reverse acceptance of the OPD. On the other hand, the intent to advance a safer package for consumer use has been fulfilled with the OPD application.

July 25, 2000
(Revised 1/2002)

©NPGA 2002