OPD is an abbreviation for Overfilling Prevention Device, which is part of national fire and safety standards designed to make the use of propane even safer. An OPD is a safety feature that prevents small propane cylinders from being overfilled. After January 1, 2003, all propane cylinders 4 pounds to 40 pounds MUST be equipped with an OPD. This standard is required by the National Fire Protection Association . Horizontal cylinders manufactured before October 1, 1998, are exempt, as are cylinders used for industrial trucks, industrial welding and cutting gas.
The National Fire Protection Association (NFPA) develops standards for the safe use of propane and other fuels nationwide. It is NFPA's Pamphlet 58, the standard for propane dealers, which requires OPDs. Thus, propane dealers are required to follow this requirement.
There are limits on how much propane can be put into a cylinder. A properly filled cylinder will have a vapor space left in the top of the cylinder to allow for expansion of the liquid due to change in temperature. An Overfilling Protection Device is a means of assuring that cylinders are not overfilled.
An overfilled cylinder may not have enough vapor space left in the top of the tank if the liquid propane expands when exposed to warmer temperatures. This can cause an increase in cylinder pressure and create potentially hazardous conditions such as:
All new cylinder wrappers and/or warning labels will include this information. Most cylinders with OPDs have special triangular hand wheels with the words OPD imprinted. Some OPDs, however, were produced before the letters OPD were required on the valve handles and valve bodies. If you have questions, check the wrapper or label or ask your propane dealer to identify the type of valve on your cylinder. For additional information and pictures click HERE.
As of January 1, 2003, cylinders without OPDs cannot be refilled.
During the refilling process, when the proper level of propane is reached, a valve inside the cylinder closes thereby stopping the flow of propane into the tank.
Your local propane dealer wants you to understand these standards and would like to make compliance with them as easy and inexpensive as possible. If you want additional information, your local propane dealer will do everything possible to assist you.