Tri-O-seal ASME Container Valves 

Field Topics are intended to provide useful information to the network of authorized LP-Gas and Anhydrous Ammonia distributors regarding the proper use of RegO® products. Warning Bulletins covering many of the hazards involved are available from RegO for more detailed information. These bulletins can be found in our L-500, and NH3-102 catalogs. Neither the Field Topic or the Warning Bulletins are intended to conflict with federal, state, or local ordinances and/or regulations, which should be observed at all times. This information also is not intended to be a substitute for or to supplement any training in the safe handling and use of propane and related equipment, as required by any applicable law. By providing this material, ECI assumes no responsibility for providing any such training. Only individuals properly trained in the safe handling and use of propane and related equipment should be permitted to do so, and by providing this information, ECI does not assume responsibility for providing such training.

For more information on LP Gas system requirements, refer to Liquefied Petroleum Gas Code (NFPA 58), National Fuel Gas Code (NFPA 54), National Propane Gas Association Safety Handbook, the RegO LP-Gas Serviceman’s Manual L-545, RegO catalogs L-500/NH3-102, ANSI K61.1 Safety Requirements for Storage and Handling of Anhydrous Ammonia, as well as any applicable local codes and ordinances.

We recently became aware of a report where an individual attempted to replace a Tri-O-seal container connection valve with NPT thread connection valve on an LP-Gas container.

LP-Gas container valves with Tri-O-seal connections were manufactured by Bastian Blessing from the mid 1950’s to the mid 1960’s for certain manufacturers for use on LP Gas containers.

Tri-O-seal valves utilize an NPS (straight thread) with gasket or O-ring, a support ring (crush ring) and washer to connect to and seal at the NPS threaded container coupling. Some Tri-O-seal valves may only use an O-ring to seal with a retaining feature incorporated into the body of the valve. All Tri-O-seal connection valves can be identified by a gasket or O-ring seal at the container coupling connection.

Tri-O-seal NPS threads are not compatible with and should not be used with NPT Threads

Below is an illustration of a Tri-O-seal and NPT connection.

WARNING: Do not change out a Tri-O-seal connection valve and replace it with an NPT type connection valve. There is a significant difference between the two connection designs; an NPT connection will not seal properly and will not engage correctly into an NPS (straight thread) container coupling. Using these mismatched connections could cause a leak and could result in a fire or explosion and serious personal injury, property damage, or both.

Should you have any questions or concern, please contact Paul Courson

Paul Courson
LPG & NH3 Technical Director
O: +1 336.446.7292

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