Best Practices for Testing Tanker Trailer Pressure Relief Valves
Last year, the Executive Committee of the Truck Trailer Manufacturers Association (TTMA) was going to approve a new list of best practices for tanker trailer owners to test pressure relief valves and re-quality for service. The pressure relief valves are designed to open at a given pressure, in order to relieve pressure from the tank. Drivers often pull off the road at convenient locations in order to check the pressure-relief valve, which consists of reclosing pressure-relief valves and non-reclosing devices such as fusible caps, fusible plugs, and rupture discs. Properly functioning pressure-relief valves are critical to tanker trailer functioning and are critical for safe operation of a cargo tank.
The goal of the TTMA document was to reduce confusion about best practices and keep drivers safe on the road. The document outlined a set of pre-test checks that drivers can do in order to protect themselves on the road, including:
● Identify the cargo tank specification and Maximum Allowable Working Pressure (MAWP) of tank to which the pressure-relief valve is mounted. After identifying the MAWP, a driver or tanker trailer owner should determine the manufacturer and model for the valve in case it is in need of replacement. There will be a stamp with a set pressure and the specifications for which the valve was made, which will also help in case there is any damage or corrosion. This information should be gathered and kept in a safe place to reference in the future.
● The pressure-relief valve should be free of residue or corrosion. If the valve is not clean, then a driver should remove the pressure-relief valve and clean any chemical residue or build-up. You can check online for information from the valve manufacturer intermittently to make sure the valve is not out-of-service.
● You can check the valve by gradually increasing the pressure in the valve. Once you have increased the pressure on the valve of the trailer tanker, then you can open the inlet valve so that the chamber is going up on the pressure gauge at about 20% full scale every 10 seconds. If you hear any leaks around the mounting of the valve then you can adjust the valve’s mount as required.
● Once you have thoroughly checked the valve, you will need to close the inlet and reset the pressure. Wait until the gauge is no longer falling before resetting the pressure. You want to make sure that the pressure is below the minimum resetting pressure if it needs to be repaired or replaced. Finally, you can open the exhaust valve and allow the test chamber pressure to fall completely if you need to remove the pressure relief valve for replacement.
These pre-test checks were accompanied by additional recommendations from the TTMA so that tanker trailer drivers will be safe on the road. If you need to replace our pressure valve then LittleJohn Tanks provides an assortment of tanker trailer parts, including additional valves. If you are looking for a specific replacement part of are looking to own or rent a tanker trailer then you can contact LittleJohn Tanks at 800-828-6555.
Posted on Tue, May 13, 2014
by Bryce Simpson