Pressure Relief in Off-Line Filter Cart

What pressure-generating device is feeding this trolley? What is its maximum delivery pressure? What is the lowest pressure rating of any item that it is connected to and therefore, is any pressure relief necessary?

If it's offline shouldn't it be isolated by valves therefore not subject to system pressure unless they leak by? There should be a manual drain on the vessel right? You see where I'm going with this?

Normally relief valve or check valve will be placed parallel to filter. It helps to protects the system, in case the pressure goes up due to filter clogging.

The type of pump and media to be filtered is not mentioned. If the media is oil and you are using gear or screw pump, then you can select a pump with in built relief valve. In built relief valve can connects delivery to suction internally, if the pressure goes beyond set pressure.

If outlet is blocked off inadvertantly for example the system pressure will spike. You can have your relief return to the inlet side of the pump. This will not be acceptable for extended periods but can be a short term remedy.

Most filter/transfer carts I have been exposed to and or built have not had relief protection. Typically the systems are designed to have limited pressure generating capabilities. That is the prime mover/electric motor is sized very small compared to the pump flow rate. You will need to analize your system for line size and length, fluid viscosity, pressure drop across filters etc. If the system is blocked off in these systems the horsepower is so small the system literally stalls and the elecrical breaker trips. A pressure spike will be generated but if hose/fittings and pump are rated for this spike your system plumbing is greatly simplified.

Alternate solution is to use a centrifugal pump and rate downstream components for max head pressure that the pump can generate plus safety factor.