1. You may check the spec of the piping which you want to install. This will be your reference point.
Ai: 20 barg
Bi: 50 barg
Di: 150 barg
Fi: 225 - 250 barg
G,Hi: over 300 barg

2. Every pump/compressor has a max pressure head point. You may check the max possible pressure you can receive from upstream system and sum them up. in this, you may check also the pump curve to see the possible flow rates. Kind of double assessment just to be sensible.

3. If a plunger type pump (frequently used for chemical injection), even if it may have a very relatively low operating pressure, when it is blocked downstream, (e.g. it may even achieve 350 barg depending on the pump characteristics.), you may theoretically need very high design pressure pump casing. Note: normally a PSV type return valve is installed downstream to divert the excess pressure back to its source (e.g. atmospheric feed tank)

If you can give me more details on your case, I may be more helpful and precise.

Just to note, when deciding design pressure, the first to guarantee the overpressure protection of the pump and the system. At this point, it does not matter on which condition it will operate.