Pressure Relief Valve

The relief valve has one orifice, usually operated by spring.

Pressure before orifice = 2000 PSI

Pressure after orifice = tank pressure + pipeline pressure drop

Pipe line pressure drop can be calculated based on - length, diameter & configuration of the pipe line, pipe characteristics, fluid properties etc.

BTW: pressure would be just after it goes through the relief valve is likely to be negative (it is likely to have an extremely high dynamic head) before it settles down.

A 2,000psi pressure relief valve should open at 2,000psi so that the pressure in your system should never get to 2,200psi. The pressure in the discharge line right after the relief valve would be therefore be less than 2,000psi (if the valve is operating corectly). This is based on the valve resetting itself as the pressure drops back down to 2,000psi after opening for a very short instant while the pressure slightly exceeded 2,000psi.

If the hydraulic system is set to work at 2000 psi and the relief valve is set to operate at 10% higher then it is supposed to open at 2200 psi as usually the case, because if the valve is set to 2000 psi then it is supposed to open at 2000 psi and not 2200 psi.

After the oil is released through the valve the pressure will go down to the pressure required to just hold the larger area of the relief valve seat that will get exposed to the oil pressure when open. Thus there is a range between which the valve opens and closes. The closed area exposed to oil pressure is smaller than the area when the valve is open.