We are developing a project where a couple of API 610 centrifugal pump are used to pump crude oil from a tank depot to a ship loading terminal through a pipeline (9600 m3/h @ 60 barg).
A recirculation line has been foreseen in the pumping station to pump back to the tank the crude oil if the terminal is not ready to accept the oil.
Recirculation line has been sized according to minimum pump allowable flow (at the minimum allowable pump rotating speed) and a restriction orifice has been selected in order to dissipate the fluid energy and have a covenient pressure drop.
Restriction orifice have been physically foreseen to be installed closed to the pump in order to have the advantage to use a lowe rating pipe and save some costs (as matter of facts pumps are located seveal hundred meters from the recirculation tank.
We have received a comment by our client asking us to move the orifices close to tank tie in in order to "avoid pressure build up in the recirculation line".
Our thinking is that the pressure in the recirculation line is given by the positive head in storage tank with the addition of pressure due by frictional losses. No other terms should be considered.
Or there is something that we are missing ?
Furthermore, there are some normative restrictions that binding to install the restriction ordifices in specific point ?
Appreciating your opinion on matter.