 The maximum pressure rating of a metering pump is actually the top of the discharge pressure range the pump is guaranteed to pump against at a reasonably controllable flow rate.The pump itself is a pressurizing device often capable of exceeding its pressure rating, although not guaranteed to.For this reason, if there is any stop valve downstream of the pump, a pressure relief valve should be placed in between to prevent overpressuring of the tubing or piping line in case the stop valve is inadvertently shut while the pump is running.