The pumps can be supplied on request with hygienic by-pass or pressure relief valves. This device protects the pump from pressure peaks or restrictions in the discharge and assures excess liquid deviation during CIP and SIP. The relief valve can be manually selected as a flow regulator in order to pass product allowing the pump to run continuously. This valve can be incorporated in the end cover that replaces the standard cover, providing a pressure relief valve loop from discharge to the suction area; alternatively it can be incorporated in the discharge pipework, relieving excess pressure by by-passing product through a loop back to the suction side. The integral relief valve is suitable for CIP process line and functions for either direction of flow: it is available on Models B100 to B550. On all models it is possible to assemble an external pressure relief valve in order to recycle the whole pumped product, this valve is especially suitable for frequently operations and for volatile, heat or shear sensitive product. For both of the valves a manual, pneumatic or automatic operation is available.