Shear pump is a kind of centrifugal pump no need safety valve at outlet. Below is reasons explained from function and pressure source.
Explain on Functions to confirm shear pump no need safety valve
Shear pump is a kind of centrifugal pump. Drilling mud get a certain amount of kinetic energy while leaving impeller under the impeller rotating centrifugal force. Mud also get some certain of pressure in the pump housing, the pressure does not vary with the change of time, pump outlet size, but only depends on impeller structure, size, and rotating speed. As the pressure at shear pump outlet is not vary per pump flow or working condition. It is no need to match safety valve.
Explain on pressure to confirm shear pump no need safety valve
Driving motor and shear pump connected directly with belt. Design speed of impeller is 2200RPM (max.). Under normal working situation, like for 60hz motor, max. speed of shear pump impeller is 1800rpm, much smaller than the design speed. The maximum pressure generated from high speed rotating of impeller centrifugal force is constant. The max. shear pump pressure is 0.47MPa. The outlet pipeline and pump casing can surely withstand the pressure. In this case, it is no need to match safety valve.
Even in the case of the outlet is blacked or the valve is closed, pressure generated from the impeller rotating is larger than pump outlet, drilling mud cannot be discharged, and circulated within pump housing under the rotating force of impeller. If the outlet is blacked or the valve is closed, and mud circulated within the pump housing for a long time, the worst condition is to increase the temperature of pump housing in some degree. The pump pressure will not increase. Therefore, it is no need for mounting safety valve in shear pump outlet pipe.