The built-in safety valve is a special safety valve designed and developed by DURREX. Displacement pump equips with safety valve is an important method to protect the pump. The rotary lobe pump with built-in safety valve is often used in conditions where a fixed pressure is required and the pressure is too high. It has sensitive response, compact structure, and has obtained a number of patents. Since the shaft of common rotary lobe pump is designed with a cantilever structure, when the outlet pressure increases, the shaft is affected by the discharge pressure, and the axial direction of the pump inlet is easily bent and deformed, which will cause the phenomenon of rubbing the pump. The newly designed pump cover adds a set of sliding bearings to improve the bearing capacity of the pump shaft, can effectively fix the rotor and the shaft to prevent the pump from rubbing