NCB internal gear pump may occur due to failure and reasons: First, the flow is small (lack of suction) reasons: 1, the suction pipe air leaks; 2, the suction pipe is not immersed in liquid; 3, suction inlet diameter is small; 4, the end face The gap is too large; 5, the pump shaft speed is slow; 6, the filter blockage; 7, the pump has worn Second, the flow instability reasons: 1, suction pipe ends may have air leaks or lack of liquid; Large reasons: 1, the current is too large; 2, the viscosity of the liquid; 3, the speed is too high; 4, the outlet pressure is higher than the rated value; 5, insufficient supply; 6, packing gland pressure too tight; Loose.