The reciprocating low temperature liquid pump needs a discharge valve to regulate the speed and pressure of the pumped liquid in the pumping process. This paper will discuss the type of the discharge valve in the reciprocating low temperature liquid pump.
The opening and closing of the discharge valve from the outlet of the reciprocating low temperature liquid pump is mainly to control the overflow rate of the pump. Generally, the internal cavity of the discharge valve has a certain size, so that the discharge valve can provide the required flow for a certain speed. When the piston of the reciprocating pump is moving, the back pressure of the liquid can drive the discharge valve to open, thus the moving liquid is discharged from the outlet, while when the piston stops, the driving pressure disappears and the discharge valve is closed automatically.
At the discharge valve of the reciprocating low temperature liquid pump, a poppet type valve is commonly used. The poppet valve is composed of a valve body, a valve seat, a valve head and a spring. The valve body has an outlet, which is connected to the main pipeline for liquid; the valve seat is mounted on the outlet of the valve body and the valve head is connected to the valve body; the poppet valve is returned by the spring. When the pressure of the liquid is low, the valve head is separated from the seat and the liquid is discharged from the primary line from the valve body to the outlet, so as to achieve the purpose of regulating the liquid flow; when the pressure of the liquid is high, the valve head is pressed against the seat by the spring and the liquid is stopped on the primary line. During the working process of the reciprocating low temperature liquid pump, the poppet valve can be driven and closed by the pressure of the liquid, which can be used to regulate the speed and pressure of the liquid.
In the applications of reciprocating low temperature liquid pumps, poppet type valves have the advantages of large flow, high precision, long life and reliable sealing performance. However, when the valve is used in low temperature conditions, it will cause freezing due to the decrease of the viscosity of the pumped liquid. Therefore, for the reciprocating low temperature liquid pump, the proper sealing choice is the rotating valve. The rotating valve has the characteristics of small volume, good sealing performance and simple structure, which can meet the requirements of low temperature liquid transportation.
In the practical engineering application of the reciprocating low temperature liquid pump, poppet valve and rotating valve can both be used in the pump depending on different temperature levels. The poppet valve has better flow performance, but it cannot be used in low temperature conditions; the rotary valve has low temperature resistance and better sealing performance, but its flow performance is slightly worse than the poppet valve. Therefore, the appropriate selection of the valve type needs to be considered according to the actual needs.
To sum up, in the reciprocating low temperature liquid pump, poppet type valves and rotating valves can both be used in the pump depending on the temperature level at the pumping site. The poppet valve has better flow performance, but it cannot be used in low temperature environments. The rotary valve has low temperature resistance and better sealing performance, but its flow performance is slightly worse than the poppet valve. Therefore, the appropriate selection of the valve type should be made according to the specific needs.
