lift check valve

employment of the lift check valve

A lift-check valve is a check valve in which the disc, also called the lift, can be lifted up off its seat by higher pressure of inlet or upstream fluid to allow flow to the outlet or downstream side. The valve is able to later reseat properly because a guide keeps motion of the disc on a vertical line. When the pressure is no longer higher, gravity or higher downstream pressure will cause the disc to lower onto its seat, shutting the valve to stop reverse flow.

Generally speaking, the lift check valve has two main functions. The one is to prevent reverse flow so as to protect any item of equipment. The other is expected to be able to reduce the pressure surges associated with hydraulic forces such as the water hammer. Actually, the hydraulic force would cause a wave of pressure to run up and down the pipework until the energy is dissipated.

During the employment, an awareness of the hazards is essential. For example, reverse flow will reduce the accuracy of the meter and cause pressure problems in manufacturing processes, affecting product quality. Thus, the carefulness should be kept in the mind all the time.

The lift check valve is popular because of the low opening force, low pressure drop, convenient installation and maintenance and long service life. For example, when the traps are needed to be installed prior to a riser, lift check valve is available to be fitted to prevent reverse flow. When condensate is discharged into a pressurised main, the lift check valve would be applied to protect trap internals from backpressure.

operation of the lift check valve

With the development of the industry, the requirements for the corresponding equipments and working conditions are generally serious and complex. A number of different check valve designs are carried out to suit specific applications. Lift check valve is one of the specified types.

Lift check valve is similar in configuration to the globe valve, except that the disc or plug is automatically operated. And the inlet and outlet ports are separated by a cone shaped plug which rests on a seat typically metal. In terms of the lift check valve, several further developed types have been carried out. They differ on the many aspects, such as the size, the manufacturing material, unique device, as well as the distinctive specifications. In some valves, the plug may be held on its seat using a spring. When the flow into the valve is in the forward direction, the pressure of the fluid lifts the cone off its seat, opening the valve. With reverse flow, the cone returns to its seat and is held in place by the reverse flow pressure. For example, the piston-type lift check valve is a modification of the standard lift check valve. It incorporates a piston shaped plug instead of the cone and a dashpot is applied to this mechanism. The special design has enabled the dashpot to produce a damping effect during operation in order to eliminate the damage caused by the frequent operation of the valve.

As we all know that the check valve, such as the lift check valve is used to guide the forward flow and to prevent the reverse flow. And the lift check valve is able to occupy its own unique specifications. The main advantage of the lift check valve lies in its simplicity. As the cone is the only moving part, the valve is robust and requires little maintenance.