What is a plunger valve？

Driven by the valve stem, the plunger moves up and down along the axis of the sealing ring to open and close the valve. It is called a plunger valve. The structure of the plunger valve is relatively simple. It consists of a valve body, a valve cover, a valve stem, and a plunger. , sealing ring, hand wheel and other parts (Figure 1-1).

Figure 1-1 Straight-through plunger valve

The nominal size of the plunger valve is DN15~400, the nominal pressure is PN6~160, and the operating temperature t≤425℃.

In plunger valves, sealing is achieved between the side of the plunger and the valve seat orifice. When the valve is opened, the medium will be released only after the plunger completely leaves the valve seat orifice. Therefore, the part of this kind of valve that is eroded by the medium is far away from the sealing surface. When the valve is closed, the plunger can wipe away particles deposited on the valve seat. Therefore, plunger valves can be used in media with suspended particles. When the sealing pair is damaged, the plunger and valve seat can be replaced on site, and the valve does not require any machining, just like a new valve.

Like globe valves, plunger valves also provide good control of the medium. If sensitive regulation of flow is required, the plunger can be fitted with a needle extension. When the medium flow resistance caused by the tortuous flow path is acceptable, the plunger valve can be used as a switch.

Compared with plane-sealed valves, plunger valves have the following characteristics: good sealing; small friction factor, easy operation; long service life; easy maintenance and easy elimination of defects; no need to shut down to relieve pressure after internal leakage occurs in the valve , internal leakage can be eliminated by adjusting the gap between the valve body and the valve cover.

Plunger valves have some advantages compared with globe valves, but they also have shortcomings, such as long opening time, slightly larger flow resistance, and limited temperature resistance of the sealing ring. Plunger valves are generally used on low and medium pressure pipelines and are suitable for steam, gas, water, oil, alkali, acid, ammonia and media with suspended particles. In recent years, with the development of the materials industry, the temperature resistance of sealing rings has been greatly improved, resulting in the emergence of high temperature and high pressure resistant plunger valves, with the maximum operating temperature reaching over 425°C and the maximum operating pressure reaching 16.0MPa.