What is a PCV valve?

I. Installation location and role:

Mainly when the main steam pressure is high, according to the pressure you set to open automatically, but its role is direct; superheated steam is discharged directly into the atmosphere, without the need to reduce the temperature, in a simple manner. 

The main role is to reduce the number of safety valve action, high pressure, the PCV valve is first opened to unload the pressure, the set pressure is slightly lower than the safety valve, if the unloading is not timely, the safety valve in action, if the pressure comes down, the safety valve does not act.

PCV valve full open process takes only a few seconds, fast action, can ensure that the boiler safety gate does not act, especially for the simultaneous opening of the steam engine bypass, reduce the intensity of combustion, maintain the water level of the steam packet and a series of complex control has won a valuable buffer time. Although the PCV valve is in action of the process of losing some of the work mass (is a disadvantage of this approach,) the PCV valve's equivalent opening time in the superheated steam emissions loss is much lower than the cost of re-lighting the furnace.

In addition to operating at a set pressure, the operator can also operate PCV valves remotely to open or seat the valve manually. The flexibility of operation is much better.

II. Structure and working principle:

(PCV valve) consists of a drive section, pilot valve and main valve. 

The driving part is composed of the coil and other components of the solenoid, steam pressure reaches the set value or the operator gives instructions when the power supply is turned on, the upper or lower end of the solenoid suction bar, so that the role of the end of the bar downward (open) or upward (closed) pilot valve in the role of the bar, the valve valve flap to overcome the resistance of the spring to move downward, the valve body of the channel through the main steam pipe from the steam is introduced into the main valve, the process is the opening of the action, and vice versa, is the closing of the process. This process is the opening action, and the opposite is the closing process.

The main components of the main valve are the valve flap, the valve seat, the spring, and the steam conduit which is connected to the atmosphere. The structure of the valve seat is similar to the cylinder, the valve structure is similar to the piston. The upper surface area of the valve flap is large, and the pilot valve to the steam pipe connection; the lower surface area of the valve flap is small, and the main steam pipe with.

When normal, the valve in the main steam pressure and the role of the spring in the upper position, the valve will be the main steam pipe and connect the atmosphere of the pilot steam pipe isolation, the relief valve is closed. When the pilot valve steam into the chamber above the valve flap, although the pressure of the incoming steam is lower than the steam pressure of the main steam pipe, but the area above the valve flap is large, and the force is large, so the valve flap overcomes the resistance of the spring and the steam pressure of the main steam pipe, downward movement, at this time, the main steam pipe and the connecting atmospheric conduit connecting the steam pipe, the main steam pipe of the steam discharged to the atmosphere.

If the pilot valve to interrupt the steam, the valve flap above the chamber of the steam pressure is reduced, the valve flap in the main steam pressure and the spring force of the action of the upward movement of the main steam pipe and the connecting atmospheric conduit is isolated, then the relief valve is closed.