Plug valves

Plug valves - type of pipe fittings designed to shut off the flow of the working medium. Plug valves are valves with cylindrical or conically tapered "plugs" which can be rotated inside the valve body to control flow through the valve. Plug valves are simple and often economical.This is one of the simplest and perhaps the most ancient types of valves. It is enough to cite as an example a samovar faucet having exactly this design. When the plug is turned 90 degrees, the flow of the working medium through the plug valve is completely blocked. The hole, as a rule, is not round, as in ball valves, but trapezoidal. Thus, the sealing surfaces of the locking element are conical surfaces - the outer surface of the plug and the inner surface of the valve’s body. Plug valves are used for liquid and gaseous media with a wide range of operating parameters: pressures up to 1.6 MPa and temperatures from -40 ° C to +100 ° C. Plug valves are used on pipelines of relatively small diameters, since the effort to control valves of large diameters increases significantly.

Stuffing plug valve

In stuffing plug valve, the force that presses the plug to the body of plug valve is transmitted through the stuffing box, which prevents the leakage of the working medium into the external space. To seal the packing, unscrew the anchor bolts and remove the stuffing box cover. In the lower part of the plug valve housing there is an squeezing bolt, which serves to facilitate the rotation of the plug when the gland is tightened too tight, the plug shutter is stuck or stuck to the body. At the same time, the closure density of the shutter to the housing decreases and the previous indicators are restored without stopping the technological process for repair and maintenance.
Also, the seal between the cork and the body can be created using a spring, which, for example, is used in brass plugs under a pressure of no higher than 0.01 MPa, which are installed at the entrances to household gas stoves.

Plug-tightening valves

The simplest devices are plug-tightening valves, in which the plug passes through the body of the plug valve through. Plug is pressed against the housing with the help of a screw, which is screwed onto the threaded shank of the plug and rests on the washer, which transmits the tightening force to the lower end of the housing. In this case, tightening the screw ensures tightness in relation to the external environment. Such a design requires very precise manufacturing of sealing surfaces and limits the use of such plug valves to a pressure of 1 MPa and a diameter of up to 50 mm.

Jacketed plug valves

These plug valves have a so-called jacket, which creates a space around the housing where steam or other coolant can be supplied. Such plug valves are designed for viscous and hardening resins, mastics and other media that require constant heating to maintain them in a condition that allows transportation through the pipeline.

Test and drain valves

Test and drain valves are installed on boilers and other containers to control the working environment or to take samples. They are used for pressure not exceeding 1 MPa and temperature up to 225 ° C.

Advantages of test and drain valves:

• simplicity of design;
• low cost of the valve;
• the service life of test valves is 5-6 years, several times longer than the service life of similar ball valves;
• it is possible to use it for abrasive particle medium;
• possible operation at temperatures above 200 ° C;

Disadvantages of test and drain valves:

• torque increases markedly with increasing diameters;
• large hydraulic losses;
• the possibility of jamming of the plug (“sticking” of the plug of the plug valve to the body);
• operation is difficult at heights above 150 mm/