Classification and application of flanged wedge gate valves with a retractable spindle

Bypass valves, which are equipped with flanged wedge valves with a retractable spindle, can significantly simplify the process of opening / closing them. Since pressure equalization occurs between the sides of the wedge, this type of valve can be easily opened even at high pressure in the line.

Classification and design features

Flanged wedge gate valves with a retractable spindle can be distinguished by the following parameters:

• According to the case material. The most common are stainless steel, brass, bronze
• According to the material of the seals. There are valves with a metal and non-metallic seal. In the first case, the valve's operability is completely preserved in the temperature range from -150 °C to +550 °C, which is suitable for hot water supply purposes. Non-metallic seals, for their part, can be used only up to temperatures not exceeding 2000C, but they are cheaper, as well as easier and easier to replace;
• By the permissible value of the liquid pressure. In particular, stainless steel gate valves are more durable and can be operated at pressures reaching 400 bar.;
• According to the method of attachment. International standards provide for two main options for connection – threaded and by welding.

Of the other design features of flanged wedge gate valves with a retractable spindle, the hardening treatment of the seat surface should be noted. By applying stellite surfacing, it is possible to significantly reduce the wear of the reinforcement, and extend its service life.

To facilitate interchangeability, the seal of the stuffing box and the gasket on the flange gate valve are made in standard sizes. If the product is operated under conditions of increased explosion hazard, the sealing material must have an appropriate safety certificate.

Selection and operation

Valves of this type are effective for conditions of complete closure or complete opening of the pipeline, and should not be used for regulation. Control of such valves is carried out by means of a flywheel or a valve (for small sizes). For large valves, special gearboxes with a set of gears and a flywheel are provided, which facilitates the control process. When the flywheel rotates, the wedge moves up and down through the spindle, as a result, the valve opens or closes. The features of the action of flanged valves are that they promptly provide full passage of the working fluid with minimal pressure loss.

This type of valves can be used for a wide range of purified liquids and gases, as well as oil and steam (contamination in the seat of the housing from the smallest particles of the sealing material can make it difficult to open the valve).

The limitation of flanged gate valves is the relatively high coefficients of friction that occurs when the flange moves. In the absence of surfacing, corrosion processes may occur and develop.

The requirements for these products of domestic production are determined by GOST 3706-93.