Design and features of the use of cast wedge gate valves

Wedge cast valves are made of cast iron or steel casting, and are designed for manual control of the speed and flow rate of the transported liquid by rotating the control spindle.

Classification and design features

The products in question are used as effective shut-off valves in pipelines with direct or reverse flow. They are usually used where the minimum pressure drop is important. Throttling is not recommended, because with partially open valves, the flow characteristics actually realized do not contribute to accurate and consistent flow control. Also, due to the high velocity of the fluid through the seats, damage to the valves is possible.

Constructive classification of cast wedge gate valves can be made according to the following parameters;

• By material – cast iron (according to GOST 1412) or steel (according to GOST 977) can be used for manufacturing;
• According to the design of the spindle – retractable or non-movable;
• According to the configuration of the case – round or oval;
• By the size of the valve section, which determines the permissible pressure of the working medium.

Taking into account the features of the cast macrostructure, the smallest dimensions in thickness are always limited in the design of the housing, which affect the safety of operation of the cast valve.

The shape of the housing determines the nature of operational loads: in the presence of local stress concentrators, the housing is made oval, in their absence – round. However, directly in the seat area, the shape is always oval, while in the upper sections of the valve, the cross-section is more often round, guaranteeing uniformity of the flow of the transported liquid.

Selection Parameters

The determining factors for choosing the standard size of a wedge cast gate valve are:

• The pressure of the working medium flow.
• Type of working medium: density, chemical aggressiveness.
• Maximum pumping temperature.
• The diameter of the valve used.

Cast valves with manual opening are recommended to be used for a temperature range of 160 ...5000C, while the permissible nominal pressure for cast iron valves should be no more than 35% of the parameters provided for with respect to cast steel valves (up to 200 bar). In turn, the allowable pressure for valves made of ordinary carbon steel should be 30...40% lower than for doped. Most often, steel grades 25L or 20GL are used for the manufacture of cast steel valves, and for cast iron – cast iron grades SCH 15-36 or SCH 24-44.

For use with particularly aggressive liquids, cast valves are provided with seals with improved surface finish. The production of wedge gate valves made of steel or cast iron is regulated by TU 3741-001-546348-53-2002.