Advantages and disadvantages of steel wedge gate valves with a retractable spindle

Wedge steel gate valves with a retractable spindle are linear displacement valves in which a flat shut-off element slides in the fluid flow, ensuring its overlap at the required moment. This type of gate valves is considered one of the most common.

Classification and design features

The presence of a retractable spindle allows minimizing the pressure drop on the valve in its fully open position, up to the complete termination of the working medium current. In this case, the flow direction does not change, and the executive diameter is equal to the diameter of the pipeline. Thus, the presence of a retractable spindle makes it possible to ensure constant pressure with a significant change in flow.

Wedge steel gate valves with a retractable spindle are designed for two-position maintenance. They are most effective in systems that do not require frequent changes in flow characteristics. These devices are designed for flow over the entire area, and since the predominant part of the flow change occurs near the cutoff, the relatively high fluid velocity contributes to accelerated wear of the disc and seat, with the appearance of fluid leakage.

The operation of such a valve occurs as follows:

• When the spindle is moved, the corresponding movement of the locking element associated with it also occurs.
• As you move, the flow is blocked.
• When the landing surface touches the valve seat, the working medium current stops.
• Wedge edges cut off macroscopic dirt on the seat surface, preventing the valve from jamming.

Valves of this type can be installed in any position, are suitable for almost all liquids and are convenient for turbulent high-speed flow.

Operational advantages and limitations

In addition to its more complex design from a structural point of view, steel wedge gate valves with a retractable spindle have a number of other limitations. They work unstably in conditions of low pressure, open / close relatively slowly, are characterized by increased erosion of the seat, do not allow throttling of the flow.

At the same time, it is worth noting the advantages of these devices:

• Possibility of use with suspensions and viscous liquids (heavy oils, lubricants, varnishes, molasses, honey, cream and other non-flammable liquid compositions);
• Easy installation and maintenance;
• Reversibility of the action.

Rational areas of application of wedge steel valves with a retractable spindle are marine engineering, pharmaceuticals (except for pumping liquid herbicides), oil and gas industry, underground pipelines, water treatment plants. An indispensable condition for stable operation is the absence of vibrations when pumping liquids. The valves can be used in difficult conditions of high temperatures and pressures.