How to choose the right stop valve

Ball valves and needle valves are two common shut-off valves in instrument piping. Maintenance personnel must check the valve system specifications required for each system.

Ball valves: Ball valves are suitable for quick closing and high flow applications. In addition, the handle helps indicate unidirectional flow or closure. However, ball valves can generate hydraulic shock or water hammer due to their sudden closure as the fluid flows, damaging upstream pressure indicators, flow meters, and other components. To avoid hydraulic shock, the following methods can be used. One method is to use a bypass circuit. Before closing the DI ball valve, the bypass circuit is opened, thus providing a flow path to avoid sudden stoppage of flow and pressure spikes. A second option is to replace the ball valve with a needle valve.

Electric shut-off valve

Needle valves: While needle valves are primarily designed for flow or metering control, many needle valves are also suitable for positive shut-off. Furthermore, the fluid system closure of a needle valve is gradual, thus preventing hydraulic shock. If used as a shut-off valve, the needle valve should be designed with a rotating valve tip or soft valve stem tip for specific applications. Special designs may be needed to prevent leakage when using needle valves. For example, metal V-valve tips may rub against the metal valve seat during closure, causing scratches.

Electric shut-off valve

Integral DBB: An integral double block and bleed (DBB) configuration achieves high reliability. Fewer potential leak points, smaller footprint, ** weight, and simpler installation will help further simplify the system.

Electric shut-off valve

Be careful to avoid inadvertently using inappropriate fluid system components in isolation configurations. Ball valves and some types of needle valves are suitable for positive shut-off, but pressure regulating valves are not, although pressure regulating valves can also prevent most flow. If a pressure regulating valve needs to be closed, the safest method is to install a ball valve upstream.

In addition to selecting shut-off valves, in isolation configurations, installing a pressure indicator downstream of the second shut-off valve is a good practice. This allows pressure to be checked during maintenance.