Each valve type has various design details that differ based on manufacturer. The following provides a brief description on types and uses of manual valves in the industry.
Ball Valve is a quarter turn (with a control lever) on-off valve featuring a stem and ball that has an opening inside of it, i.e., it is lined up with the pipe to allow flow and blocks flow when it is perpendicular to the pipe. These valves can be bought as reduced or full bore depending on usage. Full bore valves are mainly used for pigging lines, and relief lines. Ball valves are expensive and thus may end up being used mainly for isolation above 4”. Ball valves are also used more in offshore due to its compactness and lower weight.
Uses: Isolation valve, on/off valves in function. Partial open position can be used to bleed pressure out.
Globe Valve has a globular body (with a handwheel) and are designed for start and stop functions. The flow is controlled by a disc which moves up and down, i.e., perpendicular to the flow. Ideal for functions where frequent maintenance is required. Angle valves are also a type of globe valves and used in making a 90 degree turning of the pipe which helps in reducing number of joints and installation time. Angle valve provides less pressure drop compared to globe vale or an elbow.
Uses: Throttling or regulating flow especially where there is a high pressure drop across the valve. Start and stop functions. Positive shut-off for gas or air.
Gate Valve is popular in all sizes. Gate valve controls flow with a gate by turning a knob (handwheel) to raise or lower the gate, i.e., it is lifted out of the way of process fluids. The gate can be round or rectangular. Gate valve does not offer the same immediate shut off capabilities of a ball valve, but in applications where that is not needed but a high degree of control is, they are a better option than a ball valve such as preventing a water hammer from forming. They should be used only in fully open or fully closed position and never partially opened for throttling purpose. This can damage the valve body due to chattering. Gate valves should not be used where frequent operation is required.
Uses: Isolation of raw or finished water systems.
Check Valve: There are various types of check valves (e.g. swing, lift, dual plate, stop check) and location of these valves should be selected carefully. For pumps, the check valve should be placed four or five diameters of the pipe away from the pump, otherwise turbulence from the pump can cause the valve disc to flutter and wear the bearings. Vertical lines are poor location for check valves.
Uses: mainly used for preventing back flow. It is also used to prevent air inflow into pipeline filled with water and to minimize water hammering.
Butterfly Valve is popular in all sizes. It is a quarter turn valve from fully open to fully closed position in which a disc is rotated on a shaft so that the disc seats on a ring in the valve body. Butterfly valve allows quick opening and closure and can be operated by handles, gears or actuators.
Uses: Clean water isolation, wastewater treatment, fire protection, gas supply, power generation, etc.
Plug Valve are either lubricated or non-lubricated type. 90 degree turn of the valve fully opens or closes this valve and therefore plug valve is known as quarter turn type of valve. The design of the plug valve is such that solids do not accumulate and cause a jam. The valve can be fixed in an open or closed position for a long period of time.
Uses: Both the types are rarely used for isolation. Lubricated type is used if the valve in a system needs to be closed for extended time period or if it is high pressure system and can be used were tight seal is required especially in high pressure (above 150 psi) systems.