Valves Questions and Answers

Valves Questions and Answers

What is a Valve?

A valve is a device that controls the flow of a fluid or gas.

Today’s valves can control not only the flow, but the rate, the volume, the pressure or the direction of liquids, gasses or slurries through a pipeline.

What is a pressure relief valve?

Relief valves are automatic valves used on system lines and equipment to prevent over pressurization. Most relief valves simply lift (open) at a preset pressure and reset (shut) when pressure drops only slightly below the lifting pressure.

System pressure simply acts under the valve disk at the inlet of the valve.

When system pressure exceeds the force exerted by the valve spring, the valve disk lifts off its seat, allowing some of the system fluid to escape through the valve outlet until system pressure is reduced to just below the relief set point of the valve. The spring then reseats the valve.

What is a ball valve?

Ball valves, as the name implies, are stop valves that use a ball to stop or start the flow of fluid. The ball performs the same function as the disk in the globe valve.

When the valve handle is operated to open the valve, the ball rotates to a point where the hole through the ball is in line with the valve body inlet and outlet.

When the valve is shut, which requires only a 90 degree rotation of the handwheel for most valves, the ball is rotated so the hole is perpendicular to the flow openings of the valve body, and flow is stopped.

What is a check valve?

Check valves are used to allow fluid in system in only one direction. They are operated by the flow fluid in piping. A check valve may be the swing type, lift type, or ball type.

What is a globe valve?

A Globe Valve is a type of valve for regulating flow in a pipeline, consisting of a moveable disk-type element and a stationary ring seat in a globular (spherical) body.

Globe valves are named for their spherical body shape with the two halves of the body being separated by an internal baffle. This has an opening that forms a seat on to which the movable disc shut the valve.

Globe valves are used for applications require throttling and frequent operation.

What is a Three-Way Valve?

Three-Way valves has three ports. Depending on the particular valve, all three port may be open, two ports may be open, or all ports may be closed.