PROJECTS & GALLERY

Gate Valve

Gate valves are the most common type of valves found in process plants. The closing gate moves along a linear path to block or allow fluid flow. Gate valves provide good shutoff and are considered suitable for almost all fluid services including air, fuel gas, feedwater, steam, slurries and viscous liquids. Gate valves are inexpensive and easy to disassemble for maintenance. They offer low fluid resistance due to a straight path that allows the fluid to flow straight through without change in direction.

Globe Valve

A globe valve generally has a spherical body that contains a movable plug element and a stationary ring seat. The two halves of the body are separated by an internal baffle. The plug element is connected to an operating hand wheel through a stem. As the wheel is turned, the screw action moves the plug towards or away from the ring seat. Globe valves can be used for stop/start function as well as to regulate fluid flow. They are useful in applications where good flow control is desired and leak tightness is important such as cooling water systems, feedwater and chemical feed systems, and fuel/lubricating oil systems.

Ball Valve

A ball valve uses a hollow ball to stop or allow fluid flow. The perforated ball can be pivoted using the valve handle. When the hole in the ball faces the flow inlet, the fluid flows through. A quarter-turn rotary motion of the valve handle turns the ball by 90° blocking the flow. Ball valves are smaller, lighter and cheaper when compared to gate valves of the same size and rating. They allow visual detection of the open or closed state of the valve. In an open state, the handle is aligned with the direction of flow; in a closed state the handle is perpendicular to the flow direction. In addition, ball valves offer ease of operation, high volume flow, high pressure, long service life and possibility of repair of seats and seals without removing the valve body from the line.

Check Valve

A check valve is used to prevent backflow in piping systems. The valve opens due to the pressure of the fluid passing through the pipeline. Reverse flow closes the valve and prevents the fluid from moving in the opposite direction. Check valves do not require external control. They work automatically and hence do not have an operating handle or stem. The simplest check valves are designed with a one-way flap mechanism.

Plug Valve

Plug valves use a cylindrical or conically tapered plug to allow or restrict fluid flow. The plug has one or more hollow passageways that allow the fluid to pass through when the passage is aligned with the flow direction. A quarter-turn rotary motion is required to turn the plug and block the fluid flow. Plug valves perform well in slurry applications. The wiping action of the plug does not allow suspended particles to accumulate and form an obstruction. Typical applications of plug valves include gaseous, and vapor services, natural gas piping systems, oil piping systems, coal, mineral and sewage applications. They are also suitable for vacuum and high-pressure applications.

Butterfly Valve

The “butterfly” refers to a rotatable metal disc mounted on a rod. A quarter turn of the disc is required to open or shut-off the valve. In the closed position, the disk completely blocks off the passageway. In the open position, the face of the disc is parallel to the flow direction and allows nearly unrestricted fluid flow. Butterfly valves find applications in cooling water systems, compressed air or gas applications, fire protection, slurry services, vacuum service, and high-pressure / high-temperature water and steam services.

Needle Valve

Needle valves are similar in design to globe valves. The plugging element in these valves is a long, tapered, needle-like plunger which fits into a matching seat to stop the flow. A stem is turned to insert or retracted the plunger, opening or restricting the flow path. The finely-threaded stem requires many turns to fully retract the plunger; this feature allows precise regulation of the flow rate. Needle valves are typically used in small diameter piping systems where very fine control of flow is desired. Needle valves are generally suitable for systems with low viscosity fluids flowing at low flow rates. The most common application is to regulate flow to fragile gauges in order to protect them from damage caused by an abrupt pressure surge. They are also used as bleed valves to relieve pressure or to drain off the fluid for analysis or for maintenance. The valves are only suitable for low flow rates as the flow passage between the seat and the needle is small. Needle valves are not suitable for fluids with suspended solids. Use of excessive force during shut-off can damage the seat of the needle valve.

Pinch Valve

Pinch valves employ an elastic tubing and a pinching device that directly restricts the flow through the tubing. The pinching mechanism flattens the tubing to create a seal. Pinch valves can be used to start, stop, and regulate fluid flow. Since these valves have fewer components, they are relatively cheaper and more leak-proof as compared to other valves. These valves are ideal for pneumatic conveying of solid materials and for handling of slurries. Pinch valves minimize turbulence and friction during flow. They are, however, not suitable for gases and for high-temperature or high-pressure applications. A high pressure-differential or vacuum in the system can cause the tubing to collapse or deform resulting in incomplete opening of the valve.

Diaphragm Valve

A diaphragm valve, also known as a membrane valve, consists of an elastomeric diaphragm, and a saddle/seat upon which the diaphragm closes. A linear compressor is used to push the thin, flexible diaphragm into contact with the seat/saddle to close the valve. Diaphragm valves also allow partial closure of the passageway making them suitable for throttling applications. They are suitable for viscous fluids and fluids containing solid materials as the solids are not trapped in the valve mechanism. Diaphragm valves are commonly used in water treatment facilities, pharmaceutical, food and chemical plants, vacuum services and corrosive applications.

How are valves in piping systems classified?

There are several different ways in which valves can be classified. They can be grouped based on their function, type of operating mechanism, end connections, mechanical motion, construction material, pressure and temperature ratings and port size. When choosing a valve, it is important to consider each of these classifications to ensure that the valve is suitable for the desired application.

Valve function

Valves are incorporated in a process to perform different functions. They may be used to start/stop the flow or to regulate flow and pressure. They may be required to control the direction of flow, or for improving process safety. Based on flow control, valves are classified as either isolation valves or regulation valves.

Isolation valves

Isolation valves are designed to either completely restrict fluid flow or allow it without obstruction. These valves are not recommended for continuous use in the partially open state as they may provide poor flow control or suffer wear damage over time.

Regulation valves

Regulation valves are used for regulation of pressure and fluid flow with suitable precision. These valves can be safely and efficiently used in processes that require partial open or closed state. Some valves are suitable to perform both functions while others are recommended only for one. The table below classifies the valves discussed above according to their function.