Types of Valves Commonly Used In Oil and Gas Industry
- Gate Valves
- Globe Valves
- Ball Valves
- Needle Valves
- Butterfly Valves
- Check Valves
- Control Valves
- ESD valves
- Gate Valve
This is the most common type of valve in use in industry and is used to start or stop the flow of fluids. It gives a positive shut-off when closed and is often used as a ‘Block Valve’ for isolating systems.
The gate valve MUST be either FULLY CLOSED or FULLY OPEN and NEVER USED TO CONTROL FLOW, as the fluid velocity will erode the valve internals like the gate, the body, the seats, etc.
The valve consists of a body which houses the valve mechanism – the stem (or spindle), the disc(s) (or gate), and the disc and body seats. Gate valves can be operated by a hand-wheel, an electric motor (MOV), or by an air powered diaphragm, or motor, or a piston actuator.
Types of Gate Valves
Gate valves are usually divided into two types: parallel and wedge-shaped.
PARALLEL GATE VALVE
The parallel gate valve uses a flat disc gate between two parallel seats, upstream and downstream. Shut-off is obtained by the free-floating seat or disk gate which allows the upstream pressure to seal the seat and disk against any unwanted seat leakage.
Parallel gate valves are used in low pressure drops and low pressures, and where tight shutoff is not an important prerequisite.
Wedge-shaped gate valves
Wedge-shaped gate valves use two inclined seats and a slightly mismatched inclined gate, allowing for tight shut-off
Type of Gate valves used on well heads ( Slab Gates)
2.The Globe Valves:
The Globe valve is used where control of fluid flow or pressure is required and it can be operated in any position between open and closed. Globe valves are normally used in control valves and bypass valves.
A Globe valve may be constructed with a single or double port and plug arrangement. The double port type is generally used in a CONTROL VALVE where accurate control of fluid is required. Due to the double valve plug arrangement, the internal pressure acts on each plug in opposition to each other, giving an internal pressure balance across the plugs.
A ball valve is a valve which uses a hollow, perforated and pivoting ball. It is open when the ball’s hole is in line with the flow and closed when it is pivoted 90-degrees by the valve handle.
Ball valves are durable, reliable and ensure high integrity. These qualities make them an excellent choice for shutoff applications, where they are often preferred to gates and globe valves, but they are not suitable in throttling applications.
Needle valves have a thin, tapered point at the end of the valve stem that is lowered through the seat to restrict or block flow. These small valves are widely used to accurately regulate the flow of liquids and gases at low flow rates. The fine threading of the stem and the large seat area allow for precise resistance to flow. They can be used as both on/off valves and for throttling service. These valves commonly used in Instrument Impulse lines.
A butterfly valve is a valve which can be used for isolating or regulating flow. The closing mechanism uses a disk. Operation is similar to that of a ball valve, which allows for quick shut off. Butterfly valves are generally favored because they are lower in cost to other valve designs as well as being lighter in weight.
Butterfly valves are employed in relatively low pressure applications. They are preferred in vacuum services due to the use of a cartridge type seat design.
Check valves are mechanical valves that permit gases and liquids to flow in only one direction, preventing process flow from reversing. They are classified as one-way valves. Fluid flow in the desired direction opens the valve, while backflow forces the valve closed.There are various designs of check valves in use.
Control valves are valves used to control conditions such as flow, pressure, temperature, and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a “set point” to a “process variable” whose value is provided by sensors that monitor changes in such conditions Control Valve is also termed as the Final Control Element.
The opening or closing of control valves is usually done automatically by electrical, hydraulic or pneumatic actuators. Positioners are used to control the opening or closing of the actuator based on electric, or pneumatic signals. These control signals, traditionally based on 3 to 15psi or 20 to 100 kPa, more common now are 4-20mA signals for industry.
Emergency Shut-Down valves (ESD) are critical in protection of plant and personnel. These valves must operate in the event of plant malfunction or fire. The most important requirement for an ESD-valve is its reliability of operation (open or close) in an emergency.
Emergency Shut Downs are initiated using a net work of ESD valves remotely operated as per the design logic using Instrument Air supply system. The motive air is supplied using solenoid valves. ESD valves are normally ball valves.