Q : What is a valve?

A : A valve is a mechanical device which regulate either the flow or the pressure of the fluid. Its function can be stopping or starting the flow, controlling flow rate, diverting flow, preventing back flow, controlling pressure, or relieving pressure. Basically, the valve is an assembly of a body with connection to the pipe and some elements with a sealing functionality that are operated by an actuator. The valve can be also complemented whit several devices such as positioners, transductors, pressure regulators, etc.

Q : Types of Valves – By operative of the valve closure member ?

 A : Quarter-turn valve (rotary valve): The closure member as well its shaft turn 0º-90º; from the fully-open position to the fully-closed position. They are quick opening/closure valves. Types of valves: Ball valve, Butterfly valve, Plug valve, Spherical valve. • Multi-turn valve (linear motion valves): The closure member has a linear displacement generally by turning its threaded stem several times. This operation is slow, but it gives accuracy and stability to position the closure member, which is necessary in some control valves. Types of valves: Gate valve, Globe valve, Fixed cone valve, Needle valve and Pinch valve.

Q : Types of Valves – By functionality of the valve ?

A : Control: pressure / flow rate regulation. Closure at over-speed flow. (i.e. immediate closure if downstream pipeline is broken by accident). • Overpressure protection. • Back flow prevention (check valve). • On/Off service.

Q : What are Cryogenic valves?

A :  Cryogenic Valves are used in the transmission of extreme low temperature services such as LNG (liquefied natural gas), LPG (liquefied petroleum gas), Nitrogen and cryogenic applications.

Q : What is an Actuator?

A : An actuator is a type of motor for moving or controlling a mechanism or system. It is operated by a source of energy, usually in the form of an electric current or pneumatic pressure, and converts that energy into some kind of motion. (Open / Close)

Q : Types of Actuators

A : By the type of movement • Multi-turn. • Quarter-turn. • Linear. • Lever. By the energy source • Manual • Electric: they can be drived by direct and alternate current. • Pneumatic: they use pressured air or gas to create motion. They are widely used in the industry due to their low cost. In case of failure they are easy to diagnose or repair in field, rather than electric actuators. • Hydraulic Functionality • On / Off valve service • Positioning to % open • Modulating to control changes on flow conditions • Emergency Shut Down (ESD) Other characteristics • Explosion-proof • Safety integrity level (SIL) • Enclosure: IP and NEMA.

Q : What is a Limit Switch?

A : A limit switch is a device that is used to show the open or closed position of a valve.

Q : What is a Solenoid valve?

A : A solenoid valve is a type of valve that uses an electrical current to actuate or shift a spool or cartridge consisting of a solenoid coil and tube assembly. Basically, this valve type uses an electric current to shift a pin to perform simple A/B tasks such as open/close valve spools

Q : Three-way and four-way ball valves?

A : Three-way ball valves have an L- or T-shaped hole through the middle. The different combinations of flow are shown Terofox website. It is easy to see that a T valve can connect any pair of ports, or all three, together, but the 45 degree position which might disconnect all three leaves no margin for error. The L valve can connect the center port to either side port, or disconnect all three, but it cannot connect the side ports together. Multi-port ball valves with 4 ways, or more, are also commercially available, the inlet way often being orthogonal to the plane of the outlets. For special applications, such as driving air-powered motors from forward to reverse, the operation is performed by rotating a single lever four-way valve. The 4-way ball valve has two L-shaped ports in the ball that do not interconnect, sometimes referred to as an “×” port.

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