Submarine Valves Manufactured by a Specialist Valve Maufacturer

http://www.truflo.co.uk/company-history.html
Submarine Valves Manufactured by a Specialist Valve Maufacturer
How a Valve is Built

There are many types of valves which can be used for water applications. Each valve type has a different build to ensure proper operation in its specific use. The basic parts are:-
• The case of the valve holds the parts together.
• The bonnet is the cover for the opening in the body. The bonnet supports internal valve parts, such as the stem, disk, and actuator.
• Trim is a term used for the replaceable internal parts such as the disk, seat, stem, and sleeves which guide the stem. The trim is responsible for the basic motions and flow control features of the unit.
• The disk and seat are the parts that provide the capability for switching flow off and on. The system is under max pressure when the disk is closed. The seat provides a surface for the disk to seal to so it can stop the flow.
• The stem is allows the disk to move, plug or the ball for opening or closing the valve. It is usually made connected to the valve hand-wheel, actuator, or the lever by threading. The stem moves the disc in a linear or rotary movement to open or close the valve.
• Stem packing is used to form the close seal needed between the stem and the bonnet. The packing is fitted with one of many components. Packing is vital in preventing damage to the stem and fluid / gas loss.
• The yoke and yoke nut are used to connect the body with the actuating unit. The yoke must be strong enough to withstand the forces, movements, and torque produced by the actuator. The nut controls the movement of the stem.

Water Valve Actuation

The valve actuator operates the stem and disk to open and close the valve. There are several variants of actuators depending on the needs of the system. Some water valves are actuated manually, some by a hand wheel or crank, others via mechanical devices like floats and cams. Electric, pneumatic, electro-hydraulic, or hydraulic methods are also employed.

• Manual/hand operated actuators use a hand-wheel or crank to open and shut the valve. Manual actuators are used in remote systems that do not have access to power, however they are not practical for applications which use big valves.
• Electric motor actuators allow manual, semi-automatic, and automatic operation of the valve. The motor is normally reversible and used for open and close functions.
• Solenoid operated valves employ hydraulic fluid for automatic control of valve opening or closing. Manual valves can also be used for controlling the hydraulic fluid; thus giving semi-automatic operation. These valves are not practical for large systems because their size and power requirements would be too great.
• Pneumatic operated valves can be automatic or semi-automatic. They operate by translating an air signal into valve stem motion by air pressure acting on a diaphragm or piston connected to the stem. Pneumatic actuators are fast-acting for use in throttle valves and for open-close positioning.
• Hydraulic actuators also provide for semi-automatic or automatic positioning of the valve. They are used when a large force is needed to open the valve, such as a main steam valve. With no fluid pressure, the spring force holds the valve in the closed position.
• Self-actuated valves use the systems own fluid to locate the valve. These are commonly found in relief valves, safety valves, check valves, and steam traps. Because these actuators use the fluid in the system, no other power is required.

Connection Types

There are lots of connection types for water valves. Examples include compression fittings, bolt flanges, clamp flanges, union connections, tube fittings and socket welds.