Naval Marine Valves Built by a Specialist Valve Maufacturer

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Naval Marine Valves Built by a Specialist Valve Maufacturer
How a Valve is Constructed

There are many types of valves which can be used for water applications. Each valve type has a unique construction to ensure proper operation in its specific application. The basic components are:-
• The body of the valve holds the parts together.
• The bonnet is the cover for the opening in the body. The bonnet can also support 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 used to guide the stem. The trim is responsible for the basic motions and flow control features of the valve.
• The disk and seat are the parts that provide the capability for permitting and prohibiting fluid flow. The system is under full pressure when the disk is closed. The seat provides a surface for the disk to seal to in order to stop the flow.
• The stem is responsible for the movement of the disk, plug or the ball for opening or closing the valve. It is usually forged and connected to the valve hand-wheel, actuator, or the lever by threading. The stem moves the disc to open or close the valve.
• Stem packing is used to form a tight seal between the stem and the bonnet. The packing is fitted with one of several components. Packing is important in preventing damage to the stem and fluid / gas loss.
• The yoke and yoke nut connect the body with the actuating mechanism. The yoke must be strong enough to withstand the forces, movements, and torque developed by the actuator. The nut is used to control 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 types of actuators depending on the needs of the system. Some water valves are actuated manually, some by a hand wheel or crank, others with mechanical devices such floats and cams. Electric, pneumatic, electro-hydraulic, or hydraulic methods are also used.

• Manual/hand operated actuators use a hand-wheel or crank to open or close the valve. Manual actuators are used in remote systems that may not have access to power, however they are not practical for applications that involve large valves.
• Electric motor actuators permit manual, semi-automatic, and automatic operation of the valve. The motor is usually reversible and used for open and close functions.
• Solenoid operated valves use hydraulic fluid for automatic control of valve opening or closing. Manual valves can also be used for controlling the hydraulic fluid; thus providing semi-automatic operation. These valves are not practical for large systems because their size and power requirements would be excessive.
• Pneumatic operated valves can be automatic or semi-automatic. They function 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 required 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 system fluid to position 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 external power is required.

Connection Types

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