A control valve is a power operated device capable of modulating flow at varying degrees between minimal flow and full capacity in response to a signal from the controlling system. Control valves may be broadly classified by their function as “on-off” type or “flow regulating” type.
A control valve is comprised of an actuator mechanism that is capable of changing the position of flow controlling element in the valve. The valve modulates flow through movement of a valve plug in relation to the port(s) located within the valve body. The valve plug is attached to a valve stem, which, in turn, is connected to the actuator. The actuator, which can be pneumatically or electrically operated, directs the movement of the stem as dictated by the external control device. The actuator responds to an external signal which usually comes from a controller. The controller and valve together form a basic control loop.
- GS Certificates and Global Standards
- EN ISO 9001:2000
- PED 97/23/EC Module H
- DIN EN 161, DIN 3394
- TA-Luft VDI 2440 (Clean Air Act) / DIN EN ISO 15848-1
- ATEX 94/9/EC, Machinery directive 98/37/EC
- DIN, EN, AD-Merkblatt 2000, ANSI, ASTM, ISA
- EN 1349, EN 60534
- SIL 3 / 4 acc. to IEC61508
- DNV Type approval (for classification of ships)
Size Range: 0.5 to 16
Pressure Class Range: 150 and 300
- 316 s.s.
- Alloy 6 overlay
- PTFE soft seat
- Ability to throttle or control the rate of flow
- Lack of turbulence or resistance to flow when fully open – turbulence reduces head pressure
- Quick opening and closing mechanism – rapid response is many times needed in an emergency or for safety
- Tight shut off – prevents leaks against high pressure;
- Ability to allow flow in one direction only – prevents return;
- Opening at a pre-set pressure – procedure control to prevent equipment damage
Valves are available with a wide variety of valve bodies in various styles, materials, connections and sizes. Selection is primarily dependent on the service conditions, the task, and the load characteristics of the application. The most common types are ball valves, butterfly valves, globe valves, and gate valves.
Each valve has a flow characteristic, which describes the relationship between the flow rate and valve travel. As a valve opens, the flow characteristic, which is inherent to the design of the selected valve, allows a certain amount of flow through the valve at a particular percentage of the stroke. This enables flow regulation through the valve in a predictable manner. The three most common types of flow characteristics are.
- Equal percentage
- Quick opening
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