- 産業: Industrial valves
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A valve with a linear motion, push-pull stem, whose one or more ports and body are distinguished by a globular shaped cavity around the port region. This type of valve is characterized by a torturous flow path and is also referred to as a low recovery valve because some of the energy in the flow stream is dissipated; and the inlet pressure will not recover to the extent that it would in a more streamlined high recovery valve.
Industry:Industrial valves
A manual override device used to stroke a valve or limit its travel. The handwheel is sometimes referred to as a hand jack. It may be top mounted, side mounted, in-yoke mounted or shaft mounted and declutchable.
Industry:Industrial valves
A valve whose body is split. This design allows for easy plug and seat removal. Split-bodied valves are made in both the straight-through and angle versions. The Masoneilan 2600 or ANNIN is an example of a split body valve.
Industry:Industrial valves
A valve style in which the flow closure member is rotated in the flow stream to modify the amount of fluid passing through the valve.
Industry:Industrial valves
A property of metals that is discussed frequently when speaking of various component parts used in valve construction, particularly valve trim. There are two hardness scales which are commonly used, Rockwell & Brinell.
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Industry:Industrial valves
Is the distance between the face of the inlet opening and the face of the outlet opening of a valve or fitting. These dimensions are governed by ANSI/ISA specifications.
The following Uniform Face-to Face Dimensions apply.
'''SPECIFICATION VALVE TYPE '''
: '''ANSI/ISA S75.03 INTEGRAL FLANGED GLOBE STYLE CONTROL VALVES'''
: '''ANSI/ISA S75.04 FLANGELESS CONTROL VALVES ANSUISA S75.20 SEPARABLE FLANGE GLOBE STYLE CONTROL VALVES '''
Industry:Industrial valves
Differential Pressure. The inlet pressure (Pl) minus the outlet pressure (P2).
''Example''
P1 = 100 psig<br>P2 = 25 psig.<br>___________<br>Delta-P = 75
Industry:Industrial valves
This condition exists when at a fixed upstream pressure the flow cannot be further increased by lowering the downstream pressure. This condition can occur in gas, steam, or liquid services. Fluids flow through a valve because of a difference in pressure between the inlet (Pl) and outlet (P2) of the valve. This pressure difference (Delta-P) or pressure drop isessential to moving the fluid. Flow is proportional to the square root of the pressure drop. Which means that the higher the pressure drop is the more fluid can be moved through the valve. If the inlet pressure to a valve remains constant, then the differential pressure can only be increased by lowering the outlet pressure.
For gases and steam, which are compressible fluids, the maximum velocity of the fluid through the valve is limited by the velocity of the propagation of a pressure wave which travels at the speed of sound in the fluid. If the pressure drop is sufficiently high, the velocity in the flow stream at the vena contracta will reach the velocity of sound. Further decrease in the outlet pressure will not be felt upstream because the pressure wave can only travel at sonic velocity and the signal will never translate upstream. Choked Flow can also occur in liquids but only if the fluid is in a flashing or cavitating condition. The vapor bubbles block or choke the flow and prevent the valve from passing more flow by lowering the outlet pressure to increase the pres-sure drop. A good Rule Of Thumb on Gases and Steam service is that if the pressure drop across the valve equals or exceeds one half the absolute inlet pressure, then there is a good chance for a choked flow condition.
''Example''
P1 100 psig <br>P2 25 psig <br>_________ <br>Delta P = 75
P1 (ABS) = 100 + 14.7 or 114.7 1/2 of 114.7 = 57.35
Actual pressure drop = 75
Choked Flow is probable.
The style of valve (that is whether it is a high recovery or a low recovery style) will also have an effect on the point at which a choked flow condition will occur.
Industry:Industrial valves
This condition exists when at a fixed upstream pressure the flow cannot be further increased by lowering the downstream pressure. This condition can occur in gas, steam, or liquid services. Fluids flow through a valve because of a difference in pressure between the inlet (Pl) and outlet (P2) of the valve. This pressure difference (Delta-P) or pressure drop isessential to moving the fluid. Flow is proportional to the square root of the pressure drop. Which means that the higher the pressure drop is the more fluid can be moved through the valve. If the inlet pressure to a valve remains constant, then the differential pressure can only be increased by lowering the outlet pressure.
For gases and steam, which are compressible fluids, the maximum velocity of the fluid through the valve is limited by the velocity of the propagation of a pressure wave which travels at the speed of sound in the fluid. If the pressure drop is sufficiently high, the velocity in the flow stream at the vena contracta will reach the velocity of sound. Further decrease in the outlet pressure will not be felt upstream because the pressure wave can only travel at sonic velocity and the signal will never translate upstream. Choked Flow can also occur in liquids but only if the fluid is in a flashing or cavitating condition. The vapor bubbles block or choke the flow and prevent the valve from passing more flow by lowering the outlet pressure to increase the pres-sure drop. A good Rule Of Thumb on Gases and Steam service is that if the pressure drop across the valve equals or exceeds one half the absolute inlet pressure, then there is a good chance for a choked flow condition.
''Example''
P1 100 psig <br />P2 25 psig <br />_________ <br />Delta P = 75
P1 (ABS) = 100 + 14.7 or 114.7 1/2 of 114.7 = 57.35
Actual pressure drop = 75
Choked Flow is probable.
The style of valve (that is whether it is a high recovery or a low recovery style) will also have an effect on the point at which a choked flow condition will occur.
Industry:Industrial valves
An increase in air pressure to the actuator is required to cause the valve to open. This is another way of saying the valve is fail closed or normally closed.
Industry:Industrial valves
