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Is there any information available that compares selection of a parallel slide gate valve to a globe valve for isolation in power plant main steam service?
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Hi,
You can't directly compare these types of valves.
Globe valves are generally used for flow control, having a contoured valve seat providing a control characteristic. In service, it is not always possible to close 100% and not considered effective isolation.
A parallel side valve is effectively two gate valves adjacent to each other, and used for safety isolation purposes. Providing "double" isolation between the pressure source and any maintenance activities. In UK (HSE) spec double isolation for pressure systems, you need to check your local code for the exact requirements. Hope this helps.
You can't directly compare these types of valves.
Globe valves are generally used for flow control, having a contoured valve seat providing a control characteristic. In service, it is not always possible to close 100% and not considered effective isolation.
A parallel side valve is effectively two gate valves adjacent to each other, and used for safety isolation purposes. Providing "double" isolation between the pressure source and any maintenance activities. In UK (HSE) spec double isolation for pressure systems, you need to check your local code for the exact requirements. Hope this helps.
hi, the two valves have different construction and hence suggested for different applications.
Globe valves are closing down valves in which the closure membrane is moved squarely on and off the seat. Globe valves are used in applications where a moderate control or regulation of flow and hence pressure is required. it has a control characteristics which shows the flow and pressure drop with respect to percentage opening of the the valve. Since the seating surface is square shaped, it's almost impossible to close the valve fully 100% and since the valve can't be closed fully, whatever be the characteristics of the globe valve (linear or equal percentage or modified linear/equal percentage or hyperbolic), there will always be some leakage and hence 1005 isolation may not be achieved with this valve.
however, gate valves are straight through flow valves which provide positive shut-off with minimal flow turbulence and pressure drop. gate valves may be installed without consideration of direction of flow.A parallel side valve is effectively two gate valves adjacent to each other, and used for safety isolation purposes. They are not recommended for use in partially open, throttling position as excessive noise, vibration, erosion and wear can occur. hence they shall be used in fully open or closed condition and in fully closed condition it can prevent leakage 100%.
in my opinion one shud therefore always have gate valves for isolation purpose.
Globe valves are closing down valves in which the closure membrane is moved squarely on and off the seat. Globe valves are used in applications where a moderate control or regulation of flow and hence pressure is required. it has a control characteristics which shows the flow and pressure drop with respect to percentage opening of the the valve. Since the seating surface is square shaped, it's almost impossible to close the valve fully 100% and since the valve can't be closed fully, whatever be the characteristics of the globe valve (linear or equal percentage or modified linear/equal percentage or hyperbolic), there will always be some leakage and hence 1005 isolation may not be achieved with this valve.
however, gate valves are straight through flow valves which provide positive shut-off with minimal flow turbulence and pressure drop. gate valves may be installed without consideration of direction of flow.A parallel side valve is effectively two gate valves adjacent to each other, and used for safety isolation purposes. They are not recommended for use in partially open, throttling position as excessive noise, vibration, erosion and wear can occur. hence they shall be used in fully open or closed condition and in fully closed condition it can prevent leakage 100%.
in my opinion one shud therefore always have gate valves for isolation purpose.
Look on the Jordan Valve web site. This is a sliding gate valve which I think that you are referring to in your question.
You can on this siste see an electronic presentation of how the sliding gate operates.
This may assist you in making your decision.
It is different from a standard gate valve that you would think of. This design has some distinct advantages ofver the globe style valve as well as a standard gate type valve.
You can on this siste see an electronic presentation of how the sliding gate operates.
This may assist you in making your decision.
It is different from a standard gate valve that you would think of. This design has some distinct advantages ofver the globe style valve as well as a standard gate type valve.
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