We are investigating the use of a swing check valve to control reverse flow at an air compressor inlet. A swing check valve was chosen to minimize flow restriction. I am under the impression that swing check valves offer the least resistance due to the straight flow path. I am concerned that the appropriate valve size for the flow and pressure requirements will contain a heavy valve disc requiring high energy to maintain an open position. Does anyone have formulations relating disc weight, position and flow energy (velocity, pressure) for swing checks in order to estimate the head loss?
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Swing Check Valve
- Thread starter JB23
- Start date
PacificSteve
Mechanical
Swing check pressure drops are best obtained direct from manufacturer of the valves. Sorry for the vague response.
At low flow rates, the swing check may be just barely open with high head loss which may not be suitable for your application.
Swing checks always seems to get stuck part open unless the system is very very clean.
Would you consider a full bore solenoid or oversized solenoid or motor operated valve. Is there a control signal that could simply operate such a valve?
PacificSteve.
At low flow rates, the swing check may be just barely open with high head loss which may not be suitable for your application.
Swing checks always seems to get stuck part open unless the system is very very clean.
Would you consider a full bore solenoid or oversized solenoid or motor operated valve. Is there a control signal that could simply operate such a valve?
PacificSteve.
Some guidance on this subject can be found in Cranes Flow of Fluids Techincal Paper No. 410.
The minimum pipe velocity in fps for full lift of the disc is given in Crane as equal to 35 x SQRT(V) for a swing check valve with screwed ends; and equal to 60 x SQRT(V) for a flanged end swing check valve (unless U/L listed which is equal to 100 x SWRT(V) for the swing check with flanged ends).
V is the specific volume of the flowing lfuid in ft3/lb.
WIth this method, you may wind up with a check valve smaller than the normal line size; but Crane argues that this is preferable pressure drop-wise to the constant opening nad closing of an over-sized valve. The more you learn, the less you are certain of.
The minimum pipe velocity in fps for full lift of the disc is given in Crane as equal to 35 x SQRT(V) for a swing check valve with screwed ends; and equal to 60 x SQRT(V) for a flanged end swing check valve (unless U/L listed which is equal to 100 x SWRT(V) for the swing check with flanged ends).
V is the specific volume of the flowing lfuid in ft3/lb.
WIth this method, you may wind up with a check valve smaller than the normal line size; but Crane argues that this is preferable pressure drop-wise to the constant opening nad closing of an over-sized valve. The more you learn, the less you are certain of.
A swing check in air flow is probably not the best application. It requires more flow to keep open. A nozzle check or dual plate are more appropriate for air flow (not that a swing check won't work but it must be carefully chosen). Also, dual plate designs offer less resistance than most swing checks. Your question regaridng pressure drop is best answered by valve vendors.
CHD01
The vmin value of the check valve is the minimum velocity required to hold the disc fully open without oscillation. A swing Check Vmin is 12 fps and above. A Nozzle Check Vmin is a function of spring sizing and orientation and is as low as 3 fps with a weak spring. These values assume water and the fluid and must be adjusted for diffeerent fluid densities. My company manufactures these valves in the USA and has many years of applications experience.
Regards
rgormley@et.curtisswright.com
The vmin value of the check valve is the minimum velocity required to hold the disc fully open without oscillation. A swing Check Vmin is 12 fps and above. A Nozzle Check Vmin is a function of spring sizing and orientation and is as low as 3 fps with a weak spring. These values assume water and the fluid and must be adjusted for diffeerent fluid densities. My company manufactures these valves in the USA and has many years of applications experience.
Regards
rgormley@et.curtisswright.com
TerryOsser
Mechanical
Check out or (noz-chek, compac noz) for the high integrity non-slam axial flow check valves and duo-chek for dual plate.
Dual plate are much cheaper/lighter but are not non-slam / high integrity, and have higher DP's. Dual Plate have a minimum size of around NPS 2
Dual plate are much cheaper/lighter but are not non-slam / high integrity, and have higher DP's. Dual Plate have a minimum size of around NPS 2
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