Velocity Through Check Valve

[blueprint]

I have a 20 inch(DN500) pipe with a flow velocity of 4.5 meters per second, I have a few constraints and don't want to go to DN600, what are my options for putting a check valve in this line.

Cheers
Peter

 

[BigInch]

A 20" swing check?
What constraints are you worried about. All swing checks will all be full open at that velocity.

 

[ione]

- Check valve swing (for your velocity, your diameter and considering water at 20 °C pressure drop through the valve is approx 0.16 bar)

- Check valve Y patter style globe lift (for your velocity your diameter and considering water at 20 °C pressure drop through the valve is approx 0.07 bar)

- Check valve globe lift (for your velocity, your diameter and considering water at 20 °C pressure drop through the valve is approx 1.1 bar)

 

[waterpipe]

If your fluid is water then it seems a bit high velocity for water application. I am not aware why you're concern and think that a higher diameter valve would be needed. BUT make sure your check valve meets the requirements to avoid water hammer since ?V is high.

 

[SNORGY]

I think you can get a counterweight and / or damper on the swing check spindle to retard its closure time and ease its opening force, addressing both static and dynamic concerns to some degree.

Regards,

SNORGY.

 

[BigInch]

Huh! And I always thought it was for jambing it open with a car jack.

 

[stanier]

The selection of check valve is paramount in ensuring that you dont end up with a waterhammer situation. At 4.5m/s I suggest that you will need a non slam check valve.

Conventional wisdom is that a conventional swing check is one of the worst types as they have a large mass of moving parts and disc has a long distance to travel.

DUo check valves can be made to work with heavy springs but this affects the energy losses across the check valve.

For details read
Fluid Transients in Pipeline Systems ARD Thorley
or Pressure Transients in Water Systems by Ellis.

Also check out Delft Laboratories and Utah State University for technical papers on check valves.

You will need to obtain the reverse velocity and deceleration data from a waterhammer analysis and ensure that the check valve parameters meet these requirements without slamming.

The attached presentation has been given to ASME, IMechE and Engineers Australia. Take a look at the notes and references therein.

 

[blueprint]

Thanks for your replies so far, they have been most helpfu.

Can anyone advise how I can calculate the deccelartion rate on a 500NB check valve and a line velocity of 4.6m/s of seawater. Is there an industry accepted empirical formula to calculate this ?


Cheers
Peter

 

[stanier]

It is somewhat more complex than a simple formula. It depends on how your system reacts to the transient events that have occurred.

If you mean "emprical" then establish from test the time to close t secs. Then a= 4.6/t m/s^2 & gives you the average deceleration. For a more precise evaluation then have a waterhammer analysis underttaken, preferably using four quadrant data for the pump.