Can a Failed Weir Diaphragm Valve in Vacuum Service be opened with more Vacuum?

[Bambie]

The diaphragm has separated from the stem inside a weir type diaphragm valve in vacuum service.

The process vacuum is holding the diaphragm in the closed position, which appears to be intact because it is not passing.

If the bonnet was drilled and tapped for a fitting and attached to a vacuum pump, it should open if the vacuum imposed is greater than the process vacuum.

Will lifting the diaphragm by removing air pressure from the bonnet impose more or less stress on the diaphragm than 'normal' operation of the stem?

If it does, should the diaphragm deflection be controlled by 'feeling' when the stem is contacted by the rising diaphragm?

 

[Bambie]

Hackman,

Net force = (Greater Bonnet Vacuum) - (Lesser Process Vacuum)

Really quite simple.

 

[hacksaw]

state the pressures (or vacc=uums you have and there units. Good luck.

 

[hacksaw]

Bambie,

In you application, delta P = Pa - Pfluid, = 0 MPag - 0 MPag = 0.

You need a different valve.

 

[HitokiriAoshi]

My question is, if a valve have been in service for 50 years, and is elastomer in nature, how much longer do you expect it to work? and said valve have a failed stem, which is likely it failed in tension. Yes, introducing vaccum can theoretically make reduce the stress, however, with all that labor and time spent, you are still risking a failed bonnet vacuum, which potentially would put atmospheric pressure and fail close the valve again.

HackSaw is right, there are much better valve, for cheaper price, then to drill and tap. 50 year service life is great though.

Luke | Valve Hax |

https://valvehax.com/