125# FF ductile iron valve with 150# RF Cast steel flanges 1

[GasProcess]

We have to replace 125# FF ductile iron valves ( material - A536 65-45-12 & A126 GrB ) with the existing 150# RF valves. The flange on the water filter where the valve is installed is #150 RF. There is spacer installed at present between the valve and the vessel flange.

Is it possible to fabricate a spacer flange from 150# Blind flange so that the RF of the bling flange mates with the vessel and the FF of the blind flange mates with the 125# FF flange of the valve. By using a full face gasket will a leak proof joint will be ensured?

Also any tips on gasket material selection would be greatly appriciated.

Thanks in advance.

 

[kjnpiper]

The back side of the blind flange is not suitable as a gasket surface, however, any machine shop should be able to put a gasket surface finish on it for you. Depending on the service, and temperature, you could also just purchase a teflon FF spacer which also serves as the gasket.

 

[GasProcess]

Thanks kjnpiper

Have you used any such spacer sucessfully or this is a suggession ( I think it is sensible ).

By inserting this steel blind flange spacer what will be its effect on the torque requirement on the bolts and leak tightness of the joint.

The service is water at noirmal temp and 60 psig pressure

 

[kjnpiper]

I have used the teflon spacers in various applications in chemical process. Look up Crane Resistoflex and they can help you with the specifics. They specialize in lined pipe, but offer a wide range of spacers also.

If you decide to go with the steel blind flange spacer, it would be the same as using a spectacle blind, and the bolt up should be no different than normal. Care should be taken when bolting a RF flange to a FF flange when the RF flange is cast. If not done properly (spoke pattern), it could leak, and if over tightened the RF cast flange could crack. Check the manufacturers specs.