Connection of HDPE flange adapter to FF Cast Iron flange

[Dersnerman]

Does anybody know of a cost effective way to mate cast iron FF flanges to HDPE flange adapters, which are by nature RF type?

Flange connections to brittle materials such as cast iron body valves, and pump discharges, should be connected to FF flanges to avoid stress concentration on the cast item. Alternatively, extreme care must be taken to ensure the connection is not overtorqued.

Connecting a cast iron flange to steel is not problem - just specify a FF steel flange. However, HDPE flange adapter connections are by nature RF. Therefore connecting HDPE directly to a cast item is a more involved task. The only thing I could think of is include a steel adapter spool with a FF flange on one end to connect to the cast item, and a RF (or FF) flange to connect to the HDPE flange adapter.

Is there a better way?

Thanks

 

[XL83NL]

Isn’t the HDPE RF flange much sooner overtorqued than the cast iron FF flange? I’d go for a simple non-metallic IBC gasket which has a low seating stress, provided the gasket is good for the intended service.

 

[Dersnerman]

@XL83NL, In this case the HDPE flange adapter consists of a stub end made of HDPE, and a carbon steel backing ring. Sowhile the HDPE stub end is being "squeezed" (and actually provides the seal without a gasket, up to certain pressure), the carbon steel backing ring is the component of the RF system withstanding the bending stresses. Therefore as torque increased the cast iron would be the first to fail.

I know another way people get around this is simply taking extreme caution to not overtorque these types of connections. I've seen it done all the time in the field. But I'd like a more surefire method that is also cost effective.

 

[LittleInch]

Well you can get flat face PE flange fittings which weld on the line or a flange adapator.

e.g.

http://www.ipsflowsystems.com/produ...ngs/fusion_spigot/full_face_flange_25162.html

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Dersnerman]

Yes, something like that is what I'm looking for. I see that particular one has a steel core and HDPE gussets, presumably allowing for installation without a steel back up ring? I have since found other FF HDPE flange adapters that simply work with a steel back up ring too.

Anyways, glad to see the products exists.

Thanks everyone.

 

[LittleInch]

Some use a backing ring, some don't but you would need to use washers.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Dersnerman]

I see. Thanks kindly for your response.