Hi,

I have tried searching but had no luck. I'm sure that many of us have come across this problem before. When you have interface between U/G FRP pipe and A/G steel pipe, what critera for flange leakage calculation do we use? I found in BS 7159 section 10.6 mentions Flanged joints calculation. which seems ok to be used for FRP part.

Does it mean that we need to check for both sides steel flange and FRP flange? (And with different approach, of course FRP will be check by vendor but I would like to know which method they normally refer to.)

Has anyone got this situation before? Have any idea roughly how much different in term of bending moment and axial forces between the two.

Any suggestion will be very appreciated.

regards,

Waranat

That's why we use flat face flanges and elastomeric gaskets for FRP / Steel joints - they are easier to make leak tight. Although I will give odds that a system with more than a dozen or so such flanged joints will leak when first filled with water for hydro (before being pressurized).

Consult your FRP vendor for advice, and have him supply a field support engineer for construction and leak tesking the FRP.

The bending moment and axial force on the steel side of the joint will be exactly the same in magnitude, but opposite in sign, of the bending moment and axial force on the FRP side. Of course, the steel will be considerably stronger. We don't specify FRP for its strength or durability, we specify it for its low cost, light weight, low electrical conductivity, and corrosion resistance.