Checking flange loads

[KevinNZ]

Pressure vessel designers must check loads on flanges. This involves looking at the forces and moments on the flange as well as the margin between vessel design P/T and the flange rating P/T.

But why do piping designers not have to do this, or should they?

There certainly can cases where the pipe wall thickness is much more that required for design P/T (eg high corrosion allowance) and the forces generated in the pipe would fail a flange.

For example in B31.1 table 112-1 note (a)
(a)Bolting(including nuts),flange facing, and gasket selection(materials, dimensions, bolt stress, gasket factor, seating stress, etc.)shall be suitable for the flanges, service conditions, and hydrostatic tests. There shall be no over stressing of the gasket or flanges from the expected bolt loading or external bending loads.


The code does not say how to access external loads on flanges.

 

[XL83NL]

Piping designers normally dont do stress analysis, in my world, so Im assuming pipe stress engineers here;
it's a formal Code requirement for them to check loads at interfaces, such as equipment. B31.3 hints at this via (a.o.) 319.1.1(c) and 319.1.2(b). Crtl-F-ing on 'equipment' on B31.3 sect 319 also gives 319.4.3 as a result.
To me there are sufficient leads in B31.3 that restarint loads at equipment is a Code requirement. Remember the Code sets minimum requirements only.

Huub

 

[saplanti]

There should be procedure which provides the allowable external forces and moments that will a direction to the pipe designer and pressure vessel designer to consider in addition to pressure and temperature. If both parties work on the same base the result will be satisfactory.

Some international companies have the allowable external forces and moments with combinations in their specification. I guess you may create your own, but it must be logical otherwise it will be a disaster.

Hope it helps.

 

[saplanti]

You additionally need to use the flange analysis option of the pipe stress analysis software to evaluate the P/T and external forces and moments.

 

[KevinNZ]

Thanks for your comments.

I think the flange connections to equipment is well covered. The equipment designer have their requirements and can pass these on to the piping engineers.

But what about a flange pair out in the middle of a pipe run? or forces on valve flange?

 

[TGS4]

They need to be checked. There is no codified requirement or piping code methodology, yet. However, that doesn't relieve the piping engineer from their responsibilities.

 

[XL83NL]

But what about a flange pair out in the middle of a pipe run? or forces on valve flange?

Why wouldnt these be covered by the applicable piping code? What about them?

Huub

 

[LittleInch]

ASME B 31.3 section 321.1.1 would apply here I think - my emphasis.

So maybe they need to be reminded of sectin b) below??

321.1.1 Objectives. The layout and design of piping and
its supporting elements shall be directed toward
preventing the following:
(a) piping stresses in excess of those permitted in this
Code
(b) leakage at joints
(c) excessive thrusts and moments on connected
equipment (such as pumps and turbines)
(d) excessive stresses

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

 

[KevinNZ]

I see in the post about changes to B31.3 2018 that flanges can be checked with ASME V111 div 2 eq 4.16.19 (code case 2901)