WRC 537

[soletto]

Hallo all,

i have a question regarding this Norm.

I need to verify a nozzle with 67 % Thermal Load and 33 percent dead load of the required forces and moments.

I have internal corrosion and external corrosion and a design pressure of " P "

Why does the WRC Bulletin 537 not taking the design pressure in the stresses into account only the external loads.

Do i have to verify the design pressure for example with ASME Div. 1 UG 37 branch conenction and with WRC BUlletin 537 only the external loads?

And is this correct i need to multiply the required force with 0,67 (thermal load - displacement load) and check if the stress is < 3*Sa

and the 0,33 (dead load sustained load) times the required force and verify with Sa (allowable stress)

assuming the verification of the thermal load without considering corrosion allowance and verification dead load with considering of corrosion

Similar to B31.3 thermal load is displacement load and corrosion allowance does not need to take into account. But when calculating dead load stress corrosion allowance need to take into account because dead load acts the hole time with this load.

Thankx,
Regards Stefan

 

[TGS4]

WRC 537 (and it's predecessor WRC 107) are for a rectangle or cylinder on a head or cylinder for which there is no penetration. Hence, the stresses calculated do not include the stresses due to internal pressure.

For starters - definitely verify the pressure design.

Next, there is no differentiation between "thermal" loads and "dead" loads when it comes to these types of analysis. The membrane stresses from all external loads should be considered to create primary stresses (particularly primary local membrane stresses). The bending stresses in these is generally considered to be secondary.

Follow the procedure in ASME Section VIII, Division 2, Part 5 for how to handle the stresses. Any secondary stresses would need to be evaluated as a stress range (discussion here).