Cobra17
Mechanical
- Jun 18, 2020
- 165
I'm working on a project with an end user requirement to include nozzle thrust. I've talked to a few other people and no one has seen a request like this, or is sure how to do it.
As usual, the end user might as well be the Riddler (from Batman). Hopefully someone here is able to help with what I have:
Since I have Compress, and I can calculate nozzle using the Appendix 46 option, which uses Div.2's method, I figured I'd do Method 2.
according to the end user:
Div. 2 calculation give me PL (maximum local primary membrane stress at the nozzle intersection). In the Div.1 WRC 537 calculations, I've applied their 'standard' nozzle loads which gives me PL+Pb+Q, and PL. From the WRC tables, the combined stress (PL+Pb+Q) are taken from 'Primary membrane circ. stress' AKA PL, 'primary membrane Longitudinal Stress' AKA Pb, and 'Total Shear Stress' AKA Q
So I have Pb & Q from the WRC table, and Pm is shown below the table (after first calculation). Now I do the math: PL(Div.2)+Pm+Pb <= 3*S(shell) and PL(Div.2)+Pm+Pb+Q <= 3*S(shell).
I think.
For 'fun' I ran WRC 368 calculations and I got less than 400 psi difference for my maximum membrane stress intensity of the vessel compared to Compress's PL(Div.2).
Yes, Only the end user can confirm and all that. I'm asking if what I have is logical, way off, or if someone else has seen a requirement like this and can help.
As usual, the end user might as well be the Riddler (from Batman). Hopefully someone here is able to help with what I have:
Pressure thrust shall be included in the nozzle stress analysis. One of the following methods
shall be used to address pressure thrust on nozzles with external loads. In both these
cases, pressure thrust is already included in the pressure stress calculation by either
method.
Method #1: If WRC107/537 or WRC297 is used for nozzles on cylindrical shells, WRC368
pressure stress shall be calculated and added to the WRC107/537 or WRC297 stresses.
Method #2:
If WRC107/537 or WRC 297 is used, local membrane stress arising from pressure around
the nozzle shall be calculated according to Section 4.5 of ASME Sec. VIII Div. 2 (Design
Rules for Openings in Shells and Heads), and these local pressure stresses shall be added
to the WRC107/537 or WRC297 stresses.
shall be used to address pressure thrust on nozzles with external loads. In both these
cases, pressure thrust is already included in the pressure stress calculation by either
method.
Method #1: If WRC107/537 or WRC297 is used for nozzles on cylindrical shells, WRC368
pressure stress shall be calculated and added to the WRC107/537 or WRC297 stresses.
Method #2:
If WRC107/537 or WRC 297 is used, local membrane stress arising from pressure around
the nozzle shall be calculated according to Section 4.5 of ASME Sec. VIII Div. 2 (Design
Rules for Openings in Shells and Heads), and these local pressure stresses shall be added
to the WRC107/537 or WRC297 stresses.
Since I have Compress, and I can calculate nozzle using the Appendix 46 option, which uses Div.2's method, I figured I'd do Method 2.
according to the end user:
calculate PL as per Div.2 and add this PL value in to the Pm+Pb & Pm+Pb+Q and compare with the allowable stresses of each case.
Div. 2 calculation give me PL (maximum local primary membrane stress at the nozzle intersection). In the Div.1 WRC 537 calculations, I've applied their 'standard' nozzle loads which gives me PL+Pb+Q, and PL. From the WRC tables, the combined stress (PL+Pb+Q) are taken from 'Primary membrane circ. stress' AKA PL, 'primary membrane Longitudinal Stress' AKA Pb, and 'Total Shear Stress' AKA Q
So I have Pb & Q from the WRC table, and Pm is shown below the table (after first calculation). Now I do the math: PL(Div.2)+Pm+Pb <= 3*S(shell) and PL(Div.2)+Pm+Pb+Q <= 3*S(shell).
I think.
For 'fun' I ran WRC 368 calculations and I got less than 400 psi difference for my maximum membrane stress intensity of the vessel compared to Compress's PL(Div.2).
Yes, Only the end user can confirm and all that. I'm asking if what I have is logical, way off, or if someone else has seen a requirement like this and can help.