FPPE
Mechanical
- Mar 4, 2022
- 194
thread794-136321
Hi,
I would like to come back to the discussion in the thread mentioned above.
I believe, like JohnGP, that since the PED is not a design code, it is necessary to use the allowables given in the ASME, even though allowables are defined in the PED.
Section 7.4 of PED says:
For pressure vessels, the hydrostatic test pressure referred to in point 3.2.2 shall be no less than either of the following:
— that corresponding to the maximum loading to which the pressure equipment may be subject in service taking into account its maximum allowable pressure and its maximum allowable temperature, multiplied by the coefficient 1,25,
— the maximum allowable pressure multiplied by the coefficient 1,43, whichever is the greater.
In this section, reference is not made to the allowables to be used, but only to the pressures that the vessel can withstand (which can be evaluated by calculation, in this case ASME).
The first equation given in section 7.4 is in my opinion the same as in UG-99(b):
1.3*(MAWP or design pressure)*LSR
unless for the PED the MAWP is always Design Pressure and of course the coefficient 1.25 instead of 1.3.
In any case (it has never occurred to me otherwise) for the PED the governing equation is always the second one, so this question of allowable stresses is only a question of the correctness of the calculation in the mechanical calculation report, but I think it is necessary to clarify definitively.
Thanks in advance
Hi,
I would like to come back to the discussion in the thread mentioned above.
I believe, like JohnGP, that since the PED is not a design code, it is necessary to use the allowables given in the ASME, even though allowables are defined in the PED.
Section 7.4 of PED says:
For pressure vessels, the hydrostatic test pressure referred to in point 3.2.2 shall be no less than either of the following:
— that corresponding to the maximum loading to which the pressure equipment may be subject in service taking into account its maximum allowable pressure and its maximum allowable temperature, multiplied by the coefficient 1,25,
— the maximum allowable pressure multiplied by the coefficient 1,43, whichever is the greater.
In this section, reference is not made to the allowables to be used, but only to the pressures that the vessel can withstand (which can be evaluated by calculation, in this case ASME).
The first equation given in section 7.4 is in my opinion the same as in UG-99(b):
1.3*(MAWP or design pressure)*LSR
unless for the PED the MAWP is always Design Pressure and of course the coefficient 1.25 instead of 1.3.
In any case (it has never occurred to me otherwise) for the PED the governing equation is always the second one, so this question of allowable stresses is only a question of the correctness of the calculation in the mechanical calculation report, but I think it is necessary to clarify definitively.
Thanks in advance