Can PG-29 dished heads be used in ASME B31.1 Power Piping ?

[salzx64]

Dear All,

Problem is that I am designing & stress analyzing a 3000 mm dia pipe with 20 mm thick for a steam header as per B31.1.

For end caps / closures I cannot use a flat unstayed plate because thickness in excess of 120 mm comes in calculation. Can I use PG-29 dished heads as per ASME BOILER Sec I code? Are they prohibited or not ?

Prompt replies will highly be appreciated.

Regards,
Salz

[ben]

If dished end has the same thickness as of pipe you can use that, no issue.

[irish]

What's the piping size? Design pressure and temperature?
Which type of dished head do you want to use?
ASME B31.1 doesn't refer to PG-29 for piping end closures rather it directs you to the standards table 126.1 (if I remember correctly) which includes B16.9 (butt end welding fittings). See if the design dished end meets the minimum stated for caps in B16.9.

[salzx64]

Dear ben thanks for your reply. It is what I intended to confirm but do you have any reference or physical implementation that if dished end of same thickness as of pipe are installed there won't be any problems ?

Dear Irish I want to use hemispherical or semielliptical as per PG-29. As far as table 126.1 is concerned it doesn't include a 3000 mm (ID) , 20 mm (thickness) pipe fitting or even 16.9 has its limits and for that BIG size either i've to go with flat unstayed plate as indicated by B31.1 but for that my thickness comes far too much and obviously when i'll use dished ends the thicknesses will be less. Question remains can I go for dished heads (PG-29) instead of PG-31 as recommended by B31.1 code.

Regards,
Salz

[ben]

See code doesn't mention about this anywhere as you already know.
For flat end plate design, you are referred to the relevant section of PV design code like ASME Sec. VIII and as per my understanding if you have to design an end cap which is out of the scope of ASME B16.9 you can design that as per PG-29.
This is my opinion. However, I do believe you can find this in ASME B31.1 interpretations.
I will see and inform you if found.

[irish]

PG-31 is only about unstayed flat head and covers but not the dished cap you require to have at the piping end.
I would agree with ben in a way that if on pressure vessel having same service conditions as you have in piping, dished ends as per PG-29 works then there would not be any problems in piping.

[Fizza]

Table 304.4.1 of ASME B31.3 permits the use of dished head in its construction designed in accordance with UG-32 of Section VIII-1. So this statement further reinforces Irish view point that PG-29 dished head may be used in 31.1 construction.