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#34482 - 04/20/10 08:36 PM PWHT for Manway?
Han Offline
Member

Registered: 03/15/10
Posts: 16
Loc: Kuala Lumpur, Malaysia
Hi Dude & Dudettes,

I am designing a vessel, with I.D. of 1600mm and 4000 length.

the required shell thickness is 28mm , and i need to provide a 20" manway. because of the small ID off the vessel, i need to use long weld neck nozzle for the 20" manway to minimize repad dia. 20" Long weld neck nozzle has 40mm wall thickness.

My question is, Is PWHT required if i am welding the 40mm thick nozzle to shell which is 28mm. I am confused as the 40mm thick nozzle neck is more that the code's 38mm. Some say it is not required as the code only takes into account the thickness of the welded part i.e. the shell wall - which is less that 38mm, therefore no PWHT.

Another thing is, i am using the longweld neck which is supposed to be a self reinforcing nozzle, but according to PV elite i still need repads.. I have already designed internal projection to the limit yet repads are still required. Am i missing something here?

I hope i have made my case clear. Plz do offer your views. Thx in advance.

Regards,
Milk Boy



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#34495 - 04/21/10 09:05 AM Re: PWHT for Manway? [Re: Han]
Mukesh Offline
Member

Registered: 11/12/06
Posts: 125
Loc: Ahmedabad, Gujarat, India
Han,

why don't you use Hub type Self reinforced nozzle to avoid pad?

This will also avoid PWHT at that joint for the above case probably. I can say surely only if I am having complete details of your equipment.

Mukesh Chopra
www.theculminates.com
M: +91-9428500192

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#34504 - 04/21/10 10:58 PM Re: PWHT for Manway? [Re: Mukesh]
ise12345 Offline
Member

Registered: 04/14/10
Posts: 16
Loc: .
pwht requirement: 38 mm thickness is weld thickness and not the plate thickness.
What is the service, it over rides the thickness requirement.
It also depends on material, what material are you using ?
Let us also know design pressure and temperature.

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#34642 - 04/28/10 11:17 AM Re: PWHT for Manway? [Re: ise12345]
kalra Offline
Member

Registered: 06/04/09
Posts: 17
Loc: india
PWHT .. APPLICABLE ONLY WHEN THICKNESS OF BUTT JOINT EXCEEDS 38 MM. BUT AS PER ABOVE DISCUSSION BETWEEN MANWAY & SHELL NO BUTT JOINT IS THERE, IT SI FILLET WELD . SO NO PWHT IS REQUIRED.

REFER CODE CAREFULLY- PWHT is mandatory for carbon steel material when welded joints over 32mm nominal thickness through 38mm nominal thickness unless (if not) preheat is applied at a minimum temp temp. of 200 F(93 C) during welding. Means if we do pre heating during welding then over 38 mm PWHT is required otherwise over 32mm PWHT is required.

I HOPE YOU WILL BE SATISFIED NOW.

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#34652 - 04/28/10 02:39 PM Re: PWHT for Manway? [Re: kalra]
Ray_Delaforce Offline
Member

Registered: 01/02/03
Posts: 743
Loc: Houston, TX
Hello guys

kalra has very nicely explained everything. I cannot add to it.
_________________________
Sincerely,
Ray Delaforce
CADWorx & Analysis Solutions
Hexagon PPM

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#34659 - 04/28/10 09:44 PM Re: PWHT for Manway? [Re: Ray_Delaforce]
ise12345 Offline
Member

Registered: 04/14/10
Posts: 16
Loc: .
Do fillet weld not required PWHT ir-respective of fillet size ?

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#34665 - 04/28/10 11:33 PM Re: PWHT for Manway? [Re: ise12345]
Han Offline
Member

Registered: 03/15/10
Posts: 16
Loc: Kuala Lumpur, Malaysia
hi guys,

Thanks you for all your valuable inputs. Im clear now on the PWHT requirements.

However there is still the manway reinforcement issue.

If i use a hub type self reinforcing nozzle, according to PVElite i still require repads as the Area available (Aav) us less than the Area Required (Ar)

The hub thickness is the "standard" thickness, 1.56" = 40mm i got from my vendor. i have even included internal projection to increase the Aav, but it still says i require additional repad. And PVelite dosen't have the option to put repads on the hub option. Do you think custom forging a 50mm hub thickness nozzle is feasible? Or should i just ignore the "failed notice" since its supposed to be "self reinforcing"?

Allow me to share more design data:

ID : 1600mm
calculated thk required : 27.5mm (CA included) - i use 28mm plates
Design pressure : 41 barg
Material : SA 516 gr 70 / A105/ A106
horizontal cylinder body with 2 elliptical head

Again, thx in advanced.

Regards,
Han

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#34669 - 04/29/10 02:25 AM Re: PWHT for Manway? [Re: Han]
kalra Offline
Member

Registered: 06/04/09
Posts: 17
Loc: india
 PWHT is not mandatory in following conditions:-
1) for groove welds not over than 13mm size and fillet welds with a throat not over than 13mm that attach nozzle connection that have a finished inside diameter not greater than 51mm, provided the connection donít form ligaments that require an increase in shell or head thickness, and preheat to a minimum temp.of 200 F(93 C).
2) for groove welds not over than 13mm size and fillet welds with a throat not over than 13mm or less that attach Tubes to tube sheet when the tube diameter doesnít exceed 51mm. A preheat of 200 F (93 C) is applied.
3) for groove welds not over than 13mm size and fillet welds with a throat not over than 13mm or less used for attaching non pressure parts to pressure parts provided preheat to a min. of 200 F (93 C).is applied when the thickness of pressure part exceeds 32mm.

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#34670 - 04/29/10 02:27 AM Re: PWHT for Manway? [Re: kalra]
kalra Offline
Member

Registered: 06/04/09
Posts: 17
Loc: india
YOU ARE MOVING IN A WRONG WAY.. han

I will cum back to u at evening


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#34675 - 04/29/10 04:31 AM Re: PWHT for Manway? [Re: kalra]
ise12345 Offline
Member

Registered: 04/14/10
Posts: 16
Loc: .
here fillet size is not in PWHT exemption limit.
so PWHT is required.

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