Minimum linepipe circumfrential Weld Separation

[RangerBill]

Sorry if this has been covered before, search facility down at the moment.

I am having trouble locating a suitable design code (ASME, API or else) which gives design guidance on the minimum weld clearance for the following scenario:

What is the minimum clearance between a linepipe/flange/fitting butt weld and a full circumfrential doubler plate fillet weld around a piece of line pipe and which code whould I be looking at for the design of such?

This involves a subsea manifold piping system where the main through header (8" NB) is anchored to the structure at one end of the header via a bolted assembly welded to a full circumfrential doubler plate attached (via fillet weld all around)to the parent pipe directly adjacent to an API 6A weld neck flange butt weld. I would normally use a 1D clearance as a conservative layout guide if I wasn't tight for space, though quite often I find would like to minimise this.

I would like to justify with a known code section quote if possible, rather than have to try and justify on sound practical advice, which not everyone appreciates.

In a similar situation, I have used a weld clearance of 6 x wall thickness for a minimum clearance between a linepipe buttweld and a weldolet branch fitting, (toe of weld to edge of butt) though the code I retieved that one from escapes me after all this time.

 

[pipewelder1999]

I have not seen this in ASME/ANSI B31.1 or B31.3. I have heard this referred to many time by people in the field with no documentation to back it up.

There very well may be service conditions and specifications that I have never dealt with that indicate a "Minimum". Until I see those in writing required for the project I am working on, Its a wives tale.

I too would like to know where this comes from as far as a code or specification goes. Theoretical thougts and ideas that are true and valuable would make it to the code I would think.

Sorry I couldn't shed any light on this . Maybe we will both be informed here..



Gerald Austin
Iuka, Mississippi

http://www.weldinginspectionsvcs.com

 

[CLINDU]

I did not find things related to ASME, but as I knew that some big oil companies specifiedas follows:
For sockweld, 2" min clearance
For butt weld 4" min clearance

Between two circ. weld.

Clind

 

[DSB123]

RangerBill, CLINDU & pipewelder 1999,

I myself have wondered about this as there does not seem to be any help in ASME. However all I can say is that in BS2633 "Class 1 welding of pipes" (Not exact title) there is some guidance/requirements on proximity of welds. The minimum distance required between the toes of the welds is specified as being 4 times the main pipe thickness. However in general I tend to work on 40mm between the toes as a general rule for normal thicknesses but check against the 4t rule of BS2633. (BS2971 for Class 2 welds also has the 4t rule also)

Hope this is of some help.

 

[prabir]

RangerBill,

Refer PFI( Pipe Fabrication Institute)standard ES-7
Unfortunately,I am not having this with me now. This
standard gives minimum distance between two welds on pipe.
Probably this will help you.
Regards,
Prabir

http://www.pfi-institute.org/