PIPE TO FLANGE ALIGNMENT ON FABRICATION

[WillShi]

Whilst we all appreciate that a flange should normally be welded at right angle to the pipe as it is designed to do, does anyone have any absolute maximum limits for angular angular misalignment. A limiting factor will of course be the pipe outside dimater/flange internal diameter clearance to physically allow such alignment.
Thanks

 

[NozzleTwister]

The fabrication tolerances that are outlined in the Piping Fabrication Institute's, PFI Standand ES-3, Figure 1 is what I always see as the acceptance standard.

NozzleTwister
Houston, Texas

 

[SJones]

NORSOK L-004 might be an easier document to get hold of (free download)

Steve Jones
Materials & Corrosion Engineer

http://www.pdo.co.om/pdo/

 

[vzeos]

WillShi, If you are working on an oil or gas transmission line, the regulations regarding “miter joints” will likely apply to alignment of welded flanges. See below.


CFR 49, PART 192 § 192.233 Miter joints.
(a) A miter joint on steel pipe to be operated at a pressure that produces a hoop stress of 30 percent or more of SMYS may not deflect the pipe more than 3°.

(b) A miter joint on steel pipe to be operated at a pressure that produces a hoop stress of less than 30 percent, but more than 10 percent, of SMYS may not deflect the pipe more than 12 1/2° and must be a distance equal to one pipe diameter or more away from any other miter joint, as measured from the crotch of each joint.

(c) A miter joint on steel pipe to be operated at a pressure that produces a hoop stress of 10 percent or less of SMYS may not deflect the pipe more than 90°.

http://ecfr.gpoaccess.gov/cgi/t/tex...&node=49:3.1.1.1.3&idno=49#49:3.1.1.1.3.5.9.6

 

[tothepoint]

ASME B31.3 and PCC-1 list fabrication tolerances

 

[GregLamberson]

vzeos

Some clients have specs that forbid "miter joints", we usually get around it by using this code reference and calling them "crooked cuts".

Greg Lamberson
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com