DEP SPECIFICATION
SHOP AND FIELD FABRICATION OF PIPING
DEP 31.38.01.31-Gen.
February 2019
DESIGN AND ENGINEERING PRACTICE
DEM1
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DEP 31.38.01.31-Gen.
February 2019
Page 11
5.
Flange bolt holes shall straddle the centreline in following scenarios:
a.
Vertical centreline of the pipe where the flange is installed vertically.
b.
The piping isometric/piping arrangement drawing north-south line where the
flange is installed horizontally.
6.
See (Appendix H) for flange misalignment acceptance criteria.
7.
Longitudinal seams in pipes shall be separated by at least 45 degrees of rotation or
150 mm (6 in), whichever is the less.
a.
Additionally, any longitudinal welds in horizontal pipes shall be positioned so that
the weld is in the upper 120 degrees segment.
8.
Circumferential welds where post weld heat treatment is not applied shall be
separated by at least four times the nominal wall thickness (toe to toe).
9.
Attachments shall be at least two times the nominal wall thickness or 40 mm (1.5 in)
from any weld (toe to toe), whichever is greater.
10. When pneumatic leak test is performed in accordance with ASME B31.3, para. 345.5
or ASME B31.1, para 137.5 in lieu of hydrostatic leak test, the following separation
SHALL [PS] apply:
a.
for sizes DN 15 (NPS ½) up to and including DN 80 (NPS 3), keep longitudinal
welds in two adjacent pipes/wrought fittings 180 degrees apart;
b.
for sizes DN 100 (NPS 4) and larger, maintain a minimum spacing of 150 mm
(6 in) between longitudinal welds.;
c.
Longitudinal welds in pipes not to be located within 45 degrees of the pipe bottom
after installation.
11. In order to avoid excessive shrinkage stresses during weld solidification, a gap of
1.5 mm (1/16 in) shall be left between the end of the pipe and the stop of the socketwelding component before welding, in accordance with Figure 328.5.2 (C) of
ASME B31.3 or Figure 127.4.4 (C) of ASME B31.1.
Failure to include this gap can lead to premature piping failures.
12. Pipes that are required to be free of scale shall be blast cleaned before further
handling by the welding shop.
13. Radial grooves or scratches on flange faces shall not exceed the limits specified in
ASME B16.5, Table 3.
a.
Refacing shall be subject to the Principal's approval.
b.
Refacing shall not reduce the flange thickness to less than the minimum
thickness allowed by the relevant code or standard.
c.
Edge thickness of flanges shall be checked after re-facing.
14. Where the spool drawings indicate a field weld in the pipe, the relevant sections shall
be supplied a minimum of 200 mm (8 in) longer with plain ends.
3.4
WELDING
3.4.1
General
1.
2.
All welding shall be in accordance with the applicable code (e.g., ASME B31.3,
ASME B31.1) and with one of the following:
a.
DEP 30.10.60.18-Gen.;
b.
DEP 30.10.60.32-Gen.
See DEP 30.10.60.18-Gen. or DEP 30.10.60.32-Gen., whichever is applicable, for
impact test requirements for welding procedure qualification for carbon steel and
This document has been supplied under license by Shell to:
Arun.Kumar@rotaryeng.com.sg 22/11/2021 13:53:22