Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF: RANCHI (BIHAR)
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
TITLE PIPING FABRICATION AND
ERECTION
STANDARD SPECIFICATION
SPECIFICATION NO. PAGE 3 OF 62
MEC/S/05/62/06 REVISION 0
3.4 Threading shall be NPT to ANSI B 1.20.1. Threading shall preferably be done
after bending, forging or heat treatment operation. However if it is not possible,
precaution shall be taken to protect threading against deformation. Thread shall
be clean cut with no burrs or stripping. Dies shall be new, sharp and properly
designed for piping material. Ends shall be reamed to remove burrs.
3.5 All threaded joints shall be aligned properly. The pipe entering unions shall be
true to centrelines so as to avoid forcing of union coupling during make up.
Damaged threads shall be cut from the end of run and the pipe shall be
rethreaded.
3.6 Immediately before testing the piping, all threads of pipe and fittings shall be
thoroughly cleared of cuttings, fuel oil or other foreign matter. The male threads
shall be sealed with thread sealant and the piping made up sufficiently for the
thread to seize. Sealant shall be teflon tape.
3.7 Seal welding of threaded connections when specified shall include the first block
valve, cover all threads. The joint shall be cleaned of all cutting oil and other
foreign material and made up dry to full thread engagement. Instrument
threaded connections which are frequently subjected to testing and
maintenance shall not be seal welded.
3.8 All threaded connections shall be protected from rusting by applying greases or
oil when in operating condition.
3.9 When socket weld fittings or valves are used, pipe shall be spaced
approximately 1/16" to avoid bottoming which could result in excessive weld
stress.
3.10 Where the ends of the piping components being welded have an internal
surface misalignment exceeding 1.6mm, the wall of the component extending
internally shall be trimmed by machining so that the adjoining internal surface
will approximately flush.
3.11 Laying, Cutting and Fitting up
Extensive use of templates, gauges, plumb lines shall be made for laying,
cutting and fitting up of various piping components for fabrication.