Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF : RANCHI (BIHAR)
Document3
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
STANDARD SPECIFICATION
TITLE CASING INSULATORS AND END SPECIFICATION NO. PAGE 2 OF 6
SEALS MEC/S/05/62/12 REVISION 0
1.0 SCOPE
2.0 FUNCTION
3.0 DESIGN
PART-A CASING INSULATORS
This specification covers the minimum requirements of design, material,
manufacture and supply of casing insulators intended to be used for cased
pipeline crossings.
Pipeline insulators shall be used to support the carrier pipe inside the casing
pipe and electrically isolate the carrier pipe from the casing pipe at the cased
crossings.
The casing insulators shall:
- Resist cold flow and will not soften at design temperature.
- Resist corrosion
- Resist mechanical damage while being pulled into the casing.
- Have high electrical insulating value and low water absorption, thus
preventing leakage and maintain electrical isolation between carrier and
casing pipes
- Have high compressive strength in order to assure a permanent support
to the carrier pipe.
The arrangement of insulator shall be generally in accordance with Fig. 3.0. It
shall be made in segments duly held together with cadmium plated bolts and
nuts, to be supplied with casing insulators.
The number of segments shall be two for pipe diameters upto 12” (generally).
For larger diameters, the number of segments may be more than two, but their
number shall be kept minimum.
The skid height shall be such that it is slightly less than the value obtained by
following formula.