Volume-II of IV - GAIL

MECON LIMITED
REGD. OFF : RANCHI (BIHAR)
PROCESS & PIPING
DESIGN SECTION
NEW DELHI
STANDARD SPECIFICATION
TITLE WELDING OF ONSHORE GAS
SPECIFICATION NO. PAGE 21 OF 48
PIPELINES
MEC/S/05/62/02 REVISION
The width of the macrosection has to be at least three times the width of the
weld. The section is to be prepared by grinding and polishing and etched to
clearly reveal the weld metal and heat affected zone.
14.4.2 Method
Specimens shall be carefully examined under the microscope, with a
magnification of atleast 25 times (25:1). The COMPANY may ask for a
macrograph with 5 times (5:1) magnification for DOCUMENTATION purposes.
14.4.3 Requirements
Under macroscopic examination, the welded joints shall show good penetration
and fusion, without any defect exceeding the limits stated in the evaluation
criteria of the nick break test.
14.5 Hardness Test
14.5.1 Preparation
14.5.2 Method
The prepared macrosection is to be used for hardness testing using the Vickers
method with 10 kg load Indentations are to be made along traverses each
approximately 1mm below the surface on both sides of the weld.
In the weld metal a minimum of 6 indentations equally spaced along the
traverses are to be made. The HAZ indentations are to be made along the
traverses for approximately 0.5mm each into unaffected materials, and starting
as close to the fusion line as possible.
One indentation on each side of the weld along each traverse is to be made on
parent metal. Refer Fig.3. The indentations are to be made in the adjacent
regions as well on the opposite sides of the macrosection along the specified
traverses.
The test shall be carried out in accordance with Recommendation ISO R81,
Vickers hardness, using a laboratory type machine controlled as prerecommendation
ISO R146 and using a diamond pyramid penetrator set at 2.37
rad (136°) with a load of 10 kg.
\\Akjha\work contrac\standard TS for Pipe Line WC (Vol-II) MASTER FOLDER\02A welding onshore gas pipeline\Welding of Onshore Gas Pipelines with addendum - I 02A.doc