Method Statement Title: Welding Procedure
1.0 Purpose
To define the Method of Welding Pipe Lines.
2.0 Scope
The Method is applicable to all Chilled Water Pipe work using mild steel and carbon steel pipes and fittings, for pipe sizes 65mm dia and above in accordance with Specification Section 15050, Clause 3.04, Clause 3.07 and our material submittals reference M:002 & M:30
3.0 Method
- Preparation
Before commencement of any welding the following works are required to be carried out.
3.1.1 Check materials to be used have approved material submittals.
3.1.2 Check work areas are clean and safe ensuring that the area is free of all flammable or volatile material.
3.1.3 All welding work shall be carried out in open or ventilated areas.
3.1.4 Welders qualification will be verified as per requirement.
3.2 Welding Procedure
3.2.1 Measure length of pipe required, making due all allowance for any pipe fittings to be used and cut the pipe to the measured length.
3.2.2 Prepare the end of the pipe to be welded to the right angle of level and the size of the root face in accordance with procedure Specification (copy attached). The surfaces to be welded shall be smooth, uniform and free from tears, scale, slag, grease, paint and other materials that might affect the quality of welding. Power tools or hand tools will be used for cleaning, grinding or both.
3.2.3 The two prepared ends to be welded, pipe to pipe or pipe to fitting, shall be aligned as accurately as is practical and ensuring that the spacing between the abutting ends is in accordance with the procedure specification used. The alignment of the abutting ends shall minimize any offset between the surfaces caused by dimensional variations and will equally distribute around the circumference of the pipe any such offset. Hammering of the pipe to obtain proper lineup will be kept to a minimum.
3.2.4 The two prepared ends shall be tack welded together in four positions at ninety degrees. After tacking, the alignment shall be checked to confirm the integrity of the alignment has been preserved. During the welding process the tacks shall be removed by grinding.
3.2.5 The welding process will commence, ensuring that the correct filler metal, electrical current, polarity, voltage, amperage and number of passes is in accordance with the welding procedure. All slag or foreign matter shall be removed from each pass of welding, including the repair of any visible defects, such as crack, cavities, etc., prior to commencing the succeeding passes. Any such impurities shall be removed using a grinder.
- The weld shall be visually inspected to check for inadequate penetration, excessive undercutting, burn-through, and to ensure the weld is free from cracks by ETA QA Engineer.
3.2.7 Clean the joint by wire brush prior to painting.
- The weld shall not be cooled by water.
- All welds to be painted red oxide primer as soon as pipe is cool.
3.3 Welding Electrode Storage and Handling
- The welding electrodes upon delivery are stored in an airconditioned area. The electrodes are transferred to a welding rod holding oven when space in the oven available. The oven is thermostatically controlled and maintains a constant 100°F (38°F). The shelves are vented to allow an even heat distribution in the oven. All welding electrodes will be pleased in the oven for a minimum of 48 hours before they are transferred to site for use.
- Once transferred to the site the electrodes are stored in each welding operatives heated quiver. Operatives are instructed to take only the quantity they require to carryout the welding work presently undertaken. However, any surplus electrodes will be checked and stored back in the oven.
4.0 Inspection & Testing
- 100% visual inspection will be carried of all welded joints by ETA QA Engineer.
- The joint will be prepared for butt welding as shown on the sketch. 60° angle & 3.0 to 3.6mm gap. Joint inspection to be carried out by ETA/QA/QC Engineer and R&P Inspector.
- Root weld to be carried out (one of the joint sketch) for 3mm weld deposit with 3.2mm dia welding rod.
- Clean the joint by wire brush/hand grinder.
- Filler weld to be carried out (2 to 5 of the joint sketch) for 8mm weld deposit with 2.5/3.2mm dia welding rod.
- After every welding run point 4.1.3 shall be done.
- ETA QA/AC shall keep a record of all the joints with joint number, size of pipe, welder and date of weld.
- Joint number shall be marked on the pipe.
- All weld joints will be subjected to hydrostatic testing to a minimum of 1.5 times the operating pressure. See method statement ETA/MS/M-002A.
- WIR’s will be raised for Consultants visual inspection and witness testing.
- Radiographic examination of 5% of weld joints & magnetic particle testing of 5% weld joints by an independent testing agency will be in accordance with MACE, E.I.No.40.
- In the event that 10% of all tests carried out fail, all welds are tested by the same above methods and to the same proportion. All joints failed are cut and removed. All subsequent replacement welds will be tested by radiographic test.
- Refer MS No.018 for weld test method statement (by specialist)
- Reference Documents
- Applicable approved drawing
5.2 Specification Section 15050, Clause 3.04, clause 3.07
5.3 Welding Procedure Specification and PQR (Enclosed)
M&E / WPS / 1779
ETA-M&E/PQR/1698
5.4 Welders Certificates
Welder’s Qualification Certificates Enclosed.
6.0 Safety
6.1 Safety items to be provided shall include fire extinguishers and welding screens.
6.2 Welding cables to be checked regularly for visual signs of damage. Joints to be sheathed and taped.
6.3 Prior to commencement of work check welding M/C, current, voltage, earthing, etc., for safety.
6.4 Safety equipment (Example : Hardhats, Safety shoes, Overalls, Gloves, Goggles as necessary) to be worn at all times. Standard welding Safety kit of shields, gloves, etc. to be provided for each welder. Glasses to be checked for cracks / weld spatter.
6.5 Hot work permit to be obtained as per the site safety procedures prior to the commencement of work. 6.6 Site safety officer will check and ensure all safety precautions are taken prior to commencement of welding