1. SCOPE
2. REFERENCES
3. GENERAL
4. SAFETY
5. MATERIALS
5.1 Shielded Metal Arc Welding (SMAW)
5.2 Gas Metal Arc Welding (GMAW)
5.3 Shielding Gas
5.4 Field Applications
6. WORKMANSHIP
6.1 Erratic Arc Fouling
6.2 Preparation of Joint
6.3 Welding Technique and Fit-up
7. COATING OF WELDS AND DAMAGED GALVANIZED SURFACES
8. INSPECTION
Welding Procedure for Galvanized Steel Structure
1. Scope
This article is about guidelines for welding galvanized structural steel.
2. References
Reference is made in this standard to the following documents.
American Welding Society (AWS)
A 5.1 Specification for Carbon Steel Covered Arc-Welding Electrodes
A 5.18 Carbon Steel Electrodes and Rods for Gas Shielded Arc Welding
Occupational Safety and Health Administration (OSHA)
Code of Federal Regulations Part 1910
3. General
3.1 This specification applies to butt and fillet welds made in all positions.
4. Safety
4.1 Adequate ventilation shall be provided during welding or flame cutting to avoid inhaling zinc fumes as specified in OSHA 1910.252. This is important in confined areas. Ventilation of adjacent areas also shall
be ensured to protect other personnel.
4.2 Safe practices described in SES W02-F01 shall be followed on plant sites.
5. Materials
5.1 Shielded Metal Arc Welding (SMAW)
Electrodes shall conform to AWS A 5.1 Class E6010, and Class E6011.
5.2 Gas Metal Arc Welding (GMAW)
Electrodes shall conform to AWS A 5.18, Class ER70S, 4and Class ER70S-5.
5.3 Shielding Gas – Carbon Dioxide (CO2)
5.4 Field Applications –
For field applications, SMAW is preferred to GMAW.
6. Workmanship
6.1 Erratic Arc Fouling
6.1.1 Erratic arc characteristics and fouling of the gun nozzle may be encountered. These may be minimized by:
a. Spraying gun nozzle with antispatter compound available from most industrial welding suppliers.
b. Using lead angle of 10 to 20 degrees.
Best results are obtained when zinc is removed from surfaces where melting will occur. If welding is to be done without removal of zinc, precautions outlined below for avoiding entrapment of zinc shall be followed.
6.2 Preparation of Joint
- 6.2.1 Use SES W05-F02, SES W05 F03, SES W05-F01 for SMAW or W07-F01 for GMAW whichever is applicable for the fabrication of the joint.
- 6.2.2 In fillet weld between heavy sections 12.7 mm ( 1/2) in and more in thickness, a reservoir of molten zinc may become trapped at the root of the weld, which can result in cracking. To prevent this cracking, trapped zinc shall be removed by grinding or burning and brushing from the fusion area.
6.3 Welding Technique and Fit-up
- 6.3.1 Avoid joint configurations and fixturing which permit entrapment of volatilized zinc from the butting edges and back side of the joint, by providing a small gap between butting edges to be welded. Fillet welds on T-joints are best made when there is a gap between the two butting members, which allows zinc to escape via the root.
- 6.3.2 In addition to providing a gap, spacers may be necessary. Input of sufficient heat will help achieve full penetration in the welded joint.
- 6.3.3 To minimize cracking avoid restaining the joints during welding and quencing the welded joint:
- 6.3.4 Remove visible cracks and reweld area.
7. Coating of Welds and Damaged Galvanized Surfaces
Welded joints shall be wire brushed thoroughly to remove slag, loose scale, and spatter. Where coated electrode welding has been done, cleaning shall be followed with potable water washing, then drying, before applying paint. Two coats of galvanized metal primer to a total dry film thickness of 50 microns shall be used.
8. Inspection
The amount and type of inspection required depends upon the service conditions and hazards to personnel and property. It is the responsibility of the originator to define the inspection requirements. Inspection shall be in accordance with applicable code(s).