NITROGEN GAS DISTRIBUTION SYSTEM
WELDING AND CLEANING DETAILS
CERTIFICATION
Welder will be certified to a qualified welding procedure to be followed. Welder shall be certified in the use of the specific equipment and material being used in the welding process as per agreement with client.
10% of all orbital welded connections and 100% of all manually welded connections shall be inspected by certified person with endoscopic testing equipment. Pictures of the testing showing at least the starting point of the weld shall be included in the welding documentation for each tested weld.
- PROCEDURE
- Automatic orbital welding machine will be used to perform all welding of pipe.
- No ferrous material, tools or equipment (carbon steel cutting tools) to be used in the fabrication or installation of system.
GAS USED FOR WELDING
99.9% pure argon gas used during welding for shielding and purging to maintain quality of welding.
- ALIGNMENT AND TACKING
- Accomplish tack welding in a manner that will not cause any deleterious effect on completed welds.
- The tack welding will be as light as possible to reduce excessive heat that may cause structural changes to the granular composition of the system components.
- No penetration to the inner surface of components.
- Provision of maximum four tacks per joint.
- Cracks or improper welds will be rejected.
- DOCUMENTS AND LOG FOR EACH WELD WILL AS FOLLOWS:
- “As built drawing” with the weld number & details welds.(Manual, automatic)
- Welding Parameters Protocol
- Sample Approval
- Name of Welder
- WELD DEFECTS
Welds shall be rejected and removed including the heat-affected zone under the following conditions.
- Crack pinhole present in welding
- Non- uniform weld bead
- Overlap at weld bead
- Full penetration of the entire weld joint periphery: Required
- Re-welding of defective weld is not permitted
PASSIVATION
- Passivation is a chemical treatment applied to stainless steel parts to provide resistance to oxidation, rusting and mild chemical attack. The Passivation process removes free iron (ferric material) from the surface of the parts that can be created during finishing operations such as milling, buffing, lapping, cutting, etc. These contaminants create potential sites for corrosion that result in premature deterioration of the component. The acids used for Passivation dissolve much of the alloyed iron on an atomic level right at the surface leaving a chromium and nickel-rich surface. It then creates the formation of a thin oxide film that protects the stainless steel from corrosion.
- Cleaning medium shall be compatible with 0.5-micron surface finish. Cleaning is mandatory.
- Passivation is mandatory for first time only. On line Passivation shall be carried out as per written pre-approved procedure and the same shall be documented.
- All internal product contact surfaces are passivated in accordance with ASTM A967 standard and that the effectiveness of the passivation are measured.
- Both Nitric and Citric Passivation treatments on Titanium and Stainless Steel alloys that adhere to QQ-P-35C, AMS-QQ-P35A, AMS 2700C, ASTM A 967-05 and ASTM A 380-06 standards. Passivation alone will not remove heavy adherent oxide films created from heat treatment, welding, hot-forming and other high-temperature operations. Therefore AST uses different types of pickling acids designed to remove these films prior to the Passivation of the parts. Our extensive experience with Passivation allows us to choose and match the appropriate Passivation and pickling procedure for your needs and specific stainless steel grades.
- IDENTIFICATION
The whole system (Tank, valves, gauges and Instruments) shall be tagged. The tag no. will follow the numbers of the P & I Diagram.
DOCUMENTATION
Following are the documents will be submitted with system supply:
- P & ID
- Piping Drawing
- Design Qualification
- Factory Acceptance Documents
- Installation and Operational Qualification
- Test certificates of all bought out components
- Manuals of all bought out items
- Calibration certificates of all instruments
- Welding Qualification documents
