2.5.5 Operation .
Inspections of operational works are:
Co-ordination of pigging programs
Cathodic protection readings
Foreign crossing inspections
Daily reading as required
Co-ordinate R. O. W. surveillance
2.5.6 Maintenance and repair .
Pump and compressor preventive maintenance and repair
Valve maintenance and repair
2.5.7 Inspect the pipeline integrity programs
Pipeline integrity programs are very important part of both pipeline operation and maintenance procedures. There are several functions that are required to form a complete pipeline integrity program, such as:
Schedule pressure testing programs
Annual river crossing profiles
Pipeline coating assessment programs
Depth of cover surveys
Internal inspection surveys .
2.5.8 Inspection the Preparation for Welding
Safety regulations require the welding operation be protected from weather condition that would impair the quality of the welding. Before beginning the welding, welding surface must be clean and free of any material that may be detrimental to the welding. Also, pipe sections must be properly aligned for depositing the root bead. Specifications require that carbon steel with carbon content in excess of 0.32% must be preheated for welding. In some cases; steel with lower carbon contents must also be preheated. When steels with different preheated temperatures are being welded, the
higher preheat temperatures must be used to weld the seams. Preheat temperature must be monitored to ensure the proper temperature and maintain that temperature during welding.
Qualified trained welders must be employed for welding operation. TGTDCL has it’s own welder grades specified as Titas grade-A, B, C. For high pressure pipeline a welding procedure specification (WPS) is established and suggest to follows these procedure strictly. Welding conducted as per the welding procedure and must be tested to ensure the WPS requirements fulfilment. Welded joints are inspected visually, mechanically and by using non-destructive test (NDT) methods. Mechanical test includes tensile test, nick break test, macro tech test, etc. Test results are to be documented and record the procedure of welding operation [1-2].
2.6 Inspection and Testing
Pipeline welds must be inspected visually to ensure the performance in accordance with the welding procedure and the welds are acceptable under the appropriate specifications. In the
, to comply with provisions of 49 Code of federal regulation (CFR), non-destructive testing is also required on welds made on a pipeline that will be operated at a pressure that results in a hoop stress of 20% or more of the specified minimum yield strength (SMYS). There are two exceptions to this non-destructive testing requirement. Non-destructive testing is not required even though hoop stress will exceed 20% of SMYS if United States
· the pipeline has a nominal diameter of less than 6 in.
· the hoop stress will be less than 40% of the SMYS and the number of welds is so small as to make such testing impractical.
Non-destructive testing must be performed according to written procedures by specially trained personnel.
Radiography (X-ray) is the most widely used method for testing pipeline welds in non-destructive method. In radiography, a picture is made on a sensitized film by exposing the film to X-ray. Defects in the weld, such as cracks, porosity, or slag inclusions, appear as spots or lines on the developed film.