The outer – layer tape shall be a two – layer tape consisting of a polyethylene backing layer with a butyl adhesive layer .
The primary functions of the outer – layer tape shall be to provide mechanical and outdoor weathering protection to the tape system , and secondarily , to contribute to the overall corrosion – protection properties of the system . The outer – layer tape backing shall be compounded so that it will be resistant to outdoor weathering and ultraviolet – light .
The manufacturer shall certify that the backing material is polyethylene only , containing not less than 3.0 percent nor more than 7.0 percent , by weight , of non–polyethylene material consisting of pigments , antioxidants , and stabilizers .
The manufacturer shall certify that the elastomer content of the adhesive layer is not less than 20 percent by weight .
The outer – layer tape shall be made from materials that provide high electrical resistivity,low moisture absorption and permeability , and resistance to corrosive environments .
4.2.1 The plastic backing shall be smooth and uniform , free from visible faults such as fish eyes , slits , folds , break , uneven or frayed edges and other defects that could affect appearance or serviceability .
4.2.2 The adhesive layer shall be smooth and uniform and as free from lumps and bare spots as the best commercial practice will permit . There shall be no adhesive transfer when the tape is unwound from the roll .
4.2.3 The outer – layer tape shall be sufficiently pliable for normal application operations and shall be suitable for hand applied application and shop coating with wrapping machine , and no significant wrinkles or blisters shall be developed during application even under sunlight .
4.2.4 The outer – layer tape shall be compatible with the Inner – layer tape .
4.2.5 The outer – layer tape shall comply with the requirements of Table 1 , and when applied over the Inner – layer tape , shall provide an effective bond to the Inner – layer tape .
4.2.6 The color of polyethylene backing shall be white or grey .
4.2.7 The outer – layer tape shall be supplied in roll form , wound on hollow cores with a nominal inside diameter of 80 mm .
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4.2.8 Unless otherwise specified , the outer – layer tape shall be supplied in the following dimensions :
Roll length : 10 m , 20 m , 30 m
Roll width : 4 , 6 , 9 inches
4.3 Tape Tests
4.3.1 Width deviation
A specimen of outer – layer tape at least 1m long shall be removed from each of three randomly selected rolls . The width of the specimen shall be measured at several points along the length of the sample to the nearest 1.0 mm using a standard steel scale . The width deviation shall not exceed the limits stated in Table 1 .
The thickness of the outer – layer tape shall be measured at not less than 10 locations on the three rolls of tape coating used according to 4.3.1 . The measurements shall be made with a micrometer calibrated to read minimum in thousandths of an inch and having contact feet of not less than 6 mm in diameter . Thickness measurements outside the limits stated in Table 1 shall constitute failure of the tape to meet the thickness requirement . The preferred method of adhesive removal when measuring the thickness of backing shall be defined by tape manufacturer .
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4.3.3 Non–polyethylene material content
The outer – layer tape shall be tested for nonpolyethylene content in accordance with ASTM D 4218 . Sections 9.11 , 9.12 , and 9.13 of ASTM D 4218 need not be performed in this test method to obtain accurate results . The adhesive layer must not be present on the tape backing when performing the ASTM D 4218 test . The preferred method of adhesive removal shall be defined by tape manufacturer . The tests should be performed only on samples taken from tape supplied by the tape manufacturer . Five samples shall be tested and the results averaged . An average value outside the limits given in Table 1 shall constitute failure to meet this requirement .
4.3.4 The tape manufacturer / supplier shall provide the purchaser with certified test reports on each order of tape supplied .
The manufacturer / supplier shall provide sufficient information to identify the outer – layer tape and shall supply as a minimum the technical information of the product as follows :
– ISO 9001 : 2008 "Certification" for "Design , Manufacturing and Quality control" of tape coating system for "pipeline corrosion protection" issued by an internationally recognized body .
– "Certificate" and "type approval test report" obtained from an independent laboratory or institute for the coating system (primer , inner layer tape , outer layer tape) for maximum continuous operating temperature up to 50 (stress class C – 50) .
– Manufacturing product data sheets , technical catalogue , technical specification and application procedure .
6. QUALITY ASSURANCE
The manufacturer shall operate an effective documented quality system based on the relevant part of the BS EN ISO 9001:2008 and maintain records identifying the product , date of manufacture , batch numbers and all results of inspection and testing .
7. INSPECTION AND TESTING
7.1 Materials supplied under this standard specification shall be inspected by the purchaser or his authorized representative . The purchaser shall have the right to reject any material(s) supplied which is (are) found to be defective under this standard specification .
7.2 The supplier and / or manufacturer shall be responsible for the performance and costs for all laboratory test requirements as specified in this standard specification .
7.3 The manufacturer shall set up and maintain such quality assurance and inspection systems to ensure that the materials comply in all respects with the requirements of this standard specification (see clause 6) .
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7.4 Purchaser's inspector(s) shall have free access to the manufacturer's works to follow up the progress of the materials covered by this standard specification and to check the quality of materials . The supplier / manufacturer shall place free of charge at the disposal of the purchaser's inspector(s) all means necessary for carrying out the required inspection , results of tests , checking of conformity of materials with this standard specification requirements , checking of marking and packing of materials .
7.5 Unless otherwise specified by the purchaser , the number of samples for testing shall consist of 10 percent of the batch , but in no case shall be less than three or more than ten samples .
The results of the tests on the samples shall be conformed with the requirements that specified in Table 1 .
7.6 If the results of one or more tests carried out on samples are found not to conform to this standard specification , the test(s) failed shall be repeated on at least three new samples collected by the NIGC's inspector(s) . In case , any of the new samples fail to conform with this standard specification , all materials represented by such samples shall be considered rejected .
8.STORAGE LIFE AND PACKAGING
8.1 Storage Life
8.1.1 The tape shall meet the requirements of clause 4 after storage for 24 months of delivery date at temperatures between +5 to +35.
8.2.1 The tapes purchased according to this standard specification shall be rolled on a cardboard tubes with internal diameter of 80 mm (nominal) and packaged in suitable and approved containers so that during stocking and transport , full quality of performance is retained . Each roll of tape shall be protected from adhering to other rolls , to the container , or to the packaging material itself by the use of separators .