Pttchem Sp p 121 000 Wrapping
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Transcript of Pttchem Sp p 121 000 Wrapping
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PTT CHEMICAL PUBLIC CO., LTD.
BRANCH I-1: OLEFINS PLANT
STANDARD SPECIFICATION
FOR
PROTECTION COATING & WRAPPINGFOR UNDERGROUND STEEL PIPING
DOCUMENT NO. PTTCHEM-SP-P-121
REV. ISSUED DATE DESCRIPTION REV. TO
SHEET
ADDED
SHEET
MADE
BY
CHECK
BY
APPROVE
0 7 Dec 05 First Issued Prathanwit Chayan
TOTAL PAGES 12
(INCLUDED THIS PAGE)
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PROTECTION COATING & WRAPPING FOR
UNDERGROUND STEEL PIPING
PTTCHEM-SP-P-121
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SECTION CONTENT PAGE
1. SCOPE 3
2. GENERAL 3
3. MATERIALS 3
3.1 Material for pipe and fittings 3
3.2 Materials for other piping 4
3.3 Wrapping tape specification 4
4. CLEANING 4
5. APPLICATION 5
5.1 Primer Coat 5
5.2 Tape Wrapping 5
5.3 Tape thickness 6
5.4 Method and procedure for tape wrapping 6
6. INSPECTION AND TEST 6
7. REPAIRS TO COATING 7
8. HANDLING OF COATED PIPING 8
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1. SCOPE
This specification covers the requirements for application and inspection of protective coating for
underground steel piping for the National Petrochemical Corporation Ltd.
2. GENERAL
2.1 Protective coating shall consist of a coating system employing Primer, Inner Tape Wrap and
Outer Tape Wrap.
2.2 The coating system shall be applied by an approved type of cleaning, priming, and wrapping.
2.3 Coating and wrapping materials shall be handled transported, stored, and applied strictly in
accordance with the Purchaser's instruction.
3. MATERIALS
3.1 Material for pipe and fittings
Materials of the coating and wrapping shall be as described below : For straight pipe and field
joints, elbow, tee, reducer.
3.1.1 Primer : Adhesive primer
3.1.2 Inner Tape and Outer Tape Wrap
for mechanical or manual : Polyethylene tape two-layer
application (0.5 mm thickness)
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3.2 Materials for other piping
Wrapping for Valve and Flange
3.2.1 Paste : Petrolatum anti corrosive compound
3.2.2 Inner Tape Wrap
for manual application : Petrolatum anti corrosive tape one-layer
3.2.3 Outer Tape Wrap
for manual application : Polyethylene tape two-layer
(0.5 mm thickness)
3.3 Wrapping tape specification
Material of wrapping Tape shall meet the following requirement.
3.3.1 Service Temperature : 0 c to 70 c
3.3.2 Thickness of Polyethylene Tape : Min. 0.5 mm
3.3.3 Delectric strength : 10 kV and over
3.3.4 Others : Manufacture's standard
4. CLEANING
4.1 The external surface of all piping shall be thoroughly cleaned before application of the protective
coating by mechanical means to the specification SWEDEN STD. St 2. (or SSPC-SP2)
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4.2 The cleaning process shall remove all oil grease, loose mill scale, weld spatter, weld slug, rust,
paint, dirt, dust, weeds, and any other foreign matter from the pipe external surface.
4.3 Oil and grease shall be removed using a suitable solvent such as naphtha or similar. Kerosene
shall not be used for cleaning.
4.4 Manual cleaning shall be carried out by means of file, wire brushes, etc. which are capable of
producing a surface finish to the standard required in par. 4.1
5. APPLICATION
5.1 Primer Coat
5.1.1 Primer shall be thoroughly stirred before drawing from the drum. The approved thinners may
only be added to the primer.
5.1.2 Primer shall be applied to the piping system by means of blushes. The priming coat shall be
continuous and free from holidays, runs and globules, and special care shall be taken to ensure
continuity of primer film at welds.
5.1.3 Primer shall be applied at an average rate of 0.12 litters per square meter, subject to confirmation
according to manufacture.
5.2 Tape Wrapping
5.2.1 Immediately after application of the primer, the piping shall be applied with Inner Tape Wrap and
Outer Tape Wrap. The tape wraps shall be applied with tension controlled to provide a uniform,
tightly adhering coating free wrinkles, puckers, voids, or breaks.
5.2.2 The tape wrapping shall be provided the following minimum overlap under all conditions :
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Item PE Tape width PETROLATUM
Tape width
Minimum Overlap
Pipe 150mm --- Min. overlap will be
Fitting 100mm --- 55% width of wrapping
Flange, Valve 50mm 2" to 4" 100mm one-layer
6" to 10" 200mm
12" to 300mm
5.3 Tape thickness
5.3.1 Total tape thickness shall be minimum 2.0 mm
5.4 Method and procedure for tape wrapping
5.4.1 Straight pipe see page 9
5.4.2 Field joints see page 9
5.4.3 Elbow see page 10
5.4.4 Tee see page 11
5.4.5 Reducer see page 11
5.4.6 Flange, Valve see page 12
6. INSPECTION AND TEST
6.1 All coating shall be subjected to 100 % visual inspection and 100 % inspection with an electrical
holiday detector before being lowered into the trench. Voltage is 7 kV and over, but under 10 kV.
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6.2 Visual inspection shall ensure that the coating is continuous that the overlap is correctly
maintained and that there are no wrinkles in the tape.
6.3 The holiday detector shall be used to check that there is a continuous coating over the pipe
surface. Particular attention shall be given to bends and to areas where the tape has been
spliced or repaired.
6.4 The holiday detector setting shall be checked at least twice per day while it is in use.
6.5 At no time shall be the holiday detector be permitted to remain stationary around a coated
pipeline with the operating voltage switched on.
6.6 All defects, whether discovered visually or by means of the holiday detector, shall be clearly
marked, and shall be repaired and checked again.
7. REPAIRS TO COATING
7.1 All defects in the coating shall be made good immediate after their detection before lowering the
pipe into the trench.
7.2 Holidays or localized defects in the outer Tape Wrap shall be repaired by the following procedure:
a) Strip off Outer Wrap from affected area, after ensuring that completed coating on either
side is properly secured to prevent the outer wrap from unraveling.
b) Strip off Inner Wrap and Primer from the affected area and thoroughly clean the pipe
surface.
c) Reprime in accordance with this Specification.
d) Apply patch of Inner Wrap not smaller than 150 mm x 150 mm
e) Test for repaired Inner Wrap with holiday detector before replacing Outer Wrap.
f) Replace Outer Wrap and secure firmly.
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8. HANDLING OF COATED PIPING
8.1 All coated piping shall be handled in such a way that the coating does not suffer damage.
Coated pipe shall be handled at all times with wide non-abrading belts or other equipment
designed to prevent damage to the coating. All skids used to support coated pipe shall be
padded.
8.2 If the pipeline protective coating suffers damage between the coating and laying operations, thedamaged portion of the coating shall be replaced or repaired in accordance with this
specification.
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