This standard applies to the design, material inspection, construction and acceptance of buried steel pipeline anti-corrosion projects using coal tar enamel outer corrosion layer. SY/T 0379-1998 Technical Standard for Coal Tar Enamel Outer Anti-Corrosion Layer of Buried Steel PipelineSY/T0379-1998 Standard download decompression password: www.bzxz.net

1 General Principles
Petroleum and Natural Gas Industry Standard of the People's Republic of China Coal Tar Enamel for Buried Steel Pipeline
Technical Standard for External Anticorrosion Layer
Approval Department: State Administration of Petroleum and Chemical Industry Date of Approval: 1999-03-03
Effective Date: 1999-10-01
SY/T 0379-1998
Replaces SY/T0079-1993
1.0.1 This standard is formulated to ensure the engineering quality of coal tar enamel external anticorrosion layer and extend the service life of buried steel pipelines. 1.0.2 This standard applies to the design, material inspection, construction and acceptance of anticorrosion engineering of buried steel pipelines using coal tar enamel external anticorrosion layer.
1.0.3 In addition to complying with this standard, the design and construction of coal tar enamel external anticorrosion layer of buried steel pipelines shall also comply with the provisions of the relevant current national mandatory standards.
2 Terms
2.0.1 Synthetic primer Synthetic primer is a liquid coating composed of chlorinated rubber, synthetic plasticizer and solvent. This primer produces good bonding between the coated metal and coal tar enamel.
2.0.2 Coal tarenamel coal tarenamel is a product obtained by heating and boiling the heavy fraction and coal tar obtained by high-temperature coal tar fractionation, adding coal powder and filler. 2.0.3 Inner-wrap
It is a ribbon-shaped glass fiber felt bonded with a heat-resistant adhesive compatible with coal tar enamel and reinforced with glass fiber bundles in the longitudinal direction. It is wrapped in the coal tar enamel layer to improve the mechanical properties of the anti-corrosion layer. 2.0.4 Outer-wrap
is a tape made of thickened glass fiber felt bonded with a heat-resistant adhesive compatible with coal tar enamel and reinforced with glass fiber bundles in the longitudinal direction, and uniformly impregnated with coal tar enamel. It is wrapped around the outermost layer of coal tar enamel to enhance the ability of the anti-corrosion layer to resist external mechanical effects.
2.0.5 Hot-applied tape is a tape made of glass felt or polyester fiber felt (i.e. base felt) bonded with a heat-resistant adhesive compatible with coal tar enamel and coated with a thicker coal tar enamel. It is hot-baked and pasted on the surface of the steel pipe or the coal tar enamel layer as an anti-corrosion layer for special-shaped pipe fittings and patching and wound repairs.
3 Materials
3.1 Technical conditions of materials
3.1.1 Primer
1 Coal tar enamel matching primer should adopt synthetic primer, and its technical indicators should meet the requirements of Table 3.1.1. When tested in combination with coal tar enamel, it should also meet the requirements of Table 3.1.2-2. 764
Table 3.1.1 Technical indicators of synthetic primer
Flow time (No. 4 cup, 23℃) (s)
Flash point (closed cup) (℃)
Volatile matter (105~110℃) (%)
Drying time
(25℃)
Table thousand (min)
Actual drying (h)
The performance of the primer matching with hot baking tape should meet the requirements of the manufacturer. 2
Coal tar enamel
SY/T 0379—1998
Test method
GB/T 6753.4—1986
GB/T 6753.5 ~ 1986
GB/T 6751—1986
GB/T 1728-1979(89)
Coal tar enamel is divided into three types: A, B and C. Their performance shall comply with the requirements of Table 3.1.2-1. The combined technical indicators of the primer and enamel applied on the steel test piece shall comply with the requirements of Table 3.1.2-2. Table 3. 1, 2-1
Softening point (ring and ball method) (℃)
Pin penetration (25℃; 100 g; 5 s)
Pin penetration (46℃; 50g; 5s)
(10-1 mm)
Ash content (mass) (%)
Relative density (balance method) (25℃)
Filler sieve residue (rainbow 200×50/0.063
Technical indicators of coal tar enamel
104~116
10～20
15～55
25～35
GB/T600 3—1985 test sieve)?(mass) (%)B
104～116
5～10
①National standard GB/T6003—1985 has been replaced by GB/T6003.1~6003.2—1997C
120130
3～16
25-~35
Editor's note.
Table 3. 1, 2-2
Technical indexes of coal tar sealant and primer combinationNo.
(71℃; 90°, 24 h)(mm)
(80℃; 90; 24 h)(mm)
Peel test
(-29℃)
Low temperature cracking test
(—23℃)
(20℃)
Impact test (25℃, peeling area) (10*mm2)A
No peeling
No peeling
Test method
GB/T4507—1984
SY/T 0526. 3-—1993
SY/T 0526. 3--1993
SY/T 0526.11—1993
GB/T 4472—1984
GB/T 5211. 18—1988
Test methods
SY/T 0526.7—1993
Appendix A to this standard
SY/T 0526.12—1993
Appendix B to this standard
SY/T0379--1998
2The conditions for use of the three types of enamel paints, A, B and C, shall comply with the provisions of Table 3.1.2-3. Table 3. 1.2-3
Using temperature of coal tar enamel anti-corrosion layer
Peeling depth
(25℃; 100 g; 5 s)
(10-1 mm)
3.1.3 Inner and outer tapes
Lowest transportable
Ambient temperature
Standstill state
Lowest temperature
Transportation in pipe
Medium temperature
25~~70
20~~70
-5 ~~80
1 Appearance
1) The surface of the inner tape should be uniform, and the glass fiber reinforcement ribs should be arranged parallel and equidistantly along the longitudinal direction, without holes, cracks, fiber floating, edge damage and other impurities (grease, dirt, etc.). 2) The surface of the outer wrapping tape should be uniform, the glass fiber reinforcement and glass felt should be well combined, without holes, cracks, edge damage, poor impregnation and other impurities (grease, dirt, etc.), and the surface should be evenly spread with mineral particles. 2 Technical performance
1) The technical indicators of the wrapping tape should comply with the provisions of Table 3.1.3-1. 2) The width of the wrapping tape can be selected according to different pipe diameters with reference to Table 3.1.3-2. Table 3. 1. 3-1
Technical indicators of wrapping tape
Weight per unit area (g/m2)
Thickness (mm)
Tensile strength
Longitudinal (N/m)
Transverse (N/m)
Flexibility
Weight loss on heating (%)
Tear strength
Air permeability (Pa)
Longitudinal (g)
Transverse (g)bZxz.net
Technical indicators
Inner wrapping tape
≥2280
≥700
≥100
Note: The weight per unit area of ​​the thickened glass fiber felt used for the outer wrapping tape should not be less than 83g/m2. ①National standard GB/T451.3--1989 has been replaced by GB/T451.3--2002—Outer tape
580~~730
≥6130
≥4730
Editor's note.
Table 3. 1. 3-2
Pipe diameter (mm)
Band width (mm)
Band width and pipe diameter comparison table
159457
150300
457-720
300~~400
Test method
Appendix C of this standard
GB/T 451.3--1989@
Appendix D of this standard
SY/T0526.18--1993
Appendix E of this standard
GB/T 11999—1989
Appendix F of this standard
3) When the tape roll is opened at 0-38℃, the layers of the tape should be able to separate and will not be torn due to adhesion. SY/T0379—1998
4) The tape should be compatible with the coal tar enamel used in conjunction with it, and its structure and adhesive content should ensure that the enamel can penetrate well under normal coating conditions.
3.1.4 Hot-baked wrapping tape
1 Appearance
It should have a uniform appearance and uniform thickness. Both sides of the base felt should be fully covered with coal tar enamel, and there should be no phenomenon of enamel peeling off from the fiber base felt. 2 Technical performance
1) The thickness should not be less than 1.3mm, and the width deviation should not be greater than 1.6mm; 2) The adhesion should pass the adhesion test specified in "Adhesion Test of Hot-baked Wrapping Tape Covered with Coal Tar Enamel Paint" SY/T0526.22;
3) The enamel paint of the wrapping tape should be consistent with the performance of the enamel paint used on the pipe body; 4) At temperatures above 25℃, the wrapping tape should have sufficient flexibility, and the coal tar enamel paint will not peel off from the fiber base felt when the wrapping tape is unfolded;
5) When heating and baking the wrapping coating, the wrapping tape will not be torn or broken due to uniform and moderate tension. 3.1.5 Additional protective materials
1 Sunscreen paint
i) Types
a) A mixture of calcium carbonate powder, boiled linseed oil, water and sodium chloride; b) A water-floating latex paint composed of a water-insoluble polymer emulsion and white pigment; c) Other white paints.
2) Performance
It should have good adhesion with the coal tar enamel anti-corrosion layer, be water-resistant, and the paint film can withstand 90 days of exposure without damage. 2 Other additional protective materials
When the user deems it necessary, other additional protective materials such as kraft paper and rock-proof plastic grids can be used, and their performance should meet the requirements of the corresponding standards.
3.2 Material acceptance
3.2.1 Marking
The material should have a quality certificate when leaving the factory. The material packaging should have a durable product mark indicating the following: 1 Material name;
2 Material model;
3 Product standard number;
4 Production batch number or date;
5 Manufacturer name and address.
3.2.2 Inspection report and instruction manual
The manufacturer should provide an inspection report and material instruction manual, which should also include transportation and storage precautions. 3.2.3 Product packaging
1 Enamel paint can be bulked; it can also be packed in paper bags, each bag should not be more than 50kg, and the paper bag must be easy to peel off from the enamel; it can also be packed in metal barrels not larger than 2001.
2 The matching primer of enamel paint should be packed in steel drums not larger than 200I. or metal containers of 20L. 3 Tape rolls should be well packaged in plastic bags and cartons. 4 The matching primer of hot baking tape should be packed in 4L or 20L metal containers. 3.2.4 Sampling inspection
When sampling inspection of materials is required, the supplier and the buyer shall conduct sampling inspection of the products according to a certain proportion. The sampling shall be representative. Each 767
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sample is divided into two parts, one for the supplier and one for the buyer. The buyer shall inspect the materials according to Section 3.1 of this standard, and its performance shall meet the requirements.
3.2.5 Material matching
Enamel paint and primer used in conjunction shall be produced by the same manufacturer. 2Hot baking tape and matching primer shall be produced by the same manufacturer. 3Materials used for patching, repairing and anti-corrosion of special-shaped pipe fittings should be produced by the same manufacturer that supplies the anti-corrosion materials for the pipe body. 3.3Material storage
3.3.1Primer
should be stored in the original sealed container in a cool and dry place. Avoid heat and keep away from fire. 3.3.2 Enamel paint
should be stored in a cool place. When placed in the open air, it should be covered with bitter cloth. 3.3.3 Tape
should be stored in a cool and dry place at a temperature below 38°C to avoid moisture. 4 Anti-corrosion layer grade and structure
4.0.1 Anti-corrosion layer grade:
The outer anti-corrosion layer of coal tar enamel is divided into three grades: ordinary, reinforced and extra strong. The anti-corrosion layer grade is determined by the design department based on factors such as pipeline construction quality requirements, soil corrosion environment and the use of cathodic protection. 4.0.2 The structure of the anti-corrosion layer shall comply with the provisions of Table 4.0.2. Table 4.0.2 Structure of anticorrosion layer
Grade of anticorrosion layer
Total thickness of anticorrosion layer (mm)
Ordinary grade
One layer of primer
One layer of enamel paint
(Thickness 2.4 mm ± 0.8 mm)
One layer of outer tape
Reinforced grade
One layer of primer
One layer of enamel paint
(Thickness 2.4 mm ± 0.8 mm)
One layer of inner tape
One layer of enamel paint
(Thickness ≥ 0.8 mm)
One layer of outer tape
Extra-strong grade
One layer of primer
One layer of enamel paint
(Thickness 2.4 mm±0.8mm)
One layer of inner tape
One layer of enamel
(thickness ≥0.8mm)
One layer of inner tape
One layer of enamel
(thickness ≥0.8 mm)
Outer tape
Note: ① When used as the outer anti-corrosion layer of spiral welded pipe, the thickness of the first layer of enamel shall not be less than 2.4mm, and the total thickness of the anti-corrosion layer shall be increased by 0.8 mm accordingly; the thickness of the anti-corrosion layer at the weld shall not be less than 65% of the total thickness. ② Sunscreen paint or other additional protective materials shall be designed by the design department according to actual needs. 5 Anti-corrosion layer construction
General provisions
5.1.1 The quality of steel pipes shall comply with relevant regulations. Steel pipes shall be free of primer. If there is petroleum asphalt primer, it shall be removed. 5.1.2 All straight pipes shall be anti-corrosion by mechanical operation. It is advisable to adopt the operation process of continuous pouring and winding of one pipe after another to ensure the quality and appearance of the anti-corrosion layer at both ends of the pipe. 768
5.2 Preparation and supply of enamel
5.2.1 Heating kettle and filter
SY/T0379—1998
The heating kettle for melting and pouring coal tar enamel should have a stirring device and a sealed lid, and should be equipped with a calibrated thermometer that can record the temperature curve of the production process.
Before pouring enamel, a filter (preferably with a pore size of 4.00mm) should be installed at the outlet of the kettle to remove debris and granular substances. 5.2.2 Enamel feeding
Before feeding enamel, the model should be carefully checked, and it is strictly forbidden to mix petroleum asphalt and other debris. The enamel should be broken into blocks with an equivalent diameter of no more than 20cm before adding it to the kettle. 5.2.3 Melting and heat preservation of enamel
Heat the solid enamel to melt and raise the temperature to the pouring temperature. When heating, avoid overheating and deterioration of the enamel. After the enamel is melted, whether it is applied or kept warm, the enamel should be stirred frequently. Each stirring time should not be less than 5 minutes, and the stirring time should not be more than 15 minutes. Except for adding materials, the kettle cover should be kept closed. The pouring temperature of each type of enamel, the maximum heating temperature that cannot be exceeded, and the maximum heating time allowed for the enamel at the pouring temperature can refer to the provisions of Table 5.2.3, but the instructions for use of the enamel manufacturer shall prevail. Table 5.2.3 Enamel heating conditions
Casting temperature (℃)
Maximum heating temperature (℃)
At casting temperature
Maximum heating time (h)
5.2.4 Enamel use restrictions
230~250
Enamel model
230~250
240~260
Enamel that exceeds the maximum heating temperature or exceeds the maximum allowable heating time at casting temperature should be discarded and should not be mixed and used. 1
2 The retained penetration (25℃) of the enamel cast on the pipe should not be less than 50% of the original penetration of the enamel, otherwise it is prohibited to use. 3 When melting new enamel, it is allowed to retain some of the enamel that has not been used up on the last heated and melted surface, but the amount should be less than 10% of the total amount of enamel. The swabs should be emptied and cleaned regularly, and the residue in the kettle should be discarded. 5.3 Surface pretreatment of steel pipes
5.3.1 If there is oil on the surface of the steel pipe, it should be cleaned with a suitable solvent and wiped dry with a clean rag. 5.3.2 Use spray (blasting) to remove rust from the surface of the steel pipe. The treated steel pipe surface should reach the minimum Sa2 level specified in "Surface rust level and rust removal level of steel before painting" GB/T8923. 5.3.3 When the surface temperature of the steel pipe is lower than 3°C above the dew point, surface pretreatment should not be carried out, otherwise the steel pipe should be preheated, and the preheating temperature is 40~60°C.
5.3.4 After the steel pipe surface is pretreated, the primer should be applied as soon as possible within 8 hours. The steel pipe surface should be prevented from moisture, rust or secondary pollution before the primer is applied. If the steel pipe surface has rusted before painting, it must be sprayed (blasted) to remove rust again. 5.4 Coating construction
5.4.1 Primer application
1 It is advisable to carry out flow operation for the surface pretreatment and primer application of steel pipes. When the surface temperature of the steel pipe is lower than 7℃ or there is water vapor condensation, the steel pipe should be heated to 30~38℃. Ensure that the surface of the steel pipe is dry and clean when applying the primer. 2 The primer should be stirred evenly before use. The primer can be applied by high-pressure airless spraying, brushing or other appropriate methods. 3 The primer layer should be evenly connected and continuous, without defects such as missing coating and flow marks. The thickness of the primer layer should be 50μm. The primer should be applied at the places where it is missed. 769
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4 The primer layer should be prevented from contacting with rain, snow, water and dust. The primer should avoid contact with other objects outside the pipe wall during drying. 5 If the interval between the application of primer and the application of enamel exceeds 5 days or exceeds the manufacturer's regulations, the primer layer should be removed, the surface should be pre-treated and re-coated, or a thin layer should be applied according to the manufacturer's instructions. 5.4.2 Requirements for the condition of the primer layer for the application of coal tar enamel and wrapping tape 1
The primer should be completely dry and kept clean. The enamel should be applied as soon as possible within 5 days after the application of primer. When the surface temperature is lower than 7℃ or there is moisture, the pipe body should be heated in an appropriate way that will not damage the primer layer to ensure that the pipe surface is completely dry. The temperature of the steel pipe should not exceed 70℃.
2 Applying enamel and winding inner tape
Evenly pour the filtered enamel on the primer layer of the outer wall of the rotating pipe body. It should be ensured that each spiral track of enamel coating is connected with the previous track to form an enamel layer with no leakage and uniform thickness. If the weld is higher than the pipe surface, the amount of enamel should be increased so that the thickness of the enamel on the weld meets the requirements.
After pouring the enamel, the inner tape should be spirally wound onto the steel pipe immediately. The winding should be free of wrinkles and hollows, with a pressure edge of 15 to 25 mm and should be uniform. The joint overlap should be crimped, that is, when the previous roll of tape is almost used up, the end of the next roll of tape is extended into the angle between the previous roll of tape and the pipe surface, so that the next roll of tape is tightly spirally wound onto the pipe from the end. The enamel should seep out from the pores of the inner tape so that the inner tape is neatly embedded in the enamel layer. The depth of the first layer of inner tape should not be greater than 1/3 of the thickness of the first layer of enamel. The number of layers of enamel to be poured and the number of layers of inner tape to be wound should comply with the provisions of the anti-corrosion layer structure in Article 4.0.2 of this standard selected by the design. 3 Wrapping outer tape
After the last coat of enamel is poured, the outer tape should be wound while it is hot. The winding requirements of the outer tape are the same as those of the inner tape. The enamel should seep out evenly, but the amount should be small. The outer tape and enamel should be tightly bonded together, but the outer tape should not be embedded in the enamel layer. 5.4.3 Water cooling and shaping
After the outer tape is wound, it should be water cooled and shaped immediately. When the anti-corrosion layer is not shaped, the anti-corrosion pipe should not be squeezed when it is transported and placed. 5.4.4 Treatment of anti-corrosion layer at the pipe end
The surface of the steel pipe that is not required to be anti-corrosion at the pipe end should be cleaned. The length of the reserved section at the pipe end shall comply with the requirements of Table 5.4.4, and the end face of the anti-corrosion layer shall be processed into a regular slope.
Table 5.4.4 Length of reserved section
Pipe diameter (mm)
Reserved length (mm)
5.4.5 Construction of additional protective materials
159~457
150~200
200～250
When necessary, after the quality inspection of the anti-corrosion layer is passed, apply a layer of sunscreen paint or add other protective materials on the anti-corrosion layer. 5.5 Defect repair
5.5.1 Defect types and repair materials
Defects on the anti-corrosion layer can be divided into three types: pinholes or bubbles, exposed iron and large-area damage. The repair material should be the same as the anti-corrosion layer of the pipe body and produced by the same manufacturer, or hot baking tape can be used. 5.5.2 Repair of pinhole or bubble defects
Use a sharp knife to remove the outer tape of the defective part and clean out the pinhole or bubble. Avoid damaging the surrounding anti-corrosion layer when cleaning. Pour the enamel that has been heated according to the provisions of this standard on the wound and apply it to the specified thickness, and stick a piece of outer tape while it is still hot. 5.5.3 Repair of exposed iron defects
For damage with an area of ​​less than 10000mm2, use a sharp knife to remove the outer tape of the defective part and the enamel that has lost adhesion, and repair the section of the wound anti-corrosion layer into a slope. If the cleaned metal surface is rusted, it should be derusted, and the rust removal level should reach St3 level specified in GB/T8923770
SY/T0379-1998
. Apply primer to the exposed iron surface. After the primer is completely dry, pour the enamel that has been heated according to the provisions of this standard on the wound and apply it to the specified thickness. While it is still hot, apply an outer wrapping tape that is slightly larger than the repaired surface. 5.5.4 Inspection of the repaired anti-corrosion layer
The repaired anti-corrosion layer should be inspected for leaks in accordance with the provisions of Article 6.2.4 of this standard. 5.5.5 Treatment of large-area defects
Pipes with defects such as missing coating, non-adhesive or cracked enamel, large-area pinholes or insufficient thickness should be re-anticorrosive. 5.6 Marking and stacking
5.6.1 After the anti-corrosion layer is inspected and qualified, there should be a mark on the end of the anti-corrosion pipe indicating the steel pipe material, wall thickness, enamel type used and anti-corrosion layer grade. 5.6.2 Anti-corrosion pipes should be neatly stacked according to the steel pipe specifications, coal tar enamel type used and anti-corrosion grade. In the stacking site, wooden blocks and earthen platforms must be set up for pipe supports. The pipe supports should be 150mm above the natural ground. The stacking height should be based on the principle of not damaging the anti-corrosion layer. Steel pipes that fail the anti-corrosion layer inspection shall not be mixed with finished pipes.
5.6.3 Anti-corrosion pipes without sunscreen paint should be kept away from sunlight during storage, and should be covered with bitter cloth when stored in the open air; anti-corrosion pipes with sunscreen paint that need to be placed in the open air for more than 3 months should also be covered with bitter cloth. 5.7 Construction of special-shaped pipe fittings.
5.7.1 Surface pretreatment shall comply with the provisions of Section 5.3 of this standard, and primer coating shall comply with the relevant requirements of Article 5.4.1 of this standard. The treatment requirements for pipe fitting ends are the same as those of Article 5.4.4 of this standard. 5.7.2 The construction method of manually pouring enamel paint and wrapping internal and external tapes can be adopted. When pouring is inconvenient, enamel paint can be applied using a smearing tool. The temperature of pouring enamel paint shall not be lower than that specified by the manufacturer. The total thickness of the anti-corrosion layer shall not be less than the design thickness of the anti-corrosion layer of the pipe body, and its structure shall be the same as that of the anti-corrosion layer of the pipe body. 5.7.3 The construction method of hot baking and winding can be adopted. The hot baking and winding construction shall use matching thick primer, and the thickness of the primer layer shall be greater than 100μm. After the primer is completely dry, use a blowtorch or similar heater to bake the inner surface of the hot baking tape until the enamel is melted, and at the same time, heat the coated surface of the pipe fitting, and then wrap the hot baking tape and stick it to the surface of the pipe fitting. Wrap from one end and bake while wrapping. When wrapping, give the tape a certain tension to make the tape and the pipe body pressed tightly and fully bonded, without leaving hollows, and the edge should be 15~~25mm, and should be evenly hooked, and the joint overlap should be 100~~150mm. The edge positions of each layer should avoid overlapping.
The total thickness of the anti-corrosion layer shall meet the design requirements.
6 Quality inspection of anticorrosion layer
6.1 Quality inspection of production process
6.1.1 Requirements
The anticorrosion pipe manufacturer shall be responsible for the quality inspection of the production process and keep records. 6.1.2 Quality inspection of surface pretreatment
The surface treatment quality of steel pipes after surface pretreatment shall be inspected one by one, and visual comparison shall be made using the corresponding photos or standard samples in the national standard GB/T8923. The quality of surface pretreatment shall meet the requirements of Section 5.3 of this standard. 6.1.3 Penetration inspection
The penetration of enamel paint (25°C) shall be inspected by sampling at the pouring port, and the measured value shall not be less than 50% of the original penetration of enamel paint. 6.1.4 Inspection of primer layer
The primer layer shall be evenly connected and continuous, without missing coating and flow marks, and without dust and other contamination. 6.1.5 Inspection of anti-corrosion layer
The appearance, thickness, leakage points, adhesion and structure of the anti-corrosion layer shall be inspected according to the inspection method specified in Section 6.2 of this standard. 6.2 Inspection of anti-corrosion pipe
6.2.1 Inspection items
The factory inspection of anti-corrosion pipe (or pipe fittings) is carried out on the basis of the quality inspection of the production process. Each batch of products shall be inspected before leaving the factory. The factory inspection items of the products shall include: inspection of the appearance, thickness, leakage points and adhesion of the anti-corrosion layer. 771
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6.2.2 Appearance inspection
1 Visually inspect each pipe. The surface of the anti-corrosion layer shall be uniform and flat, without defects such as bubbles, wrinkles, bulges and uneven hooks of the wrapping edge.
2 The end face of the anti-corrosion layer shall be a neat slope. The length of the reserved section at the pipe end shall comply with the provisions of Table 5.4.4 of this standard. 6.2.3 Thickness inspection
1 Check with a non-destructive thickness gauge.
2 According to the requirements of the anti-corrosion grade, the total thickness of the anti-corrosion layer shall comply with Table 4.0 of this standard.2. The total thickness of the hot-baked tape anti-corrosion layer shall comply with the design requirements.
3 One pipe shall be randomly inspected for every 20 pipes, and three sections shall be measured for each pipe, with the sections evenly distributed along the length of the pipe. Each section shall be measured at four points: top, bottom, left and right. The thinnest point shall prevail. If unqualified, another two pipes shall be randomly inspected. If still unqualified, each pipe shall be inspected one by one. 4 Unqualified pipes shall be downgraded or re-anticorroded. 6.2.4 Leakage point inspection
1 Each pipe shall be fully inspected.
2 The leakage detection voltage shall be calculated according to the following formula.
V= 7843 V t.
Where: V---leakage detection voltage (V);
t-anti-corrosion layer thickness (mm).
(6.2.4)
3 The leak detector probe shall contact the anti-corrosion layer and move at a rate of 0.15-0.30m/s. No spark shall be considered qualified. Unqualified areas should be marked, repainted and leak tested again until qualified. During continuous testing, the leak detection voltage should be calibrated every 4 hours. When the probe stops moving, the power of the leak detector should be turned off or the probe should be moved away from the anti-corrosion layer.
6.2.5 Adhesion and structure inspection
1 After coating, the anti-corrosion layer should be inspected when the temperature is between 10 and 27°C. If the penetration of the enamel on the anti-corrosion layer is less than 10, the temperature during the inspection should not be lower than 18°C. Use a surface thermometer to measure the temperature of the anti-corrosion layer. If the temperature conditions are not met, hot or cold water should be used to adjust the temperature of the anti-corrosion layer and the steel pipe at the test site, and the temperature difference between the anti-corrosion layer and the steel pipe should not exceed 3°C. 2 Due to different materials used, there are two detection methods: 1) For the cast enamel anti-corrosion layer, use a hard and sharp knife with a blade width of 16 to 19 mm to cut two parallel lines about 100 mm long and with a spacing equal to the blade width on the anti-corrosion layer. The anti-corrosion layer should be completely cut through. Place the blade at one end of the parallel lines, so that it is within the two parallel lines and perpendicular to them. Insert the knife into the anti-corrosion layer at an angle of about 45°. The anti-corrosion layer should be completely cut through. Carefully apply uniform thrust to the knife so that the anti-corrosion layer about 13mm long is peeled off the surface of the pipe. Clamp the peeled anti-corrosion layer with your thumb and the knife, and pull it up slowly and steadily together with the knife.
Measure the length of the peeled anti-corrosion layer when it is pulled off. The bonding strength is qualified if the length is not greater than the incision width. At the same time, observe the anti-corrosion layer with a complete cross section. Its structure should comply with the provisions of Table 4.0.2 of this standard. 2) For the hot baking tape anti-corrosion layer, use a hard and sharp knife to cut two parallel lines about 150mm long and about 50mm apart on the anti-corrosion layer. The anti-corrosion layer should be completely cut through. Use the blade to pry up the inner base felt from the end for about 50mm, hold the pried tape tightly with your hand, and quickly pull it to the other end.
Check the situation of pulling off. If: a) the base felt breaks at the prying point or b) the exposed area of ​​the primer and metal under the pulled base felt is not more than 10%, the adhesion is qualified. At the same time, observe the complete anti-corrosion layer of the cross section. Its structure should meet the design requirements. The thickness of the enamel layer between the steel pipe surface and the fiber base felt should be not less than 0.4mm. 3 Measure one point on a pipe. If the inspection of the test point fails, two more tests should be conducted on the same pipe (or pipe fitting) at two different locations more than 0.9m away from the inspection point. If both tests are qualified, the pipe can be considered qualified; if one fails, the pipe is unqualified.
4 Every 20 pipes are a batch, and 1 pipe is randomly inspected in each batch. If it fails, 2 pipes are randomly inspected. If there is still 1 unqualified pipe, all are unqualified. 772
5 Anti-corrosion pipes that fail the adhesion and structure inspections should be re-anticorrosive. 6.3 Type inspection of anti-corrosion pipes
SY/T 0379—1998
6.3.1 For each continuous production of no more than 200 anti-corrosion pipes or when there are changes in the purchase batches of different raw materials or in the production process conditions, a type inspection of the sub-products shall be carried out.
6.3.2 Type inspection items of products:
(1) The quality inspection of the anti-corrosion layer shall comply with the provisions of Articles 6.2.2 to 6.2.5 of this standard. (2) When the raw materials change, the raw materials shall still be inspected. The technical conditions of the raw materials shall comply with the provisions of Section 3.1 of this standard.
7 Patching and repairing
7.1 Patching
7.1.1 The end face of the anti-corrosion layer at the pipe end shall be a neat slope, otherwise it shall be processed. The quality of rust removal on the surface of exposed steel pipes shall reach the Sa2 level specified in the national standard GB/T8923. After rust removal, primer shall be applied immediately, and the application of primer shall comply with the relevant provisions of this standard. 7.1.2 Patching with hot-baked tape:
Apply in accordance with Article 5.7.3 of this standard. The overlap length of the patching anti-corrosion layer and the pipe body anti-corrosion layer shall not be less than 150mm. 7.1.3 Patching with enamel pouring:
Prepare enamel in accordance with Section 5.2 of this standard and apply in accordance with Article 5.7.2 of this standard. The overlap length of the patching anti-corrosion layer and the pipe body anti-corrosion layer shall not be less than 150mm.
7.1.4 Inspection of patch anti-corrosion layer:
1 Appearance inspection shall be carried out in accordance with Article 6.2.2 of this standard; 2 Thickness inspection shall be carried out in accordance with the method specified in Article 6.2.3 of this standard. For each patch, select the top, bottom, left and right points for inspection. The thinnest point shall prevail. The thickness shall not be less than the thickness of the anti-corrosion layer of the pipe body; 3 Leakage point inspection shall be carried out in accordance with Article 6.2.4 of this standard; 4 Adhesion inspection method shall be carried out in accordance with Article 6.2.5 of this standard. When the test temperature conditions cannot be met on site, the following method can be used for testing:
Inspection shall be carried out when the temperature of the anti-corrosion layer is between 10 and 35°C. Use a thin and sharp knife to cut out a 50mm×50mm square block on the anti-corrosion layer. The anti-corrosion layer should be completely cut through to the metal surface. Operate carefully to avoid damage to the small square. Insert the knife into the enamel between the first layer of tape and the pipe body, and gently pry up the small square. Observe the pipe surface after prying up the anti-corrosion layer. If there is no obvious separation between the enamel and the primer, or between the primer and the pipe body, and the area of ​​any continuous separation interface is less than 80mm2, the adhesion is qualified. At the same time, observe the anti-corrosion layer with a complete cross section, and its structure should comply with the provisions of Table 4.0.2 of this standard. Every 20 ports are a batch, and one point on each port is randomly checked in each batch. If it is unqualified, two ports are randomly checked again. If there is still one port that is unqualified, all are unqualified.
7.1.5 Unqualified ones must be repaired or reworked until they pass the inspection, and the results of each inspection must be recorded for reference. 7.2 Repairing damage
7.2.1 The repair of defects and damages of the anti-corrosion layer shall be carried out in accordance with the relevant provisions of Section 5.5 of this standard. For damages with an area greater than or equal to 10000mm2, it is advisable to use hot baking tape for repair. When repairing, the outermost layer of hot baking tape should be wrapped around the pipe body for one week. It can also be repaired with the same material and the same anti-corrosion layer structure as the pipe body anti-corrosion layer. Before repairing, a sharp knife should be used to remove the outer tape and the enamel paint that has lost its adhesion at the defective part, and the cross section of the anti-corrosion layer should be repaired into a slope. If the cleaned metal surface is rusted, it should be rust-removed, and the rust removal level should reach the St3 level specified in the national standard GB/T8923. All anti-corrosion layer repairs should be inspected for leaks according to the method specified in Article 6.2.4 of this standard, and the thickness of the repaired anti-corrosion layer with an area greater than or equal to 10000mm2 should be inspected according to the method specified in Article 6.2.3 of this standard. Those that fail to meet the requirements should be repaired again until they meet the requirements. 7.2.2 Other materials for repairing and patching:
In addition to the hot-baked tape and coal tar enamel materials included in this standard, other materials with good adhesion to coal tar enamel and equivalent anti-corrosion performance can also be used for repairing and patching after consultation between the design department and the user, and the corresponding construction and acceptance specifications should be implemented. 8 Loading, unloading, transportation, trenching and backfilling
8.0.1 The loading, unloading, transportation, pipe laying, leak inspection of the anti-corrosion layer before trenching, trenching and backfilling of anti-corrosion pipes shall comply with the relevant requirements of the "Oil and Gas Pipeline Line Engineering Construction and Acceptance Specifications" SY0401. 8.0.2 The transportation and trenching operations shall be carried out under the condition of air temperature above the lowest ambient temperature for transportation. Special wide slings shall be used for hanging pipes. When the anti-corrosion layer without sunscreen paint is softened by exposure, the anti-corrosion layer shall not be touched. 8.0.3 The anti-corrosion layer shall be protected from the influence of sunlight. Anti-corrosion pipes without sunscreen paint shall be covered with bitter cloth during transportation; when placed for a long time, the requirements of Articles 5.6.2 and 5.6.3 of this standard shall be met. 8.0.4 Anti-corrosion pipes shall not be trampled or walked on. If necessary for construction, soft-soled shoes such as rubber shoes must be worn. 9 Labor hygiene, safety and environmental protection
9.0.1 Construction units should formulate labor safety and hygiene regulations and equip fire-fighting equipment. 9.0.2 Primer is flammable. Fire prevention should be taken into consideration during storage and use. 9.0.3 Workers at the enamel heating kettle, pouring nozzle and pouring and patching positions, as well as workers doing on-site patching and patching, should wear labor protection equipment (gas masks, goggles, protective clothing and gloves) and apply anti-scald ointment on exposed skin. 9.0.4 The safety of the pre-treatment process and ventilation purification should comply with the requirements of the national standard "Safety Regulations for Coating Operations - Safety of Pre-treatment Process for Coating" GB7692. The work site should be well ventilated. The mandatory exhaust conditions of the fume at the pouring port must be guaranteed to prevent the escape of fume. The anti-corrosion operation line must be equipped with a fume treatment device. The discharge of waste gas and wastewater should meet the relevant provisions of "Asphalt Industry Pollutant Emission Standard" GB4916.
10 Delivery Materials
10.0.1 After the anti-corrosion construction is completed, the construction unit shall provide the following documents to the user: 1 Factory certificate and inspection report of enamel paint, primer and wrapping; 2 Anti-corrosion pipe material certificate and re-inspection report, anti-corrosion layer quality inspection report and factory certificate; 3 Patching construction record and inspection report;
Repair record and inspection report;
5 Other relevant information required by the user.
Appendix A
Test method for peeling off the anticorrosive coating of coal tar enamel This method is equivalent to the test method of ANSI/AWWAC203-1991 "Coal Tar Protective Coatings and Linings for Steel Water Pipes (Hot-applied Enamels and Tapes) - Laboratory Peeling Test", and is applicable to the peeling off test of the anticorrosive coating of coal tar enamel. A.1 Instruments and Materials
A.1.1 Constant temperature water bath: temperature control accuracy ±1°C. A.1.2 Constant temperature box: temperature control accuracy ±1°C. A.1.3 Steel plates: two pieces, 305mm×305mm×13mm. A.1.4 Knife: total length is about 180mm, the blade is medium hardness steel, thickness is 3.2mm, the blade width is 16~19mm, and the blade is an angle of 40°~50°.
A.2 Sample preparation
SY/T 0379—1998
A.2.1 Use spraying to remove rust from the steel plate surface. The rust removal level should be at least Sa2 as specified in GB/T8923, and ensure that the surface is clean and dry.
A.2.2 Apply primer to the steel plate surface. The primer should be uniform and the thickness should be about 50μm. A.2.3 Melt 2 to 5 kg of enamel fragments not larger than 100mm. The melting temperature should not exceed the coating temperature of the enamel. Stir continuously during the melting process, and the container should be covered to prevent the light components of the enamel from volatilizing. A.2.4 After the primer is completely dry, pour the melted enamel on the horizontally placed steel plate, adjust the inclination angle of the steel plate or use a scraper to make the thickness of the enamel layer on the steel plate reach 1.6~2.4mm. A.2.5 Cool the enamel-coated steel plate to room temperature. A.3 Test procedures
A.3.1 Laboratory peeling test (12h)
Place the first steel plate with the enamel side facing upwards horizontally at room temperature for 12 to 24h, and then place it in a water bath at (27±1)℃ for half an hour.
Take the steel plate out of the water bath and immediately cut two parallel lines 102mm long and 19mm apart through the enamel layer with a knife. At one end of the two parallel lines, place the blade within the two parallel lines and perpendicular to them, insert the blade into the enamel layer at an angle of 45°, and ensure that the entire blade is in contact with the steel plate, apply a uniform thrust, and remove the enamel layer about 13mm long from the steel plate. Then, place the blade under the enamel strip, clamp the enamel strip with the thumb and the knife, and slowly and steadily pull it upward until it breaks. Repeat the above test at temperatures of (38±1)℃, 49±1)℃, (60±1)℃, and (71±1)℃, respectively. If the penetration of the enamel at 25℃ is less than 10, the peeling test at 27℃ may not be performed. A.3.2 Laboratory peeling test (72h)
Place the second steel plate with the enamel side facing upward in a constant temperature box at (71±1)℃ for (72±2)h. Then, remove the steel plate from the constant temperature box and cool it to room temperature.
According to the method specified in A.3.1, the coal tar enamel anticorrosive layer peeling test is carried out at (27±1), (38±1), (49±1), (60±1), and (71±1)℃ respectively. If the penetration of the enamel at 25℃ is less than 10, the peeling test at 27℃ may not be performed. A.4 Test results
A.4.1 Measure and record the length of the enamel strip peeled off before breaking. If it does not exceed 3.2mm, it is judged as "no peeling". Appendix B
Method for impact test of coal tar enamel anti-corrosion coating This method is equivalent to the test method of ANS1/AWWAC203-1991 - Laboratory impact test, and is applicable to the impact test of coal tar enamel anti-corrosion coating.
B.1 Instruments and materials
B.1.1 Constant temperature water bath: temperature controlled at (25 ± 1) °C. B.1.2 Falling ball impact test apparatus:
1 Falling ball guide tube: length greater than 2.45m, with height scale, smooth inside of the tube to ensure free fall of the steel ball. 2 Steel ball: mass 650g, polished surface.
3 Wooden board with smooth surface - one piece1 Constant temperature water bath: temperature controlled at (25 ± 1) °C. B.1.2 Drop ball impact tester:
1 Drop ball guide tube: length greater than 2.45m, with height scale, smooth inside to ensure free fall of steel ball. 2 Steel ball: mass 650g, polished surface.
3 Smooth and flat wooden board - one piece1 Constant temperature water bath: temperature controlled at (25 ± 1) °C. B.1.2 Drop ball impact tester:
1 Drop ball guide tube: length greater than 2.45m, with height scale, smooth inside to ensure free fall of steel ball. 2 Steel ball: mass 650g, polished surface.
3 Smooth and flat wooden board - one piece
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