Zhang Lian
(Langfang Donghua Anticorrosion Engineering Co., Ltd., Langfang City, Hebei Province 065000)
I. History
1974 successfully developed the first generation of epoxy coal tar pitch coating, and 1979 successfully developed the second generation. 1987, the Ministry of Petroleum compiled the technical standard SYJ 28-87 for epoxy coal tar pitch coating of buried steel pipelines. 199 1 year formulated the code for construction and acceptance of epoxy coal tar pitch anticorrosive coating for buried steel pipelines (SYJ 4047-90). 1996, the Ministry of Petroleum merged and revised the above two standards again, and promulgated the China oil and gas industry standard.
The first batch of epoxy coal tar pitch coating samples 1974 were buried in Daqing, Qinhuangdao, Zhengzhou, Wuhan, Zhanjiang and other places. 1982, the second generation product GH2 was used for anti-corrosion of the first station of Qinhuangdao Oil Transmission Company11km φ 720mm pipeline. The first time is the largest industrial use, and the effect is still very good. The coating is tightly bonded and as hard as ever.
Typical anticorrosion projects using epoxy coal tar pitch paint include underground water pipes in front of the Military Museum of Beijing Water Supply Company, Harbin gas pipe network, and water supply pipes with a diameter of 2.2m over 40 kilometers in the first and second phases of Beijing Water Source No.9 Factory, which have been used normally for nearly 20 years, creating a precedent for external anticorrosion of large-diameter water supply pipes in China.
Examples of the application of epoxy coal tar pitch coating in the corrosion protection of petroleum storage tanks and other petrochemical equipment include the overhaul of the top of the first station in Binnan, Shengli Oilfield 1990,1KLOC-0/5000 m3 oil tank, 1989 anti-corrosion of activated sludge tank (concrete tank) in Asian Games Village Sewage Treatment Plant, and anti-corrosion of activated sludge tank and sewage pipeline in Beijing Gaobeidian Sewage Treatment Plant.
At present, epoxy coal tar pitch coating has been applied to tap water, gas, natural gas, heating and other pipelines in petroleum, chemical industry, electric power, urban public facilities and other industries, and it is a widely used anticorrosive coating in China.
Second, experience
After more than 20 years of application practice, it is concluded that the epoxy coal tar pitch coating has the following advantages and disadvantages.
Advantages:
1, the anticorrosion coating has stable performance and long service life.
2, the construction is convenient, the coating is naturally cured, heating equipment is not needed, and the construction can be mechanized, semi-mechanized or manual.
3. The coating cost is relatively low, and its comprehensive cost (including transportation, processing, loss, etc.). ) is lower than that under the same derusting condition.
There are also anti-corrosion materials, similar to petroleum asphalt.
4. After more than 20 years of experience, the Ministry of Petroleum has developed a set of epoxy coal tar pitch anticorrosion from design to construction.
Technical standards, indicating that its technology is mature and reliable.
Disadvantages:
The curing reaction of 1. coating is affected by temperature. Low temperature (below 10℃) is slow to maintain, and winter construction in the north is limited.
2. At present, coating manufacturers are all over the country, and low-priced and inferior products impact the market, affecting the engineering quality and damaging the image of epoxy coal tar pitch.
3, because a small amount of solvent can be added in the construction, it is easy to provide some construction units with opportunities to cut corners (adding excessive solvent to dilute the paint to reduce costs).
4. Because it is two-component, the proportion of curing agent is inaccurate or uneven in site construction, which often leads to poor curing or uneven quality after curing.
5. Glass cloth is used in the coating, which contains wax and affects the adhesion between layers.
Third, innovation.
Zhang Lianyuan, general manager and senior engineer of Donghua Company, is the person in charge of the second generation epoxy coal tar pitch development project. After summing up the experience and lessons of application practice for more than 20 years, he invented a new type of epoxy coal tar pitch anticorrosive material-epoxy coal tar pitch cold winding tape, and obtained the patent of China (patent number ZL 98205622.2).
Epoxy coal tar pitch cold winding tape consists of cold winding tape and rubber compound. The cold-rolled strip is made of polypropylene non-woven felt impregnated with epoxy coal tar pitch paint by cutting and rolling. The standard cutting width is 125mm and 250mm, and the length of each roll is 20m and 40m (it can also be adjusted according to the special requirements of users). According to the thickness, it can be divided into strengthening level and Gatt strong level. Sizing glue is composed of component A and component B, which can be divided into two types according to the use temperature: permanent tissue temperature type (used above 5℃) and low temperature type (used only below 5℃). The products are equipped with cold winding tape and setting glue when they leave the factory. During construction, the components A and B of the curing adhesive are mixed in equal amount, and then coated on the surface of the protected object according to the structure of curing adhesive-cold winding tape-curing adhesive, and naturally cured after standing, thus forming an epoxy coal tar pitch anticorrosive layer.
The characteristics of epoxy coal tar pitch cold rolled strip are as follows:
1. The base material of the cold-rolled strip is polypropylene non-woven felt, which is a synthetic fiber with high mechanical strength and good corrosion resistance. The surface is wax-free, so the surface of the anti-corrosion layer is flat, with strong adhesion and few pinholes, and it has excellent electrical and anti-corrosion properties.
2. The curing glue adopts a special formula, so that the curing speed of the anticorrosive coating is fast, the construction period is short, and it can be constructed normally all year round, thus solving the construction problem in winter.
3. The construction is convenient and quick. The reinforced or extra-reinforced anticorrosive coating required by China petroleum and natural gas industry standard SY/T 0447-96 can be coated once, which is more labor-saving and convenient than using epoxy coal tar pitch paint and glass cloth.
Fourth, technical performance.
According to China petroleum and natural gas industry standard SY/T 0447-96, the technical performance of epoxy coal tar pitch cold winding tape was confirmed to meet the requirements of the industry standard by China Petroleum and Natural Gas Pipeline Research Institute (1August 1999) and Henan Product Quality Supervision and Inspection Institute (165438+20001October).
Table 1 Comprehensive Properties of Cold Rolled Strip (Setting Glue-Cold Rolled Strip-Setting Glue Structure)
Management Science Research Institute Henan Quality Supervision Research Institute project unit line standard product index test result number
test result
1 dry surface h ≤ 4 ≤11_ _
Strive for H ≤16≤ 64 _ _
2 color and appearance: black with light, black with light,
shop front
No empty drum, tight bonding, black light,
The surface is flat and meets the standard.
ask
3 Thickness strengthening grade ㎜ 0.4 ≥ 0.59 0.59 _ _ _ _
Special strengthening grade ≥ 0.6 ≥ 0.60.71_ _
4. The enhanced level of electric spark leak detection kV ≥ 2.5 ≥ 2.5 3.0 _ _ _ _ _.
Special reinforcement grade ≥ 3.0 ≥ 3.0 5.0 _ _ _ _
5 Cohesion
(180 peeling) n/≥1220.2 ~ 21.7 _ _ _ _
6 impact resistance? ㎝ ≥50 _____ 50 ______
7 power frequency electrical strength mv/m ≥ 20 _ _ _ _ _ _ _ _ > 20
8 volume resistivity ω? m≥ 1× 10 10 _ _ _ _ _ _ _ _ _ _ _ 2.9× 10 12
How to use verbs (short for verb)
1, surface treatment. Remove loose materials such as oil stains and dust on the surfaces of steel, wood and cement to expose a flat and solid surface. Poor treatment will affect the adhesion and reduce the coating quality. The higher the surface treatment quality, the longer the coating life.
2. Apply setting glue. The compound is divided into component A and component B, which are mixed according to the ratio of 1: 1. After mixing evenly, brush evenly and fully, without omission.
3, wrapped in cold tape. Winding or pasting the cold-rolled strip immediately after coating the sizing agent, and the bonding state of the sizing agent must be maintained. If the gluing time is too long, it must be glued again before winding the tape. After winding the cold winding tape, apply the sizing adhesive again. If the corrosive environment is harsh and high insulation performance or protection is required when backfilling the trench, a layer of cold adhesive tape or a layer of solidified adhesive can be coated. The construction method is the same as above, which plays a double-layer protection role.
Economic indicators of intransitive verbs
The construction method of epoxy coal tar pitch cold winding belt is relatively simple, and it can be glued as soon as possible, which can save a lot of labor costs and corresponding management fees (secondary charges). One layer of reinforced cold-rolled strip can reach the reinforcement level stipulated in petroleum industry standard SY/T 0447-96, and one layer of super-reinforced cold-rolled strip can reach the super-reinforced standard. (See Table 2)
Table 2
The SY/T 0447-96 standard requires GH4 cold-rolled strip.
Thickness of anticorrosion grade coating
(㎜) Resistance detection voltage
(5) Resistance of the model to detection
(5) Coating thickness
(㎜)
Strengthening grade ≥ 0.4 2500 Strengthening grade 2500 0.4
Special reinforcement grade ≥ 0.6 3000 Special reinforcement grade 3000 0.6
Comprehensive cost analysis of common pipeline anticorrosion coatings at home and abroad. (See Table 3)
Table 3
Comprehensive cost of serial number variety manufacturing method (yuan/㎡)
1 polyethylene sheath melt extrusion method 65-75
2 powder epoxy polyethylene sheath three-layer coating electrostatic spraying, melt extrusion 90- 100.
3 Polyethylene tape, rubber adhesive and polyethylene tape 55-65
4. 70-80 parts of coal tar enamel and non-woven glass felt are hot-poured.
5 Hot pouring petroleum asphalt coating and glass cloth 55-65
6 epoxy coal tar pitch coating cold coated glass cloth 50-60
7 epoxy coal tar pitch cold winding belt cold winding belt plus setting glue 50-55.
Seven. Comparison of comprehensive properties of pipeline external anticorrosion coating
Practice has proved that all kinds of anti-corrosion coatings have their unique advantages and disadvantages and applicable conditions. Each anti-corrosion project should be comprehensively verified and optimized according to its corrosive environment, climatic conditions, working conditions of conveying media, service life requirements, investment tolerance, supply of goods and other factors.
See Table 4 for the main performance comparison of the above seven anti-corrosion coatings.
Table 4 Comparison of Comprehensive Properties of External Anticorrosion Coating of Pipeline
material
Engineering petroleum asphalt anticorrosive coating polyethylene
Adhesive tape extrusion polymerization
Ethylene layer melted epoxy resin
Powdered coal tar
Enamel coated epoxy coal
Asphalt layer epoxy coal asphalt cold winding belt
Excellent electrical insulation performance.
Cathodic protection has excellent electrical shielding.
Excellent chemical stability.
Mechanical properties are poor, excellent, medium and good.
Anti-microbial erosion is poor, excellent and excellent.
Tu bu you, poor you, poor you.
This is good for the ecological environment.
The service life is poor, good and excellent.
Low comprehensive cost (second floor)
(Three floors) High, high, low, medium and low.
Note: the performance comparison ranking is excellent, good, medium and poor; The comprehensive cost is ranked by high, medium and low.
Eight. conclusion
The epoxy coal tar pitch cold-rolled strip has obtained the national patent (patent number ZL 98205622.2), and Langfang City has issued the production license (Langfang Xuban 1 106). Since 1996, mass production has started, and the technical supervision department of Langfang City has rated it as 200 1 reliable product.
The epoxy coal tar pitch cold-rolled strip is cheap, easy to construct and can be used immediately. After curing, the coating has high mechanical strength, excellent electrical and chemical properties, and can be used in low temperature and wet conditions. The coating thickness is uniform and the construction quality is stable. The coating has the properties of corrosion resistance, waterproof, acid and alkali resistance, impact resistance, low temperature resistance and high temperature resistance.
Cold winding belt can be widely used in oil and gas transportation, water transportation and pipelines, chemical plants, sewage treatment plants, oil tank bottoms and crude oil storage tanks, and can also be used for roofing waterproof and basement waterproof and moisture-proof projects.