corrosion protection
1. Type of parts for anticorrosion treatment
1) Under corrosive soil and water environment conditions, the outer surface of the pipeline shall be treated with epoxy coal tar pitch for anticorrosion.
2) permanently exposed steel structure members (such as flange short pipes).
3) Short-term anticorrosion treatment of steel surface (socket steel ring, etc.) coating. ).
2. Corrosion protection of external surface of pipeline
1) range
Including standard pipelines, special-shaped pipelines and fittings in designated areas, and epoxy coal tar pitch corrosion protection on the surface of pipeline mortar protective layer. Anti-corrosion treatment: one primer and two topcoats, with a total thickness of 400μ m..
See table 5.4- 1 for the anticorrosion scope of epoxy coal tar pitch.
Table 1 Anticorrosion Scope of External Surface of Pipeline
2) Technical indicators of anticorrosive coatings
(1) quick-drying ultra-thick slurry epoxy coal tar pitch coating is used as the anticorrosion layer. The technical indexes of epoxy coal tar pitch coating, that is, the technical indexes of the paint film after component A (coating), component B (curing agent) and component A and component B are mixed in proportion and sprayed according to the specified method, shall be no less than Table 3. 1.2- 1 in SY/T0447 "Technical indexes of epoxy coal tar pitch anticorrosive coating for buried steel pipelines".
3. 1.2-2 and 3. 1.2-3; Not less than the requirements in Table 5.4- 1 of technical terms.
Table 2 Quality indexes that epoxy coal tar pitch coating should meet at the same time
⑵ Coatings shall have factory certificate, product specification, batch number and coating process parameters.
(3) The contractor shall reinspect the quality indicators of each batch of coatings and provide the reinspection report.
3) surface pretreatment
(1) During anti-corrosion construction, the water content of cement mortar protective layer should not be greater than 6%, and there is no water stain on the surface.
(2) Remove cement slag and loose objects on the surface with manual or electric tools, and then clean the surface with a clean brush, compressed air or industrial vacuum cleaner.
4) coating configuration
(1) The epoxy coal tar pitch coating should be placed in a cool, ventilated and dry place, and it is forbidden to expose to the sun or get close to the fire source.
(2) The contractor shall formulate safety operation procedures to ensure the personal safety of construction personnel, prevent environmental pollution and clean tools.
(3) The coating (component A) should be evenly mixed before use. Components A and B are prepared by special personnel according to the proportion specified in the product manual, fully stirred and aged for 30 minutes before use. The coating should be prepared in batches according to the engineering requirements, and is now ready for use. The prepared paint should be used up within the specified service period.
(4) In principle, no diluent is added to the component A of the primer and the component A of the topcoat. When necessary, thinner ≤ 5% (weight ratio) can be added to the prepared coating.
5) Construction of anticorrosion coating
(1) When painting, the relative humidity should be no more than 85% and the ambient temperature should be no less than 5℃. Outdoor construction is not suitable under strong wind, rain, fog and strong sunlight.
⑵ High pressure airless spraying can be used, and the coating thickness must be uniform.
⑶ Primer: Pipes with qualified surface pretreatment shall be primed as soon as possible, and the interval shall not exceed 8 hours. Uniform coating is required, and no missing coating is allowed. Topcoat: After the primer is dried, the topcoat can be applied. Brush evenly, don't miss the brush. At room temperature, the interval between primer and topcoat should not exceed 24h.
(4) After painting is completed, it can only be transported after painting is completed.
6) Inspection of anticorrosive coating
(1) surface drying, hard operation and curing of anticorrosive coating: surface drying-non-sticky by hand; Push hard-push without moving your fingers; Curing-Re-carving with nails without nicks.
⑵ Appearance inspection: The appearance of the coating is smooth and even, with no bubbles, sagging, cracking and peeling. Check the coated pipes one by one.
⑶ Thickness inspection: based on the thickness specified in the coating grade, use the coating thickness gauge for inspection. Every 20 root canals were randomly selected 1 root, and each root was measured by three sections at regular intervals, and each section was measured by four points: up, down, left and right. If the thinnest point is lower than the specified thickness, it is unqualified. Two more are randomly selected, and when 1 root is still unqualified, all of them are unqualified. Anti-corrosion pipes with unqualified thickness shall be repaired before coating curing.
⑷ Leak inspection: The leak inspection shall be carried out at the designated place according to the provisions in 5.4 of SY/T0447 Standard for Anticorrosive Pipes.
5] Adhesion inspection: After the anticorrosive coating is cured, it shall be inspected according to Article 3.4.5 of SL 105. Every 20 root canals were randomly selected 1 root, and each root canal was measured 1 point. Unqualified, randomly selected 2 pieces, 1 piece still unqualified, all unqualified.
[6] Transportation and storage: rubber pads and nylon slings must be used during transportation, loading and unloading and storage; And there are measures to prevent mechanical collision so as not to damage the coating. After storage for more than 28 days, the anticorrosive coating must be effectively covered to prevent the coating from being exposed and aging.
3. Corrosion protection of exposed surface of metal structure
1) implementation standard
Corrosion protection of exposed surfaces of metal structures shall be carried out in accordance with Specification for Corrosion Protection of Hydraulic Metal Structures SL 105.
2) Variety and thickness
Primer: epoxy zinc-rich primer with dry film thickness of 80μ m; Intermediate paint: epoxy micaceous iron antirust paint with dry film thickness of 00μ m; Ultra-thick slurry epoxy asphalt anticorrosive coating with dry film thickness of 70μm m. ..
3) Surface treatment before painting. Corrosion protection of flange and short pipe surface. The metal surface shall be derusted by compressed air sandblasting or electric tools, and the derusting level shall reach the Sa2.5 level in GB8923.
4) Construction of anticorrosion coating
(1) When painting, the relative humidity should be no more than 85%, the steel surface should be above the dew point temperature by 3℃, and the ambient temperature should be no less than 5℃. It is not suitable for outdoor construction in windy, rainy and foggy days.
⑵ Brush coating, spraying or high-pressure airless spraying can be used, but the coating thickness must be uniform, and the brushing direction of each coating should be perpendicular to each other when brushing.
(3) Pipes with qualified surface pretreatment shall be primed as soon as possible, and the interval shall not exceed 4 hours. Uniform coating is required, and no missing coating is allowed. After the surface of primer (intermediate paint) is dry, intermediate paint (top paint) can be applied. Brush evenly, don't miss the brush. At room temperature, the coating interval between two coatings should not exceed 24h.
Ensure that the surface of each coating is not polluted by sand, dust, water and oil, which will affect the coating quality.
(4) After painting, the coating can be transported only after curing, and reliable measures should be taken to prevent the coating from being damaged during transportation.
5) Quality inspection and acceptance data shall comply with the relevant provisions of SL 105.
4, socket anticorrosion
The corrosion protection of the socket steel ring shall meet the requirements of the Specification for Corrosion Protection of Hydraulic Metal Structures SL 105.
The socket is only coated with a 40μm thick epoxy zinc-rich primer. ..
Breakthrough progress has been made in pipeline anticorrosion technology.
Internal coating of small diameter pipeline
Internal corrosion protection technology of pipelines has been a research topic in petroleum industry for many years. Water injection pipeline, sewage pipeline and polymer injection pipeline are all coated with anti-corrosion, among which liquid epoxy and epoxy powder are the most widely used. In many projects, sand blasting, electrostatic spraying, airless spraying or high-speed rotary spraying are used for rust removal of medium and small caliber. Prefabrication in single pipe factory is the most widely used and the quality is the easiest to ensure. Post-welding joint repair of pipeline is the main research topic. Among them, the in-pipe crawling joint repair vehicle has been developed in recent years, and it has many applications in Shengli Oilfield and Daqing Oilfield. Beijing Yang Qi Science and Technology Development Co., Ltd. is a professional internal coating joint repair company. The pipeline trolley above D2 19 can be remotely controlled wirelessly, and the internal coating joint repair tool is developing rapidly. In many projects, the technology of prefabricated expansion internal coating nipple is adopted, which is also very successful in many oil fields. Daqing Building Materials Company is the most widely used epoxy powder internal coating pipeline in polymer injection engineering. There are also many whole-section extrusion coating processes for pipelines after welding. These different technologies have also formed a certain market, and most of them have been successfully applied.
Spraying technology of large diameter pipeline
With the demand for internal coating of drag-reducing coating for gas pipeline in the West-East Gas Pipeline Project, shot blasting and internal spraying technology for large-diameter inner wall have been introduced and developed in China, which has filled the blank of domestic shot blasting technology and greatly improved the derusting efficiency. Among them, PetroChina Pipeline Anticorrosion Engineering Co., Ltd. introduced the internal shot peening coating production line, and Qingxian No.1 Machinery Factory designed and manufactured the internal shot peening coating production line by itself. Several large steel pipe factories have also established internal spraying production lines. This is in line with the needs of the West-East Gas Pipeline Project. The general situation of these production lines is as follows: steel pipes are preheated and derusted, and the internal shot blasting efficiency reaches 300 ~ 400 m2/h. After shot blasting and derusting, residual sand is sucked out by vacuum or poured out by inclined pipes, and cleaned by high pressure. Spraying adopts high-pressure airless spraying and internal connecting rod spraying. When the steel pipe rotates in situ, and the inner telescopic rod is inserted into the steel pipe and retreats, the thickness of spraying can reach 50 ~ 100μ m at one time ... After spraying, check whether there is any missing coating with glass specimen, then naturally cure or thermally cure, and finally seal the nozzle with a cover plate to prevent pollution. There are 5-6 such operation lines in the West-East Gas Transmission Project. China's large-diameter internal coating technology has reached the contemporary international advanced level.
Internal spraying of drill pipe tubing
The corrosion and fatigue damage of drill pipe during drilling is a great loss during drilling. In order to reduce corrosion, North China Petroleum Machinery No.1 Factory introduced American drill pipe internal coating production line and foreign PC200 coating, and coated drill pipes or tubing for 500 ~ 654.38+00000 meters every year, which can prolong the service life of drill pipes by 654.38+0 ~ 2 times. The process flow is as follows: the drill pipe is degreased with hot water wire, and heated in a heating furnace at 400℃ for 30 minutes to remove organic matter on the surface. Sand blasting for rust removal in Sa2.5 class, spraying one-component epoxy primer, continuous oven drying at 80 ~ 150℃ for 30 min, spraying one-component topcoat, batch oven curing at 200℃ for 30 min, and pre-factory inspection. The technical index of the coating is: the coating thickness is 250 ~ 300μ m. Wear resistance 12.5L sand/1μ m. After soaking at high temperature and high pressure, the coating remains unchanged for 24h at pH = 12.5, 150℃ and 70Mpa pressure. The coating has been used for 10 years and achieved good results. At present, the one-component SN222 coating of domestic products has passed the drilling test of 6.5438+0.2 million meters. At present, Shanghai Saineng New Materials Co., Ltd. has been produced and used on a large scale, and its indexes and technological properties have reached the international advanced level.