Quality Control Of Anticorrosive Coating In Pipe

- Dec 02, 2017 -

Pipeline transportation with less material loss, high efficiency, pollution-free, has become the ideal tool for water, gas, oil and other transportation. In view of the diversity of transportation mediums in oilfield pipelines, the transportation medium is generally crude oil, sewage, oil-water mixture, natural gas, and is acidic with the corrosion of sulfides. Therefore, a variety of anti-corrosion coating technology within the pipeline, cement mortar lining technology, glass pipe lining technology, anti-corrosion epoxy powder technology, such as plastic pipe.

Zhongyuan Oilfield, based on its medium conditions, years of accumulated experience, the use of 100% solids two-component epoxy coating anti-corrosion, to ensure that no corrosion pipeline leakage for 3 years, greatly increasing the life of the pipeline. However, the high temperature on-site welding will cause the coating on both sides of the weld to scorch or fall off and lose the protective effect on the pipeline. In order to ensure the corrosion resistance of the welded part of the pipeline, a welded inner jointing port and a stainless steel joint France and the combination of measures to solve the connection and protection of pipe joints. But after welding within the mouth and stainless steel fittings are completed at the scene, not as good as the quality of anti-corrosion pipe factory operations on the whole pipeline of reliable, stable and easy to control. Therefore, it is necessary to strengthen the quality control on the spot after welding and the stainless steel joint.

1. The impact of raw materials and control

1.1 100% solids two-component epoxy coating

Due to the very harsh environment in which the paint is used and the corrosion is very serious, the medium in the pipe is not only acidic but also corrosive with sulphide. Generally, the paint can not resist such corrosion. In addition, the pipeline under the pressure of high-pressure flow medium erosion, also requires coatings with good adhesion and wear resistance.

At present, 100% solid content two-component epoxy coating in the market a wide range of quality is not uniform, therefore, should be based on pipeline media and the use of third-party inspection, the general test include: impact strength, adhesion, Shear strength, cathode peeling, hot and cold cycles, wear resistance, etc., in line with the requirements and testing of qualified paint to use.

1.2 stainless steel connector

Stainless steel joint method is to weld two stainless steel short sections at both ends of the pipe first, and then coat the coating. When stainless steel joint is used, the stainless steel short sections can be welded together with stainless steel welding rod.

Stainless steel fittings have excellent corrosion resistance, pressure resistance and installation, easy maintenance, etc., but the material requirements of stainless steel short section is very strict, therefore, before the use of stainless steel short section of the material for third-party inspection, in line with the drawings Design requirements before use.

In addition, in order to prevent the welding of stainless steel short section without damaging the internal anti-corrosion coating, should ensure that stainless steel short section length should not be less than 100mm.

2. The impact of equipment and its choice

2.1 anti-corrosion intelligent complement machine

Internal anti-corrosion intelligent fill mouth machine that is dedicated to welding within the mouth filling operation of the car. At present there are positioning nozzle nozzle device, weld within the nozzle spraying car, automatic advancement, automatic surface treatment and coating of the pipe welding mouth filling device and automatic internal filling machine. The scene to use more automatic propulsion, automatic surface treatment and coating of the pipe welding mouth filling device.

As the internal fill port is completed in the hidden state, so that the filler on the equipment put forward higher requirements: ① weld positioning system, requiring accurate positioning. ② feeding system to ensure unimpeded feed nozzle. ③ Rotary spray system to ensure that the atomizer to high-speed rotation, to atomization requirements. ④ observation system to ensure that the transmission image is clear, easy to observe the working condition of the naked eye. ⑤ smooth walking, flexible control of the car system requirements.

2.2 pipeline endoscope and EDM

In order to ensure the quality of the project, it is necessary to inspect the inner coating and the inner fill. As the detection equipment is in a hidden state, it must ensure that the EDM is working properly, reliable wiring; monitor image is clear, can be observed directly with the naked eye effect within the mouth.

3 process methods and countermeasures

Pipeline fill mouth is due to on-site construction, can only be completed with the help of equipment in a concealed state, the factors that affect the preservative effect and solutions are the following:

3.1 welding process

When the use of anti-corrosion spray process, the welding should be used TIG welding primer to avoid welding tumor appears to affect the quality of the mouth.

3.2 weld surface treatment

Voucher, clean weld surface is coated with a guarantee of good adhesion. First of all, in the anti-corrosion plant spraying anti-corrosion, the two ends of the pipe length reserved for the 100mm coating can be coated with a coating to ensure that the pipe installed in the field before welding does not rust. Second, the site after the installation of welded seams, the use of rust car rust weld surface rust removal, and clean the dust near the weld purge.

3.3 clear water vapor

Due to the change of temperature, the moisture in the air in the pipe tends to condense into water droplets, which are usually accumulated on the top of the pipe. If coated in this condition, it is difficult to bond with drops of water. In order to ensure the coating adhesion, rain spraying should be prohibited within the mouth of the construction, the relative humidity of the construction environment should not exceed 75%.

3.4 paint atomization

At present, the use of centrifugal spray coating more than non-air spray atomization than the air spray smooth surface, and spraying paint droplets moving distance. However, it is still affected by the temperature, the temperature is too low, it can not ensure that the coating atomization, it is difficult to guarantee the quality of internal corrosion. Therefore, the spray coating mouth construction operating ambient temperature should be greater than 10 ℃. If the construction in winter, warm-up measures should be taken, the weld temperature to maintain a constant temperature of about 30 ℃, paint preheat temperature control between 10 ℃ ~ 20 ℃.

3.5 coating dry

Normally, the weld is sprayed 2 times to ensure the quality of the weld in the weld. Spraying the second time, more than the time interval road coating hard work is appropriate. After all the coating coating is completed, the general need for natural drying 7 - 10 days and nights before the quality inspection and put into operation.

4. Installation and construction of the impact and countermeasures

In the pipeline loading and unloading process, such as crowbar inserted into the pipe end of the pipe, grounding wire directly welded on the pipe, these tend to destroy the coating has been made, resulting in secondary site injury, the quality is not easy to control. Pre-installation workers should be responsible for the installation of construction specifications and precautions education, installation and construction in accordance with norms and standards to eliminate brutal construction, reduce pipeline corrosion due to improper construction and operation leakage.

In summary, the main factors affecting the fill in steel pipe coating raw materials, construction and testing equipment, installation process and construction norms, etc., for these factors, as long as the correct choice of raw materials and construction equipment, development and implementation of a suitable installation process In strict accordance with the standard construction standards, we can ensure the quality of the coating within the mouth to delay the pipeline corrosion and prolong its service life.


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