External Coating Plant

Ahvaz Pipe Mills Co. put the “3-layer polyethylene” coating plants to the operation in the year 1993 utilizing the latest available technology of the world, thus for the first time in Iran and throughout the Middle East, took an effective step towards improving the quality of oil and gas pipelines in this industry in the country, and prevented the import of this product.Polyethylene plants no.1 and 2 were launched for the external coating apply of pipes with diameters from 2” to 56’’ according to the latest international standards; because of its high capabilities and supplying the best raw materials from companies such as BOREALIS, Daewoo, 3M, BASF and MPB and some well-known companies in this field, its products were widely used and warmly welcomed by international companies. Among the products were 42’’ pipeline, the Aghardalan Project as ordered by Germany, the 32’’ project by Total of France, the 40’’ project of Turkmenistan and the 56’’ project of Agip of Italy.
In pipe coating plant no. 1, where “HOSE” method coating is performed for 2-16’’ pipes, the pipes are put in the beginning of the plant feed line one by one, after passing the inspection station no.1 they enter pipe drying station by gas oven. After losing moisture and increasing the pipe surface temperature over Dew Point, they enter shot blast unit, where surface of the pipe is cleaned of iron fine particles and rust with shot hits with speed of 80 m/sec.
While the pipe surface roughness for coating process is also provided according to the customer’s order. Dust remover no. 1 removes the dusts of he pipe surface. Then the pipe reaches inspection station no.2 . After acceptance, near the coating transmission line, special couplings are put inside pipe ends. Then it is put on the coating transmission line and enter into the Caterpillar machine. In this stage, to make sure of pipe movement continuation, it is necessary that pipes enter the Caterpillar one after another. Then they enter the induction furnace and under a magnetic field frequency of 2,000 Hz, they reach to a temperature of 180-220 °C. After heating, they enter the cabin of epoxy powder spray. Under an electrostatic field with a voltage of 50-100 KV, a sufficient amount of epoxy powder is applied on the pipe surface. Due to the pipe surface heat, the epoxy power is melting, and before its complete drying, after pipe enters to the adhesive cabin, adhesive power is applied to the pipe surface with an electrostatic field with the same voltage. As a result of the pipe surface heat, the adhesive powder melts and is merged to the epoxy coating, then pipe enters rewarming coil, passes through adhesive layer leveling rubber, enters extruder head vacuum chamber ,when leaving it, the polyethylene layer sticks to the layer of adhesive. To gradually cool down the pipe by cold water, it is put in a 84 m long path and cooling process is performed immediately. In the end of the cooling line, pipes go through the annular probes of the hole finding system (Holliday detector) and in case of detecting a hole in the coating surface, the operator will be warned.
After the hole detecting station and cutting the coating on both ends of the pipes for separating the pipes from each other, in the brushing station the two pipe coating ends are cut to facilitate the installation and welding operations as the customer’s request. Then the coated pipe is sent to final inspection at the technical inspection station by appropriate tests for coat thickness, extent of coat adhesiveness and other requests of the customer. After this and in the final phase, the logotype of Ahvaz Pipe Mills Co. and the technical specifications of the pipes such as the project number, the pipe number and length and other specifications requested by the customer are printed by the marking machine on the pipe and according to the type of order the pipes are loaded for leaving the factory or temporary storing in the warehouses.
In the coating plant no. 2 which coating according to wrap method for pipes of 18’’ to 56’’ is carried out, the pipes are put in the beginning of the plant feed line one after another. First, washing operations are applied inside and outside the pipe, for removing the dust and probable grease layers . Then the pipe enters the gas dryer station and, after removing humidity and increasing surface temperature of the pipe to above the dew point, it enters the grinding station for grinding. After that, the pipe enters the sandblasting machine and, according to the cleaning standards, the pipe surfaces are cleaned of rust and other things while the pipe surface roughness is provided as required by the customer for coating. The pipe surface is dusted off by duster no. 1. Then the pipe reaches inspection station no. 2 and after being accepted, the inside of the pipe is cleaned in aerating station and then it is put on the coating conveyance line. Then they enter the induction furnace and under a magnetic field frequency of 2,000 Hz, they reach a temperature of 180-220 °C and after heating, they enter the cabin of epoxy powder spray. A sufficient amount of epoxy powder is applied on pipe surface under the effect of the electrostatic field with a voltage of 50-100 KV. As a result of the pipe surface heat, the epoxy powder melts and is merged to the epoxy coating, before complete dry off of epoxy the adhesive layer is applied on it then polyethylene layer is added to the adhesive layer. To gradually cool down the pipe by cold water, it is put in a 36 m long path and cooling process is performed immediately.
Then, in the brushing station, the two pipe coating ends are removed as the customer’s request and at a sufficient amount for facilitating the installation and welding operations. After brushing, the statistics station deals with registering the coated pipe specifications. After this, the two pipe ends bevels are inspected for cleaning any probable brushing debris. Then the coated pipe goes to the technical inspection station for carrying out the appropriate operations such as checking the coating thickness, extent of coating adhesiveness to the pipe, the hole detecting test and other requirements of the customer. The accepted pipe is prepared for the marking station so that the specifications of the pipe and coating are printed on the pipe by the machine and the coated pipe accepted by the production inspection station is permitted for release the plant and timely delivery to the customer.
Now, after more than one decade since the establishment of these plants and in coordination and in line with overall development movement in Ahvaz Pipe Mills Co., the Plants Engineering Department has developed comprehensive programs for updating and equipping this industry in proportion to increasing capacity and quality of pipe coatings. The implementation of these programs, in addition to appropriate responding to the increasing and varying needs of the customers, result in increase of the capacity of the plants, increase of quality control of the product and, finally, launching out a hot polypropylene coating system.
The future goals of the company, which are soon to be implemented, include inside coating of pipes from 20’’ to 56’’. Such coating reduces friction between the inside wall and the fluid, removes pumping stations and, consequently, reduces 20% of the fluid conveyance expenses.