Coating Application

Coating Application


General description :

ERW Photo Gallert

The plant consist of two main lines , being the cleaning and blasting line and the coating line . The separation of the two lines is to enable inspection subsequent treatment of the blasted pipe and to create a buffer pipes . Continuous feed of pipes to the coating line is necessary (pipes are joined head-to-tale in the lines ) there are various orientation possible for blasting and coating line . this process description is based on the Z shape layout .


Process description :

  1. Blasting area :

    • Internal & External pipe wash station :
      The pipes shall be put on the in bound pipe racks by means of Liftruck or loader then it can be taken over by mechanized transport system ( pipe Indexer carts ) and bring it to the first station which is the Internal pipe wash station. Before entering into this station pipes are visually controlled ( Eg:dent - flat end - gouge - ovality - straightness, etc ) by QC inspectors . In the internal wash station wash boom enter inside of pipe and with high pressure water spray remove contaminants. After the internal washing the conveyor transport the pipe spirally through an external pipe wash booth, where a medium pressure water cleaner is fitted to remove contaminations from the pipe surface ( exterior ) such as sand, mud, dust, e.t.c.
    • Blasting conveyor :
      Once the conveyor is ready to accept a new pipe . pipes can be joined in the incoming part of the conveyor and separated on the out going part by speeding it up
    • Gas Heater :
      Here after the pipe enter the preheating oven, where it is dried and heated in order to vaporize moisture from out side surface and to prevent flush rust on the surface, after blasting and secondly the elevated temperature of the pipe will increase the efficiency of blasting .
      Then pipe enter the blasting station where in two steps the pipe surface is blast cleaned to a surface roughness of 50-100 µm and cleanness min sa 2.1/2 according SIS 055900 or ISO 8501-1
    • Chemical treatment station :
      In this unit when it is specified by the customer phosphoric Acid (H3P04) wash solution is sprayed on to the pipe surface in order to further remove possible contamination which might be present on the pipe namely soluble salt such as chloride , sulphate , light oxidation , trace oil , grease , dust and carbon residues .
      After the acid fluid has sufficient time to perform it's remove from the pipe surface by high pressure water rinsing with clean water ( RO or DI ) .
    • Abrasive removal :
      At this station has to function to remove particle of abrasive and dust from inside of pipe .in order to clean the pipe internally with a suction boom . ( the boom is connected to a vacuum generator )
    • Inspection after blasting :
      Pipe surface by QC man is inspected for cleanliness and surface profile and possible faults such as sliver- Lamination and dust – rust – salt degree and etc. I after visual inspection of the pipe it is decided that needs more blasting. It can be removed from the main process and send back to start of blasting line .
  2. Coating Area :

    • External dust removal :
      Pipe enter to coating conveyor and passes alongside a dust removal unit where a soft brush which is rotating against the pipe brushed of dust is collected in a dust filter which is connected to the dust brush .
    • Chromate station :
      When it is specified by the customer, the Chromate unit is used on the blast cleaned pipe prior to the application of protective coating .
      The process from an amorphous chromium , iron , silicon oxide conversion coating on the pipe which requires protection to the metal and improves the performance of the subsequently applied organic coating as defined by cathodic disbanding and hot water immersion testing .prior to chromate application pipe surface temperature is raised in by a preheater.
    • Induction :
      The pipe is heated to the coating application temperature by induction coil in which an alternating current is generated which causes an induction reaction in the magnetic pipe.
      After the pipe leave the heating system , it enter the coatings section the epoxy powder is sprayed on to the pipe by means of guns unit electrostatic chargers which are fitted in a cabin the electrostatic charged powder settles on the pipe and start to melt up on which it forms a uniform layer .
    • Adhesive & polyolefin coatings :
      The adhesive film is applied on to the epoxy primed pipe surface in order to obtain maximum adhesion between the epoxy anti corrosion layer and the poly olefin layer of the pipe .
      The adhesion layer are extruded from flat head die and wrapped around the rotation pipe . the polyolefin ( PE , PP ) coating layer are extruded as adhesive layer .
      To reduce consumption of coating material for spiral and longitudinal pipe a weld seam coating compensation is forseen.
      capacity of coating = 800 sq. mtr./hr .
      after coating has been applied the pipe move in to the quenching section ( cooling tunnel ) where it is adequately sprayed with water. Just before entering the quench, the soft coating on the pipe joints allow pipe separation (Manually)
    • Pipe end cleaning & Final inspection :
      the pipe transferred to the water removal station where the remaining cooling water is removed and then pipes transferred to dual pipe end cleaning . at the cutback area pipes cleaned by means of steel wire brushes .
      after the cutback surface of coating pipes in the holiday station con be inspect by the flat on ring brushes moves along the pipe and detect 100% of the coated surface . ( a spark will arise causing a visual and audible alarm ) .
      ( D-C voltage = up to25 KV ) .
      At the end of line inspectors ( QC man's ) check it all of the parameters ( based on standards ) such as: thickness – visually – continuity , etc
      After the pipe has been inspected it can be transferred to the out side or to the internal coating plant ( Lining Area )