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APC Pipes


 Extruded Polyethylene Coating

Technical Specification

1. General
    This specification describes the demands and characteristics of APC
    pipes (steel pipes coated with PE / PP extrusion). APC pipes are
    externally coated by extrusion coating technology. The pipes are
    designed for transportation of fluids at temperatures not in excess of
    70ºC and are suitable for bedding below both soil and water.



2. Sorting and Naming
    The coatings are sorted and named according to the amount of layers:
    2.1 APC-3: Three-layered Polyethylene coating.
    2.2 APC-4: Three-layered Polyethylene coating with an additional
                      external 20mm cement mortar layer.

3. Material and Coatings
    3.1 Pipes and Materials
          The pipes and materials used in preparation of the coating are
          manufactured according to the standards and specifications
          relating to them, as detailed below:
    3.1.1 Pipes
             the pipes comply with Israeli Standard SI 530
    3.1.2 Materials
             a. Epoxy base material
                 A special epoxy suitable for use on heated pipes, cured by pipe
                 heat.
             b. Adhesive material
                 A thermoplastic copolymer based on polyolefin resins used for
                 adhesion of the coating to the pipe surface.
             c. Coating material
                 High density polyethylene (HDPE) containing color agents and
                 stabilizers against oxidization and radiation.
    3.2 Coating Layers
          The pipes' coating consists of three layers joined together by heat as
          follows:
    3.2.1 Epoxy base layer
             Foundation layer and base for 100 epoxy resin coating.
    3.2.2 Adhesive layer
             Intermediate layer of adhesive material acting as connector
             between epoxy and coating layers.
    3.2.3 Coating layer
             External layer of high density Polyethylene (HDPE) – painted and
             stabilized.
    3.3 Coating process
    3.3.1 Preparation of pipe surface
             Prior to the actual coating, the pipe surface is cleaned of all
             superfluous materials, such as oil and rust. The surface is grit
             blasted to a level of SA 2½ according to international standard
             ISO 8501-1. The roughness 0f the pipe following cleaning (Rz)
             will be in the area of 49-90 µ according to International Standard
             ISO 4287-1.
    3.3.2 Pre-heating
             Prior to application of the coating the pipe is heated to the
             temperature recommended by the manufacturer.
    3.3.3 Base layer coating
             Immediately following heating, epoxy resin is sprayed onto the pipe.
    3.3.4 Protective layers coating
             Both adhesive + PE protective layers are applied using co-extrusion
             technology on the pipe surface.
    3.3.5 Cooling
             Follow coating, the pipe is water-cooled.



4. Requirements and tests – According to SI 5089
    4.1 Level of cleanliness and roughness
          Cleanliness is assessed according to International Standard
          ISO 8501-1. The level of pipe roughness following cleaning is
          assessed according to International Standard ISO 4287-1
    4.2 Overall thickness of coating
          The minimum coating thickness is noted in table 1 below:

Table no.1
                                
Minimum wall thickness (mm.)
Nominal diameter of pipe (in.)
1.50
Up to  Ø 4"
1.80
From  Ø 6" up to  Ø 10"
2.00
From  Ø 12" up to 20"


The coating thickness may be up to 10% smaller than the
declared thickness, on condition that the thinnest part is more
than 5cm along each running meter of the entire pipe length. In
pipes with spiral seams the permissible deviation is up to 10% of
the declared thickness as shown in table no.1. The end 100mm of
the pipe will be coating free for pipes up to Ø 4", and 150mm for
those above Ø 6", unless otherwise agreed between the
manufacturer and the client.

    4.3 Coating continuity
          The coating should be continuous (without any holes). The coating is
          considered whole if a Holiday Detector activated at 10kv along each
          millimeter thickness of the coating does not reveal any fault.

    4.4 Bond strength
          When testing the coating according to clause 5.3.3 and the latest
          revision of standard DIN 30 670 from 1991, not less than 24 hours
          from the time of manufacture, the average required strength
         (minimum) for separation of the coating from the pipe will be as shown
          in table no. 2

Table no.2

Testat 50 ± 5ºc
Test at 20 ± 5ºc
Type of coating
At least 35 N
per cm
 
At least
100 N per cm 35
APC-3






    4.5 Impact resistance
          A 25mm diameter ball-shaped weight is dropped on the coated area
          from a height of 1 meter. This exercise is repeated at ten points along
          the length of the pipe with intervals of at least 30mm between each
          point. The energy produced by this impact is as appears in table no.3

Table no.3

Impact energy per mm of coating thickness
Nominal diameter of pipe
3.50 J
Less than 2.5"
4.30 J
From 2.5" to 8"
5.00 J
Above 8"


Following the impact, the continuity and integrity of the pipe is tested according to the above clause 4.3. Total continuity is mandatory in this test.

    4.6 Penetration assessment
          In the test according to clause 5.3.5 and the latest revision of
          standard DIN 30 670 from 1991, the penetration depth will not
          exceed 0.2 mm at a temperature of 50 ± 5ºc. In this test, a piece
          of detached coating (maximum thickness of 2cm) is loaded with
          2.5 kg round steel pin with a cross-section area of 2.5 mm2

    4.7 Elongation at breakpoint
          In the test according to part 3 of Israeli Standard 878, the elongation
          at breakpoint will be at least 300%. An A' class sample is tested
          (diagram 2 in standard 878) at 25mm/min.

    4.8 Electrical resistance of coating
          The coating resistance assessed following acclimatization of the
          sample over 100 days will not be less than 108Ωm2.

    4.9 Heat ageing
          A coating sample (of at least 2mm thickness) is exposed to
          temperature of 100ºC for 100 days. The melt flow rate (MFI)
          is then measured. The MFI will not deviate more than 35%
          from its original value.

   4.10 Light ageing
           The melt flow rate (MFI) will not deviate more than 35% from its
           original value. A coating sample with a maximum thickness of
           2mm is exposed to a filtered xenon beam while being doused with
           water. The MFI is measured at the end of the test.

   4.11 Cathodic disbonding
           In the test according to appendix K of European Standard
           PREN – 10285, the average peeling radius will not exceed the values
           stated in table no.4

Table no.4

Maximum peeling radius
Type of Coating
 6 mm
APC-3