Plastiline™ - Humes

12 Repairs
12.1 Any areas revealed as defective shall be repaired in
accordance with the following clauses.
12.2 For isolated pinholes or for straight cuts and tears
where the cut or torn edges can be brought together, the
repair is made by welding flat welding strip over these
areas, taking care that it is centrally located.
12.3 Damaged sections equivalent in area to about 40,000
mm 2 which cannot be repaired by the method
described in Clause 12.2 shall be treated as follows.
The defective area of the sheet is to be cut, preferably to a
rectangular shape, and removed. A piece of plain
Plastiline sheet cut to shape is tack welded in place, or
fixed with adhesive in the opening of the sheet, leaving no
gap greater than 4mm. The gaps are then sealed by
welding centrally located flat welding strips over them.
Alternatively the plain Plastiline patch may be cut
larger than the defective area by at least 12mm all round,
the edges chamfered and the patch sealed with flat
welding strip.
12.4 Where damage covers an area greater than
40,000mm 2 but a patch not greater than 100mm in width
can be used to effect the repair, the methods described in
Clause 12.3 shall be used.
12.5 Plastiline damaged over an area greater than
40,000mm 2 during handling and laying of a pipe, may be
repaired at the discretion of the Supervising Authority.
The repair would be at the expense of the contractor (refer
Humes for specialised procedure).
12.6 Where brittle field welds occur due to overheating or
charring, the defective area must be cut out and patched
with plain Plastiline sheet as described in Clause 12.3.
Where the existing weld strip interferes with the new
welding, the operation is completed by carefully heating
the plastic junctions until they are soft and can be
worked together.
12.7 Short lengths, less than about 25mm individually, and
not more than 250mm in any one metre of weld, where the
probe will enter more than 3mm under the edge of the
weld strip, are classified as short incomplete welds.
(Occurrence of frequent short incomplete welds is general
evidence of substandard welding.) These faults may be
corrected by lifting up the unsealed edge with a blunt knife,
carefully directing the heat into the opening and pressing
the strip down firmly.
12.8 Where incomplete welds longer than specified in
Clause 12.7 occur, they are to be treated by the methods
described in Clause 12.6.
12.9 All repair operations must be subjected to the same
stringent control as stipulated for joint welding. Upon
completion of repair work, all tests and inspections laid
down in Section 11 must be performed again and restored
areas spark tested.
13 Handling — storage — laying
13.1 Proper handling and welding of plastic lining is
primarily a matter of care and common sense. Personnel
must be aware that in the manufacture of Plastiline and
its application to concrete pipes, careful control is exercised.
This care is nullified if the material is subsequently damaged
by carelessness and faulty practices. Failure to carry out
simple precautions against damage cancels the customer’s
investment in protection.
13.2 Personnel must have the clear understanding that
after jointing, the Plastiline must form a continuous sheet
lining (i.e. free of pinholes, cuts, burns, abrasions)
throughout the length of the pipeline.
Personnel should have theoretical and practical basic
training in welding of plastics.
Plastiline welding repairs.
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