MIL-HDBK-1004/10
application are normally achieved under the more controlled conditions at a
stationary plant. The coating should be inspected upon receipt at the
construction site when unloading. Inspections should be performed immediately
prior to placing the pipe in the ditch after all joint and field patches have
been made.
Joint and Damage Repair. Joints and field repairs should be made
10.3.3
with coatings compatible with the primary coating system used. Joints and
field patches should be carefully inspected before placing the pipe in the
ditch.
Inspection. Electric Holiday Detectors should be used for all
10.3.4
coating inspections. If properly used they can detect flaws in the coating
which may not be visible. In addition to the use of the Holiday Detector, the
inspector should also make detailed visual inspection of the coatings and
occasional measurements of the bond strength. Visual inspection should also
include observation of the following:
a)
surface preparation and coating - if practical
b)
handling of the pipe
c)
lowering of the pipe into the ditch
d)
backfilling operations
Any material, even the highest quality, when applied and handled carelessly
will perform poorly, but a marginal quality material will perform well when
carefully applied and installed.
Coatings for Other Structures. Coatings on other structures are
10.4
equally critical when the cathodic protection system relies on the quality of
the coating to achieve protective potentials with the available system
current. Inspections during surface preparation, coating, handling,
placement, and backfilling are vital to the performance of the overall system.
Pipeline Installation. The use of casings to give mechanical
10.5
protection to the pipeline at grade crossings, etc., is sometimes required by
law, code, or physical condition. The use of casings should be avoided
wherever possible due to the difficulty of protecting the pipeline within the
casing and difficulties in maintaining isolation between the casing and the
pipeline. The use of proper techniques when foreign pipeline crossings are
made is necessary to minimize interference. Insulating joints should be
properly installed. Effectiveness is achieved using adequate test and bonding
stations.
Casings. Casings should be uncoated. The casing should be
10.5.1
isolated from the pipeline with insulators and cradles which must be properly
installed. The annular space at the ends of the casing should be sealed to
prevent the entry of moisture between the casing and pipe. Extra thickness of
coating on the pipeline for the section to be placed inside the casing may be
required in order to prevent damage to the coating when the pipe is pulled
into the casing. The annular space between the casing and the pipe must be
kept dry until it is sealed. Casing-to-pipe resistance should be measured. A
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