⠿ NDT
(^06) ⠿ MARINE MAINTENANCE TECHNOLOGY INTERNATIONAL | APRIL
Thermal imaging surveyors Geo Therm
Ltd, based in Lowestoft, UK, and with
offices in Australia, the Middle East and
USA, carries out regular thermographic
inspections all over the world. MD Tony Dale,
a Level 3 thermographer (the highest level)
and an International Institute of Marine
Surveying (IIMS) surveyor, says, “We are
often flying out to offshore drilling rigs,
oil and gas platforms, and most types of
commercial shipping. We look at all aspects
of the vessel including engine exhaust
systems and insulation, bulkhead surveys
in engine rooms, and hull surveys during
drilling rig flaring operations when excess
gas is burned off, and cooling and electrical
distribution systems.”
The company has been operating since
2002, with work divided between preventive
and reactive inspections.
RIGHT: Cable connections
showing heat build-up
(red) with cooler cables
nearby – remedial action
is required
BELOW RIGHT: Hot ducting
showing insulation failure
at a hot spot, which is
indicated in red
There are many marine uses...
the biggest value is in prediction
Dale continues, “The class societies
under the auspices of SOLAS stipulate
that anything with a temperature over
220°C needs a survey to identify and
direct maintenance attention to missing or
degraded insulation, to prevent fire from a
leaking fuel-oil source coming into direct
contact with a hot surface. Dangers arise
when the magic triangle of air, heat and a
fuel source are all present, as found in every
engine room. There are simply far too many
engine room fires as it is. According to DNV
statistics, a shipowner operating 20 vessels
can expect one major engine room fire every
10 years – the consequences of a fuel line
breaking and spraying fuel-oil onto a hot
surface is an everyday threat, and engine
room thermal surveys should be taken
seriously and performed regularly, and
hot spot corrective actions prioritized.
“We typically uncover things like poor
maintenance after removal of exhaust
insulation, and potential electrical hazards,
often caused by poorly crimped wire
ferrules and cable termination tightness
- albeit these are often a consequence of
heating, cooling and vibration creating a
localized hot spot.”
Retrofits
Dale says that where it is impossible to
get a direct line-of-sight due to interlocks
preventing electrical cabinet access,
infrared inspection windows can be
retrofitted, permitting safe inspections
on live systems at any time.
Thermal imaging can also be used to
detect corrosion – for example, in paint
blistering, the blister contains air and/
or moisture, which has a different thermal
capacitance and hence thermal signature
to the surrounding super-structure.
Dale adds, “A ship survey usually takes
a team of two people a couple of days,
depending on size and survey requirement.
Large offshore platforms as found in the
North Sea will take a few more days. One
person usually undertakes an electrical
inspection with the assistance of an
onboard electrical engineer who knows all
the locations of the electrical equipment.
We wear the full arc-flash PPE [personal
protective equipment], the safety crook and
insulated gloves are never far away.”Dale says, “Survey inspections would
typically cover electrical systems, including
the main switchboards, transformers, and
distribution boards dotted around the ship,
in addition to generator terminal boxes,
rotating electromechanical equipment such
as motors, and pumps to identify failing
bearings, shaft and pulley misalignment
issues and even DC motors looking at the
carbon brush temperatures against the
commutator. Exhaust manifolds and exhaust
piping would be checked, and those transit
points through bulkheads would be checked
for any heat transference. Refrigeration
systems can also be checked, looking
for such things as air infiltration that can
potentially contaminate stored produce and
[produce] ice build-up. In such a case, the
thermographic inspection will show where
the air is getting in.”