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Non-destructive testing explained

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Non-destructive testing explained Powered By Docstoc
					December 2004


Non-destructive testing explained
Less intrusive testing methods

Zurich Risk Services is actively looking at new methods of inspecting plant
and equipment that benefit customers and meet the requirements of
current legislation. Zurich is able to offer the following services to assist
and compliment its existing range of inspection activities.

Eddy Current Testing
Eddy current testing (ET) is a non destructive testing technique based around the
principles of inducing electrical currents into the material to be inspected and
observing the resultant interaction between those currents and the material. The
technique is flexible enough for use with both ferrous and non-ferrous conductive
materials.

ET is used for detecting surface crack type defects in welds, castings and forgings
and also for the detection of through wall holes, stress corrosion cracking and wall
thinning due to erosion at or near baffle plates in heat exchanger tubing.

Unlike conventional methods of testing which often require expensive preparation
by descaling and paint removal of the plant item prior to testing, it is possible for
ET to be carried out with a minimal amount of effort which presents a saving in
both cost and equipment downtime.

Beneficial savings have been realised when utilising this inspection method to
examine hazardous material storage vessels when compared with the normal
method of magnetic particle inspection.

Remote Visual Inspection
The introduction of the Confined Space Regulations 1997 has meant that
customers have to look at alternative methods to internally inspect vessels. This
includes remote visual inspection (RVI).

RVI can enable the internal inspection of hazardous bulk storage tanks, on line
inspection of air receivers, pipework, paper drying machines and hydro-pneumatic
accumulators by introducing inspection cameras through small diameter inspection
openings.




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Internal surfaces are required to be free from dirt and process deposits and should
ideally be presented in a dry state. The results of inspections can be recorded and
used for comparison with future inspection data and along with the thorough
inspection report may be presented as supporting evidence for technical reviews to
possibly increase the inspection frequency for a vessel under the Pressure Systems
Safety Regulations 2000.

Thermographic Inspection
Often used in conjunction with a fixed wiring inspection programme, heat can
indicate the impending failure of electrical and / or mechanical systems in buildings
or production equipment. Infrared thermography is such a method and uses
thermal imaging to non-invasively identify problematic ‘hot spots’ in a wide
spectrum of industrial equipment and processes. It is an effective preventative and
predictive maintenance tool that can be utilised during normal equipment
operation.

This technique is also utilised in the early identification of unexpected temperature
differentials to help eliminate costly downtime and reduce the likelihood of fire,
explosions, leaks and other potentially catastrophic events.

An example might be a customer trying to maintain a cold store at -30'C. Infrared
thermography can be used on cold stores to identify the threat of thermal
insulation breakdown, and reduce the threat of unprepared downtime.

For any further information and advice on the services provided above please
contact your broker, local Customer Risk Centre or alternatively contact Steve
Harris, Senior Engineer for NDT and RVI at Zurich Risk Services. Steve’s contact
details are; Mobile: 07760 170781;Email: steve.harris@uk.zurich.com




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