Product category:
Plant services equipment
News Release from: Telespection Services | Subject: Remote visual inspection
Edited by the Manufacturingtalk Editorial
Team on 14 May 2004
Remote visual inspection playing a
greater role
Remote visual inspection is playing an increasingly important role in preventative maintenance and troubleshooting across a broad spectrum of industries.
Remote visual inspection is playing an increasingly important role in preventative maintenance and troubleshooting across a broad spectrum of industries The technique uses remotely controlled video cameras, video probes or fibre-optic probes to obtain detailed visual information from inaccessible locations
This article was originally published on Manufacturingtalk on 14 Oct 2004 at 8.00am (UK)
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Recent developments in camera technology are allowing the technique to be used in a growing number of areas and in many cases, the inspection forms part of a wider investigative program.
This may involve debris retrieval, corrosion assessment or routine repairs and, where applicable, video images can be used to support data from other techniques such as crack detection.
Although it is possible for companies to perform inspection work themselves, Stockport based Telespection Services Limited, who have over 25 years experience in remote inspection, firmly believe there are significant reasons why it makes sense to employ the services of a professional and experienced inspection company.
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As Ken Lambert, Technical Manager at TSL points out: "Although it may seem straightforward to hire the cameras and equipment, actually carrying out the work effectively and safely, is far from simple.
Without the experience and use of purpose built accessories for positioning cameras, companies who carry out their own inspections usually end up with low quality images which often do not provide sufficient useful information.
In addition, interpreting the results and carrying out further work based on the data requires considerable expertise.
We know full well that inexperience can cause great frustration and lead to expensive mistakes." Remote Inspection can be divided into internal and external applications.
Cameras are typically used for external inspections in areas where health and safety issues prevent direct human inspection.
This includes applications in designated hazard areas, where high temperatures are involved and where inspections have to be carried out above permitted working height restrictions.
Internal inspection is ideal for use in closed structures such as pipes, boilers and gas turbines.
A prime example of where the multi-function capabilities of video inspection are effective is in the oil and gas industries.
Flare stacks are a common sight at oil refineries and perform a vital part of the overall process.
Carrying out effective inspections of the stacks and the support structure in order to assess life expectancy presents a number of challenging problems.
The flare support structure at Shell's Stanlow refinery supports four stacks, 93 metres high.
On-site health and safety restrictions prohibit human access above a height of 27 metres and therefore the only way to carry out a thorough assessment of the condition of the structure is to use remote cameras.
Initially Shell tried using a camera attached to a remote controlled miniature helicopter.
However this proved unsatisfactory, with the vibrations causing the images to lack sufficient clarity.
To solve the problem, Shell called on the services of TSL, who have devised an ingenious method of fitting a camera to one of the flare stacks itself.
The stacks are made up of three sections.
For maintenance or replacement purposes, each stack can be dismantled section by section and lowered to the ground via guides on the support structure.
The final section is lowered to the horizontal position; assembly is achieved by reversing the process.
TSL designed and built a special assembly so that a TV camera can be fitted to the top section of the flare stack.
The camera, which is fitted to a remotely operated boom assembly, is then lifted up with the top section.
With this section bolted in position, the boom can be moved so that the camera can be positioned inside the support structure.
The high resolution, high sensitivity camera is mounted to the boom via a manipulator arm which provides pan and tilt remote control.
The camera has extensive remote-operated zoom and focus facilities allowing the operator to focus in on key parts of the structure.
The drive arrangement uses an electric motor, driving through a remote-operated electromagnetic clutch.
In the event of power failure or fault condition, it will automatically de-energise, causing the manipulator arm to fall to the horizontal position, thereby allowing the flarestack to be lowered without damaging the camera.
An important associated part of remote inspection is debris retrieval.
'Debris' may include material left after construction or repair work or parts that have broken off.
It is not uncommon to find objects such as steel beams, tools, nuts and bolts.
At Stanlow, engineers knew that material had been left behind on the support structure but had no clear idea of what was there and its precise location.
The inspections carried out recently by TSL have identified where the debris is and plans are now underway to effect a method of retrieval using electromagnets in conjunction with a camera mounted suspended from a mobile crane.
Remote inspection is also very effective for checking the condition of the flare heads and burners.
The use of a camera with a high quality zoom lens, mounted on a crane at a safe distance from the flame, allows a detailed inspection of the individual components to be carried out.
In addition, the high quality colour images make it is possible for engineers to view the tip whilst changing flare operation settings to obtain detailed information on flare control.
Work in pipes typically involves routine inspections of welds, valve seat conditions, blockages and build-up of process product.
In addition, checks are often carried out after work has been carried out to ensure no tools or other objects have been left behind.
Filming inside pipes and similar enclosed spaces requires a mixture of the right equipment, ingenuity and skill.
For small diameter, short length inspections up to six metres, fibre optic endoscopes or video probes are used.
For larger and longer inspections, a video camera mounted in a multi-legged centralising cradle allows pipe lengths up to 300 metres to be inspected.
The cradles are usually propelled either by flexible rods or a remote controlled, motorised carriage.
These remote crawlers give greater flexibility and are used in longer distance, more complex situations.
In these applications, great operator skill is required to ensure that the crawlers do not become stuck or lose contact.
Waterproof cameras are available for underwater inspection and a wide range of accessories including lateral view heads, headlamps, and air-cooling jackets for high temperature applications, increase the possibilities for remote inspection.
As with all professional photography, essential to providing clear and usable images is ensuring correct lighting and focus.
Although most of the inspection work TSL carry out is of a routine nature, sometimes they are called in to solve more awkward and tricky problems.
In one such case, they were asked to extract a spanner, which had fallen down a 50mm inspection tube on a nuclear submarine.
The vessel had been in dry dock for a complete refit and just after being refloated, on completion of the work, an engineer accidentally dropped the spanner down a tube leading into the hydroplane compartment.
There was no way they could risk leaving it there and at first it appeared that the problem would require extensive (and expensive) work, resulting in the vessel having to return to dry dock for several more days.
Luckily, before embarking down this onerous route, they contacted TSL.
Using a small camera attached to a flexible rod, they managed to locate the spanner, which was over five metres down from the deck.
Eventually, with much holding of breath and crossing of fingers, the TSL engineer, guided by the images from the camera, managed to hook the spanner and slowly withdraw it- much to the delight of the errant engineer and his colleagues.
As Lambert concludes: "It is clear that remote inspection provides a very powerful tool.
Our experience has shown that combining this technology with practical ideas and sound mechanical engineering methodology significantly extends its capabilities.
We advise clients to discuss their application with us before they try to carry out any work themselves.
As part of AV Technology and Shell Services, we offer a highly professional service with all the relevant health and safety, QA and insurance certification.".
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