Product category:
Asset Management and maintenance planning
News Release from: AV Technology | Subject: Remote visual inspection
Edited by the Processingtalk Editorial
Team on 04 April 2007
The new role of remote visual inspection
Remote visual inspection is playing an increasingly important role in preventative maintenance and troubleshooting: Ken Lambert of AVT gives some recent examples
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 Processingtalk on 9 Mar 2007 at 8.00am (UK)
Related stories
Power generation needs remote visual inspection
Remote visual inspection - video images - are playing an increasingly important role in preventative maintenance and troubleshooting at power generation plants
Alliance increases use of portable vibration data
As part of their ongoing expansion in the field of vibration analysis, leading consultants AV Technology have announced a strategic alliance with Sheffield based Drive Management Services
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 programme.
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 AVT, who have over 30 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.
Further reading
Spi-VR condition monitoring on UK and Greek plants
The innovative and powerful Spi-VR hand-held vibration data collectors from AV Technology are playing vital roles at two quite different manufacturing plants in the UK and Greece.
Condition Based Maintenance in petrochemical plant
Condition Based Maintenance (CBM) is an important and integral function of petrochemical plant management and should be part of an all encompassing asset management function
AVT launch Spi-VR data collector at Maintec 2008
Leading condition monitoring consultants AV Technology (AVT) are using this year's Maintec exhibition to launch their innovative Spi-VR hand-held vibration data collector
As Ken Lambert at AVT 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".
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.
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.
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 the Shell 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 AVT 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.
AVT 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 remote visual inspections carried out by AVT identified where the debris was located, allowing an effective method of retrieval to be devised using electromagnets in conjunction with a camera 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 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, sufficient lighting, 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.
In a very different application, an ingenious remote video monitoring-cum-cleaning system developed by AVT is saving significant time and money at the Huntsman Tioxide plant in Grimsby.
The titanium dioxide liquor is refined using three Broadbent solid bowl decanter centrifuge rotating units.
During normal operation material build-up occurs in and around the four water spray nozzles, steadily reducing the efficiency of the centrifuges until they become blocked.
Normal access to the nozzles can only be achieved by completely stripping down the unit even though, once accessible, the nozzles are easy to clear.
Strip down and rebuild typically costs several thousands of pounds so any remote method of cleaning is very beneficial.
AVT were invited by Huntsman Tioxide to investigate the possibility of cleaning the nozzles remotely without the need for strip down.
When the nozzles are starting to block up the product falls out of specification.
This gives a warning of impending blockage and thus the cleaning can, to some extent, be planned in over a few days.
After the preliminary investigation using a video probe, AVT realised this would need a very special solution indeed.
Gaining remote access to the nozzles involves going 1500 mm along a 100 mm diameter tube and then dropping vertically down a distance of approximately 300 mm to the nozzle chamber.
Undaunted Ken Lambert set to work with some unusual components and came up with an ingenious solution based around a length of motorbike drive chain and a heavy-duty boden cable.
The assembly consists of a 1500 mm metal channel used to guide the 300mm length of drive chain, which is attached to an aluminium bar.
The cleaning tool, comprising the cleaning tip, operating cable and two concentric plastic tubes is fixed to the free end of the drive chain.
Using detailed drawings of the centrifuge, AVT were able to carry out a mock bench top cleaning exercise to demonstrate the principle of operation to their client.
With the channel in situ in the tube the bar is fed along the channel until the chain drops into the nozzle chamber.
The centrifuge can be moved by hand to position the first nozzle ready for cleaning.
Once the cleaning system is in the nozzle chamber, accurate positioning, guided by the video probe, can be achieved by moving the cable and chain relative to each other.
The weight of the chain ensures that the cleaning system sits over the nozzle and does not move about during the cleaning process.
Once the cleaning system is in position the tee bar on the end of the drive cable can be rotated to clean the nozzle.
There are a variety of interchangeable cleaning ends, including a chisel tip, pointed tip, screw tip and wire brush tip.
Once the nozzle is cleared of deposit an air line can be used to blow out any loose debris.
A vacuum hose can also be positioned over the nozzle or in adjacent areas to clear out any loose debris which might block the nozzle on start up.
This whole process is recorded on videotape and the tapes are retained by the client for their records.
A growing area for visual inspection is in buildings, shops and offices.
For example accessing areas above suspended ceilings can be very disruptive.
By removing only one tile, remote cameras with zoom lenses can gain access and then used to locate problems such as leaks.
Although most of the inspection work AVT 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 50 mm inspection tube on a nuclear submarine.
The vessel had been in dry dock for a complete refit and just after being re-floated 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 AVT.
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 AVT 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 Ken 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.
We offer a highly professional service with all the relevant health and safety, QA and insurance certification". Request a free brochure from AV Technology ...
• AV Technology: contact details and other news
• Email this article to a colleague
• Register for the free Processingtalk email newsletter
• Processingtalk Home Page
Search the Pro-Talk network of sites
