Inspection services reach difficult places

Edited by the Engineeringtalk editorial team Mar 9, 2007

AV Technology (AVT) can provide comprehensive internal visual inspection services at all types of plants, including oil, gas, coal, CHP, nuclear and hydro-electric.

Remote visual inspection is playing an increasingly important role in preventative maintenance and troubleshooting at power generation plants.

The technique uses remotely controlled video cameras, video probes or fibre-optic probes to obtain detailed visual information from inaccessible locations.

In many cases, the inspection forms part of a wider investigative program, which may also involve debris retrieval, corrosion assessment or routine repairs.

Where applicable, video images can be used to support data from other techniques such as crack detection.

AV Technology (AVT) can provide comprehensive internal visual inspection services at all types of plants, including oil, gas, coal, CHP, nuclear and hydro-electric.

Work includes inspections on boiler headers, turbines, attemperator nozzles, pipe work and pipe linings and valves.

The trend towards increased outage periods means that inspections, when they are carried out, must be very thorough.

AVT's vision inspection expert Ken Lambert 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 and presenting the results so that further work based on the data can be carried out requires considerable expertise".

Work in pipes typically involves routine inspections of welds, valve seat conditions, blockages and build-up of process product.

Visual inspections can also be effective in assessing the effects of flow accelerated corrosion.

Filming inside pipes and similar enclosed spaces requires a mixture of the right equipment, ingenuity and skill.

Entrance apertures may be relatively small and radial inspections require specially converted camera assemblies.

For small-diameter, short-length inspections up to 6m, 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 300m 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.

During the past decade there have been an increasing number of incidences of failures or crack indications in utility boiler pressure components.

This is primarily due to the aging of the steam generating equipment base.

Also, the condition of the components can be severely impacted by the continued trend towards cycling and load-swinging modes of boiler operation.

Of particular concern are the ongoing occurrences of header and drum internal cracking.

An important associated part of remote inspection is debris retrieval.

Debris can include parts that have broken off or material left after construction or repair work.

It is not uncommon to find objects such as tools, nuts and bolts.

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, the pre-requisite for clear and usable images is ensuring correct lighting and focus.

As Ken Lambert concludes: "It is clear that remote inspection provides a very powerful tool".

"Our experience in the power industry 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".