Inspection camera adapted for anaerobic digestion tank

When a British local utility company needed to conduct a routine surveillance check on one of its anaerobic sludge digesters, the specialist company Hayes GFS  contacted Ashtead Technology in its search for an intrinsically safe-rated inspection camera. Following discussions with Ashtead Technology’s engineers a suitably certified push-rod camera was deployed from a customised access point that enabled the Hayes’ staff to produce comprehensive images and videos showing the condition of the digester’s roof and walls.

Anaerobic digestion (AD) is becoming increasingly popular in Britain because it diverts biodegradable wastes from landfill, reduces emissions of greenhouse gases and generates biogas, which can be used as an energy source. This has resulted in a significant growth in business for Hayes GFS Ltd, a specialist provider of Glass-Fused-to-Steel Tanks and ancillary items.

GFS is a unique tank finish that has been used widely in the agriculture and water industries for decades. The two materials are fused together to achieve the best properties of both – the strength of flexibility of steel combined with the corrosion resistance of glass. GFS is therefore ideal for aggressive environments such as those inside anaerobic digesters with high temperature, high humidity, methane and hydrogen sulphide. However, this also presents a significant challenge for internal inspection.

Most of Ashtead Technology’s push-rod cameras and remote-control crawlers are employed for the inspection of drains, culverts and pipes. However, these environments can also be potentially explosive due to the accumulation of methane, so Ashtead also stocks intrinsically safe instruments and a Pearpoint P374 camera system in conjunction with a digital video recorder, was recommended for the AD application.

Commenting on the success of the project, Hayes GFS Managing Director Stephen Skinner said: “The camera which Ashtead Technology recommended proved to be ideal for this job. We built a customised ‘launch tube’ on one of the purge points on the roof and attached nylon to the camera tip so that we could video every surface once the probe was lowered into the ‘live’ digester.

“We were delighted with the results of the survey because we were able to demonstrate the condition of the tank very effectively, without having to decommission the digester.

“We were very impressed with Ashtead Technology because they ensured that we utilised exactly the right kit, and it was delivered and collected very quickly, which helped to keep our costs to a minimum.”