During the early eighties and speaking generally, the sole internal pipeline inspection was either performed by the sewer inspection companies, who would be inspecting mainly dry sewer pipe sections over short distances; typically not exceeding 150m and who stop in the event the pipe became surcharged to the point where the camera would become submerged and also the oil industry support companies who’d run ‘intelligent pigs’ though the oil pipes to evaluate weld integrity, pipe wall thickness and symptom in to assess pipeline longevity and safe operating pressure.
At this time the water companies have been largely oblivious for the internal condition of their pipelines, adits, aqueducts and tunnels were beginning to have concerns concerning the integrity of these assets, most of which was constructed throughout the Victorian era or even more recently in the early fifties coupled with never been inspected and were unsuccessfully searching for companies and/or equipment that could execute such surveys.
In some instances these folks were capable of de-water the pipelines and if just right diameter, they will send a confined space team directly into carry out a visual survey; such surveys were obviously fraught with potential dangers, most famously which included the danger of collapse, flooding and also the accumulation of toxic gasses.
De-watering was included with its set of potential risks on the structural integrity of the concrete, tunnelled and brick constructed pipelines; in many cases, small leaks manufactured by displaced joints, erosion and localised damage etc. enabled the leaking water to locate a path with the ground as well as over many years, earth can be passed from throughout the pipe, often resulting in large water filled voids forming across the outside of the pipeline.
The newly de-watered pipeline which could regularly be partially dependent on the head water inside pipeline (trying to push the walls out), to keep its structural integrity, could suddenly encounter several a lot of water away from the pipeline (trying to push the walls in), creating localised regions of external high pressure, which would often result in pipe failure and localised collapse, causing subsidence in the ground over the pipeline manifesting as holes in the ground that could appear ‘over-night’.
Around now there was an ever-increasing demand in the Water Companies for you divers up water filled pipes furnished with CCTV cameras, to survey at as far as his or her nerve or umbilical length would permit.
In just a very short period of time the HSE Diving Executive, showed a passionate desire for the security part of sticking divers up pipes and eventually a trip selection of around 30m as a maximum was considered safe, providing that all the essential security precautions were available.
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