In early eighties and speaking generally, the only internal pipeline inspection was either performed by the sewer inspection companies, who does be inspecting mainly dry sewer pipe sections over short distances; typically not exceeding 150m and who does stop if your pipe became surcharged to the point where your camera would become submerged and the oil industry support companies who’d run ‘intelligent pigs’ the oil pipes to assess weld integrity, pipe wall thickness and overuse injury in order to assess pipeline longevity and safe operating pressure.
At this time water companies who were largely oblivious to the internal condition of their pipelines, adits, aqueducts and tunnels were starting to have concerns concerning the integrity of the assets, a few of which had been constructed through the Victorian times or more recently in early fifties together never been inspected and were unsuccessfully looking for companies and/or equipment that could perform such surveys.
In some instances they were capable to de-water the pipelines of course, if large enough diameter, they might send a confined space team in to conduct a visual survey; such surveys were obviously fraught with potential dangers, such as that included the possibility of collapse, flooding and the accumulation of toxic gasses.
De-watering had its own list of potential risks towards the structural integrity with the concrete, tunnelled and brick constructed pipelines; most often, small leaks manufactured by displaced joints, erosion and localised damage etc. enabled the leaking water to discover a path from the ground and also over a number of years, earth will be beaten up from across the pipe, often causing large water filled voids forming around the outside of the pipeline.
The newly de-watered pipeline which may get partially dependent on the top water from the pipeline (trying to push the walls out), to keep its structural integrity, could suddenly experience several a great deal of water outside the pipeline (trying to push the walls in), creating localised parts of external high pressure, which may often bring about pipe failure and localised collapse, causing subsidence in the ground across the pipeline manifesting as holes in your yard that might appear ‘over-night’.
About on this occasion there was clearly a growing demand in the Water Companies to deliver divers up water filled pipes armed with CCTV cameras, to survey for as far his or her nerve or umbilical length would permit.
In just a very short period of time the HSE Diving Executive, showed an desire for the safety part of sticking divers up pipes and eventually an excursion selection of around 30m being a maximum was considered safe, providing that most the mandatory health concerns were available.
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