Safely making probe holes for subterranean gas inspection

Cadent seek alternative approaches to forming small holes in hard footpath and road surfacing materials to enable potential underground gas leaks to be located. Current bar-holing tools or searcher bars are unsuited to some physiques and bring an ergonomic hazard. Solutions need to maintain or better the current performance - speed, versatility, single operative use, safe spark risk and 22kV isolation without significantly increasing the transported weight.


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Challenge closes



Cadent seek alternative approaches to forming small holes in hard footpath and road surfacing materials to enable potential underground gas leaks to be located. Selected solutions may be trialled and/or procured by Cadent, with the potential for industry wide adoption. There is also potential for co-development of promising lower TRL solutions.


Cadent is the UK’s largest Gas Distribution Network Operator (GDNO), bringing gas to 11 million homes and businesses. They manage a network of more than 82,000 miles of pipes, most of them underground, which transport gas throughout the North West, West Midlands, East Midlands, South Yorkshire, East of England and North London.

A brief description of the problem:

When determining the presence and existent of gas from leaks, it is necessary to form a series of small holes through hard surfacing materials to then insert a small gas detection probe. Currently this hole is formed by a hardened steel tool driven by a manually lifted drop-weight, the tool is termed a Bar-Holing tool or Searcher bar.

Bar-Holing is one of the first steps in verifying and identifying possible gas leaks from underground pipes. The tool is operated by a single worker and is carried in their service van. Typically, between 15 and 30 holes are required to verify the presence of a leak and to pinpoint the likely source. The holes are 15mm diameter to allow insertion of a 10mm gas detection probe and are 200mm deep in the footway and 380mm deep in the carriageway.
The holes can be required in a variety of common construction materials from reinforced concrete, dense bitumen macadam (road construction), sub-base and compacted soils and stone. It is observed that the time to create a hole varies from a minute or less in softer materials to as much as 10 minutes or more in concrete. In instances where 20+ holes are required, this can represent a significant time cost.

There is an ergonomic hazard when using the current tool due to the tool weight of 10kg, its natural imbalance during use and position relative to differing physiques. Repeated use can also be uncomfortable for the operator due to the percussion.
Cadent are keen to explore alternative tools or devices which can significantly reduce employee health and safety risk without a loss of efficiency and without substantially increasing the weight/bulk to be transported 
Because of the risk of striking underground cables the tool is 22kV isolated, the tool is also considered intrinsically safe with low risk of sparking, which could cause an explosion risk. Solutions must be similarly intrinsically safe, when considered in the past this has precluded the use of electrical power tools due to the heighted likelihood of sparking at the cutting bit.

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