KJ Tait

There are widespread issues of failure of thin wall carbon steel pipe, particularly when partnered with phenolic foam insulation when it gets wet.

An additional problem has arisen at a property in Leeds recently where stainless steel braided trace heating tape has been used rather than the usual plastic coated tape. This appears to be causing pin holing of the pipework at every point where it is taped to the pipe (approximately every metre) through galvanic corrosion. This is coupled with damp phenolic foam insulation and a poorly finished PIB coating that is allowing rain water in but sadly not out again.

The use of stainless steel braided trace heating tape is not going to be a common place situation but definitely one to look out for.

The below images give you a very small snapshot of the situation we’re facing at this property, particularly if you consider there is circa 1000m of this pipework in the same situation located externally!

Whilst the installation of thick wall screwed steel pipe has an increased labour resource, typically taking around 30% longer, the risks of reactive corrosion are vastly reduced and the CIBSE economic life expectancy is increased.

If thin wall carbon steel is to be used, it should be coupled with a glass fibre/rockwool insulation rather than phenolic foam to reduce the risk of corrosion. Most importantly, especially where it is located externally, the lagging should have a correctly finished vapour barrier.

Documents BSRIA BG50 2021 and SFG20 both recognise the issues with this type of pipework and each provide guidance on operational and monitoring guidance for such systems.

We would not advocate the use of thin wall carbon steel pipework on projects.