CROSS Safety Report
Specifying resin by colour causes confusion
A mistake occurred on-site when resin for fixings was selected by colour of packaging rather than by colour of resin. The actual resin used did not reach sufficient strength and the installed fixing failed under a pull test.
Key Learning Outcomes
For the construction team:
- At all stages of the construction process, all products must be referenced by their full identifying name/marks to prevent products being selected incorrectly
- Fixings must be selected and used strictly in accordance with manufacturer's instructions
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A reporter confirmed they typically use two different resins (type A and type B) for anchoring fixings. The resins used are different formulations for application in differing ambient conditions. The resins are dissimilar colours and come in packaging of a different primary colour to the contained resin. The reporter confirmed a misconception occurred on-site which led to a pull test failure.
The engineer in charge of work was aware that in wet situations, such as those seen in a shaft bottom, type B resin was required. The Engineer specified resin type B, by resin colour, for that location.
The mix up occurred when type A was used instead of B because the resin was selected on-site by colour of packaging rather than by colour of resin. This resin installed in a wet drill hole didn’t reach sufficient strength and the fixing failed under a pull test.
The site pull testing regime was sufficient to catch this honest mistake and briefings have highlighted this misconception to site staff. The reporter has highlighted the issue to the manufacturer but also wanted to share their experience with others through CROSS.
CROSS has previously published a number of reports and an alert concerning epoxy fixings; these include Failure of epoxy resin bonded anchors in concrete and CROSS alert The selection and installation of construction fixings.
Expert Panel Comments
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Selecting, installing and testing of fixings
The design and installation of fixings should be treated as an engineered activity because of its complexity and safety-critical nature. CROSS would draw attention to the need for the correct design, specification, and execution assurance, including supervision, inspection and testing, in accordance with:
1. BS 8539:2012: Code of practice for the selection and installation of post-installed anchors in concrete and masonry
2. The Construction Fixings Association provides extensive guidance and other resources upon selection, installation and testing of fixings
3. Strict adherence to manufacturers installation guidance
It is not good practice to specify the resin by its colour and further information as to the actual properties required should have been given and checked by the operator, indeed in some cases it would be appropriate to record details of the batch of resin used as part of the QA process. However, it is also good to hear that the pull out testing regime was rigorous enough to catch this error before it became a danger. It also highlights the benefits of ongoing testing after any initial suitability testing.
it highlights the benefits of ongoing testing after any initial suitability testing
Design out the potential for human error
This is an interesting report and falls into a generic group of issues where design has inadvertently caused human error.
A good example is the Camelford town poisoning incident in 1988 when it was possible for a driver (by confusion) to open the wrong water tank and dump in 20 tonnes of aluminium sulphate (creating drinking water with 3000 times the permissible limit). This could have been avoided if there had been only one key and one lock that the single key could release.
In this reported case, relying on colour alone for a safety-critical component (packaging or product) seems foolhardy as many people are colour-blind and unwilling to say so.
In designing anything (even packaging) avoid the possibility of confusion and human error.
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