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Asbestos Containing Fuse boards (Old BS3036 type)

The risks associated with asbestos are now widely known, thousands of people have reportedly been affected by the inhalation of asbestos fibres either directly or indirectly and sadly hundreds have already lost their lives as a result and many more sadly will.

The gestation period of asbestos related disease can be twenty or thirty years.

Large amounts of asbestos were used in new and refurbished buildings before 2000. Usage began to decline in the 1970s and blue asbestos (crocidolite) had a voluntary ban in 1970. Blue and brown (amosite) asbestos were banned by law in 1985. Uses of white asbestos (chrysotile) were banned in 1999. Everything else, and most secondhand supply (except for very high performance materials) was banned by 2000.

Legislation has forced all businesses to have asbestos surveys carried out, to hold a register of the findings and to take precautionary or remedial action where asbestos is found to control or remove the risks associated.

A little known area seems to have in many cases "slipped the net", this being Chrysotile woven asbestos rope found in most older BS3036 re-wireable type fuse boards. Chrysotile asbestos although by no means the most lethal form of asbestos, is still potentially hazardous to life.

In fuse boards it is in a "rope" form which can give rise to air-born particles being released if disturbed which could, like any other form of air-born fibre be inhaled and become lodged permanently in the lungs. This has been proven to be a catalytic cause of fatal lung disease.

In most surveys carried out by specialist asbestos surveyors, old fuse boards are usually listed as "potentially containing asbestos". This is because, in most cases asbestos surveyors are not electrically qualified and therefore not deemed competent to open fuse boards, pull fuses and inspect. So fuse boards are generally not accurately identified as potentially hazardous in terms of asbestos.

From an electrical safety viewpoint, theoretically there may be no risk. The fuses in the fuse board may well comply with the required disconnection times and may be able to handle prospective fault currents quite safely. So electrically, it would not be cause for concern or require replacement on those grounds. But it cannot be safely tested to prove this fact for the reasons described below.

Why was asbestos fitted to fuse boards in the first place?

Although thought of as an explosion, when a fuse-wire blows it actually melts and opens the circuit. In the process of disconnecting an overload or short circuit, the electricity tries to keep flowing through the fault (the path of least resistance). As it does so, it creates an arc across the fuse carrier where the fuse-wire was. This can generate incredibly high temperatures and release an extremely large amount of energy, all within a few fractions of a second.

The function of the asbestos rope, being a non-flammable and absorbent material is to "arrest", absorb and extinguish the flash safely without allowing the destructive energy released to destroy the fuse carrier or worse explode out of the carrier and cause wider destruction and possibly serious injury or death.

So What's the Risk?

The risk is very low under normal conditions as long as fuses are not pulled, thereby exposing the Chrysotile asbestos rope.

However, if a fuse-wire should blow then it will need to be replaced. This will involve isolating the supply, opening the fuse board, pulling the fuse carrier out and replacing the ruptured fuse-wire.

The asbestos rope has already now been disturbed by the energy which it has just had to absorb from the fuse rupture and is therefore highly likely to release asbestos particles readily when the fuse is pulled.

The Solution to Risk Management.

Under controlled conditions and by following HSE Guidelines for handing asbestos in this situation (download HSE guides a30 & a33), it is perfectly safe theoretically to replace blown fuses.

In virtually all cases however, this will not be the case, as a blown fuse needs replacing "right now". Control measures required when exposing asbestos require area sheeting-off, the use of PPE by the operative, shadow vacuuming of the area and more. In other words, it is a major task and will probably result in long-term loss of power to the affected circuit and will also involve the engagement of operatives suitable trained and competent to work with asbestos.

In practical terms, the only logical solution is either asbestos removal and fuse carrier and fuse replacement (assuming replacement carriers are still available) or complete replacement of the fuse board with a modern MCB type distribution board, thereby removing the risk.

Replacement of Asbestos containing boards

This will involve the implementation of a number of control measures, in all practicality the engagement of a registered asbestos removal contractor and a planned shut-down of all circuits fed by the fuse board being replaced. For detailed procedures download the following ETS risk assessments & method statements relating to testing / removal & replacement "Asbestos in electrical distribution boards INSPECTION" & "Asbestos in electrical DBs REMOVE using asbestos contractor" & "Asbestos in electrical DBs REPLACE carriers using asbestos contractor"

 

Article written by:     Martin Lancaster Electrical Testing Surveyors Ltd

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