The slip risks resulting from machining dust became a point of discussion when a HSE inspector slipped on the workshop floor during a routine health and safety visit. The inspector was not hurt but the company did agree that processing dust finding its way onto the floor in that area did make it rather slippery. Workers too said that the walkways and working area floors were very slippery, even more vulnerable were visitors to the workshops (such as staff from the offices) as they were often taken unawares by the slippery nature of the floors.
Carbon dust on the floor
The painted concrete floors of the workshop could not be completely prevented from becoming contaminated with fine dust (up to 10 microns) from the cutting and machining of graphite components. Extract ventilation at machines was effective up to a point but the filtration systems did not seem to be able to capture as much of the dust as was needed allowing some to be deposited on surfaces. This was compounded by the system of emptying by hand the bags holding the filtered out dust; the manual process resulted in some dust being re-released and contaminating walkways.
The company set about dealing with this in two ways. Improving the floor grip so that it was better able to cope with the conditions and reducing dust contamination finding its on walkways.
Tests were carried out on various areas of workshop floor to measure its microroughness and its slip resistance. When the floor surfaces were free of dust contamination they actually offered reasonable grip for pedestrians but when they got any dust on them, as they inevitably would, their slip resistance became very low. These were exactly the results that the company had expected the tests to reveal.
Treated walkways and work areas
Trial treatments were carried out on various parts of the floor using epoxy paints with 'inclusions' of various sorts to give some surface roughness and grip. The best seemed to be gritty particles in a two-part epoxy - workers found it gave secure footing whether clean or with dust on it. Tests confirmed that the surface (with about 33 microns of surface roughness) did indeed give very good slip resistance when clean and still performed well when deliberately coated with carbon dust. The treatment was progressively extended throughout the workshop. Workers, who were somewhat sceptical to start with, quickly realised how well the treatment worked and were soon asking "When is my work area going to be done?"
The company even found the treatment worked on chequerplate metal stairs that, although only occasionally used, had been said to be especially slippery when dusty.
Treated metal stairs
Floor audits are carried out as part of scheduled safety checks and any areas needing attention are identified. Indications are that the service life of the 'grit paint' finish is between 12 & 48 months depending on the type and amount of use of the area. Treatment costs for the whole of the workshop worked out at around £1000.
Cleaning of the new floor finish is no more demanding with industrial grade dry vacuum cleaners doing the job day to day supplemented by a period clean with a mechanical scrubber-dryer.
When the company looked at the amount of carbon dust being deposited throughout the workshop they resolved to do something about that too. They saw benefits in the contribution that it would make to preventing slips, providing a better working environment and reducing the size of the general cleaning task. The existing dust capture and extraction system serving the workshop machines was not 'state of the art' and the filtration system was housed within the workshop. Plans were formulated to integrate all local exhaust ventilation into a single, more effective and efficient centralised system with the filtration plant located outside the workshop to avoid recontamination.
Of course, in addition to these benefits, the company hopes that the next HSE inspector's visit will pass without any 'slip ups'.