Industry emphasis on LEV (local exhaust ventilation) systems heightened last year when the HSE updated its guidance on welding fume after new evidence showed exposure to welding fume can cause cancer. As a result, part of the HSE’s revised COSHH (Control of Substances Hazardous to Health) advice for welding now sets out best practice when using LEV systems.
Of course, the best practice use of LEV systems can only be achieved if they are correctly tested, maintained and cleaned. Such a strategy can ensure that operators are protected from exposure to a range of airborne contaminants, such as fume, dust, mist, vapour or gas.
According to COSHH, most LEV systems (with a small number of exceptions) must be thoroughly tested by a competent person at least once every 14 months. “Although this is the maximum time permissible, the recommended testing frequency for specific systems should be specified by the LEV system provider, as factors including the nature of the application, frequency of operation and usual running time can all impact on system performance,” explains Carl Latham, UK LEV and service sales manager at Filtermist, a supplier of filters that block coolant oil mists produced by metalworking machine tools.
The HSE also states in guidance ‘HSG258 – Controlling airborne contaminants at work: a guide to LEV’ – that ‘thorough examination and test’ (TExT) must be carried out by a ‘competent person’, which could be someone in-house or an external provider. According to the HSE, ‘competent’ means ‘people having the sufficient training, knowledge and experience to carry out the job they are employed to do’.
When assessing an LEV system, Filtermist’s tests include face velocities, in-duct velocities, static pressures and filter differential. The company also performs Tyndall beam tests (the phenomenon by which colloidal particles scatter light), qualitative smoke tests, visual inspections, process inspections and workplace air monitoring.
Its P601-accredited LEV engineers (P601 is a BOHS-approved LEV training course) use a hand-held anemometer to measure the velocity of air being extracted at source and in the ducting. Results are compared with the specification of the original installation report to ensure the system is performing as intended. If the air flow speed has decreased, this can indicate an issue with the system, such as a blockage or ‘blinded’ filter material.
|“Companies may think that by installing an LEV system they are adhering to COSHH regulations, but there are other factors which should be considered to ensure a clean and safe working environment. For instance, there are a number of daily, weekly and monthly checks that machine operators should undertake alongside the required LEV TExT to ensure any potential issues are identified and resolved as quickly as possible. Filtermist provides LEV logbooks with all units sold to help customers keep accurate records," Carl Latham, UK LEV and service sales manager at Filtermist.|
The logbook is designed to help avoid one of the most common failings encountered by LEV engineers at Filtermist: poor housekeeping and planned preventative maintenance (PPM). “Notably, the logbook sets out recommended PPM points for various running time milestones,” says Latham. “This includes a comprehensive clean of the inner drum and outer case, and replacing the seal, filter and silencer pads. Further checks comprise checking the inlet grille is clear, cleaning the swarf arrestor, checking the ducting and oil return hose for wear and tear or damage, and checking that the after-filter [if fitted] is not saturated.”
Simon Cook, MD at Airbench, also stresses the importance of effective cleaning and maintenance: “Regulations specify that equipment must be maintained in good working order and in clean condition,” he says. “Here, intervals should be determined either based on manufacturer recommendations or, if none are available, on in-house experience.”
Assuming suitable information is available, routine maintenance on a well-designed system can be performed in-house by a competent person, as assessed by the employer. “Depending on the system, this may require training or simply the provision of an instruction sheet,” says Cook. “Many manufacturers will offer training on more complex systems. If cleaning and routine maintenance must be performed by the supplier, consider these costs when purchasing the system.”
He adds: “With regard to testing, when our P601-qualified engineers arrive at a facility, they always want to see a system that is kept in good working order. Unfortunately, many operators do not record routine maintenance in a logbook, which is a standard HSE requirement. In a lot of cases, LEV systems are viewed as a ‘black box’ – feed in dust and it disappears. It’s not totally unusual to see systems where filters have not been touched or looked at for years, which means dust bins are full. Operators and employers need to make sure regular checks and maintenance are part of their routine.”
Although every LEV system is different, most comprise a hood, fan, filter and, possibly, a filter cleaning mechanism. “If you are operating the hood correctly – making sure the fan still runs correctly and maintaining filters – then there is a good chance you're doing it right,” says Cook. “However, every system should come with a manual detailing the cleaning and maintenance routines required, and if you do not have one, a good LEV supplier should be able to examine your system and provide recommendations."
Another expert in the testing, maintenance and cleaning of LEV systems is BOFA International, which again offers services via a team of trained and independently P601-qualified engineers. BOFA LEV systems are used for a variety of industry operations, including soldering and additive manufacturing, as well as a host of laser-based processes, such as marking, engraving, cutting and welding.
“COSHH regulations are not the easiest thing to read, so the HSE did our sector a big favour when it introduced HSG258, which broke down the COSHH regulations as they apply to LEV,” states Graham Mattok, UK sales manager at BOFA International. “HSG258 made it easier for us to talk to customers about testing, maintaining and cleaning LEV systems, setting it out as a best-practice standard.”
Once appointed to examine and test an LEV system, experts at BOFA International commence their routine, which typically focuses on checking the air flow at point of extraction and through the machine. If the testing indicates that maintenance or repair is required, BOFA can provide assistance via its service division. However, to help avoid this outcome, there are certain tasks that users can perform to ensure LEV systems remain in optimum condition.
|“Good housekeeping is important. HSG258 recommends that a logbook be kept for each LEV system, and we would encourage users to set up inspection schedules. Unfortunately, many of the filters are integral and cannot be seen, making them difficult to clean. However, you can observe the general condition of an LEV system, including whether there is sufficient flow," Graham Mattok, UK sales manager at BOFA International.|
“On-tip extraction in soldering, for example, involves pulling fume through a small diameter tube. It’s quite easy for objects to get drawn up these tubes, causing a blockage. Or, if best practice cleaning is not observed, tubes can fur-up and restrict flow. As 14 months is quite a long time between testing, we would recommend that users clean their tubes on a regular basis. Brass brushes or fluid baths can be used for this purpose.”
Wherever an LEV system is deployed, it is clear that good housekeeping – involving defined cleaning and maintenance routines – is an essential part of protecting operators from inhaling anything that could be harmful to health.