Welding Fume and Grinding Dust: Structural Steel Case Study
The client on this project was one of the largest structural steel companies in the UK and Europe and specialise in the design, engineering and production of specialist structural steel products. The company has unrivalled capabilities and process around 100,000 tonnes of fabricated steelwork per year.
Auto Extract Systems were tasked with proposing and installing a comprehensive LEV (local exhaust ventilation) system in one of the workshops to safely capture and remove the welding fumes and grinding dust that was being emitted into the workplace’s environment air during the structural steel businesses’ operations. The LEV system was installed as part of a project to ensure the site meets stringent operational requirements and to work strictly in accordance with HSE’s ‘HSG258: Controlling Airborne Contaminants at Work – A Guide to Local Exhaust Ventilation (LEV)’ guidance.
In 2019, the WHO’s (World Health Organisation) International Agency for Research on Cancer (IARCH) reclassification of welding fume to a carcinogenic after new scientific evidence came to light. The research found that exposure to mild steel welding fumes can cause lung cancer, possibly kidney cancer and neurological effects similar to Parkinson’s disease in humans. As a result, the Workplace Health Expert Committee (WHEC) (a part of HSE (Health and Safety Executive)) endorsed the reclassification and updated their enforcement expectations for mild steel welding fumes, stating: “Regardless of duration, HSE will no longer accept any welding undertaken without any suitable exposure control measures in place, as there is no known level of safe exposure.”
The enforcement expectations came into force with immediate effect; primarily because general ventilation does not provide the necessary local control required to safely protect welders and associated staff. In the STSU1 – 2019 Safety Alert Bulletin: Change in Enforcement Expectations for Mild Steel Welding Fume, businesses were advised to “Make sure exposure to any welding fume released is adequately controlled using engineering controls (typically LEV).”
The structural steel company knew that action had to be taken to improve the quality of the air in the workplace for employees, however, given the nature of their products, they were unsure of which the best method would be most effective to safely capture and remove fumes and dust from the workplace, given the scale of structures they fabricate. Various methods of local exhaust ventilation had been trialled, though none had proven to be successful. The biggest challenge was to provide a solution that met their vast-scale requirements which didn’t change their workshop’s production operation.
The solution was proposed and agreed to supply and install two new LEV systems to capture and safely remove welding fume and grinding dust at-source as part of a comprehensive LEV system. Both systems included the installation of new galvanised steel ducting and fittings, the first system was specified to accommodate eleven points consisting of nine 11-meter and two 9-meter; whilst the second consisted of nine 11-meter ⌀160mm welding fume and grinding dust hose extraction arms. The points in each system ran to a centrifugal fan through a common duct via a reverse-pulse dust extraction filtration unit, which each has the capacity for six filter cartridges and gives the filter unit a total filter surface area of 117m2 (19.5m2 per sleeve).
The hose extraction arms specified featured metallic fume capture hoods, gas-powered support struts and four-way knuckle joints. The arm’s design means they are fully flexible and can be turned virtually 360° to be operated above and below their mounting height, which allows the user to position the hood at-source with a simple operation. This extraction arm also provides the workshop with 25% increased airflow over a traditional-styled internal knuckle extraction arm, as they feature an externally mounted supports, which reduce static pressure airdrops. An ergonomically designed hood which is ideal for the collection of hot welding fumes, gases and grinding. The capture hood features a flat base to take benefit from the Coanda effect; the phenomenon is known to Science when a jet of air clings to a flat surface over a longer length than it would over towards an open collection area, enabling a greater collection of fumes over a longer length than any traditional type all round hood.
In addition, the extraction arms were specified to each feature a 24-volt LED internal light. The lights are pre-fitted energy-efficient lights are located in the centre of the arm’s capture hood to help illuminate the workpieces whilst being worked on and have a switch located on the arm’s external support bracket.
Whilst the filtration unit specified for this LEV system was a modular dust bank collector filter that could accommodate six cartridge filters. The filtration unit featured the latest innovative technology and is capable of self-monitoring, self-cleaning and filtering up to 99.9% efficiency. A high level of filtration is achieved in this filter by a reverse-pulse process, whereby compressed air is manually released down the inner side of the filter cartridge over internal ‘torpedo’ shaped filter carrier. This process allows for the pneumatic air to be used more effectively down the full length of the filter (compared to conventional cage carried or shaker type filters). It also prolongs the life of the filters and reduces maintenance costs replacing them more frequently. Dust collects in a metal waste bin below and has a 95-litre capacity.
The fans specified for the two LEV systems exceed the E.U Directive 2009/125/EC ErP, which is aimed at reducing CO² emissions by 20% by using energy-efficient motors in conjunction with industry-leading blade design.
The LEV system’s fan outlet was ducted to atmosphere via the nearest wall, where it was upwards to be vented to atmosphere through high-velocity cowls, as per HSE guidance. LEV systems were designed to fully compliant with the latest HSE guidance and 100% utilisation, so all points have the capacity to be open at once).