Welding Fume and Grinding Dust: Industrial Fabricator Case Study
The client on this project was a specialist industrial fabricator with over 30 years of experience serving the oil and gas industry. The industrial fabricator prides themselves on their adaptability and innovative approach to the work offer a wide range of fabrication solutions and services to its customers. As part of their fabrication services, they can meet very tight delivery schedules and have the facilities on-site to cover all types of welding and fabrication requirements. Those include carbon steels, stainless steels, duplex, super duplex, titanium, nickel and copper-nickel alloys.
Auto Extract Systems were tasked with proposing and installing a comprehensive LEV (local exhaust ventilation) systems in the multiple workshops the industrial fabricator has to safely capture and remove the welding fumes and grinding dust that was being emitted into the workplace’s environment during the business’s fabrication operations. The LEV system was installed as part of a project to ensure the fabrication workshop 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.
The company had no form of LEV (local exhaust ventilation) in their welding workshops and were aware they needed to improve the air quality for all employees, particularly so after HSE issued a new safety alert about a change in enforcement expectations for the fumes created by the welding of mild steel.
The change in enforcement expectations for mild steel welding fume have been brought in after new scientific evidence from the International Agency for Research on Cancer came to light 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 has endorsed the reclassification of mild steel welding fume as a human carcinogen. The reclassification will see HSE’s enforcement expectation for mild steel welding fumes come into force with immediate effect; primarily because general ventilation does not provide the necessary local control required to safely protect welders and associated employees.
With such a vast and large-scale operation at the industrial fabricator’s site, the proposal that Auto Extract Systems put together was split into four sections; the Carbon Shop, the Exotic Shop and; the Fabrication Shop.
The Carbon Shop
The two identical LEV systems were installed in the carbon shop were designed to safely capture and remove welding fumes and grinding dust at-source. For these systems, Auto Extract Systems supplied and fit new galvanised steel ducting and fitted to accommodate two identical systems, which comprised of five, 5-meter long welding fume and grinding dust hose extraction arms. These five arms were ducted through a common duct to a reverse-pulse dust extraction filtration unit, which has the capacity for four filter cartridges and gives the filter unit a total filter surface area of 78m2 (19.5m2 per sleeve).
The Exotic Shop
The LEV system in the exotic shop was designed to safely capture and remove welding fumes and grinding dust at-source. For this system, Auto Extract Systems supplied and fit new galvanised steel ducting and fittings to accommodate eight, 5-metre long welding arms. The hose extraction arms were ducted through a common duct to reverse-pulse dust extraction filtration unit, which has the capacity for four filter cartridges and gives the filter unit a total filter surface area of 117m2 (also 19.5m2 per sleeve).
The Fabrication Shop
The fabrication shop was approximately 60-metres long by 15-metres wide and had a split-level roof with two heights, 9-metres and 13-metres tall. This was for the larger fabrications with the extended height and larger capacity crane. The production manager of in this facility was assured that if at-source extraction arms were installed, they would be damaged. With this in mind, a general ventilation ‘wrap-around’ LEV system was designed to safely capture and remove residual welding fumes and heat given off from the welding and grinding process.
As an at-source extraction solution wasn’t installed in this building and in the scenario that at-source extraction arms were to be retro-installed in the future, it was proposed and agreed that a comprehensive centrifugal fan and filtration system capable of managing the airflows and filtration required for both the ‘wrap-around’ and at-source extraction system was installed, thus to save the company money in future by upgrading the fan or filter.
The wrap-around general ventilation system works whereby any residual plumes of dirty hot fumes, gases and dust, that have risen into the roof space are captured and expelled. As the fume leaves the work-piece, it quickly rises to a high level and will eventually meet the cooler roof fabric, which it cannot pass through. The fume will then cool and begin to return downwards settle, but as it still has buoyancy, it can be seen to hang in the roof space (2 to 3-metres from the roof), typically around crane track height. The ‘wrap-around’ system is carefully positioned in the space above the bays and will continually capture and remove fume.
The system featured dampen-able grilles along a dual ducting run that was located above the gantry crane track. The dual run of ducting was connected to a common duct to a dust bank collection unit; a reverse-pulse filtration unit, which has the capacity for eight filter cartridges and gives the filter unit a total filter surface area of 156m2 (also 19.5m2 per sleeve).
As the systems were being used for both welding and grinding processes, to adhere to HSG258 guidance. The filtration units specified for these LEV systems were modular dust bank collector filters that could accommodate up to eight filter cartridges. For this installation, two four cartridge filters, a six cartridge filter and an eight cartridge filter were installed which all feature the latest innovative filtration technology and 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.
All fans specified for the LEV systems for this client exceed the E.U Directive 2009/125/EC ErP. This directive is aimed at reducing CO² emissions by 20% by using energy-efficient motors in conjunction with industry-leading blade design. All supplied extraction fans must now meet or exceed this.
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).
The HSE manager for the industrial fabricator stated: “We recently contracted Auto Extract Systems to install four LEV systems to comply with the HSE welding fume control guidance. The process from start to finish was simple, their team was professional and the quality of their workmanship was first class. I would have no hesitation in recommending Auto Extract Systems n the future.”