Issues with wood dust collectors - FROM A DSEAR ATEX PERSPECTIVE:
Issues with wood dust collectors - FROM A DSEAR ATEX PERSPECTIVE:
What are the important factors regarding ATEX DSEAR in wood-dust dust collector design:
We carry out a number of DSEAR risk assessments on wood dust extractors where the dust collectors are made from a thin 0.8mm or 1mm galvanised sheet with no bracing or strenghtening, they have however been fitted with an ATEX explosion relief panel.
In addition, the fans are fitted on the product / inlet side; blowing product into the dust collector. The wood dust collector manufacturer has in many instances wrongly certified the dust collector as suitable for an ATEX Z22 or Z21 which has been copied directly from the explosion relief panel. The dust collector manufacturer may have failed to realise a number of important points;
1. The finess and structure of the wood dust is crucial: in general the finer and more uniform in profile, the more likely the wood dust will explode, rather than burn.
In general if > 40% of the woodust size is below 200 micron?? the explosion risk can greatly increase.
2. The moisture content is crucial: the lower the moisture content - the higher the explosive risk ie < 8% moisture ? TBC is sufficient for an explosive event; note the moisture content can vary due to environmental conditions.
3. What are likely quantaties of fine wood dust being collected?
4. What is the air volume of the dust collector?
5. Assuming the dust is 'explosive' can the initial ignition be contained to create a sufficient pressure rise within the vessel ie dust extractor, to create an explosion (pressure rise) rather than fire.
So what should be done if you have one of these types of dust collectors fitted in your factory, or are being offerred one as a dust control solution for your woodwork shop?
The very first thing to do, if you have existing dust collectors, is to have dust classification test carried out on a representative sample of wood dust. This is a relaively low cost test, 1 sample price £350 (with discounts for 2 or more samples). Approx 0.5kg ssmple is required, sealed in box or bag / ensuring moisture content will be un-changed.
R&B Indistrisl's dust classificstion test consists of;
1. A sieve test of the complete sample
2. A moisture content test
3. Various ignition tests to determining whether the sample will ignite and sustain combustion or not.
From the results it is possible for us to determine the suitability of the dust / product with respect to the dust collection system design. For instance:
- In many instances the fitting of explosion relief panels is not a requirement from a DSEAR / ATEX perspective and no further control mitigation measures are required: here the dust would be generally course and flammable but not an explosive risk.
- In other cases additional control measures may also be recommended, such as flame suppression / water deluge systems in order to reduce risk to a satisfactory level.
- In other applications the incorrect dust collector has been specified / supplied and in these circumstances a complete re-design of the system should be carried out.
In many applications it will be difficult to determine the above characteristics of the dust prior to the actual collection of dusts from the woodworking machines. However, the risk increases depending on:
- If the dust contains a reasonable % of mdf, hardwood.
- Types of wood working machines in use ie sanders, x cut / table saws, ....... tend to create finer dusts.
In these circumstances a correctly specified ATEX certified dust collector should be specified / installed. This can include some or all of the following:
- A wood dust extractor built with the correct vessel strength / bracing etc. This includes the discharge / bin design.
- Strengthened duct to the explosion valve.
- Correctly sized explosion relief panels; taking into account such things as explosive dust properties, vessel strength, and volume, ....
- Water deluge or other suppression system.
Another important consideration should be the amount of fine dust layering within the workplace or within the clean side of the dust collector. This can create a secondary dust explosion far greater than an initial fire / explosion.
These are the results from a recent dust testing which was carried out on the wood dust from the Mill.
Without predjudice, I have provided the following information which I hope is useful?
Wood waste usually has a dust explosion risk where the mean particle size is less than 200 microns, and where as little as 10% of the mixture contains dust less than 80 microns in size. Only weak explosions are likely where the mean particle size are outside of these limits. Note the higher the quantity of fine dust below 80 micron, the higher the risk.
The dust sample received had approx. 20% below 125 micron with approx 8% < 90 micron, at 11% moisture w/w.
This would indicate that if ignition took place, only a weak explosion would occur, with the mix of dust received. If dust separation can occur where the fine dust can then form a cloud in air, there will be a higher risk of explosion.
At Mill Brook Beds it could be conceived that an explosive fine dust formation, could occur during the cleaning period (when dust collector shut down) i.e. due to the separation of fine / course dusts within the dust collector / filters etc, although the agitation will not be as much compared to either shaker or reverse pulse jet systems. At the same time as the dust cloud formation there would also need to be an ignition source: The most likely cause for an ignition would be either:
- Tramp wood say, caught in a wood work machine saw blade which is heated to ember temperature and then sucked into the dust collector.
- Metal impact on fan impellor i.e. via nail or metal object, or again tramp wood caught in impellor & heated to ember temperature before releasing into hopper.
- Static ignition either from filters or plastic collection bags (low risk)
We would recommend that the plastic collection bags are replaced for antistatic type and placed within an earthed metal collection bin; currently if a fire were to occur this could spread due to the splitting of the collection bags.
When replacing filters ensure antistatic filters are fitted.
It must be ensured that dust / product is not allowed to build up within the duct which could also facilitate the spread of fire to other areas.
In addition, if the above scenarios are likely or foreseeable then we would recommend a heat / smoke detection & deluge system should be fitted into the dust collector. A magnetic separator within the duct leading to the dust collector should also be considered.
If funds are available a new ATEX dust collector should be considered, however we feel the risk of explosion is low with the types of control measures specified above.
The above is also dependant upon:
- Processes (connected to LEV) do not change, i.e. if more sanding or processes that create more fine dust are envisaged.
- The type of wood used does not change, i.e. very little hardwood / MDF dusts.
Is your LEV functioning the way you think it is?
This clip shows respirable fumes exiting from a component collection bin.
The face of the hopper has been covered, but the components are ejected from the tool using a pulse of air which overloads the LEV system. Each ejector pulse can be seen forcing respirable fumes into the working environment.
The highlights of our year 2018
The last 12 months have flown by and on reflection this year has been very busy and productive for us all. With our biggest achievement in winning a prestigious award for our energy saving SmartAIR® System.
We wanted to share with you the highlights of our amazing year:
At R&B we believe that training is paramount to success and development of our employees. We reguarly visit sites that require noise assessments, therefore we wanted to expland on our knowledge in this area and decided that we would put resources into training. W503 is a recognised noise assessment course and Nick, our Electrical Design Project Engineer, was the appointed member of staff to undertake this training in Portsmouth. Noise risks in the workplace should be carefully managed to ensure that employees are protected from this specific risk in the workplace.
R&B Industrial were shortlisted as a finalist for the CIBSE Energy Efficient Product or Innovation of the Year Award for our patended SmartAIR® System.
The CIBSE building performance awards have been running for over a decade. As an organisation they award people, products and projects that demonstrate engineering excellence in the build environment that achieve efficient technology to reduce the amount of energy required to products and services.
The awards were held at the Grosvenor Hotel in London. Suited and booted with a prosecco in hand we sat down to dinner with the other finalists to all share in celebrating our achievement.
At the start of the year many of us around the country were greeted with polar like scenery. Isolated and snowed in, the majority of the UK enjoyed a snow day with loved ones. Our vans stayed parked up at the industrial park which meant no site visits for our lads that day and a very cold walk for our employees to work that morning!
From a small independant company in the early 80s, R&B has gone from strength to strength growing in numbers and establishing a positive reputation in the engineering industry and this year we celebrated 35 years, marking a significant milestone for us as a company.
For the third year running we exhibited at the BOHS Exhibition, along with some other well known names in the industry.
As a collective we contributed in furthering the knowledge of all the attendees on all aspects of dust and fume extraction. We particuarly focused on the use of ATEX certification and ways in which companies can reduce their Carbon footprint in the coming years. This was delivered by our specialist team members, Dr Roger Watson and Mr Clive Bates.
April also marked a successful month in terms of awards. We were shortlisted and won the SHAPA 2018 Innovation award for our energy efficient SmartAIR® system.
Our SmartAIR® system delivers incredible cost savings along with market leading energy efficiency. The event was held on board the SS Great Britain in Bristol. We were over-whelmed and honoured to be given this award and it recognises all the hard work that the team have put in to developing the system.
Saw some of our team undertaking the P601 LEV course. This course trains delegates to undertake Thorough Examination and Tests (TET) on basic testing of LEV systems. This was held in our upstairs meeting room. A good pass rate all round well done guys!!
Congratulations to Gareth and Vicky on their wedding in June!
We also retained our Safe Contractor status! This means as a company R&B are now approved and recognised as in health and safety assesssment schemes for contractors who want to demonstrate that they are taking responsibility for their legal health and safety requirements.
In July Clive went up North to Lichfield to give a speech at the SHAPA solids handling event about our SmartAIR® system
The world cup final of 2018 meant Nicky, who doesnt even like football, won the sweep stake for France!
This saw our first reseller sale of our energy saving SmartAIR® system. This small diagram giving a brief explanation how it works. For more info please visit our SmartAIR® page.
We also employed two work experience students over the summer period. One of which still works for us part time as our stores and warehouse controller whilst still undertaking her college course in mechanics.
Celebrated the companies founders Roy and Beryls Diamond Wedding Anniversary! 60 years wow! September also saw the start of two new employees. Graham, who will be assisting with air monitoring and DSEAR assessments and Sophie who has joined our admin team. Welcome aboard the team guys!
For the first time we attended the W Exhibition in Birmingham. We were delighted that Francesco from our partner company GEF in Italy was able to come over and spend a few days with us. It was a very productive and successful Exhibition where the company were recognised for our achievement in our energy saving system and were shortlisted as a finalist for the Elements of Innovation award 2018. We also had some fantastic news that Roger and his wife had a lovely little boy, Peter. Congratulations!
Although the winter doom and gloom was upon us, we still welcome rainbows from the office any day of the year!
Had a Fabulous time at our works christmas meal. A good time to celebrate with the team and let out hair down after a busy year all round!
Climate change, are we doing enough?
How is R&B Industrial contributing to reducing the impact on the changing climate?
Climate change is rapidly becoming the most important single issue that has consequences for every living species on our planet and with the Intergovernmental Panel on Climate Change (IPCC) releasing their report in October 2018; its key message is that we have 12 years to limit global warming to not exceed 1.5°C above pre-industrial temperatures. The observed increase for the decade 2006 to 2015 alone was 0.87°C. To do this, we must reach & sustain net zero anthropogenic emissions & quickly.
Given our species dependency of fossil fuels, this seems like an impossible task and it will take a communal effort not seen since the 2nd world war to stand any chance of succeeding.
R&B Industrial has long acknowledged the need to decarbonise our operations and be mindful of how we use our resources. In the past 5 years we have installed a 20kW/hr array of solar panels to our factory roof which generates more than our annual consumption of electricity. We have converted all of the factory and office lighting to ultra-efficient LEDs & fitted an efficient heat recovery ventilation system.
We are aware that this alone is not enough and are striving to identify other areas where we can save energy & reduce our material consumption.
Transport is our highest source of emission, so to address this, we are in the process of procuring a battery electric van. Four of our staff either walk, cycle or use electric vehicles to travel to work.
Our efforts to reduce CO2 emissions don’t stop at our premises. With the launch of our patented SmartAIR technology, we are now helping our customers to reduce their electricity consumption whilst maintaining the highest level of control of exposure to hazardous materials in the workplace. Many of these systems recover the initial cost within 2 years and are saving many megawatt/hrs of energy.
If you would like advice on how to reduce your Local Exhaust Ventilation’s or dust extraction system’s energy consumption whilst not compromising on its effectiveness, contact us on the above telephone number or email address.