Solutions to create additional dust collector capacity
With changing levels of production and modifications to existing systems becoming a solution, some of you may be asking how can I get extra capacity out of my dust collector?
Wood dust extraction system, LEV COSHH testing and LEV Thorough Examination & Test in East Sussex - South East England
Here we show you an example of how we have ahcieved this for one of our customers.
Screen solutions in East Sussex, recently asked us to review their wood dust extraction system, where they believed there had been a drop in performance. Although this wasn't identified by the previous LEV COSHH testing company.
Screen solutions had also installed a new CNC machine and the extraction did not appear to be adequate, although they had been told otherwise.
Our P601 P604 certified LEV COSHH testing engineer went to site to carry out a brief inspection of their wood dust extraction system. Having reviewed the previous LEV Thorough Examination & Test reports there did indeed appear to be a drop in overall performance, although no reason was given. It could potentially be due to a much higher resistance to flow with the new CNC machine.
Our LEV Testing Engineer carried out a number of system checks and noticed that the fan inlet pressure appeared to have risen significantly (although this had not been directly recorded in the last LEV thorough eA balancing damper to the new CNC machine was also found to be approx 50% closed although this made little difference to the overall system airflow examination & test report). Note the fan was on the product / wood dust extractor 'dirty' side.
A balancing damper to the new CNC machine was also found to be approximately 50% closed although this made little difference to the overall system airflow.
There also appeared to be some external damage to a silencer or duct fitted on fan inlet, although it was unclear the extent of the internal damage.
It was also noticed that a tight 90 degree bend was fitted to the fan inlet. This is not good LEV design practice and a significant drop (10 - 15%) in performance can occur.
A centrifugal fan should always be fitted with either 3 - 4 duct diameters of straight duct. Alternatively the LEV proposals engineer should have the capability of producing a well designed fan inlet loading chamber to provide maximum fan efficiency. Often this will take up little more room than a 1.5 - 2D 90 degree bend. Other checks were done to confirm the filter differential pressures, duct flows.
Following these initial brief checks various calculations were done to check the LEV design pressures & flows and compare against measured.
Using fan laws, improvements in air flows were calculated based on the above data. The data showed that there did indeed appear to be a partial blockage in the inlet duct (silencer) of approx 500pa. It was also deduced that a balancing damper would need to be fitted to a beam saw, in order to achieve the airflow on the CNC mc.
With these improvements and the fan inlet plenum an increase in airflow of 15 -20 % was predicted. We gave a guarantee of the performance improvement stating we would achieve the required airflow for the CNC m/c and Screen Solutions ordered the works.
Our LEV site installation engineers did find a partial collapse on the fan inlet duct with a substantial amount of product. A fan loading chamber was designed manufactured & installed by R&B Industrial together with new inlet ducting and other minor works, including fitting of airflow indicator gauges on the beam & CNC machines.
We then carried out system balancing and an LEV Thorough Examination & Test on the 17 branch LEV system. As a minimum Screen Solutions wanted the beam saw, CNC & at least one other machine to be run consecutively. We were able to achieve this & in addition a further 2 machines could be run consecutively.
Air Sampling In Your Workplace
You know your work-shop is dusty.....but do you know how much is inhalable and what your wood dust hazards and risks are?
Read below and find out the main causes of exposure to dust in your work environment ...
(i) Using ash for manufacturing sports equipment … and finding decreasing lung function?
(ii) Installing Birch flooring … and getting dermatitis?
(iii) Repairing boats with Western Red Cedar … and developing rhinitis?
(iv) Manufacturing packing cases from Gaboon … and becoming asthmatic?
Get your wood work-shops monitored and dust levels measured. Ensure you are compliant with EH40.
Give R&B Industrial call.
An urgent solution to enable the use of a diesel manitou in a food warehouse.
How can R&B Industrial help you overcome an LEV problem in your company? An example of a solution from an urgent enquiry
A large food manufacturing company in Milton Keynes, recently sent an urgent enquiry through to us to help come up with a fast result in solving their LEV problem in the main factory.
We set out to advise and come up with a quick plan for a vehicle exhaust extraction system solution to extract fumes from their telehandler in the building. The customer had initially been looking at a diesel particulate filter however this was unsuitable as it does not remove NOx or CO and it was important that any contamination risk was eliminated. As this particular filter has a high value we suggested a cost-effective temporary vehicle exhaust extraction system consisting of 30m of high temperature crush recoverable hose, fan and additional standard hose to atmosphere.
With all parts luckily in stock in our stockroom our engineers assisted by setting up a ‘plug in’ system to ensure quick and easy fixature for the customer and tested within 4hrs. Packed on pallet and shipped to site on an overbite delivery the same day to reach the midlands by the morning. All in all, a successfully swift service.
"Due to the need of an internal 120 meter steel gantry to be installed 10 meters high I had no option but to use a diesel powered tele-handler, however as we produce food there is no way I could have diesel fumes inside the factory. My search for an electric tele-handler was in vain and could see my only option was an exhaust extraction system purposely built for the project.
I contacted 4-5 fume extractions companies only to hear back from two, one of which was www.rbindustrial.co.uk , I explained the project and the lengths (50 meters or more) of hose I needed to run outside for exhaust the fumes. The team at www.rbindustrial.co.uk were amazing and pulled out all the stops getting a system on to site the very next day, I put the new system to work on to the tele-handler and after a few tweaks got 100% of all fumes out of the building. The system was used for 3 weeks solid without fail and even though I had opted to rent the systems I bought the system to keep on site for future use.
Without the help of www.rbindustrial.co.uk the project would have ground to a holt, engineers would have gone home & total disaster.
Thank you to the team at www.rbindustrial.co.uk"
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.