News is a bit light on this month because of my absence on holiday. I’d like to thank Tony and the leadership group for their efforts in making sure the shop ran smoothly during that period.
There are a few small contract jobs available for anyone wishing to become more involved. One is making breadboards. Have a chat to Tony if you are interested.
Because there is not too much else to say I am taking the opportunity to communicate a few ideas about risk management and dust extraction. Some of you may be aware of the destructive power unleashed when dust explodes while others may never have turned their minds to the subject. Coming from the grain industry I have a reasonable knowledge of the matter.
All sorts of dust can explode. Particle size, product source and moisture content are just some of the elements that have an influence. However, the three fundamentals for an explosion are containment, density of dust in the air and a source of ignition. The rule of thumb in the grain industry is that if a dust cloud is such that would be hard to see a 60 watt light bulb held at arm’s length then enough fuel is available. If that fuel load is in a contained space a spark can set off a devastating explosion.
After I retired, my former employer had a major explosion at a facility I’d had a hand in building. I was invited back to assist evaluate what had gone wrong. Put simply, the external dust extraction plant was operating sub optimally while the dust load in the product was excessive and ultra low in moisture content. As the product flowed into a 6,000 tonne capacity silo, the density of dust in the bin exceeded reasonable limits and a piece of loose metal, probably from a machine in the handling stream , struck the man safety metal grate of the silo opening causing a spark. The resulting explosion lifted the 40 tonne concrete roof off the silo, it went at least 100 feet in the air, rolled over like a tossed coin and fell back into the silo. Repairs cost was $2.7m. Because of good facility design, automation ( inherently low manning levels) and luck, no one was killed.
Others have not been so fortunate. If you Google 'grain silo explosions in USA' you will find, in the past, there have been massive explosions, many lives lost and huge damage bills. Major concrete grain export facilities, holding hundreds of thousands of tonnes, have been reduced to rubble in a second. Other industries have had failures as well.
Why raise this? The answer is to minimise risk. We have almost nil risk of a dust explosion in the workshop while ever we keep the facilities reasonably clean. What we do have is a low level risk of fire in the dust room if we fail to regularly check and empty the dust bags. The mode of failure goes something like this. No one checks the bags, they fill, then shavings fill the upper filter sock until continued running of the machine causes particles to lodge in the fan, these overheat and start to smoulder especially once the plant is turned off. Over a day or so, the smouldering spreads and fire consumes the dust plant. In our situation, the placement and construction of the dust room would probably contain the damage. It would still be inconvenient and unnecessary!
The above scenario can be avoided by regularly monitoring the state of fill of the collection bags. If they are half full it is time to stop the plant and empty the bags. Don’t leave this checking to the leader of the day. He is not your mother! If you have been using the planer or jointer for more than a few minutes go and check. Before removing a dust bag turn off the relevant extractor at the isolation switch in the room. Tell others you are doing it. You will have the plant up and running again in a few minutes and cleaning will enhance suction at the pick up points. If in doubt, ask.