The following video looks at an example of a well-designed local exhaust ventilation (LEV) system in a school that controls well, is easy to operate and maintain and has low running costs. It looks at the use of an Atex compliant centralised vacuum extraction system used in a schools woodworking classroom and the benefits it can deliver.
Effective Local Exhaust Ventilation Systems
Craft design and technology departments in teaching establishments must comply with the COSHH regulations to protect staff and pupils from the dangers associated with wood dust. Over the last 5 years centralised vacuum extraction systems specifically designed for the education markets have become available. These extract dust from multiple machines simultaneously and incorporate plug in points for portable tools and floor and bench cleaning. The system is Atex compliant.
Centralised Vacuum Extraction Systems
These systems operate at higher pressures and velocities than traditional systems. Performance can be maintained even with long duct runs. They can be fitted with automatic valves at each hood to overcome the problems of blast gates or dampers being left open and reducing the effectiveness of extraction. Airflow indicators are fitted as standard.
Blockages are reduced by using grills to stop large items entering the system. The dust extracted from each machine is transported through discrete ducting back to the central collection point.
Additional Plug in Points for Portable Tools & Cleaning
These systems also incorporate plug in points for portable tools and for floor and bench cleaning. This keeps the workshop clean and free from dust and avoids the need to brush surfaces. On starting machines automatic valves open to start the extraction. This ensures the extraction is always on when required.
Variable Speed Drives
The use of variable speed drives ensures that when more machines are in use the variable speed drive will increase the fan speed and the correct extraction flow rate will be applied to each machine. This will also control energy consumption and noise.
The low noise outputs of these systems mean that they’ll always be quieter than the machines. This makes the teaching workshop quieter. This is a key advantage for teachers when communicating with pupils under instruction.
Automatic Filter Cleaning
Systems are fitted with a bag full indicator that will automatically stop extraction and machine. Automatic filter cleaning ensures that extraction performance is maintained. Dust bags can be sealed in situ reducing the risk of exposure to wood dust. Full dust bags fit into purpose built trolley reducing lifting and the risk of back injury.
The Benefits of Well-Designed Local Exhaust Ventilation (LEV) System
This is a wood lathe being used without any extraction and with normal lighting. It’s hard to see the amount of dust being produced from the machine but if we change the lighting conditions we can clearly see how much dust is being produced and escaping into the air.
Here is the exact same test only this time with an extraction arm connected to a centralised vacuum system. This clearly shows the dust being effectively captured by the hood before it can enter the operators breathing zone.
Predesigned work identified that in teaching the maximum required extraction would be for 50% capacity. These systems are designed to take account of the required level of use by only operating when machine are on and therefore the total requited system volume flow can be managed.
Exceptional demands are monitored and machines will operate if there is insufficient extraction. These systems are flexible low noise and cost effective. There is only one filter to be changed. Variable speed fans drives and automatic dampers ensure that the system is only providing extraction for the machines in use. This makes it the system of choice if you want to reduce your energy consumption and help reduce your carbon footprint.
Following installation each system is commissioned in accordance with HSG258 guidance and supplied with user manuals and log books.
Effective local exhaust ventilation system in a classroom – Local Exhaust Ventilation (LEV) – Health & Safety Executive
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