Exhausts are used wherever there is a need to remove dust, splinters, gas or solvent from a work area. However, the power requirement is considerable: In industry, exhaust systems consume 10 - 15% of the power, and for wood manufacture enterprises even over 50%. Consistent application of energy saving measures can cut power requirements in half in relation to a classical system (approx. 20 years old). The savings amortize the systems in a few years.

Apart from direct power requirements, exhaust systems need very large amounts of air. If exhausted air cannot be recycled after a filtering (e.g., with smoke, chemicals or solvents, in contrast to dust), then fresh air must be supplied and heated. Thus the heating energy requirement can be more than doubled by the exhaust systems.

A further problem is blowers and/or fans. If the raw gas (e.g. with dust) is fed across the blower, then such designs must be chosen that can convert only 50% of the current into kinetic energy. It is better to draw out exhaust on the side of the clean gas (after filtering) with high-quality blowers that have over 80% efficiency.

Problems in exhaust maintenance

• Exhaust runs even if there is no need
• Ducts congested with varnish, dust, etc.
• Wrong air due to leaky lines (high capacity without efficiency)
• Filter congested with deposits
• Space under the filter is full but not removed
• Intervals too long for cleaning filter with compressed air
• No differential pressure measurement at filters

Immediate measures

• Training of workers
• Insert sliders to avoid unnecessary exhaust
• Under-pressure regulation of the exhaust with frequency converter
• If metal ducts are leaky and have high internal friction, then these should be replaced with modern ducts.
• Use synthetic tubes (metal spiral in the synthetic tube needs to be
  grounded)
• Automatic disconnection of machines and their exhaust (e.g., after work)
• Automatic switching on
• Consult with several plant engineers and/or advisors

Long-term measures and investments

• Installation of a modern exhaust system with separate lines, whereby each machine is exhausted only as necessary
• Speed regulated exhaust fans in order to assure the set under-pressure
• High efficiency exhaust fans on the clean-gas side
• Run straight exhaust ducts; bends considerably increase the required
  exhaust power
• Chip transport if possible with conveyors, oscillating trough, or worm gears
• If chips must be transported by air, an air circulation system is best

Source: Austrian Chamber of Commerce