A knife system, which cuts roof tiles to shape, was producing 92dB at 1m from the operator's side. Most of the noise arose from the exhaust on the pneumatic cylinders used to move the knives up and down. There was also a contribution from the solenoid valve exhaust. In this instance conventional pneumatic silencers would have caused a backpressure which would result in an unacceptable reduction in throughput. Such silencers can clog with oil and/or debris after a period of time.
In this case six pneumatic exhausts were piped to a manifold which in turn was piped to a straight through silencer.
This silencer was located away from the work area to further reduce the noise impact and orientated downwards to allow oil, etc to drip away naturally.
The noise levels were reduced by 12dB.
The total cost was circa £800 (2005 rates).
Information supplied by
Marley Eternit Ltd. & PDA Ltd.