Document ID: chunk:federal_register_of_legislation:F2016L00426:reg:10:p4
Version: federal_register_of_legislation:F2016L00426
Segment Type: reg
Provision Reference: reg 10 (pt 4/5)
Character Range: 94731–97487

make the difference between success and failure:-
  — back pressure : fit a larger coupling and silencer
  —  clogging : fit a straight-through silencer that cannot clog (and has no back pressure)
  —  multiple exhausts : manifold them into a single, larger diameter pipe fitted with the rear silencer from virtually any make of car (from your local tyre and exhaust fitter). Typically  25 dB reduction.
Note : a well designed silencer will not increase system back pressure.

  6.      PNEUMATIC NOZZLES

Typical applications - Cooling, drying, blowing
Technique
In most cases, it is possible to replace existing nozzles (usually simple copper pipe outlets) for quiet, high efficiency units. These not only reduce noise levels by up to 10 dB, but also use less compressed air. The types of nozzle to look out for are entraining units (schematic at right) from various manufacturers and in a variety of sizes.

  7.      VIBRATION ISOLATION PADS

Typical applications - Machine feet, pumps, mezzanine installations
Technique
Mounting motors, pumps, gearboxes and other items of plant on rubber bonded cork (or similar) pads can be a very effective way of reducing transmission of vibration and therefore noise radiated by the rest of the structure. This is particularly the case where vibrating units are bolted to steel supports or floors. However, a common error with the use of these pads is for the bolt to "short-circuit" the pad, resulting in no isolation. Additional pads should be fitted under the bolt heads as shown.
There are many types of off-the-shelf anti-vibration mounts available, for instance rubber/neoprene or spring types. The type of isolator that is most appropriate will depend on, among other factors, the mass of the plant and the frequency of vibration to be isolated. Any supplier of anti-vibration mounts will be able to advise you on this.

  8.      EXISTING MACHINE GUARDS

Technique
The existing guards on many machines can often be improved to provide a significant noise reduction. The two principles involved, which must be used in combination, are:-
(i) Minimise gaps
Reducing by half the "gap" open area in a set of guards can reduce the noise by 3 dB. If you can reduce the openings (flexible seals, additional close fitting panels etc) by 90 per cent, then a 10 dB noise reduction is possible.
(ii) Acoustic absorbent
Lining a significant proportion of the inside of the guards with acoustic absorbent (foam, rockwool / fibreglass) will reduce the noise "trapped" by the guards.
Consequently, less noise will escape through any gaps. Failure to line the inside of the guards could result in an increase in noise at the operator's position if the gaps have been minimised as in (i) above.
In most cases, both sets