Noise Impact Assessments
Under the AEUB Noise Control Directive ID 94-4, oil, gas and utility operators are required to conduct a Noise Impact Assessment prior to the installation of new or modsified facilities. While this is often not much of a problem in remote areas, this can create potential difficulties in moderately populated rural areas. If there are any residences within approximately 1000 metres of a single gas compressor or approximately 1500 metres of a small/medium gas processing plant, then a Noise Impact Assessment will usually indicate that some degree of extra noise control may be necessary to meet the Directive. In any event, even in remote areas, the facility should be designed not to exceed 40 dBA at 1500 metres.
Noise control included at the design stage of a new or modified facility, will usually add no more than 0.5 to 2.5% to project cost - depending upon the size of the facility and the proximity of the nearest resident. Noise control considered as a retrofit after complaints arise will usually cost two to four times (or more) as much as the same control included with the original design.
In predicting noise levels, operators can often work successfully with silencer suppliers to predict engine exhaust noise with some accuracy. However many operators have difficulty accurately assessing fan noise and engine casing noise. Cooler fans and engine casings are often incorrectly assumed to be point noise sources. This leads to under-estimation of the total noise emissions. Many styles of cooler fans are also highly directional with regard to noise propagation. This effect is sometimes misunderstood with the result that cooler fan orientation is sometimes not optimized at the design stage.
Engine casing noise is often ignored altogether. Building attenuation is often over-estimated resulting in optimistic environmental assessments. In practice, the building attenuation is limited by the open area required for ventilation, which is often inadequate for the task.
This is proven by the need to leave the building doors open in summer to prevent overheating. The open doors, of course, eliminate most of the noise control offerred by the building. The design of compressor buildings and ventilation systems to suppress and minimize the effect of engine casing radiated noise is relatively simple at the design stage and more complicated with field retrofits.
Patching Associates handle some 100+ oil, gas and utility noise control projects annually. Approximately half of these tend to be the more expensive retrofits rather than initial design considerations. We would like to remind our clients that we are available to work with your project or contracting engineer at the design phase in order to eliminate the need for potentially costly retrofits once the facilities are commissioned and subject to potential resident complaints.
