The first step in the economic control of noise from a complete plant is to evaluate the contribution which each individual item of equipment makes to the total noise level. This involves determination of the sound power level of each source and estimation of the attenuation of noise between the source and the point where noise level is to be controlled. The second step is to identify the possible methods of noise reduction and to select the best by cost-benefit analysis. A computer program based on the OCMA Specification is helpful in this work.
La première étape dans le contrôle économique du bruit provenant d'une usine entière est l'évaluation de la contribution de chaque élément particulier de l'équipement au niveau du bruit global. Ceci nécessite la détermination du niveau de puissance sonore de chaque source, et l'estimation des effets d'atténuation du bruit entre la source et le point de contrôle. La deuxième étape est la recherche des méthodes possibles de réduction-du bruit, et la sélection de la meilleure d'entre elles d'après son rapport qualité prix.
On peut utiliser avec profit pour ce travail un programme d'ordinateur basé sur la norme OCMA.
The usual basis for justifying expenditure in petroleum plant is that of return on investment. This basis works well in the usual business situations, but it is not adequate for evaluating expenditure for environmental conservation. For environmental projects the need will be determined by the criteria set by the control authorities or by the good-neighbour policy of the company.
In an extreme case, the choice may be between carrying out the improvement work or shutting down the plant. If the cost of the required improvement would make operation of the plant totally uneconomic, the decision is simple. This situation seldom arises, however. In most cases the criteria can be met at a cost which can be borne by the plant operation. The engineering need then is to find the lowest-cost route for satisfying the criteria.
Cost-benefit analysis of neighbourhood noise control measures makes two requirements with regard to noise evaluation. First, there must be a consistent basis for the evaluation and comparison of by PETER SUTTON, Esso Petroleum Co. Ltd, Esso Refinery, Fawley, Southampton SO4 ITX, England alternative noise regimes. Second, there must be a reliable method of estimating the effect which treatment of individual equipment items will have on the total neighbourhood noise level. These two steps will enable the benefit element to be expressed in numerical terms; the cost can be determined by conventional cost engineering procedures. This paper is concerned primarily with the estimation of the effect of in-plant silencing measures on neighbourhood noise level.
Frequent reference will be made to the UK Oil Companies Materials Association (OCMA) Noise Specification.
