The Equitable Distribution of Security Expenditure in Local Gas Supply Systems

Abstract

It is the engineer's natural tendency to build into gas supply systems, security against mechanical failure. This can be done either by the provision of spare capacity in alternative means of supply or by the duplication of the less reliable items of equipment. However, such expenditure to protect customers against rare events can be expensive and often may not appear justifiable when compared with other weather security criteria already established in the gas industry. The paper describes the development of a methodology for maintaining consistency of security expenditure within the industry. The measure of added security accruing from a project was chosen to be the expected quantity of gas saved from non-supply. The problems associated with placing a value on unsupplied demand are discussed, and a valuation method derived from existing weather security expenditure is described. Some examples of the evaluation of projects for added security are given. The main conclusion reached was that a single criterion could be derived which was useful in evaluating the various engineering schemes for added security.