3682. Allowance Versus Contingency in the Offshore Oil & Gas Industry
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Paper
Abstract
Weight management in the offshore oil industry uses the terms allowance and contingency when describing weights that cannot be defined during the present design stage – but are known to be required. These terms are frequently accompanied with much debate – between Owner/Operators and Engineering Contractors – as to their meaning and interpretation. Depending on the past experiences of the Owner/Operator or the Engineering Contractor, one term will have preferential use over the other. In reality, the terms may be used interchangeably as they describe the same aspect of weight management.In any industry where weight is an important design parameter, determining the total weight of an assembly of parts (e.g. an aircraft, a ship, or an offshore platform) is a part of the design and fabrication process. Before completion of fabrication, an assembly’s total weight is a combination of two weight categories – definable (i.e. based on quantities, unit weights or densities), and indefinable (i.e. estimated or assumed). As the design matures, the portion of definable items increases while the portion of indefinable items decreases. The total weight – definable plus indefinable – should remain constant during the design and fabrication phases.Definable weights are determined from preliminary documents (e.g. drawings and specifications), 3-D CAD, equipment vendor data, and other sources. Indefinable weights are estimated based on the level of design maturity of definable weights at any point in time. Common industry practice is to calculate the indefinable weights by application of a percentage factor (known as an allowance or contingency) to the definable weight. Combining the definable and the indefinable weights determine the total weight.This paper describes how the terms allowance and contingency are synonymous, and proposes the use of a replacement generic term to provide a clear meaning for the intent of the terms it should replace. Information provided in this paper is based on the author’s experiences in the offshore oil industry. Principles described should be applicable to weight management in any industry.
