Energy Metering Audit Procedure

Abstract

This paper describes the recent audit of the utility distribution meters in a petrochemical plant. These meters measure the steam, condensate, natural gas, water, nitrogen and air flows to the different process units within the plant. This audit started as an attempt to resolve discrepancies between the 650 PSIG steam distribution and supply meters. Theoretically the sum of the 650 PSIG steam flows to the units should have matched the total of the steam supplied to the plant. However, in this plant the monthly totals of the distribution were consistently 15% - 25% lower than the supply meter totals. The plant is billed on the basis of the supply meters. Therefore, these discrepancies represented a significant utility cost, approximately $150,000 a year, that was arbitrarily allocated among the different units. The plant commissioned an audit of the 650 PSIG distribution and supply meters. The purpose of this audit was to: 1. Certify that there were no users not monitored by the existing distribution meters. 2. Verify the operability and accuracy of the meters. Hopefully, the results of the audit would allow the plant to account for at least 90% of the steam supplied. This accounting was necessary for equitable distribution of utility costs and accurate determination of unit production costs. The project was eventually expanded to include all utility streams. The audit of the following utilities was funded and implemented due to their relatively high unit costs: 650 PSIG steam, 200 PSIG steam, natural gas, and nitrogen. The audit of the other utilities is planned but a schedule has not been established.