The purchase or sale of natural gas often includes check-measurement to ensure that reported volumes and energy values are accurate. When the other party is responsible for measurement at the point of sale, installing and maintaining a custody-transfer-quality check meter may be the most valuable tool available to verify the accuracy of gas volumes being delivered. Despite the best of intentions
, standard industry measurement practices can break down. Accordingly, utilizing check-measurement to minimize "Lost and Un-Accounted For" (LUAF) volumes often proves to be an especially cost-effective investment.
A measurement audit was conducted on behalf of a natural gas producer over a six-month period to reconcile an approximately 17.8% loss in volume between the check meter and sales meter. The audit confirmed that the discrepancy began on the exact time and day of the sales meter inspection, and continued until the next sales meter inspection. [View the trend plot by clicking here
.] Fortunately, the check meter was inspected multiple times during the period in question and was found to be measuring within tolerance. However, hourly volume comparisons between the check and sales meters during this time provided especially strong evidence that the sales meter was faulty.
While the detailed activities which took place during the sales meter inspections were not immediately known or fully documented, based on the measurement differences and timing it was strongly suspected that the meter manifold was left partially equalized. Since no problems were documented on the sales meter inspection report, this error could have continued to go unnoticed indefinitely. The purchaser eventually acknowledged that a problem existed based on evidence from the check meter and made an equitable full correction on behalf of the seller.
The error mentioned in the example case above is just one of numerous sources of orifice measurement error, many of which cannot be identified without a properly installed and maintained check meter. For more information on common sources of measurement error, gas sales verification, and related technical topics, you can click here
. And be sure to consult with your organization’s measurement experts, whether in-house or contract servicer, for further guidance.
"Remember, people will judge you by your actions, not your intentions."
~ Maya Angelou, American poet, author, and civil rights activist