ANALYSES OF ULTRASONIC FLOWMETERS FOR LEAK DETECTION IN LIQUID HYDROCARBON PIPELINES.

A program was conducted to determine repeatability and linearity of the ultrasonic time-delay types of flowmeters, so that their applicability to leak detection on underwater pipelines could be assessed. Field tests using merchantable crude oil were conducted on two off-the-shelf, commercially available flowmeters at a refinery meter proving station. These tests showed a short-term repeatability of 0. 2% for both meters. Long-term (7 hours) repeatability was 0. 6% for one meter and 2. 5% for the other. For a leak detection system in which line balance is continually computed and line packing is compensated for, slow drifts in line balance due to drifts of meter factors can be compensated for by periodically adjusting meter factors. For a meter with drift characteristics similar to those measured, a computerized simulation indicates that the probability of detecting a leak greater than 0. 6% of the total flow in 10 minutes is greater than 99%. The probability of a false alarm for the same conditions is about once per week.