Passing Grade: Clamp-on gas flowmeter passes test for German pipeline and gas storage company
July 11, 2003
Controlotron performed two field clamp-on gas installations for a pipeline and gas storage company in Germany. Tests were conducted at 40 bars on both a 20-inch-pipe and a 16-inch-pipe.
Three types of meters are manufactured for these pipe sizes, all using externally mounted sensors:
• Meters for custody transfer performance (typically within 0.5 percent) are pre-installed on a spool section and include calibration. They utilize three paths to provide adequate flow profile averaging for these pipe sizes.
• Meters for check-metering are very similar to the spool-based meters but utilize two paths and are configured for semi-permanent mounting to the existing pipe. Repeatability is within custody transfer standards (0.1 percent) but absolute accuracy and linearity is typically within 0.5 percent to 1 percent.
• Transportable meters are intended for temporary and convenient installation. They utilize a single path and have accuracy of within 2 percent of rate for these pipe sizes.
An evaluation test was planned for a 20-inch-line, as a check against the accuracy of three insert-type ultrasonic meters where there was a suspected error. A meter was installed using a dual path, reflect mount transducer configuration. The results confirmed the suspicions of the error in the existing flowmeters. The dual path meter indicated the expected value and was within its expected accuracy band of 0.5 percent to 1 percent of rate.
To verify the accuracy of the clamp-on flowmeter, the customer asked if it could be installed next to a five-beam meter on a 16-inch-pipe. There was very little time left to accomplish this task. Since the customer wanted a quick ballpark check of the meter, Controlotron agreed to proceed with only one set of transducers mounted in reflect mode. The 16-inch-line had just 10 diameters straight run after a 90-degree elbow, so some error due to flow profile effects was expected.
The installation was accomplished in less than 15 minutes. A flow check of the meter indicated that the meter was reading within 1.5 percent of the installed permanent 5-path meter. Considering that only a single path was used in this application which had limited straight run, this impressed the customer and they requested to have the meter at this location so they could run additional tests the following weeks. At the conclusion of the long term test, the customer purchased two Trans-Portable models with transducer sets to cover a full range of pipe sizes.
For more information on the clamp-on flowmeters, contact Controlotron Corporation at 631-231-3600 or visit www.controlotron.com.