Measurement accuracy and stability is a critical function in leak detection to catch a potential pipeline leak quickly, efficiently and reliably. Numerous customers working with ultrasonic flow meters have partnered with TechnipFMC for many of their challenging applications. Some expressed concerns regarding measurement accuracy and its dependence on fluid profile and Reynolds number. Others made observations with regard to data transmission reliability within their leak detection system.

One of the few cases reported involved one of our customers, a major oil company in Western Canada experiencing false alarms during pipeline operations, resulting in increased downtime and costs. After TechnipFMC was consulted, it was determined the false alarms were frequent in those areas where adverse flow conditions were likely to occur. It is worth noting our customer was running a leak detection system with an installed base of 6-path ultrasonic meters.

Well known in the industry is that this measurement technology, when used for leak detection, does not compensate sufficiently for adverse conditions in the pipeline such as swirl and crossflow. These are some of the most common causes of false alarms occurring in measurement systems for leak detection. With a lack of visibility, the growing problem was challenging and frustrating as there was no way to determine if a real incident was occurring.

What are swirl and crossflow conditions?
Imagine a section of a pipe with liquid flowing in a clockwise or counter clockwise motion across the complete section. This fluid dynamic effect is called swirl. Swirl is typically created by a double bend out of plane. A T-bend can amplify the swirl.

Imagine the same section of a pipe cut in half with liquid flowing in a clockwise motion through the top half of the pipe and in a counter clockwise motion through the bottom half. This fluid dynamic effect is known by crossflow. Crossflow is typically created by a single bend.

Both effects derivate in the appearance of transversal components of the flow velocity, which eventually influences the accuracy of an ultrasonic meter as it will either over or under read depending on the measurement path being analyzed.

A 6-path ultrasonic meter is ideal for applications with stable flow profiles and process conditions. But when adverse fluid dynamic effects occur such as swirl and cross flow, the 6-path ultrasonic measurement may read erratically due to its ultrasonic path distribution. Following TechnipFMC recommendation, some customers have replaced 6-path meters with 8-path meters in applications where complex process conditions are known or likely to exist.

When our customer advised us they were experiencing these pipeline issues, TechnipFMC developed a solution to enhance the existing installed meter base and mitigate the challenges in a quick and cost effective way. With decades of expertise in ultrasonic technology, we embarked on a program led by TechnipFMC Revolve™ department to upgrade the existing installed base of Ultra™ Series B meters to the Ultrasonic Series C with 8-path technology by adding two additional paths and using our Series B to C Upgrade Kit.

Additionally, “health bits” were introduced in our ultrasonic software, increasing the reliability of the metering readings and the performance of the complete leak detection system. The number of health bits available are 0 to 5. When a health bit is 0 (clear), it indicates a normal value. When it is 1, the value is suspect and indicates a situation that may compromise the accuracy of the reading. In such a case, the value would be disregarded by the leak detection system, improving significantly the data reliability concerns reported by our customer.

TechnipFMC was able to leverage its existing inventory to immediately upgrade our customer’s meters in the field. As an upgrade, it was not necessary to waste operational time by shutting down the pipe insert spool. We appointed a dedicated engineer at the customer worksite and dedicated project managers across our facilities. The project managers coordinated the upgrades to align with pipeline outages and synchronized with our engineering and test center for testing and calibration. The process consisted of replacing an installed Ultra™ 6B by an upgraded Ultra™ 8c meter, shipping that Series B back to our facility, performing the upgrade to Series C 8-path technology and sending it back to the field to a suitable location. That process was repeated in a coordinated way multiple times.

How can our ultrasonic 8-path technology help mitigate false alarms? It’s a complete monitoring system.

Our Ultra™ 8c offers advanced crossflow and swirl compensation, an intuitive touchscreen interface and an array of communications options, allowing our customers to connect ultrasonic meters to a network and easily monitor data remotely. The meter also includes a state-of-the-art interface with diagnostic capabilities, which allow customers to monitor and analyze product flow from almost anywhere. With advanced diagnostic features, physical property estimates and configurable alarms, the Ultra™ 8c is more than a meter: It’s a complete monitoring system.

This meter has eight crossing measurement paths distributed over four parallel planes across the pipe section for complete measurement and cancellation of the transversal components of the flow velocity. As a result, the Ultra™ 8c maintains its measurement accuracy in the most difficult applications, including no flow conditioning, 5D upstream and transition region flow.