Pipelines: Striving for Reliability

It doesn’t help matters that Plains Midstream Canada, Pace Oil & Gas and Enbridge are currently dealing with spills in Alberta, giving anti-pipeline activists ammunition to stall or stop the projects.

DeGaetano has been associated with the pipeline industry for over 25 years. “The industry has advanced dramatically in that time,” he says. “At first, government regulation was the driver, but the industry has developed a culture of continuous improvement and implementation of “best practices”. Lines are inspected internally and externally more often than ever before.”

Risk management tools are employed at all levels to identify and mitigate any operation and process risks. Valves and actuators are of course key components of any risk analysis and in addition to industry standards, operators have their own standards and specifications when choosing them for each project. A crucial component of operators’ protection layers are the control valves. Their reliability is crucial for safe operations and preventive actions.

Design and material selection must be the best fit for any potential or incipient cavitation. The right trim, stem/shaft, packing and body material is chosen to handle the various hydrocarbon products with their different ranges of viscosity, density and temperature. These products could include high vapor pressure or sour products, presenting extra challenges for the components.

Valve size selection is also an integral part of pipeline reliability. In mainline applications, line diameter determines the size of what are typically ball or v-ball valves. Future operational opportunities for higher flow as spare capacity are also considered in the design and size selection, and generally the largest possible size is used to accommodate expansion and increased flow through the line.

DeGaetano discussed the precautions taken for mainline delivery. “Mainline valve applications include both Flow Control and Emergency Shut Down control,” he said. “These valves are remotely monitored 24 hours and in many cases are solar powered, or have multiple redundant power supplies to insure operability in critical services.”

With respect to actuators, because so many hydrocarbon pipelines are in remote areas, electric actuators are utilized only for on-off or isolation applications. Electro-hydraulic actuators are used for throttling even for remote valve sites.

According to publicly available materials from Trans Canada, control valves are located approximately every 20 miles along most pipelines and a pressure drop results in automatic shut off . To protect against corrosion, Trans Canada also sends a very low-voltage electric current called cathodic protection to the pipe during operations.

Naturally all pipeline operators monitor the system 24/7, using computerized sensors and controls. Also, most systems utilize smart pigs, electronic in-line inspection devices, to periodically check sections of the pipeline system to detect defect. Piggable valves are full port and their actuation in isolation applications are crucial to insure they get fully open in pigging time.

DeGaetano added that Partial Stroke Testing is now being used to prove that valves will in fact operate in an emergency. He explains, “This involves shutting the valve part way, typically 20%, so pipeline flow is not interrupted, but proves system operability. Part of that testing includes the ability to measure the force required to operate the valve and compare that with the “as new” force profile which allows for maintenance to be planned and scheduled rather than waiting for an equipment breakdown.”

Also, according to DeGaetano, these “ESD” valves are being installed in more locations than ever before as a means of reducing the potential for spills. Valves that were originally installed with manual operators are being converted to automatic remote operation to allow for fast and orderly shutdown.

While operators and manufacturers continue to strive for 100% reliability for pipelines, the unfortunate fact is, accidents do happen. With well maintained ESD valves, reliable actuators and state of the art monitoring and control systems combined with constantly evolving response plans, loss of product and damage to the environment can and is being kept to a minimum.

Tom DeGaetano is General Manager of Flow-Quip Inc. and has been associated with both gas and liquid pipelines for over 25 years as an equipment supplier, specifically valve actuators.

Kate Kunkel is Senior Editor of Valve Magazine. You may reach her at kkunkel@vma.org