October 2019, Vol. 246, No. 10

Integrity Management

Utility Finds Big Assist with Low-Pressure Issue

Real-Time Monitoring Helps Distributors Guard Against Outages

By Tom McGee, Abriox

Half-human, half-Atlantean Arthur Curry – Aquaman’s alter ego – traveled the deep ocean in DC Comic’s 2018 film, as his unique physiology made him immune to pressures of 3,000 to 9,000 pounds per square inch (psi). 

In contrast, those of us living at sea level experience atmospheric pressure at 14.5 psi. Some gas mains (2-24 inches in diameter) can operate at 200 psi, while small service lines that deliver gas to residential customers typically function under 10 psi.

While psi levels vary depending on the application, real-time pressure monitoring is essential for utilities that supply natural gas to residential and commercial endpoints on their distribution networks. 

“Regardless of a station’s size, it’s critical, and in many cases, mandatory to monitor and record gas pressures continually,” said Wes Reidhead, gas/water superintendent for Graham County Utilities (GCU), based in southeastern Arizona.

The member-owned distribution cooperative serves more than 5,500 households in communities that rely heavily on mining, cotton farming and cattle ranching.  

In addition to two water distribution systems, GCU maintains and supports 205 miles of natural gas distribution main line, with an additional 85 miles of gas service lines equipped with 55 different-sized gas regulator stations. Some communities are located as far as 50 miles from the home office. Terrain is remote and often difficult to reach.

“Because we’re spread out, we have a high number of regulator stations or taps [where the gas is drawn off of our high-pressure transmission pipeline and transferred to our lower pressure distribution system],” Reidhead explained.

The stations range from small farm taps that provide gas service to just a handful of residents to our large city gates that support hundreds of residential and commercial customers. Many natural gas operations can supply compact spaces with high population densities from just a few strategically located stations.

In addition to being a cooperative, GCU performs new construction in-house. A small team of welders, service technicians and foremen operate and maintain the company’s gas and water systems. 

“The landscape and the number of miles we have to cover made regular observation challenging,” said Reidhead. “It prompted us to consider remote pressure monitoring.” 

In December 2015, the region experienced a sudden cold snap. When that happened some of the regulators froze causing a loss of service for nearly half of the customer base. 

“The outage lasted several days and cost us a substantial amount of money in terms of restoration and lost revenue,” Reidhead recalled. “It became clear to us that if remote monitors had been installed prior to this incident, employees likely would have been alerted by low-pressure alarms and saved our company from experiencing the largest outage in its history.”

But GCU found its choice of a remote monitor “cost prohibitive and hampered by marginal customer service.” When the company attended the 2016 Western Regional Gas Conference in Tempe, Ariz., high-performance remote gas pressure monitoring solution caught Reidhead’s attention. 

“Osprey was capable of responding to abnormal pressure levels by issuing instant alerts,” said Reidhead. “One of the features we found attractive was a built-in GPS module. It provides a precise timing reference so that measurements are logged accurately, with no drift. Other products on the market don’t have that.”

Measurements from different pressure points can be profiled simultaneously. Computer models can use that data to predict how the network will react to planned infrastructure developments. 

It can also run scenarios of exceptional climatic events. Calculation of position relies on accurate timing referenced from atomic clocks on board satellites orbiting the Earth. It allows individual Osprey readings to be time-stamped to within milliseconds.

In 2017, GCU began field testing its first Osprey unit. The natural gas distributor also agreed to serve as a testing platform for the technology to provide feedback for ongoing improvements. 

GCU technicians reported finding the unit easy to set in place, connect to the gas supply and activate with a magnet. A green light flashes when installation is complete. The entire process takes between 20 and 30 minutes regardless of weather conditions. A true roaming SIM allows unrestricted access to a host of networks. 

GCU has since installed a second Osprey with plans to add more. It uses the units to observe pressures remotely and as tools for high and low pressure alarms.

“We have the ability to find out what our gas pressures are in real time from a P.C. or a smart phone,” said Reidhead. “And the high/low pressure alarm feature has proven invaluable in helping us catch possible problems early on.”

“We currently run tests on the monitors monthly to ensure they are working correctly and thus far their performance has been flawless,” he said. “The monitors hold up extremely well even in our harsh desert climate.” P&GJ

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