October 2011, Vol. 238 No. 10

Features

Vapor Extraction Unit Valued In LDC War On Leaks

An experienced gas utility field distribution crew struggled with frozen ground and sub-freezing January temperatures in northern Idaho a few years ago. They were seeking to pinpoint and resolve a natural gas leak in a rural corner of Avista Utilities’ three-state service area. Avista is based in Spokane, WA. The search for the leak was routine, at best, for the crew, but time-consuming.

Today, Bill Baker, gas training and codes coordinator for Avista, looks back with a measure of frustration on that incident that unfolded in a subdivision of five-acre residential properties.

Avista’s crew was attempting to mitigate the leak without knowing its precise source through a traditional hunt-and-peck method of punching a series of holes in the ground and allowing the migrating gas to escape harmlessly into the air.

Flash forward to 2011, and Baker cites the Idaho example as one from the costly, inefficient past. The same crew today relies on a trailer-mounted, mobile, diesel-powered Vapor Extraction Unit (VEU) that sucks up the migrating gas and pinpoints the leak’s source in hours – not days – at about 20% of the cost of the old methodology.

The unit that Baker and his colleagues at Avista now rely on is from M-B-W Inc., a Slinger, WI-based company. The concept for the unit was originally developed by Marc Chapman, director of operations at the Dallas-based Atmos Energy’s Mid-Tex Division. EGASCO LLC eventually patented and licensed the product to M-B-W for design, prototyping and manufacturing.

“It cost about $120,000 to mediate that situation in (northern) Idaho,” Baker said. “If we had had the VEU unit back then, we would have been in there less than five days and it would have cost us less than $20,000. And we would not have had to tear up all the (customers’ yards and then re-do them).”

A vapor extraction unit in use by M-B-W Inc.

Around the nation, other utility operations managers tell similar tales. They began with one VEU and have progressed to multiple units in distribution/transmission operations. Although they either don’t have, or do not want to make public, quantitative data on the equipment’s track record, the utilities are convinced that each unit they employ pays for itself.

“We have not tracked specific quantitative data (on the VEU’s applications, average hours of use/job, estimated cost savings),” said Reid Hess, operations supervisor at Salt Lake City-based Questar. “We do know that it saves us time and money, though.”

Hess emphasized the VEU’s ability to evacuate gas from the ground more quickly than the utility’s conventional method using an air mover. He likes the fact that crews can pull gas from either a broad area or a more compact coverage, varying with the number of hoses that are deployed.

“You may have a small area that gas is being pulled from and you may choose to limit the number of hoses and the area they are being deployed in,” Hess said. “If the area is larger, we may choose to use more hoses and spread the hoses in a larger area to pull gas from the wider space.”

Safety and cost-savings are two big benefits of the units, the utility operating representatives say, and – although none has tried it yet – longer term the units may be helpful in tracking and reporting greenhouse gas (GHG) emissions from natural gas utility operations. A few utilities are at least beginning to think about the VEU’s application here.

The vacuum-based technology was conceived by Atmos Energy’s Chapman to encompass a piece of mobile equipment that creates 850 cubic feet/minute of suction as a means of pinpointing leaks and clearing concentrations of gas building up underground, beneath streets and buildings.

A three-cylinder diesel engine in the VEU drives a positive displacement vacuum pump that pulls trapped gas from underground. The gas stream is diluted with fresh air, monitored to maintain safe air-gas mixtures and released into the atmosphere.

Chapman touted the VEU for leaks with wide migration patterns underground. “With the VEU you can pinpoint the leak and come down right on it, and this produces considerable cost savings,” he said. “Each day that you don’t have a crew out hunting for the leak and repairing the leak represents dollars saved.”

Bart Hill, manager of engineering services at Nicor Inc.’s gas utility in northern Illinois, said the VEU cuts work crew time more than half compared to conventional methods of identifying and dealing with gas leaks. Nicor can do the work in 75-80% less time than conventional methods, Hill said.

“We’ve found it is a very beneficial tool to have” in eliminating residual gas underground, particularly under pavement, he said. “We’ve been very successful with that.” Nicor obtained its first VEU in summer 2008 and has added three more.

“If you talk with field supervisors, everybody wants one of the units,” Hill said. “I can see maybe doubling and having four to six of them.”

Covering the northern third of Illinois and serving 2.2 million meters, Nicor has mostly urban and suburban territory, although some of its applications for the VEU are in rural areas, too. The utility uses the units exclusively in its distribution pipeline system, although Hill said there may be some applications on its transmission system in the future.

Hill recalled a distribution leak in front of the Frank Lloyd Wright Museum in the Chicago suburb of Oak Park on a busy residential street. “We probably saved as much as $8,000 in restoration costs in that one job alone,” he said.

In the past, traditional methods of leak detection and repair were all “makeshift,” and they left the impressions with the general public and customers that the utilities didn‘t always know what they were doing. The VEU is a confidence builder for the utility crews using it and for the customers and general public who come in contact with one.

“From the way we did things here with the makeshift aeration process, this is so much better, just the way it is set up, how it works, the safety aspects, it’s simple enough for anyone to use it,” said Gary Dodge, supervisor of construction and maintenance, in South Bend, IN for NIPSCO. “There is minimum training required on it.”

A NiSource VEU on the bed of a truck.

Like several other utilities that are using the VEU, Dodge has made some modifications to the unit to fit his needs. Instead of purchasing the optional trailer, he put the equipment in an enclosed trailer and refitted the tooling inside, customized to suit NIPSCO’s needs, and he added an automatic, “easy” drilling unit made by another company.

“You hook an air hose up and all you do is hit levers, and you’re able to drill through asphalt and concrete,” Dodge said. “It saves as far as ergonomics for my employees.”

Several other utilities indicated they modified the trailer used for the unit, so it had double axles and would enclose the VEU.

“When we were out in neighborhoods, we received complaints that the unit was too noisy,” Avista’s Baker said. “An insulated, enclosed trailer with a muffler on the diesel-fired engine powering it really has made a difference.” (A new model VEU that was scheduled to be released earlier this summer was touted as having “significantly reduced” noise levels, according to M-B-W officials.)

The experience of Avista, Nicor, NISPSCO and Questar all underscores what Chapman has been preaching at Atmos for some time – “tremendous cost savings” are the norm with the use of the VEU.

Individual utility crew costs and city repaving requirements will determine ultimate savings, but Chapman is convinced all utilities can realize big savings from being able to clear residual gas out of the ground up to 15 times faster and avoiding the costs of digging and repairing dry holes under traditional hunt-and-peck methods.

“Bare steel, covered steel or even PE pipe, being able to suck the gas out of the ground back to the source of the leak, you save a tremendous amount of time and dollars,” Chapman said. “(Atmos utility crews) have embraced the technology from day one. They saw it as an advantage to making their work life a little bit easier.”

Along with the hard dollar savings, the utilities employing VEUs stress many safety and public relations benefits, which carry some soft dollar savings associated with promoting better customer understanding and support.

Nicor’s Hill said it all basically boils down to safety. “With the VEU we can pinpoint leaks faster, remove residual gas in the ground faster, and be able to eliminate gas inside of a building and draw it out from around foundations. It aids our productivity for pinpointing and removing residual gas.”

For Questar’s Hess “safety happens on almost every job.” With the VEU, his crews can deploy their response and begin withdrawing gas very quickly. “It has decreased the amount of time we have to spend getting gas out of the ground.”

An intangible in the use of the VEU, Avista’s Baker said, is the fact that when it’s employed in the field, customers have a clear idea that the utility is doing something proactively to mediate the problem. “In the past, we couldn’t do anything except keep people away. So, the customer perception was that we were not doing anything.

“The major benefit is public safety to get the gas concentrations away from the building a lot sooner than just through digging holes and letting it naturally migrate out of the ground. It brings the gas away from the building in a timely manner, a lot shorter time than through digging holes and natural migration,” he said.

There is no doubt in Gary Dodge’s mind that the VEU provides more comfort to customers. He remembered using similar, early primitive types of the machine in New York state in the 1990s when he was working with National Fuel Corp. Although primitive, the early machines were still an improvement over the dig-and-burn approach used back then, he said.

Said Dodge, “This machine is above and beyond anything that I experienced in the past.”

Author
Richard Nemec is the West Coast correspondent for P&GJ. He can be reached at rnemec@ca.rr.com.