By David Kligman
FELTON—If you live in parts of Santa Cruz County you would never have noticed a difference the past 12 days while taking a hot shower or using a gas range to cook dinner.
Yes, natural gas was heating the water and fueling stovetops. But the energy was being delivered in a far different manner.
In what is the largest operation of its kind for PG&E, the utility has used portable liquefied natural gas or LNG to provide nearly two weeks of uninterrupted natural gas for 20,000 residences and businesses.
PG&E used LNG to provide customers with natural gas while the company was strength testing a nearby gas pipeline as part of its safety enhancement efforts. To conduct a pipeline strength test, also known as a hydrostatic test, a pipeline has to be taken out of service, so the utility chose to use this alternate method for providing natural gas for customers in Felton, Scotts Valley and northern parts of Santa Cruz.
‘Absolutely no impact’ to customers
“The customer knows no difference,” said PG&E gas engineer Thane Pilkington. “When they turn their hot water on everything is normal. There’s absolutely no impact to them even though we’ve taken a major pipeline out of service.”
Earlier this month, eight 48-foot tankers filled with LNG were delivered from Yuba City to a vacant lot in Santa Cruz County. On July 16, the operation started providing natural gas to customers. But what’s so unique is how the gas gets from the tankers to customers.
It’s a multi-step process, a kind of automated assembly line:
- Each tanker, filled with about 10,000 gallons of LNG, is like a large Thermos. The liquid is so cold—minus 250 degrees—that the stainless steel pipes carrying the gas are coated with a thick layer of frost. PG&E workers wear protective shields and gloves since touching the pipes with your bare hands would cause instant frostbite. The advantage of using LNG is that more of it can be transported because of its temperature (1 cubic foot of the liquid converts to 600 cubic feet of natural gas).
- The liquid is then pumped into a vaporizer, which converts it into a gas and heats the gas to 70 degrees. During this stage, the odorless liquefied natural gas is injected with mercaptan, which gives the gas its distinct odor.
- From there, a compressor boosts the pressure of the natural gas from 140 pounds per square inch (PSI) to 275 PSI.
- The gas is then discharged into a natural gas pipeline.
It’s an operation that has lasted 24 hours a day, seven days a week. Twelve employees and contractors are dedicated to the site, constantly monitoring the temperature of the natural gas and the flow rate while checking for leaks. The team communicates with the hydro test operators at least once a day. Two new tankers filled with the liquid arrive every day.
The project was scheduled to end today (July 27) just as the hydro test was completed.
A large-scale operation
In the past, PG&E has used LNG for small planned outages, emergencies or to provide supplemental gas during winter months when more natural gas is used. But the utility hadn’t done anything for this duration until now. Later this summer, the utility is planning similar operations in Napa County and South San Francisco.
By the end of the project, PG&E will have injected nearly 16 million cubic feet of gas from 180,000 gallons of LNG. Most important, it will have prevented 240,000 customer outage days.
Pilkington said the effort allowed PG&E to provide safe and reliable service.
“The huge advantage of LNG is that it allows us as a company to ensure our pipelines are safe—whether it’s hydro testing or installing valves or that kind of thing—and provide uninterruptable service to our customers the whole time that work is being done,” he said.
E-mail David Kligman at David.Kligman@pge.com.