The growth of compressed natural gas (CNG) and, to a lesser extent, liquefied natural gas (LNG) as alternatives to diesel fuel has forced many transit agencies to confront new maintenance challenges.
Although neither of those alternative fuels is new to the marketplace, CNG and LNG are expanding their presence in transit bus fleets, in some instances as a consequence of mandates issued by air-quality regulators. In any case, this article discusses keys to adapting a fleet facility for CNG and LNG buses. The adaptations required for other alternative fuels, such as electric, hybrid and hydrogen, will be discussed in an upcoming issue.
Choosing partners is a critical part of the process. Few transit agencies have the in-house expertise to tackle a project as demanding and complex as modifying a facility for CNG or LNG.
Principal partners should include a consultant with a background in alternative fuels and building code requirements, an architect and engineering firm with experience in CNG/LNG fueling operations and the local fire marshal. It also helps to consult with fuel suppliers and manufacturers of storage tanks and alternative-fuel buses.
The process of converting a facility for CNG or LNG buses can take more than a year, from the issuance of the notice to proceed to the sign-off by code officials. But the duration depends, of course, on the complexity and size of the project.
At Metro Regional Transit Authority in Akron, Ohio, the modification of the facility for CNG buses took about nine months. According to Bob Fitzgerald, maintenance director, the renovation included changes to the ventilation, heating and electrical systems as well as the installation of a compressor station.
“We had to rewire the entire building and modify the ventilation system to increase the flow of air significantly,” Fitzgerald says. “We also changed the heating system from an open-air type to closed chamber.”
Most of those changes were dictated by industry standards for natural gas vehicles. The most commonly used standards are published by the National Fire Protection Association (NFPA). Other pertinent codes and standards are issued by Underwriters Laboratory, the American Society of Mechanical Engineers, the American National Standards Institute and state and local governments.
The fire marshal, in particular, plays a critical role. “Get him involved as soon as possible,” says Val Eikanas, senior project manager and alternative-fuel specialist at Stone and Webster Inc. in Boston. Stone and Webster, owned by The Shaw Group, provides advisory services to the energy industry.
Even if the building modifications satisfy state codes and NFPA standards, the local fire marshal (or other local building code enforcement officials) could have more stringent requirements. “The fire marshal is the most important person in the entire process,” Eikanas says.
The construction phase is a good time to prepare maintenance staff for the arrival of the new fuel. “It does take a mindset change,” concedes Fitzgerald. “You always have to be thinking about staying on top of safety.”
Eikanas says the initial fears among the maintenance staff about working with CNG can be strong. “It’s a very scary proposition when you’re talking about CNG,” he says. But the concerns generally melt away once the buses are in operation. “In most cases, after a month of operation mechanics love CNG because they don’t go home smelling of diesel fuel,” he says.
What does it cost?
The cost of improving a facility for CNG or LNG fueling and maintenance varies widely, depending on, among other things, the age of the facility, the number of buses to be serviced and the type of the fuel storage and delivery system.
Eikanas, who says his firm provides guidance on facility modifications to 20 to 30 transit properties each year, estimates the cost of improving a standard diesel bus facility for CNG operation at $20 to $40 per square foot.
Last fall, the Orange County Transportation Authority (OCTA) in Orange, Calf., completed a $4.5 million renovation project for LNG buses. Jim Kramer, principal civil engineer at OCTA, says the turnkey project included shop modifications as well as installation of underground storage tanks. The shop modifications accounted for about $1.5 million of the total, he says. Currently, OCTA is operating 61 LNG buses. It expects delivery of 171 more this summer.
A little foresight can keep costs to a minimum. “We recommend that all new facilities be designed to accommodate modifications for CNG,” Eikanas says. “It’s inexpensive and prudent.” Those accommodations could include penetrations in the roof so fans can be added later if CNG buses are acquired. “When you design a facility with the idea that you might add CNG buses, it’s peanuts to make the modifications later on,” he says.
Training is essential
Especially when CNG or LNG is being introduced at a transit facility, it’s important that staff members are given a clear understanding of the inherent dangers—and relative safety—of natural gas fuel.
At OCTA, staff training both for the maintenance of the buses and the facility is a top priority. “Employee safety is always the first thing you need to consider,” says Kramer. “There’s always a hesitancy with the introduction of any new fuel.”
In reports on the use of CNG and LNG at transit operations (see sidebar, “Guidelines Are Available”), the Federal Transit Administration recommends that staff training include drivers, driver trainers, fuelers, dispatchers, mechanics, site maintenance workers and supervisors. Outside agencies, such as police and fire departments, should also be included in the training.
Mechanics need instruction in the fundamentals of CNG/LNG systems as well as specific training on safe procedures in dealing with natural-gas fuels, leak detection and response to a leak. Fueling specialists should be taught not only how to fuel the bus, but also how to respond to an emergency, such as an accidental spill.
Bus driver training should focus on the properties of CNG/LNG and how to respond to an on-the-road emergency. The latter training component should include passenger evacuation skills specific to a natural-gas emergency. For example, use of the wheelchair lift, which contains sparking equipment, might not be a wise choice during a CNG emergency.
Manufacturers of LNG tanks and engines and methane detection systems generally provide training to support their products. A contractual agreement for technical support and training is a good idea.
A proper training program, Eikanas says, requires the commitment of executive and administrators of transit properties. “Training is the key to a successful operation,” he says. “Management needs to ensure that the facility is clean and safe and that personnel understand their roles and responsibilities.”
The final piece to the education program involves the public. Because there have been rare, but highly publicized, instances of CNG-related accidents, some riders may be uneasy about the fuel’s safety. A driver who understands the properties of CNG and the safety features built into the fueling system should be able to address any concerns.
Although it’s safer to fuel a transit bus with CNG or LNG than it is to fuel your family car with gasoline, you’re still dealing with, in one case, a flammable gas under very high pressure and, in the other, a cryogenic liquid that quickly vaporizes into a flammable gas when exposed to outside air. The chance of an explosion or other accident is small but real.
That’s why it’s important to avoid complacency.
“We used to check the detection systems monthly, but now we’re doing it weekly,” says Fitzgerald. “You can’t be too safe. CNG is not necessarily dangerous, but the potential is there.”
Eikanas says the trend in methane detection is toward the use of point or open-path infrared systems, which last longer and require less maintenance and fewer recalibrations than catalytic detection systems. “They’re also faster to react,” he says.
Detection systems are a key link in the CNG/LNG safety protocol. More than just monitoring gas levels and providing audible and visual alarms when gas concentrations reach critical levels, they can be set to automatically activate emergency functions, such as increasing the rate of air changes, turning off non-essential electricity and opening the service doors.
When the gas detection system signals its highest alert, evacuation of the facility is required. Eikanas suggests that trained personnel check the suspect area before any emergency operations are canceled. “Nothing should be restarted automatically,” he says.
Although evacuation drills should be practiced at least annually, few employees need encouragement to leave the building when the high alert is sounded. “Believe me, when you get that alarm, everybody knows how to get out of the building,” Eikanas says with a laugh.
Some final tips
The following are additional safety recommendations for maintaining CNG/LNG buses:
No open-flame heaters should be present anywhere in the building.
Fueling areas should be equipped with blowout panels in the roof or walls.
To help release pressure in the event of an explosion, specify overhead doors made of heavy fabric rather than metal.
Use self-testing gas detection systems.
Ensure that buses are defueled before any repair work. This is especially true if work is to be done on the fuel system.
Post “No Smoking” signs in the maintenance and fueling facilities.
Try to exceed all code requirements when modifying a facility for CNG/LNG.
Don’t forget to provide refresher training courses for staff.
Guidelines Are Available
The following FTA papers are available through the U.S. Department of Transportation’s Volpe National Transportation Systems Center in Cambridge, Mass., and can be ordered through the Website (transit-safety.volpe.dot.gov/publications/Info.asp).
Cylinder Issues Associated with Alternative Fuels (1999)
Design Guidelines for Bus Transit Systems Using Hydrogen as an Alternative Fuel (1998)
Design Guidelines for Bus Transit Systems Using Liquefied Natural Gas (LNG) as an Alternative Fuel (1997)
Use of Hydrogen to Power the Advanced Technology Transit Bus (ATTB); An Assessment (1997)
Design Guidelines for Bus Transit Systems Using Alcohol Fuel (Methanol and Ethanol) as an Alternative Fuel (1996)
Design Guidelines for Bus Transit Systems Using Liquefied Petroleum Gas (LPG) as an Alternative Fuel (1996)
Liquefied Natural Gas Safety in Transit Operations (1996)
Dispersion of CNG Following a High-Pressure Release (1996)
Summary Assessment of the Safety, Health, Environment and System Risks of Alternative Fuel (1995)
Compressed Natural Gas Safety in Transit Operations (1995)
NGVI Offers Training
The Natural Gas Vehicle Institute (NGVI) in Las Vegas, Nev., offers a certification program for safe operation and maintenance of natural gas vehicles.
Leo Thomason, who co-founded the institute with his wife, Annalloyd, said the curriculum is designed for people who design, bid or maintain natural-gas vehicles, fueling stations and facilities.
“We’re seeing a lot more bus people,” Thomason says. “The transit area is starting to grow.”
Thomason said the single most important thing to remember while fueling a CNG vehicle is not to stand in direct line with the receptacle or nozzle. “The most dangerous thing about natural gas is the pressure involved,” he says. “You have to consider that the force from the pressure creates the potential of a bullet in that tube.”
The NGVI offers a two-day certification program for fueling station personnel that includes 11/2 days of classroom instruction and a half-day tour of a CNG fueling station. There’s also a one-day safety training program for mechanics and drivers. Thomason says the institute also offers on-site training.