The same liquified petroleum gas that cooks a steak in the back yard might save your bacon when powering your plant’s standby generator.
Liquified petroleum, also known as LP gas or propane, is a clean-burning fuel that can power a standby power generator. You may be familiar with smaller tanks used with backyard barbecue gas grills. The cylinders or tanks used to power standby applications are much larger. Both large and small LP gas cylinders work on the same principle: the gas comes from the vaporization of the LP gas in the cylinder.
“LP gas vaporizes around 32 degrees Fahrenheit,” said Michael Ketchem of Superior Commercial Services in Alva, Fla.
“The vapor is what powers the grill or the engine on a generator set.” His company installs LP gas services and equipment in the southern part of that state.
While most standby generators are powered by diesel fuel, many are powered by natural gas, the rest by LP.
LP gas has some advantages. It has a long shelf life, it is a clean burning fuel, and it is easily stored in small or large tanks.
Even in a worst case, an LP gas generator can run for a little time on one of the backyard-sized cylinders, which could be available during a wide electrical outage, where fuels that may have to be pumped electrically (fuel oil and diesel, for example) cannot be pumped. If an LP gas cylinder is ruptured, the gas is flammable; but unlike diesel, it will vaporize and not contaminate the ground around it.
LP gas has a most distinctive odor that helps users to detect leaks.
There are also limitations to using LP gas.
The cylinder (of whatever size) is a pressurized cylinder of flammable gas. The fuel system is somewhat more complicated than one used on a diesel generator set, which results in a higher installation cost. The tanks are not aesthetically pleasing, and may present an unattractive sight unless buried.
The size of the tank dictates the amount of run time. It also can prevent against freezeups. If the tank is too small for the application, the LP gas won’t boil as quickly and release gas at the rate necessary to power the equipment connected to the tank. You can see this when the outside of the tank shows frozen condensation. The tank temperature affects the process as well.
Daniel “Bud” Larsen of Cummins Power Generation Business Development in Temecula, Calif., says the choice of fuel to power a standby generator “comes down to what kind of fuel is convenient for the customer. Propane generators, typically under 100 kilowatts, can be 30 to 40 percent less expensive to purchase” than diesel generators. “The price usually drives choices.”
Larsen’s company also sells diesel and natural gas-powered generators.
Jon Scaptura is the engineering manager for the six-station Clear Channel Radio cluster of stations in the Binghamton, N.Y., radio market; he has an LP gas standby generator, a reconditioned Onan powered by a carbureted V8 engine, outside his studio complex.
“We have all the studios, the rack room equipment and the studio air conditioning — everything needed to keep us on the air — connected to our generator.” He has a 400-pound tank to power the unit, which gets unexpected exercise thanks to its location.
“We exercise our generator every week without a load, but this year we’ve had the generator kick on at least two times this year. Our power comes out of a (utility) substation, and we are at the end of a branch line.”
Scaptura says one of the biggest advantages he found with an LP gas generator set is “not having to deal with adding anti-bacterial additives, stale fuel or water in the tank,” which can plague users of diesel.
“Where we’re located, you have to keep a circulator going to keep the engine coolant at the correct temperature so the unit will fire right up even when it gets cold.” The unit is maintained under a maintenance contract and the fuel tank is on an automatic fill routine from the local LP gas supplier.
Know the rules
Ketchem says working on a LP gas installation isn’t as easy as hooking a full LP gas cylinder to your barbecue grill.
“In Florida, people who work on LP gas systems and equipment must be licensed. It is a felony to do that without a license.” His advice for planners: “Do your research and crunch the numbers. Prior planning prevents poor performance.”
Both Scaptura and Larsen stress the importance of a regular test or exercising of a standby generator as well as proper maintenance.
“Don’t let this become a ‘set it and forget it’ operation. The unit needs regular maintenance either from a local representative or from the factory,” said Scaptura.
Larsen says that in Cummins’ experience, the most common type of failure of a standby generator set is a failure to start and run because of a low battery charge.
Is LP gas the answer for your facility’s standby power questions? It depends on location, availability and cost.
If your plant is near a neighborhood where diesel fumes would cause bad relations, it might be your best compromise. If you have two or more suppliers of LP gas who can compete for your business (perhaps one can be persuaded to trade gas for air time) and you can enter into an auto fill agreement, this is a consideration.
What often will drive this choice is the cost of a new or reconditioned unit with factory or local maintenance included.