Hydrant Systems


Deciding to install is a matter of cost/benefit; fuel management becomes easier; technology advances

BY John Boyce, Contributing Editor

September 1999

There don't appear to be any rules, business or otherwise, to guide airport managers in deciding if their airports should install a fuel hydrant system. When all is said and done, it comes down to simple cost/benefit analysis.

"There is no rule of thumb," says Sara Smith, president of Madison Environmental, an aviation consulting firm based in Boxford, MA, of what determines if an airport needs a hydrant system. "Size is definitely one reason; you'll see hydrant systems at big airports and not at smaller ones. Atlanta Hartsfield Airport, for instance, couldn't run without a hydrant system. There are just too many gates and you couldn't have that many fuel trucks at an airport like that.

"Then there's the Hartford, Connecticut airport. It's a good size airport and they're spending a lot of money at that airport, but they have no plans to put in a hydrant system; everything is run by truck. They're comfortable with that. Then you look at Chicago Midway and they have a hydrant system and they're probably smaller than Hartford. It just depends; every airport is different. It comes down to cost/benefit analysis because they're very expensive to put in."

One thing seems clear about the installation of a hydrant system: The airport can be small or large, but it has to have a large volume of fuel flow to justify the installation.

"Most of the major airports do have hydrant systems," says Mario Larrea, vice president for fueling at URS Greiner Woodward Clyde, a major fueling systems design and construction firm.

"It depends on the amount of fuel that gets picked up at a particular airport. It's not so much the number of gates but rather the destination of the flights. If a flight originates in Miami and it stops in Palm Beach, Palm Beach probably wouldn't want a hydrant system because the aircraft wouldn't pick up fuel there. It depends on the amount of fuel that is uplifted and that depends on the range of the flights — the longer the flights, the more the possibility or need for a hydrant system.

"...There is a certain point where the number of gallons justifies the investment. Each airport has to look at how much real estate the fuel farm is going to take up, how much money it's going to take to build one versus how much money it will take to pay for itself. A hydrant system is a big investment, it requires a large quantity of fuel being dispensed to make it economically feasible."

Of course, as with any airport construction project, retrofitting a hydrant fueling system means disruption in airport operations. "It's not like you can do a little bit of work at night and let the aircraft come in the next day," Larrea says. "You're cutting the pavement, you have welding equipment, you have cranes, equipment, trucks, backfill material. Usually, you end up cutting two gates out of service at one time. It takes time."

A hydrant system does make fuel management easier: inventory control is facilitated, a leak detection system can be built in, and compliance with environmental regulations, overall, is simplified. Many airports have installed new or upgraded their fuel hydrant systems. Most notable is Boston's Logan International Airport (see sidebar), which wanted to ensure that its system was completely safe and in compliance with environmental regulations.

"The biggest difference between modern systems and the older systems," Larrea says, "is that the newer designs take more into consideration the environmental concerns, leak detection, corrosion control — more automation so that you have better inventory control in the tanks and the lines. You can detect a leak much quicker than before."

Smith says Logan planned for the future by upgrading. "Although the rules weren't specific to have automatic leak detection," she says, "Massport decided they want it. They were looking into the future and it was cheaper to put it in now versus trying to add it in five years from now. They have a very long line and they wanted assurance that it was tight. In some states it might not be a requirement but it makes sense to have automatic leak detection."

Leak detection systems have become increasingly sophisticated in detecting extremely small leaks. The old method of hydrostatic testing is largely obsolete.

"In some places," Larrea says, "they just run the lines and pressurize the system and measure the pressure in the line. If the pressure hasn't changed, then they say there is no leak. But that's not scientific, it's not as accurate (as modern systems). The hydrostatic tests do not take into consideration the difference in temperature, and so you could get a false reading. Hydrostatic testing is something you do when you first install a hydrant system to test the integrity of the system; it's just not as accurate as you need in an operating system."

Currently, there are two major, currently certified leak detection systems for hydrant lines which can be built in and programmed for periodic testing. The German Hansa system relies on a sophisticated pressure test; the Vista Research system of Mountain View, CA, relies on a volumetric test that is similar to a pressure test. Both are able to take into account the variability of temperature.

The Vista test, as explained by the company's product manager, Mike Fierro, "is a static test that's similar to a pressure test, but instead of letting the pressure decay, our system keeps the pressure constant and measures how much volume has to be added or removed from the system to keep the pressure constant."

It is a volumetric test run once at high pressure and once at low pressure. "By making measurements at two different pressures," Fierro says, "we can temperature compensate so that we don't have to make temperature measurements anywhere in the line. If there is a leak in the line, the leak rate is going to be different at the two different pressures. The temperature changes that are going on will continue to go on regardless of the pressure in the line, so by changing the pressure I've changed the leak rate without changing the thermal environment."

Hansa's is similar in that the lines are tested under high and low pressures — but Hansa measures pressure change and Vista measures volume change. (Tracer Research of Tucson, AZ, which manufactures a leak detection and location system that inoculates the fuel lines with an inert gas, is the North American representative for Hansa.)

"Using a pressure step method," explains Patrick Mumme, vice president for government sales at Tracer, "Hansa does an automated hydrostatic test over a short period of time and you basically eliminate or minimize the thermal effects by doing the test at two different pressures. The Vista is doing almost the same thing except they're measuring a volume change rather than pressure. The results would be very similar, quite frankly."

Both systems require that the fuel line being tested be out of service. Testing is done during off-hours, unless there's a dual feed line.

Although Hansa and Vista can detect leaks in a system and can even narrow the leak site to a single section of fuel line, neither technology can pinpoint the exact location of a leak.

"Once we determine that there is a leak," Fierro says, "then you have to go to a different technology to locate the leak."

There are a few technologies that pinpoint leak location. Vista is developing an acoustic system or "a high tech listening system" that the company expects to have on the market in the near future.

UCISCO of Houston has developed a system in which a combination of nitrogen and helium is injected into a pressurized line. The line then has be inactive eight to 24 hours before a portable vacuum pump with a probe can detect any amount of helium rising to the surface in which the line is buried. It's a system that has been used by the Air Force, which can more easily manipulate its schedule to accommodate extended downtime.

Tracer Research's leak detection and location system is widely known as an effective way to locate leaks. The line is inoculated with the tracer element and at points along the line probes are inserted into the ground to detect the element. However, because FAA and aircraft engine and airframe OEMs don't allow any foreign agent to be introduced into aviation fuel for use in passenger aircraft, Tracer has to get approvals from the OEMs, FAA, and the airlines at a particular airport for use on an ongoing basis. Tracer elements can be used if the line is taken out of service and the inoculated fuel does not go into an aircraft.

Mumme says approval of one of their tracers is almost assured by the American Society for Testing Materials (ASTM) because Subcommittee J, the turbine fuel testing committee, has "unanimously approved" its use. "Now that is not an entire Committee D2 (petroleum testing committee) approval, but that will occur; it's merely a formality. The FAA defers to ASTM."

Because of the current restrictions, Tracer, at commercial airports, has largely been called in for emergency situations where a leak is suspected and the airport needs to pinpoint its location. Military installations have no such restrictions and Tracer currently has a permanent installation at Dover Air Force Base, DE.

At Reagan National Airport in Washington, Tracer has installed a combination of Hansa and Tracer products into its hydrant system. "If the Hansa system determines that there is a leak," says Mumme, "our probes are already installed and we can go about locating the leak using the Tracer method."

He goes on to say that "It's a good combination because the Hansa system is a lot more retrofittable than the permanent, automated Tracer system (alone)."

Tracer has guaranteed Reagan National that it will not have a false positive. "If the Hansa system shows a leak and then we do a test and there is no leak, they don't pay. If there is a leak, we locate it and there is a fee."