Case Study: Integrating a Successful Fuel Oil System at University Hospital Complex

-David Eoff

Preferred loves this system because the engineer contacted us early on in the design process and had the same goals Preferred has for a fuel system. He wanted a system that would be reliable, robust, redundant, and include the features Preferred has proven to work for large generator fueling systems like this one in Mission Critical, Hospital, Federal, and Data Center applications.

This university hospital is adding a wing to this hospital complex. The electrical consumption of this new wing would put the local electric utility into a low reserve situation on hot summer days, so they offered the hospital very inexpensive electricity if they would install backup generation so the hospital could go off grid during periods of high electrical consumption.

The generator building consists of eight 3 MW Caterpillar generators with DEF systems, and two 20,000 gallon above ground storage tanks. Preferred supplied two duplex pump sets, each to service four of the 3 MW generators and be able to pull from either main storage tank, eight 620 gallon day tanks, a filtration system that can polish either main fuel tank, and the controls for the generator DEF supply system. Preferred linked the controllers for the pump sets, day tanks, and polishers via the Preferred two channel redundant nodnet system. So the pump sets, day tanks, and polishers were hard-wired in the Preferred factory, and then connected via parallel three conductor Belden cables in the field to massively reduce field wiring material, labor, and expense. This photo shows four of the 3 MW generators installed in one wing of the generator building.

Most of the fuel oil system devices are part of the generator day tanks. These 620 gallon day tanks provide about 2 ½ hours of full load fuel to their local generator. Each day tank includes a PLS-5 float switch assembly, a separate high level switch, a vent switch, a flow manifold, and a return pump. All the wiring for these devices was done and tested at the Preferred factory. During the startup of these day tanks we found no wiring errors, and just one faulty vent line switch that may have gone bad during shipping. Turning on power and having these eight day tanks work right out of the box greatly decreased start-up time. These day tanks included a function Preferred rarely supplies, but turned out to be very nice. The engineer insisted on flow switches in the day tank fill manifolds and return pump piping. So whenever a day tank was calling for fuel, you could see on the local touchscreen that fuel was actually going into the day tank. Because all the control panels were connected via nodenet, you could see from the local day tanks, or the remote supply pumps, or the control room that fuel was actually getting to the day tanks when they were calling for fuel. The same was true of the return pumps—the flow switches proved flow, and you could get visual confirmation from any touch screen.

This picture shows a PF-505-CA-WR filtration system on the left and an ATPSF-207 pump set on the right. The ATPSF-207 includes Preferred’s new telecommunication-style NEMA 3R weatherproof enclosure. These enclosures keep the pump sets cool, dry, and bug-free in any weather. They provide a nice shade so you can see the touch screen in bright daylight conditions. I was priming one of these pump sets during startup when a thunderstorm moved through. I stepped inside the enclosure and pulled the door shut behind me and was able to continue working high and dry until the shower passed.

The ATPSF-207 isn’t in the Preferred price book yet, but each of these pumps will move over 1900 GPH of diesel fuel. The 1200 GPH fuel polishing system will ensure the university never has to worry about water, sludge, or other contaminants shutting down their generators.

Shown (right) is one of the 20,000 gallon above ground main storage tanks and a Preferred FA-AV-3-SS overfill alarm cabinet. There is room for a third 20,000 gallon main tank if the university ever decides to add more fuel storage. These main tanks include platforms and ladders that allowed for easy access to the Preferred wire floats, high level switches, and leak detectors during commissioning, without having to climb out on the tank, which is a big deal to the contractor’s safety inspector. I also like the bollards surrounding the main tanks to ensure a truck doesn’t accidentally, or on purpose run into one of the tanks. This generator building, like many generator systems, is mission critical to the operation of the hospital, so it’s good to see the building was designed with physical security in mind.

Below shows one of two 2,000 gallon DEF tanks and the Preferred DEF control system on the right. The tanks are made out of polyurethane and include a submersible pump and Preferred magnetorestrictive level sensor. The engineer designed this DEF system, Preferred just did the controls. This system used inexpensive components designed specifically for DEF applications. It’s a great design that Preferred will recommend on future fueling systems requiring DEF systems for NOx reduction.

This Preferred fueling system was designed from the ground up to be reliable and robust. Redundancy is built into the main tanks, supply pumps, day tanks, and control system. In the event of a control failure, any pump can be put into hand to fill day tanks. There are belts, suspenders, and extra belts installed to prevent overfilling a main tank or day tank. Information related to a pump set or day tank can be seen on any of the 13 touch screens supplied with this system, on the Preferred Cloud, or on the university’s building management system. The fuel system is integrated into the building’s fire detection system to shut down the fuel system and prevent it from adding fuel to a fire. The general contractor and engineer are very happy with this system and the support they’ve received from Preferred so far. The university is just getting trained on the operation of this generator building, but now they have the ability to run their hospital at full speed without grid power in the event of a utility curtailment, or a repeat of last February’s unusually cold weather. Hopefully the fuel system for this generator building becomes the template for other large fuel systems in the future.

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