YQA 24 Generator Fuel System Sensors

24.01 Where are differential pressure sensors used and how do they work?

Differential pressure sensors are used in commercial fuel systems primarily to monitor filters for dirt accumulation and indicate a need to change filter elements. The sensor is typically a diaphragm or piston with the upstream and downstream pressures on either side. Movement of the diaphragm or piston to a defined limit cause the closure of an electrical contact which generates an alarm signal. Differential pressure sensors are often integrated with a differential pressure gauge.

24.02 Where are pressure transducers used and how do they work?

A pressure transducer is installed into a fuel pipe to provide a proportional electrical signal to the pressure range. A typical example would be a transducer that has a 0-10 VDC 9 (or 4-20 mA) output for a 0-200 PSI range.The pressure transducer is used as a means of proving the performance or pumps, or as a primary control input for VFD pump controllers. They are also used for pressurized line leak detection tests.

24.03 Where are temperature sensors used and how do they work?

Temperature sensors are typically RTDs which measure temperature based on a device with a variable resistance based on temperature. RTDs are sometimes provided as transmitters to provide a standard 0-10 VDC or 4-20 mA output signal. Temperature sensors are also integrated into tank level transmitters to provide temperature compensated tank volume measurements.

24.04 What type of pressure gauges should be used?

We recommend liquid filled gauges either 2.5” or 4” diameter.

24.05 What type of level switches should be used?

Level switches for fuel systems are typically reed switch type devices. Switches should be rated at a minimum 20 VA. We recommend metal stems, either brass or stainless steel with Buna or stainless steel floats, 1 inch diameter or larger. Smaller floats have a tendency to be less reliable when there is turbulence in the tank typical of day tanks. Common level switch applications are day tank level sensing, and high / low level sensing in bulk tanks.

24.06 What type of flow sensors should be used?

Simple flow switches are best as shuttle type valves, which operate reliably with less than perfect inlet and outlet conditions. Vane type or thermal type flow switches can be used where the inlet and outlet conditions can be reliably provided. Flow switches are commonly used for pump proof of flow.

24.07 What type of level transmitter should be used?

Level transmitters for fuel tanks are typically magnetostrictive technology. Most underground tank gauges have adopted this technology because its high accuracy allows conformance with EPA requirements. The transmitters typically have embedded temperature transducers to provide temperature compensated volume calculations. There is some use of ultrasonic sensors for tank level sensors. However, these are not typically reliable enough to be used without a supplementary high level sensor for overfill protection.