With expanding fuel system sizes and additional compliance monitoring requirements, we’ve seen many new devices and technologies added to the fuel system in the last few years. The addition of these devices and systems increases the need for good wiring practices to ensure safety and data integrity throughout the fuel system.
This shared learning will put forth recommended wiring practices to be used in conjunction with local code requirements, industry standards, and manufacturer installation requirements of these fuel system devices.
FUEL SYSTEM DEVICES
In a fuel system, measurement devices such as probes and sensors are utilized to monitor fuel storage and fuel containment for environmental compliance. These measurement devices are generally low voltage (intrinsically safe) devices to ensure safety in these fuel storage applications.
Local codes and standards require these low voltage devices be kept separated from fuel system high voltage sources such as 110V dispenser handle signals and 220V submersible turbine pump wiring.
Inside the automatic tank gauge and in wiring troughs, separation is generally accomplished between low and high voltage cable routings by means of a physical barrier, but whenever possible its recommended that separate wiring troughs be
used for low and high voltage cable routing.
In addition to safe cable routing in the electrical room, measurement devices also require good wiring practices to be followed all the way to the monitoring location to ensure data integrity.
Whenever possible, it is recommended to maintain not less than 12 inches of physical separation between low and high voltage cable routing in underground conduits within well tamped earth.
When separation is breached to crossover conduits, they should cross at a 90 degree angle to avoid parallel low and high voltage cable routing as much as possible.
If proper physical separation or crossovers of underground cable routing cannot be maintained, steel conduits on high voltage cabling is recommended to provide a barrier between low and high voltage cabling.
Additionally, installers should maintain physical separation of measurement devices in the fuel storage and fuel containment per the manufacturer installation requirements, typically not less than 12 inches from a submersible pump or other fuel system equipment that could compromise monitoring operation.
GROUNDING & SHIELDING
Data integrity can be compromised by electrical noise on the signal to and from these measurement devices if good wiring practices are not followed.
In a fuel system, electrical noise can be generated by several types of fuel system
equipment including lights, compressors, submersibles and other high voltage appliances.
To mitigate electrical noise from these measurement devices, always follow local
code requirements, industry standards, and manufacturer installation requirements for proper grounding of equipment to the electrical panel and to the system earth ground.
Also follow local code requirements, industry standards, and manufacturer installation requirements for proper shielding of signal cabling to these measurement devices.
LARGER FUEL SYSTEMS
In addition to the devices and systems being added to fuel systems in recent years, fuel systems continue to grow larger.
Larger systems inherently require more low and high voltage cables routing throughout the fuel system, which will require even further consideration of the above wiring practices to ensure data integrity.
With these larger systems, consider increased cable separations in all areas beyond 12 inches (especially on longer parallel cable runs) or utilize steel conduits on high voltage cabling to provide a barrier between low and high voltage cabling
throughout the fuel system.