YQA Fuel Tank Monitoring and Leak Detection

13.01 What is typically monitored in fuel tank and piping systems?

The monitoring of fuel tanks and piping is determined by US EPA requirements, State, and Local regulations. The points of monitoring typically include the following:

  • tank gallons, tank temperature compensated gallons, ullage (empty space in the tank), fuel inches, water inches, water gallons, tank temperature.
  • tank interstitial leak detection, or hydrostatic monitoring for wet interstitial systems, or vaccum monitoring for vacuum systems
  • tank sump liquids, and double wall tank vacuum, or hydrostatic
  • double wall piping interstitial dry, hydrostatic, or vacuum
13.02 What are the leading tank monitor brands?

Veeder Root Tank Monitors are used in a reported 80% of all tank installation. This is worldwide brand that is extremely well supported by local technicians.

Secondary brands include: Pneumercator, Omntec, OPW (former Petrovend) and Incon / EBW (Franlkin Electric)

13.03 What is line leak detection for piping?

Many State and local regulations require a line leak detector for pressurized underground piping. Line leak detectors for underground piping are used to detect a loss of integrity in the piping with a consequential shut down of the pump. There are 2 types of line leak detectors – mechanical and electrical.

Mechanical line leak detectors install on the submersible pump body. The pump must start against a closed valve to allow pressure to build in the line sufficiently to allow the line leak detector to open and flow. If pressure does not build in the line properly, then the mechanical line leak detector trips and restricts the pump flow.

Electronic line leak detectors operate in conjunction with a tank monitor such as a Veeder Root panel. After each pump run cycle, the panel turns on the pump automatically and measures the pressure in the line using a pressure transducer. The panel displays a pass / fail test result and may be required to be configured to disable th submersible pump.

Line leak detectors are designed to work reliably with motor fuel dispensing operations where dispensers include solenoid valves to work in conjunction with the submersible pumps. In emergency generator applications, especially mission critical applications, the devices can be problematic where test failures can shutdown the fuel supply system. Control systems need to include appropriate valve / pump timing controls to allow successful tests, and also detect failure and switch to a secondary pumps.

13.04 What is vacuum monitoring for tanks, sumps, and piping?

The State of California requires continuous active monitoring of underground fuel systems including tanks, sumps, and piping. The concern was that dry interstitial spaces at atmospheric pressure could fail without recognition, and that a leak could escape from the containment prior to flowing to a sensor and being detected.

The regulation allowed pressure, vacuum, and hydrostatic methods of monitoring fuel containment secondary spaces. The hydrostatic method had been used for many years successfully in underground fiberglass tanks. The same method was extended to fiberglass sumps and double wall fiberglass piping. Pressure based systems have not been widely adopted.

The vacuum system has been widely adopted in California for a several reasons:

  • The leading tank monitor developed systems to generate and monitor vacuum systems
  • The vacuum generating device is the submersible fuel pump already present in most UST systems
  • The vacuum method works for either fiberglass of flexible plastic piping system
  • The vacuum method works for steel or fiberglass tanks and sumps

The vacuum monitoring system works essentially as follows:

  • The Veeder Root monitor activates the submersible pump which is detailed to draw a vacuum on the interstitial spaces of tanks, sumps, and piping
  • A Veeder Root vacuum sensor measures the vacuum and the vacuum decay rate.
  • The control monitor determines if the vacuum decay rate is within the test pass parameters or not
  • The tank monitor indicates a pass or fail result for the test.
13.05 How does a Veeder Root communicate with BMS equipment?

Tank monitors are integrated into fuel system controls by 2 methods: (a) output relays for tank conditions, and (b) through a serial interface – ASCII via RS-232 or Ethernet.

Typical output relay functions are: high level, low level, tank leak, sump leak, pipe leak.

Typical serial information is: tank volume, temperature compensated volume, ullage – space available in tank, and temperature.

13.06 What is intrinsically safe wiring?

Intrinsically safe wiring is a method of operating instruments, sensors, and devices in the hazardous electrical areas around flammable and combustible liquids and gases. Essentially, the electronics within the control panel limit the amount of energy through the wiring to the sensor or device, such that the energy is insufficient to create an electrical spark that could ignite the flammable liquids or gases.

Intrinsically safe installations are an alternative to explosion proof conduit and wiring systems, which are typically designed to contain the energy of an explosion caused by an electrical spark

Most standard tank gauges are used primarily in gasoline tank installations at retail service stations. For this reason, their instruments and sensors are designed as intrinsically safe devices.

In planning fuel system controls, and important consideration is that intrinsically safe conduit systems must be separated from other wiring.