UST Leak Detection Systems Annual Inspection Requirements for New Hampshire and Massachusetts
Troubleshooting a tri-state sensor
This article explains tank leak detection systems, describes the test methods for each sensor, probe, and line leak detector, and provides the testing requirements for Massachusetts and New Hampshire.
In Massachusetts, Underground Storage Tank (UST) leak detection equipment must be tested and certified every 12 months by a technician with current training from the manufacturer of the monitoring equipment as required by MassDEP 310 CMR 80. The State of New Hampshire requires the tester to have manufacturer training in accordance with New Hampshire code of administrative rules Env-Or 406.
Fuel system maintenance contractors inspect underground storage tanks at a variety of businesses and organizations. Yearly monitoring system inspections help protect our shared water supply from potential contamination. Underground tanks are typically made up of several components. These include the underground storage tanks, turbine or product sumps, underground piping, under dispenser containment, spill buckets, fuel dispensers, sensors, and a monitoring panel. The inspector confirms the functionality of leak detection systems by performing annual inspection or recertification of the equipment.
Veeder-Root Sensor Testing
Veeder-Root 420 and Omntec BX-LS Sensors
There are two types of sensors; discriminating and non-discriminating. Discriminating sensors provide a different alarm response for each liquid it encounters and different detection points. Discriminating sensors are not common in UST installations and have slow response and recovery time. The non-discriminating sensor activates the same alarm response for each liquid it detects and it has a single detection point or element. The non-discriminating sensor has a quick response and recovery time and is the most common sensor installed in leak detection systems.
Most sensors are monitored via the Veeder-Root monitoring system which measures a resistance on the line. If the resistance measured is within tolerance then the monitoring system declares the sensor is operational. A sensor will show as offline if the Veeder-Root measures infinite resistance on the circuit. This can occur if a line is accidentally cut by workers, the wires become frayed or the seal pack (a junction of 2 sets of wires joined with epoxy) has corrosion.
Veeder-Root Annular Space Alarm
The Veeder-Root Model 420 sensor is an example of a sensor used as an annular space alarm. This bell sensor consists of a metal housing shaped like a bell with a float that slides up and down on a rod. This sensor is typically found in the annular space of double-wall steel tanks. The float indicates an alarm state when raised and a normal state when lowered. An inspector will test this sensor by removing it from the annular space and placing it in a liquid to confirm it is operational. If an alarm state is indicated on the tank monitoring system display then the sensor passed the test. It is not uncommon for the retainer clip that holds the float to corrode on older sensors. In this case, the float will no longer indicate a high alarm state.
Non-discriminating Annular Sensors; Optical (left) and Reed Switch (right)
Another style of annular sensor is the wrap-around sensor. It detects the presence of liquid in the interstitial space of a double-wall fiberglass tank. The length of the sensor depends upon the diameter of the tank. A piece of string is used to pull it up from the annular space through the riser pipe. The proper test method for wrap around sensors, according to Veeder-Root protocol, is to raise it up to grade, examine the sensor to ensure it’s not damaged, and then place the sensor in a liquid. If an alarm state is indicated on the tank monitoring system display then the sensor passed the test.
Tank Monitor Sump Sensor
Piping Sump Sensor - Non-discriminating
Another common sensor is the dispenser pan or piping sump sensor. It is a non-discriminating sensor that detects the presence of hydrocarbons or other fluids. There are no moving parts in this type of sensor and they will continue to work after exposure to hydrocarbons and in freezing temperatures. The sensor is created using a conductive elastomer that is mounted in a polyester housing. To test this sensor the inspector places the sensor in water and waits 5 minutes for the sensor to trigger the alarm in the tank monitor. After cleaning and drying the sensor, the inspector then places the sensor in fuel and waits 5 minutes for the sensor to trigger the alarm.
Leak Detection Probes
A leak detection or automatic tank gauge probe is designed for accurate inventory control and in-tank leak detection. It utilizes magnetostrictive measurement technology to provide highly accurate 0.1 GPH volumetric tank tightness testing and 0.2 monthly testing. It is certified for use in gasoline and diesel tanks. The probes will also provide overfill prevention when programmed to trigger a remote alarm if the fuel levels reach 90% capacity. Leak detection probes are used in single-wall aboveground tanks to provide leak detection where there is no annular space to place a probe. The upper float monitors the fuel level and the lower level is used to monitor water levels in the tank. These probes are installed vertically in the tank through a riser pipe which allows access for maintenance and testing.
The leak detection probe must be removed from the riser pipe to verify the operability of the sensor. The inspector will print the water warning and product height settings prior to testing. Test containers are used to simulate water and fuel levels. By filling the test container to just above the water warning height set in the Veeder-Root console, the water alarm height can be tested. The same procedure can be used to test for low product levels after filling the test container with product.
Line Leak Detectors
Red Jacket 4" Submersible Turbine Pump with line leak detector
Line leak detectors are another type of leak detection equipment. There are two types of line leak detectors; mechanical and electronic. The mechanical detector is triggered when there is a loss in pressure in the line between the in-tank turbine pump and the fuel dispenser. The mechanical detector responds to this state by reducing flow to the dispenser. An electronic line leak detector also looks for a loss in line pressure but it responds to the state by disabling the in-tank turbine pump. Leak detectors can trigger an audible or visual alarm instead of restricting or shutting off product flow and still meet EPA release detection requirements.
The inspector will generate a 3 gallon/hour line test failure in order to manually test a mechanical line leak detector. The test is performed by de-energizing the circuit and depressurizing the line, connecting a test plug at the bottom of the sheer valve, opening a test valve to simulate a small leak, then energize the circuit, authorize the dispenser to pump and allow the line to pressurize. These steps will cause the tank monitoring system to run a 3 gallon/hour line test.
The Veeder-Root tank monitoring system tests electronic line leak detectors automatically. It has control of turning on the submersible pump to run a full test manually and it runs mini-tests automatically just after it sees the dispenser handle signal and compares that line pressure after pumping to the threshold based on the length, diameter, manufacturer, and type of piping of the system that is programmed into the Veeder-Root.
Restoring Sensors to the Proper Location
Sensors must be located at the lowest possible point so they can detect a leak as soon as one starts to occur. Technicians may handle sensors during testing or maintenance but it is the responsibility of the UST owner and operator to ensure sensors are always in the correct position. Fines and penalties are possible if sensors are not at the lowest point. The image above shows a technician replacing an annular space sensor. Veeder-Root now provides a calibrated sensor positioning strip for installing sensors in the annular space of a fiberglass tank. This strip ensures that the sensor switch reaches the bottom of the tank and is set facing upwards in order to operate correctly.
The sensors described in this article can be found in Veeder-Root TLS-450, TLS-350R, TLS-350, TLS-350J, ILS-350, TLS-300i or TLS-300C. TLS-250i and ILS-250 models.