Automatic tank gauging (ATG) systems are used to monitor product levels and detect leaks in underground storage tanks. Many tank operators use ATG systems as the primary method of leak detection and inventory monitoring, as they are both highly accurate and convenient to use. Learn more about how ATGs work, and how to maintain them, in our blog.
Automatic Tank Gauging Systems and Underground Storage Tanks
How They Work
The gauge is a probe the is permanently installed in the tank. The probe connects to a processor and a monitor in a nearby facility where the operator can observe readings from the probe. Multiple probes can be set up to connect to one processor, which means readings can be taken from multiple tanks at the same time. The system must be able to detect leaks as small as 0.2 gallon per hour.
ATG systems have two modes of operation, and some systems use a blend of both.
The ATG measures the level of product and water in the tank.
Leak Test Mode
The ATG measures product level continuously over a period of time to determine if there may be a leak. Temperature is also measured in order to take into account the fact that temperature changes can affect product levels.
Continuous Statistical Leak Detection (CSLD)
Instead of using leak test mode, the system analyzes data from inventory readings taken over the course of the month to determine if there is a leak.
Using an ATG
Leak tests can be initiated manually by the operator, or automatically by the automatic tank gauging system.
- Underground storage tanks must pass a leak test at least once a month.
- The test should be performed when the tank is full or close to full.
- The test generally takes 3-5 hours.
- The product should not be delivered to or withdrawn from the tank for at least 6 hours before or during the test. This means the test is usually done at night.
- The tank needs to be taken out of service during the test.
- If using a CSLD ATG system, the tank does not need to be taken out of service. But if the system has not been able to collect conclusive data over the course of the month, the tank should be taken out of service and the ATG should be put in leak test mode.
- The test must be repeated until a conclusive (passing or failing) result is obtained.
There are a number of reasons that a tank that is not leaking could generate an inconclusive result on a leak test. These include:
- Not enough product in the tank.
- Product was added or withdrawn during the test.
- Poor weather conditions.
- Probe malfunction.
- Vibrations from traffic.
If a failing result is obtained, the test must be repeated to verify the result. If the ATG continues to generate a failing result, you must contact the relevant government agency for your state.
Automatic tank gauging systems must be properly maintained in order to generate accurate results. The manufacture will provide a schedule for calibration of the ATG, which can be provided by a local contractor. ATGs can malfunction for a number of reasons, such as power outages. A contractor can provide ATG diagnostics and repair services.