How does the leak detection method work?
The ATG (Automatic Tank Gauge) systems method uses automated processes to monitor product level and inventory control. A probe, permanently installed in the tank, is connected to a monitor to provide information on product level and temperature. These systems calculate changes in product volume that can indicate a leaking tank. This method operates in either Inventory Mode or Leak Detection Mode. In the Inventory Mode, the ATG system replaces the use of the stick gauge to measure product level, and perform inventory control. In Leak Detection Mode, ATG systems can be set manually or automatically to perform a leak test. Manual leak tests are in-tank static tests, and automatic leak tests are continuous in-tank leak detection tests. When we refer to ATG systems, we’re referring to testing performed while in the in-tank static test mode. ATG systems operating in continuous in-tank leak detection test mode are covered under Continuous In-Tank Leak Detection.
Preventing and Detecting Underground Storage Tank (UST) Releases
Regulations require that USTs are installed properly; protected from spills, overfills, and corrosion; equipped with release detection; and properly closed.
Automatic Tank Guage Reporting:
Record Keeping for ATG Systems:
UST owners and operators must keep records for a minimum of one year on leak detection performance and upkeep. They must include the previous year’s monitoring results, the most recent tightness test results, performance claims by the leak detection device’s manufacturer, and records of recent maintenance and repair.
What additional records will you need to keep?
Beginning on October 13, 2018, you must also keep these records:
Common Components of an ATG System
ATG Unit : There are multiple unit manufactures on the market today. Knowing your individual unit is very important. The unit is the brain of the system. This is where all the system information and capabilities are located. The unit displays the current product levels and any alarms present within the system.
The Tank Probe : The tank probe is located in a riser on the tank top. The probe extends down inside of a tank and rests on the tank bottom. Most tank probes these days are equipped with both a product float and a water float. The product float rises and descends with the fuel level present in the tank. The water float is designed not to float below the fuel stored in the tank, to monitor the water level present at the bottom of the tank. Most ATG systems are programmed to alarm when a determined water level is reached.
Monitoring Sensors : There are multiple manufactures of sensors on the market these days. Monitoring sensors are usually installed in dispenser containment sumps, Submersible Turbine Pump (STP) containment sumps, piping sumps, and in the interstitial space of a UST. Single float sensors only detect that a liquid is present. Dual float discriminating sensors do just what the name states; discriminate between water and product. Hydrostatic sensors are used in interstitial applications when the interstitial is to be flooded with a brine liquid. The hydrostatic sensor is set to a determined height in the liquid, and will alarm if a loss or gain of interstitial liquid is detected.
Interstitial Monitors : Monitors are used to check the area between the tank and the barrier for leaks and alert the operator if a leak is suspected.
Some monitors indicate the physical presence of the leaked product, either liquid or gaseous. Other monitors check for a change in condition that indicates a hole in the tank, such as a loss of vacuum or a change in the level of a monitoring liquid between the walls of a double walled tank.
Monitors can be as simple as a dipstick, used at the lowest point of the containment to see if liquid product has leaked and pooled there. Monitors can also be sophisticated automated systems that continuously check for leaks.
Know Your System : The market is flooded with ATG (Automatic Tank Gauge) manufactures. Picking the right system for your application can be a daunting task. Doing your research can go along way in choosing a system. Knowing what you need is only half of the battle. The other half is making sure your new system can perform the tasks at hand. Many systems can perform basic functions like inventory control. Others can do much more, from inventory control to off-site remote monitoring, to a full-site shut down in case of an emergency. ATG systems come in a range of capabilities. It’s up to you to pick the correct system, based on your sites needs and requirements.
Secondary Containment Monitoring : If you’re involved with UST’s (Underground Storage Tank), the new rules regarding secondary containment should be of interest. New EPA mandated regulations require that UST installations and upgrades meet the new secondary containment guidelines. These guidelines include the installation of double wall tanks, double wall piping, and piping sumps (tank-top, intermediate, and under-dispenser containment). According to the US EPA rules, “Beginning on April 11, 2016 owners and operators must install secondarily contained tanks and piping when installing or replacing tanks and piping.”
The primary method of monthly leak detection for these tanks must be monitoring of the interstice (space between the inner and outer tank walls). In most tanks, the interstitial space is monitored electronically with a liquid sensor, but some tanks do allow for a manual or “sticking” process. The same is true for the piping system; if you are installing a new system or planning an upgrade, secondary containment must be installed. This includes double wall pipe and sumps at all piping connections.
Again, monthly monitoring of the pipe interstice and sumps is required to be the primary method of leak detection. The sumps can be monitored with a liquid sensor or by physically checking the condition of the sump. This method of leak detection requires that the containment be liquid-tight; meaning that all entry boots, conduits, and walls are not damaged and are intact. It also requires that the double wall pipe drains freely between dispenser sump and tank-top sump (i.e. piping test boots are open).
For more information, visit the EPA’s Release Prevention for Underground Storage Tanks (USTs).
Documentation : A very important part of secondary containment is correctly documenting that you are monitoring and maintaining your double walled UST (Underground Storage Tank) system. This must be done to satisfy your monthly leak detection requirements. Remember that you must continually maintain these monthly records for 12 months. If you are monitoring electronically with liquid sensors, then you must retain the sensor status reports or manual log (if the monitor does not print a report). If you are physically checking the interstitial spaces/sumps, then you must update the manual log every time you confirm the status. Obviously, any issues indicated by this monitoring must be addressed immediately. Even though secondary containment is now required on most upgrades and new installations, it really does make good sense. Adequate secondary containment will capture a leak before it is released to the environment.