Overfill Prevention

Bulk storage tank overfills are a common cause of product release and pollution at tank farms, terminals and refineries. Some overfills are small and easily contained, but the accumulation of product from repeated overfills or a single large spill can cause significant soil and ground water contamination. Throughout the bulk liquid storage industry, it is increasingly being viewed as “good practice” to provide some form of overfill prevention on all hazardous material storage tanks.

Technology Advantages

We select the best technology from industry leading manufacturers for the application at hand.
There is minimal disruption in system operations as tanks remain in-service during installation and testing.
All installed overfill prevention systems are independent of other level measurement and inventory systems.
SCADA capabilities allow the overfill measurement device to directly shut down system devices, such as pumps or valves or divert product movements.

Service Benefits

Single point of contact for environmental compliance - We handle all contracting services, leaving you to manage your facility. We communicate with all parties involved to ensure even the smallest project is managed and implemented effectively and on time.
With over 15 years of experience in the field working to EPA and API standards, we are able to provide impartial advice, allowing you to make the correct decisions.
We ensure that all required testing is performed prior to the “out-of-compliance” date and all reports are verified before they are submitted to approval agencies or local authorities.
Help desk support is available 24 hours a day, seven days per week to solve technical and application problems.
On-site or formal classroom instruction is available to complete the technical and functional awareness of your staff.

Ensuring Safety

Varec, Inc. has been a leading innovator in the petroleum and chemical sectors for over eight decades – working with industry leaders to pioneer inventory tank gauging instrumentation and fuel management systems, setting standards, assisting with best practices and introducing new technologies. We understand the safety and environmental issues, as well as the local, federal and industry regulations required for petroleum storage tank overfill prevention and environmental compliance. In the U.S., a small spill could cost a tank farm or terminal $3-4 million in clean up and fines. For a fraction of this price, a new system with new level alarm devices could be placed on a few hundred tanks for independent overfill prevention. This system would ensure safety and assist with avoiding unplanned budget overruns. Make a single call to our team and we will ensure your facility meets or exceeds the specific guidelines for the U.S. oil & gas industry as defined by the American Petroleum Institute (API 2350).

Independent Protection

It is widely agreed that independent high and high-high level alarms provide adequate prevention measures. The height of the alarms on the tank will depend largely on company, local, state or federal regulations and are based on the individual application, tank height and product transfer rate.

Overfill Prevention System Considerations:

Measurement of the level for overfill protection independent of other gauging systems installed on the tank
High and high-high level alarms that can be seen or heard by the operator controlling the tank transfer, such as audible sirens or horns and visual lights
A device that, when activated, can automatically trigger a diversion plan or shut down procedure for the process causing the alarm

More stringent regulations may be required for facilities
with:

Permeable ground materials that are inside the containment area
“Old” tanks that can be more susceptible to corrosion
Tanks near surface water, such as rivers, wetlands or lakes

Measuring Against Overfill

There are two defined methodologies to measure for overfill protection - single point measurement and continuous measurement. Within each group there are a number of technologies that can be utilized successfully. Varec recommends installation and integration of third-party equipment from industry leading manufacturers into FuelsManager for remote monitoring and alarm in addition to the required local alarms at the Crucial Process Value (CPV) point.

Single point measurement devices tend to be simple and very reliable with a low cost of ownership that can be installed at the high and/or high-high level. Common technologies used are mechanical switches, electronic ‘tuning fork’ or optical sensors.

For continuous measurement, a standard level gauge is a common solution. Any of the major gauging technologies can be used: float and tape (mechanical), servo, radar or magnetostrictive technologies. Your operators can check the status of the gauge at any time and the gauge’s operation can be monitored for deviation against the primary level device. The main benefits - you know if there is a problem with the gauge before it becomes an overfill problem and your operators do not need to climb a tank to check the operation.

Software Alarms

Varec’s FuelsManager is capable of providing audible and visual software alarms from every connected tank gauge. An integrated alarm toolbar and pop-up alarm notification provide real-time visual and audible notification of alarms or events. The toolbar also provides access to an active alarm summary, a historic alarm log and an alarm log file browser that allows your operators to view and print reports of alarms or events in detail.

FuelsManager also tracks and prevents unauthorized modifications to the CPV. Any product that requires seasonal CPV changes can be managed easily - eliminating any errors when updating CPVs across
your facility.

Approved Instrumentation

Varec recommends utilizing instruments, such as the 7200 Series Radar Tank Gauges, that are internationally approved (such as SIL, SIG or TUV ) to meet standards that guarantee safe and accurate operation to protect against overfill.

This service is available under authorized GSA Schedules. For more information, Email GSA Services.

Example Real-World Solutions

Radar Tank Gauge Application
In a small terminal, 10 tanks had existing 2500 ATG with transmitters that provided a primary level measurement back to the office for inventory control. Each tank also had an independent mechanical float switch. After many reliable years of service, the terminal manager could no longer rely on these old switch devices for overfill protection.

The Varec solution - install a 7240 Radar Tank Gauge on each tank to provide independent and continuous level measurement for overfill protection. The loop-powered radar utilized the same two wires that were used by the mechanical switch. The gauge was also installed on a small, 1.5" NPT fitting on the top of the tank. This resulted in a very low cost installation.

The existing float and tape gauges continue to provide inventory control grade measurements that are appropriate for the terminal operations. The two systems, both of which are continuous measurements, can be checked against one another for operation and accuracy of measurement. Finally, the SIG/TUV approval for this application gives the terminal owner extra peace of mind knowing the local environment is well protected.

Mechanical Level Switch Application
A major oil company applies risk assessment values to processes in their terminals and sets minimum guidelines. After assessment, one facility in Latin America, without any tank gauging or measurement of any kind; was required to meet their minimum rating. In this case, each of the eight Mogas cone roof tanks would require a level gauge and high level alarm switch. This switch would have to be independent of the gauge and also follow API 2350 guidelines for high level alarms.

Based on the tank types and measurement accuracy needed for the refined products stored and distributed at the terminal, float and tape level gauges (2500 ATG) and a mechanical (displacement) level switch were selected. The level switch provided independent high-high measurement and testing. A lever could be pulled to perform a routine manual test required by the site on a monthly basis. The installation offered a non-obstructive approach to the day-to-day operations of the facility and provided the most economic, reliable and user friendly solution for this particular terminal and its employees. The terminal is now in a position to upgrade its tank gauging system and company safety level by installing transmitters with inputs for temperature as the need arises in the future.

Tuning Fork Application
The same oil company applied the risk assessment to a facility in Florida, USA. The facility currently met their internal requirements, but the existing 26 high level alarm devices (2 devices per tank) were deemed obsolete technology. Based on age of the infrared technology, the manufacturer was unable to support the facility for maintenance and repairs. Each switch, high and high-high, on each tank was completely independent from one another and was fed into an electrical panel that provided audible and visual indication to the operators. They were also located at grade level for easy access and the sensor was positioned in an overfill pipe design, as some of the tanks contained internal floating roofs. Located in Florida , the site also needed to maintain state regulations for overfill protection.

Varec proposed a direct replacement device that utilized tuning fork technology. This allowed the customer to use the existing wire, conduit and mounting arrangement, which meet the original internal risk assessment guidelines. The new level switch also requires no calibration and is tested with a compact device that carries a SIL rating of II - a complete solution with a distinct advantage over the older system. During the upgrade, a new, compact electrical panel was also installed that allowed each tank to be outfitted one at a time, with no disturbance to the daily operations of the terminal.

Moving Forward
Before a particular solution is chosen and a system installed into your facility, your application and operating requirements should be clearly defined and any regulations known. Understanding the implications of each factor will allow selection of the most appropriate system for your needs. For tanks with no gauging or systems, the choice may be clear and simple based on the alarm requirement, the tank and the application. If you have existing gauging, it may be possible to use that system for standard daily inventory tank gauging measurements and install a new, independent measuring device for overfill protection or visa-versa.