Tank Gauging and Overfill Prevention System

In January 2014, the city of Charleston was affected when a tank containing 4-methylcyclohexane methanol leaked, causing contamination of the Elk River, which provides over 300,000 people with drinking water. Residents were without tap water for at least five days. But it may be months or even years before the total effect of the spill is known.

The company that owned the storage facility where the leak occurred — Freedom Industries — is now facing at least 31 lawsuits, along with state and federal investigations. As a result, the company has filed for bankruptcy.

Overfill and spillage can happen to any tanking operation. However, with a few precautions and a relatively minor investment, this event could have been identified early on, and action could have been taken to mitigate the leak and its destructive consequences.

Instrumentation exists that can monitor the contents of a vessel and provide an alarm in the event of a leak or overfill event. These products have been used for years and are well-established and reliable.

Properly specified, installed and maintained instrumentation will warn of possible spills and overfills, giving operators plenty of time to react. Overfill prevention systems regulate storage-tank fluid levels to avoid spill over and dangerously high pressure levels that can damage tanks and cause explosions.

Greenpeg Engineering is committed to supporting our customers with Tank Gauging Solutions that prevent overfill, spillage and leakages and the attendant.

Greenpeg through our partnership with Endress+Hauser, a global leader in process instrumentation, is committed to supporting our customers with Tank Gauging Solutions that prevent overfill, spillage and leakages and the attendant consequences. The schematic below gives an overview of the system arrangement.

Types of Overfill Prevention System

AOPS includes SIL3 Safety Shutdown Relay instruments that will automatically shut down process components such as valves and pumps when it detects that the fluid has passed the high point level.

MOPS has no Emergency Shutdown components per tank and it requires an operator to turn off the valves and pumps. However, it includes additional safety signalization components such as Signal Alarm and Flashing Beacon.

These overfill prevention solutions can be deployed for any number of tanks. The instruments on each tank can also be connected using cables or wirelessly depending on the client’s preference or the plant layout. The solution can also be linked with other existing or new solutions such as custody transfer, loading, and offloading metering solutions.

The entire system can be configured to be monitored remotely from the office or from any part of the world.

Benefit of the Tang Gauging and Overfill Prevention System

  • It prevents loss of income that may result from loss of spilled product and shut down for repairs and cleanup
  • It protects the environment from the harmful effects of chemical and oil spillage.
  • It prolongs the live span of plant installations by reducing wear and tear resulting from constant human contact.
  • Constant tank monitoring improves accountability and prevents revenue loss from theft.

An instrumentation and monitoring system like the one discussed above detects spills and leaks at multiple levels — with tank monitors, HMI software and receiver testers providing redundancy.

The events in Charleston make it clear that chemical storage tanks need to be secure and that spills and leaks must be prevented where possible. This should extend to any industry — chemical, oil and gas, water and wastewater, foundries, and others — storing chemicals that could contaminate water supplies.