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Con Edison Media Relations
Richard D. Mulieri, Director
Telephone: (212) 460-4111

For Immediate Release: September 3, 1997


As part of Con Edison's program to achieve environmental excellence, company engineers, working with ASTTest Services Inc. of Melbourne, Florida, have developed a device capable of detecting oil leaks as small as one-half gallon per hour from a one million gallon tank. The device is designed to test tanks to ensure leak-free operation and can be used prior to or following internal inspections to detect leaks.

A United States patent was granted to ASTTest Services Inc. for the leak-detection system on April 17, 1997. Con Edison will share the patent royalties.

"The standpipe leak-detection system shows great promise for testing large underground and above-ground oil tanks," said Vincent dePass, Con Edison's senior environmental engineer. "The test doesn't require the tank to be drained and can be completed in 48 hours after a short setup time. It's a winner for the environment and a practical tool," he added.

The fuel oils and kerosene that are used by Con Edison in its power plants to generate electricity and steam, are sometimes stored in above-ground and underground tanks.

Regulatory Requirements and Testing Difficulties
New York state code requires that all large underground and above-ground tanks with access via a hatch or manway be internally inspected every 10 years. An ASTTest Services tank-bottom study determined that routine internal inspections may not detect very small holes in tanks. This can mean that after incurring expensive tank draining, oil sludge removal, cleaning and integrity testing of the tank bottom, a very small leak may still go undetected.

Internal tank inspections also require the tank to be out of service for extended periods of time and unavailable to supply oil to company power plants. In addition, if internal inspections miss a small hole, a tank could be returned to service with a small leak that could contaminate the environment.

A New Testing Device Is Developed
Engineers from the company's Environment, Health and Safety, and Research and Development departments worked with ASTTest Services to develop a new leak- detection system using an open bottom vertical tube, or standpipe. While the tank is full of oil, the standpipe assembly is inserted. It contains a level sensor and several oil temperature detectors, or thermistors, inside the pipe's entire length. Other thermistors measure the temperature on the outside skin of the tank. The system works by developing a correlation between the downward pressure of oil called the pressure head, temperature and level in the standpipe as compared to the bulk oil in the tank, taking into account thermal expansion and contraction. A nearby van equipped with electronic equipment periodically polls and records data from the detectors.

A portable weather station monitors barometric pressure, ground-level temperature, dew point and wind direction and speed during the test. These measurements make it possible to correct for any abnormal test results due to weather.

Tests Are Successful
A test of the system was conducted on a one million gallon oil tank at the company's Arthur Kill power plant over a 116- hour period with an indicated leak of 0.25 gallons per hour. The test met the objective of detecting a leak of less than 0.5 gallons per hour, which can occur through a hole of 0.5 millimeters or 0.02 inches in diameter, the size of a pencil- point.

Future Approved Use
In December 1995 the American Petroleum Institute (API) amended Standard 653 Tank Inspection, Repair, Alteration and Reconstruction to include a statement approving the use of leak detection tests for periodic assessment between internal inspections.

New York State Department of Environmental Conservation officials have agreed that testing with the Con Edison/ASTTest device of in-service large underground and above-ground tanks would provide an immediate environmental benefit with early detection of suspected leaks. The device can be used to test these tanks prior to or after internal inspection in order to identify leakage.

Con Edison is one of the nation's largest investor- owned utilities, with nearly $7 billion in annual revenues and $14 billion in assets. The company provides electric, gas and steam service to three million customers in New York City and Westchester County, New York.

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