Patrick Vieira, leak detection expert at VEGASE Controle, an Emerson OEM in France, writes in his article, Hydrocarbon Leak Detection in Tank Farms, in the Jul 2017 issue of Control magazine about using wireless to detect leaks and prevent incidents, like this one:
“As a result of Buncefield and other incidents, refining and petrochemical storage areas are under increased pressure to monitor for tank leaks,” he says. “While level switches and redundant level instruments can guard against tank overflows, a storage tank can leak from several sources such as inlet and outlet piping and valves, chopper mixers, pumps and cracks in the tank.”
Because of the high cost of leak detection, in an average refinery with 100 storage tanks only 5% have leak detection. Considering that the U.S. currently has 122 refineries, that means more than 10,000 storage tanks are operating without leak detection in U.S. refineries alone.
A storage tank is an “island” in the center of a retention pond, so fuel leaks drain directly into the pond, requiring the use of a hydrocarbon leak detection system. Unfortunately, the costs of installing wired hydrocarbon leak detectors can be very high. A single storage tank may require six or more leak detectors, all of which must be wired back to the automation system.
“One way to reduce the high cost of hydrocarbon leak detection is with WirelessHARTTM leak detectors, which not only cut or eliminate the cost of wiring, but also allow alarm processing to be performed by a PC,” Patrick explains.
At a tank farm in southeastern France, VEGASE installed WirelessHART hydrocarbon leak detectors on 46 storage tanks. The sensors check to see if hydrocarbons are leaking into a tank’s retention pond from overflows, valves, pumps and cracks. Patrick describes the system:
“The entire tank farm required 141 detectors. Emerson’s AMS Wireless SNAP-ON software was used to design the WirelessHART mesh network, determine how many gateways and repeaters were required, and where each should be installed. Based on the software results, three Emerson 1420 wireless gateways were installed, along with 40 Emerson 708 wireless transmitters acting as repeaters.”
Today, the entire tank farm is monitored with leak detectors for 100% coverage of any incidents. The cost for the entire turnkey system was about $1 million, one-third the cost for a wired system, and the system has been operating to the satisfaction of the facility since its installation.