BP adds wireless to check oil tank temperatures
15 Dec 2009
London – BP Exploration has installed wireless temperature transmitters to check the performance of an existing tank protection system at its Dalmeny onshore terminal, near Edinburgh, UK. The facility, which can store about four million barrels of stabilised crude oil from the Forties oil field, uses eight interconnected storage tanks, 40-50m in diameter, to regulate the flow of oil between production wells and the tankers or pipeline that transport it to the refinery.
BP was already measuring oil temperature at the side of the tanks, but was concerned that there could be significant differences between temperatures at the edge of the massive containers and at the centre. Confirming any differences in temperature presented a challenge, however, because the tanks needed to remain in use, making installation of temperature probes impossible.
An out-of-service tank with no existing temperature measurement in place provided an opportunity to install the necessary instrumentation. However, there was no cabling infrastructure in place for this specific tank so if BP had installed wired transmitters it would have also had to install a cable recoil system to cope with the floating roof at a cost over £15,000.
Wireless therefore offered a cost effective alternative for BP, which already applied Emerson’s Smart Wireless technology to monitor wellhead annular pressure at its Wytch Farm site.
“We were keen to install a wireless infrastructure that would enable us to expand and add additional devices beyond this application without the need for additional cabling infrastructure and the cost associated with it, “ said Robin Hamill, electrical instrumentation engineer, BP Exploration Operating Co.
Two Rosemount wireless temperature transmitters were installed, one in the centre and one two thirds across to determine if there was a difference in temperatures throughout the tank. A further transmitter was installed on the main inlet feed. The transmitters are located roughly 300m from a Smart Wireless Gateway positioned on the outside wall of the control room. Using a serial connection, data is fed from the gateway into the existing SCADA system.
Data from the wireless transmitters showed that there was not a significant difference in temperature at different points in the tank.
“We were able to quickly and cost effectively install the temperature measurement equipment required.” said Hamill “The results we have obtained mean that we have not needed to add additional devices to the other tanks.”
BP has continued to measure crude oil temperatures in the tank using the Smart Wireless devices. As part of the network, engineers placed two additional wireless transmitters at strategic positions within the facility to act as repeaters. Despite the long distance, all of the devices communicate directly with the gateway rather than via the repeaters, Emerson reported.
The extra transmitters increase the reliability of the network by offering additional paths for the data to travel to the gateway should a path become obstructed, explains the vendor. The self-organising wireless network, it adds, adjusts automatically to re-route signals around any obstructions, resulting in greater than 99% communications reliability.
