Emerson technology validates crude oil temperature

Emerson Process Management wireless temperature transmitters have been installed at the BP Exploration Dalmeny onshore terminal.

Dalmeny, located near Edinburgh, UK, has the capacity to store about four million barrels of stabilised crude oil from the Forties oil field.

Eight interconnected storage tanks, 40-50m in diameter, are used to regulate the flow of oil between production wells and the tankers or pipeline that will transport it to the refinery.

BP was already measuring oil temperature at the side of the tanks.

But, because of the size of the tanks, there was a concern that there could be a significant difference between temperatures at the edge of the tank and at the centre.

A number of measurements were therefore required to confirm any differences in temperature.

This presented a challenge because the tanks needed to remain in use, making the task of installing the temperature probes impossible.

An out-of-service tank with no existing temperature measurement in place presented 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.

This would have cost more than GBP15,000.

Wireless presented a cost-effective alternative, and having applied Emerson Smart Wireless technology to monitor wellhead annular pressure at its Wytch Farm site, BP was confident that it would be suitable for this application.

'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 costs associated with this,' said Robin Hamill, electrical instrumentation engineer, BP Exploration Operating Company.

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.

Using the data from the Smart Wireless transmitters, BP discovered that there was no significant difference in temperature at different points in the tank.

'Using Smart Wireless we were able to quickly and cost effectively install the temperature measurement equipment required,' said Hamill.

'The results have meant that we have not needed to install additional devices to the other tanks,' he added.

BP continues to measure crude oil temperatures in the tank using the Smart Wireless devices.

The wireless transmitters are part of a network that uses self-organising technology.

As part of the network, two additional wireless transmitters were placed 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.

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.

The self-organising wireless network adjusts automatically to re-route signals around any obstructions, resulting in more than 99 per cent communications reliability.

The resulting wireless infrastructure enables additional wireless instruments to be added as required.

It took a day to complete the entire project including configuring the serial link to the SCADA system.

Emerson AMS Suite predictive maintenance software is used to manage the wireless network.

Since the wireless network was installed there has been no data lost.

Smart Wireless is an extension of the PlantWeb digital architecture that offers solutions for field instrumentation and plant operations.

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