AkzoNobel warms to wireless
31 May 2011
Ghlin, Belgium – Paints and coatings major AkzoNobel has adopted wireless technology at its Ghlin surface chemistry plant. The unit produces fatty nitriles and amines, which are stored in 40 tanks in the tank farm area of the site near Mons, Belgium.
When loading final product into road tankers, the fatty nitriles and amines must be kept within specific temperature parameters. Too cold and the products are difficult to handle; too hot and the quality of the products can be affected. Steam is used to heat the tanks,usually starting a few days before a load is due to be collected.
This task had required operators to manually open a steam valve to begin the heating process, explains Nicolas Delfosse, process engineer surface chemistry at the AkzoNobel’ plant.
No existing temperature measurement devices were in place on the tanks, Delfosse noting: “We merely used operator experience to determine when to start heating. We then took manual temperature readings at the main outlet valve, if the product was too hot the steam valve would be closed; if the product then cooled too much the valve would be opened and heating restarted.”
After some customers complained that the delivered product was too hot, AkzoNobel decided to automate this process by introducing a simple closed-loop heating control.
Delfosse and his team initially considered fieldbus, but this would have incurred significant cabling infrastructure costs, requiring trenches and cabling between the tanks and the control room over distances of 200m.
Another issue was that only a small amount of I/O was available in the control room. With future modifications and additional measurement points planned, the company did not want to use it all for this project.
Another option was to modify the existing DCS system and control room, but, said the process engineer, this would have been expensive and might have taken the control system offline for a period of time. In addition, he added, there was not enough room for the additional cabinets required.
Faced with these issues, AkzoNobel identified that wireless could eliminate the need to dig trenches and install cable trays to house the new power and data cables. It also established that data from the wireless transmitters could be fed via a gateway directly into the existing DCS without consuming any I/O.
“We recognised that wireless offered benefits beyond this first project, especially the ability to expand the network by adding new devices quickly and at little cost compared to wired devices,” said Delfosse.
“With a continuous programme of process improvement at the plant, we anticipated that more devices would be added at some point in the near future,” he added. “By implementing a wireless network now, we would create an opportunity for installation savings every time a device was added in the future.”
Several wireless options were considered, but AkzoNobel wanted to adopt an open standard technology that would not tie it to a single vendor, which could restrict its ability to select the best instruments for each measurement task.
The approval of IEC 62591 (WirelessHART) by the International Electrotechnical Commission (IEC) was a factor in AkzoNobel’s selection, as was the number and range of existing implementations of Smart Wireless around the world.
Four of Emerson’s Rosemount WirelessHART temperature transmitters have been installed so far to control the temperature of a number of the storage tanks. From these devices, measurement data is transmitted every minute to a wireless gateway and is then integrated into the existing DCS. The DCS then automatically controls a simple on/off steam valve that heats the tanks.
“The temperature of the tanks can now be maintained using this wireless closed-loop control, enabling us to ensure that the final product is delivered within the appropriate temperature parameters,” said Delfosse.
“By automating this process, we removed the requirement for the operator to go into the field and manually operate the steam valve to get the desired result. This has allowed the operator to focus on higher value tasks.
“We also gained much tighter control over the amount of steam used. Although we have yet to calculate the impact of this improvement over a long period, we know that there is a significant reduction in steam consumption, which will create a saving on our operating costs.”
Expanding the network
A second application for automating pressure monitoring on our venting system would also have required new cable infrastructure to be installed. This application was necessary to meet our corporate guidelines and new local environmental legislation requiring chemical processing companies to monitor and control all gas emissions.
Ammonia gasses and organic vapours are produced from the fatty nitriles and amines stored within the tanks. These gasses are collected via a venting network and then incinerated.
In addition, gasses are collected via the same vent network from large basins that hold storm water and process water. To identify any blockages in these vents, pressure is monitored, with any drops below the level of atmospheric pressure indicating a potential problem.
“Previously, we used manual gauges that required an operator to make regular trips into the field to take ‘snap-shot’ readings. This was time-consuming and failed to provide the continuous and immediate information we required,” said Delfosse.
A total of ten Rosemount WirelessHART pressure transmitters have been installed to replace the gauges.
“Again, by automating the measurements we have improved the efficiency of our operators by enabling them to focus on higher value tasks,” Delfosse explains. “The continuous pressure data we are now receiving has enabled us to identify blockages immediately, and we solve this quickly by flushing the vents.”
“A third application presented itself almost immediately. It had become apparent that additional thermal measurements were required from within the venting conduits.
“This information would be used to prevent potential fires arising from the high temperatures. In this application, an important issue was the short timeframe available to install the new devices to obtain these additional measurements.
“We were keen to do so before the next government inspection, which would have been very difficult to achieve if we had proceeded with a wired solution.”
The established WirelessHART network enabled us to install three Rosemount WirelessHART temperature transmitters quickly and easily. These devices provide us with the required temperature information and will raise an alert in the control room should levels rise above preset limits.
Adding devices is so simple that I would describe the Emerson Smart Wireless solution as ‘plug and play’. Once the devices are in place, they quickly connect with the network and operators can view data almost immediately.
Future applications
Delfosse estimates overall savings from adopting wireless instead of installing cabling and making changes to the DCS at around Euro180k. The returns, he said, has led to plans to upgrade the temperature gauges on all 40 storage tanks.
“We are now also considering a number of other applications at the Mons site. New legislation requires redundant automated level monitoring technologies to be applied to ensure against overfilling,” added the process engineer.
AkzoNobel also plans to make use of the wireless network again when implementing Emerson’s Rosemount wireless vibrating forks that will identify levels in tanks to help provide overspill protection.
Another application being considered is a drain switch system on the gas venting line. Here wireless vibrating forks will be used to monitor condensate levels in the venting system. When these reach a certain level the vents will be drained automatically.
“We are even considering the possibility of using wireless to help us monitor the position of existing process valves,” said Delfosse. “To ensure against tank filling errors we would like to bring currently unavailable position information from a number of manual valves into our DCS. Here, Emerson’s wireless position monitor will forward the stranded position information.”
(Article based on a case study from Emerson, first published in CHEManager)