08 October 2009
All elements in the system, the sensors, the pump motor, and even the PLC, were connected together in a wireless mesh network. The demonstration took place in the Honeywell stand on the floor of the ISA show in Houston.The demonstration was evidence that some companies, especially those that support the ISA100 protocol, have confidence in wireless networking and are pushing the technology to be used to a greater degree in industrial control, even in closed-loop situations. So far several manufacturers have introduced the concept of wireless networking, such as Wireless HART, but limit its used to gathering data from field-mounted sensors, which may or may not be critical to operation. Andrew Nolan, Network & Wireless Sales Consultant for Honeywell Process Solutions, was on hand to give visitors an overview of the system. It consists of two cylindrical plastic water tanks with a reversible pump between them to transfer water from one tank to the other. On the left tank a differential pressure transmitter monitors the level; on the right tank is a Honeywell Enraf Flexline wireless level gauge. The Flexline, a high accuracy custody transfer instrument, is designed for much larger tanks but worked for the purpose of the demonstration.There are a total of 12 wireless nodes in the system. Some, like temperature transmitters on both tanks, were not necessary for closed loop operation but were there for the purpose of demonstrating wireless mesh networking. There are two “discrete” inputs that take signals from the PLC to operate the valve and pump motor, and a third discrete input Mr. Nolan used to turn the demonstration on and off. A position indicator on top of the valve was also in the network, as well as an Equipment Health Monitor (EHM) that kept an eye on the motor and pump.All the control decisions—such as when to stop pumping into one tank and pump the water back into the other—were made by the Honeywell HC900 PLC, which was connected wirelessly into the network via the master radio station that is visible at the top of the photo between the two tanks.The same radio connects the wireless HMI station, a PC tablet that Mr. Nolan is holding in the lower photo. “All our equipment is fully compliant with ISA100.11a-2009,” he said. Early in 2010 we will have the software fully compliant as well. The nice thing about it is, for customers who install the equipment now, we will be able to provide them with a simple firmware upgrade to comply with the final standard. And we’ll be able to supply the upgrade through our wireless system.”“With our wireless, we’re at least four years ahead of our competitors,” said one staffer who was standing nearby. The others nodded their heads in agreement.
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