Wireless Pakscan controls the flow at Nevada gold mine
The Newmont underground mine utilises Geotube® dewatering technology to separate sediment from both ground and extraction process water. The filter systems, which are installed above ground, are fabricated from a woven material which is permeable to water while retaining solids and sludge. Excess water drains through small pores, resulting in effective dewatering of the contained material, which is then processed to extract the gold.
The large scale filtration operation has been automated by the motorisation of 15 widely distributed inlet and isolating valves with Rotork IQ actuators and a Modicon PLC to supervise the operation of the plant.
A Pakscan P3 master station communicates with the Modicon PLC using Modbus TCP Ethernet protocol for the monitoring and control of the valve actuators over a wireless Pakscan network. The wireless network delivers a reliable and economical solution, eliminating the cost of installing any additional site wiring apart from the actuator power cables. All the actuators are in ‘line-of-sight’ of the Pakscan coordinator module, with the distance to each actuator ranging between 68 metres to 132 metres. The externally mounted coordinator is connected to the Pakscan P3 master station in the control room by a 15 metre cable.
The Rotork Pakscan P3 wireless network control system is a further development of the Pakscan system used in thousands of plants throughout the world today. Simply stated, the system establishes a secure wireless mesh network that is used to control actuators and other field devices throughout the plant and to gather important operating data for asset management and preventative maintenance from the connected valve actuators.
The wireless system consists of three main hardware components:
A Pakscan P3 master station fitted with a wireless interface module, which is typically connected to the plant’s control system using industry-standard Modbus protocol over either a serial or Ethernet connection.
A Pakscan P3 wireless coordinator module, which can be mounted, either indoors or outdoors, up to 200 metres away from the P3 master station (further if standard fibre optic converters are employed) and which functions as the base station for the system’s robust mesh network.
A wireless actuator module installed on each actuator on the wireless network.
The wireless system operates on the license-free, globally recognized 2.4GHz ISM (Industrial Scientific and Medical) frequency band and has a line-of-site operating range between each device of approximately 30 metres indoors and 100 metres outdoors. Up to 60 actuators can mesh with a wireless coordinator.
In a Pakscan wireless mesh network, each actuator on the network can act as an independent router to help signals get to their intended destination. A correctly designed network will be configured to provide two or more paths between each actuator and the wireless coordinator. Therefore, if the normal traffic route is blocked or if a hardware or communication failure should occur, it can be overcome as the network dynamically determines an alternate route for the data to travel. This self-healing network mimics the loop-back capabilities of the established Pakscan two-wire loop.
In such a network, privacy and security are high priorities. To prevent unauthorised commands being sent to devices over the wireless network, all control data is encrypted using the Advanced Encryption Standard (AES). Additional encryption is incorporated into the system to prevent unauthorised devices joining the network and to prevent a message replay attack.
The Pakscan P3 wireless network card gives the user access to all the standard control and monitoring features and data available from the wired Pakscan system, together with the diagnostic and asset management information stored as standard by Rotork IQ actuator data logger and configuration files, which is otherwise only downloadable locally, using the IQ hand held commissioning and communication tools. Using built-in web pages it allows easy extraction of these files from the control room over the wireless network.