Gold standard for actuator control

Jon Lawson

Shelley Pike reveals how a wireless network is controlling the flow at a Nevada gold mine

A gold mine in Nevada, USA has been able to take advantage of wireless digital control for intelligent electric valve actuators on the water filtration plant.

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 that 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 68m to 132m. The externally mounted coordinator is connected to the Pakscan P3 master station in the control room by a 15m cable.

The Rotork Pakscan P3 wireless network control system establishes a secure wireless mesh network that is used to control the actuators and to gather important operating data for asset management and preventative maintenance. The 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 200m 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 recognised 2.4GHz ISM (Industrial Scientific and Medical) frequency band and has a line-of-site operating range between each device of approximately 30m indoors and 100m 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. To prevent unauthorised commands being sent to devices over the wireless network, all control data is encrypted using the Advanced Encryption Standard (AES).

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Shelley Pike is with Rotork Controls

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