At first glance, wireless network control and its application to valve actuation might not impress many plant engineers as being an earthshaking technological development. Yet, because of the tremendous cost savings that can result, the benefits associated with its adoption can be dramatic – an evolutionary achievement that is likely to change the process plant landscape for decades to come.
A Recent Installation
A large wastewater treatment plant in the USA faced a significant problem. It needed to retrofit actuators that controlled scum skimmers on several aeration tanks. Originally, the actuators were hardwired to the control room through a conduit that was embedded in concrete. To hardwire the actuators for network control, the plant was presented with two very expensive options. The first was to demolish the existing concrete structure to install new conduit and then refinish.The second was to run external conduits on the surface of the structure. However, in order to avoid trip hazards and other health and safety issues, all external conduits needed to be clear from walkways. Therefore, any new conduits would need to be located along the edge of the aeration basins. If that option was selected, the basins would have to be decommissioned during installation.
In both cases the plant faced considerable costs. With an average distance of over 100 metres from actuator to control room plus the associated cost of decommissioning the tanks during construction, the estimated cost to run the new wiring was in excess of $1.5M.
The plant therefore decided to install the Pakscan P3 wireless solution, which was achieved at a small fraction of the estimated cost of the hardwiring options. In addition to eliminating the need for control wiring, another major benefit gained is that the wirelessequipped actuators can now communicate vital actuator data logger information to the host control system.