Rotork valve actuators

When the UK’s largest producer of recycled newsprint had a valve actuation problem, Graham Covus of the Aylesford Newsprint mill in Kent, UK contacted Rotork “Problems with unreliable electric actuators in our water treatment works were increasing the operating costs of our filtration plant. I was confident that replacing them with Rotork actuators would enable us to run the filters with the efficiency and economy that was expected, and save us tens of thousands of pounds a year.” Aylesford Newsprint recycles about 500,000 tonnes of newspapers and magazines annually. At the eighty acre mill site, the used paper is mixed with water and pulped, and then undergoes an ink removal and cleaning process before being re-made into reels of ‘Renaissance’ newsprint. The waste water from the recycling process is passed through an on-site three-stage biological treatment plant, enabling it to be drained into the River Medway in an environmentally clean condition. On entering the water treatment works, the dirty water is pumped into three primary treatment filters that remove the larger suspended solids by trapping them on rotating screens. The specially designed filters are equipped with integral flushing nozzles that regularly backwash the rotating screens to keep them clean by spraying them at high pressure. The backwashing process uses filtered water from the units, still containing the small amount of particulate that would be removed at the next stage of treatment in the plant’s settlement tanks. However problems with the actuators fitted prevented the satisfactory operation of the flushing valves when mill paper effluent was used. As a result it was necessary to use clean and expensively dosed process water to ensure that the flushing nozzles did not become blocked and interrupt effluent backwashing. Solving the actuator problem achieved significant cost savings. Graham Covus: “The actuators that came with the filters lacked the necessary power to operate the flushing valves properly. Adjusting their torque and position settings was an incredibly complicated and time consuming operation that still failed to solve the problem. Rotork actuators gave us the robust and durable service demanded by this type of repetitive application.”

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