Product category:
Process Hardware (Pipes, Nozzles, Heaters, etc)
News Release from: Rotork Controls | Subject: Electric actuators
Edited by the Engineeringtalk Editorial
Team on 02 May 2001
Valve actuators just the job at
newsprint plant
When the UK's largest producer of recycled newsprint had a valve actuation problem, they turned to Rotork electric actuators for their demanding and arduous applications
When the UK's largest producer of recycled newsprint had a valve actuation problem, they knew exactly who to contact for the solution Graham Covus, in charge of utilities maintenance at the giant Aylesford Newsprint mill in Kent, had previously worked in the power generation industry at Kingsnorth Power Station, where he had been impressed by the reliability of Rotork electric actuators in demanding and arduous applications
He explained the situation at Aylesford: "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, collected from some 120 local authorities, paper merchants and waste management companies throughout the UK.
At the ultra-modern 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 40 tonne reels of 'Renaissance' newsprint on machinery capable of producing a mile length of 9.2 metre-wide paper in a minute.
The waste water from the recycling process is passed through an on-site three-stage biological treatment plant at an average rate of 15,000 tonnes (cubic metres) a day, 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 which 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.
For economy, the backwashing process was designed to use 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 by the filter manufacturer 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 would therefore achieve significant annual running cost savings.
Graham Covus explained "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.
In my experience, Rotork actuators would give us the robust and durable service demanded by this type of repetitive application, together with straightforward setting up and commissioning.
"In the event it was the strength of a basic Rotork actuator design, rather than the brains of the intelligent version, that best suited our requirements for this application, enabling us to change over with the minimum modification to existing site wiring for starter circuits and linking to the Honeywell Measurex DCS that supervises plant wide operations.
"However, our first Rotork IQ intelligent actuators have also recently been introduced in other plant areas to control parts of the process steam distribution network." To complete the water treatment plant upgrade, an identical fourth filter, used for tertiary treatment, has also been equipped with Rotork actuators.
All the actuators have now been commissioned and are enabling the filters to operate as designed, in accordance with Aylesford Newsprint's commitment to continuous improvement for the achievement of the highest possible operational and environmental standards.
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