Wrexham, UK – Clwyd Compounders is employing variable frequency drives (VFDs) from Invertek Drives to help it meet the BS EN 1417:2014 safety standard for rubber mills.
The Wrexham-based compounder required the solution with its recent move to a new bespoke manufacturing facility close to its existing site where it was founded in 1979.
Clwyd’s rubber mill and mixing machines had previously been exempt from the regulations but had to meet the standard when they were moved and recommissioned.
Under the EN standard, if a safety bar is pressed in an emergency, the mill rolls have to separate by 35mm within three seconds.
The rolls must also stop within a sixth of a revolution and reverse automatically within two seconds of the mill stopping.
“Our mills vary in size, carrying a lot of bulk with 30kw to 250kw motors operating at speeds up to 1,000rpm,” noted John Haywood, founder and chairman of Clwyd Compounders.
“The rolls themselves typically operate around 30RPM depending on the material,” Haywood added.
This, he said, means in an emergency situation, and to meet the EN standard, "there is a lot of danger as you’re having to stop and then place the rolls into reverse almost instantly."
Another challenge is that the mills – capable of operating with bulk weighing up to three tonnes – must shut down safely if the mains power supply is lost.
Furthermore, the drive must be able to recover enough energy from the mill to ensure safe-stopping within the allowed time.
“Some of the mills can go to a massive overload in short time periods and so we needed drives capable of handling this,” Haywood pointed out.
To address these issues, a Clwyd team met with Invertek’s technical specialists to identify a motor control solution using its VFDs.
Kes Beech, technical manager at Invertek Drives, said he was confident from the outset that the ‘fast stop on mains loss’ feature of the Optidrive P2 along with the motor control performance would ensure the machines met the safety-standard requirements.
Additionally, said Beech, the function block programming has allowed the creation of a "simple system" to meet the requirements for automatic reversing.