March 2019

Drives help meet rubber mill safety standards Three-way monitoring S tandard components specialist norelem has launched a new range of oil level gauges that can help engineers and manufacturers steer clear of dangerous situations involving oil. Oil level gauges are crucial to indicating oil levels and temperatures inside of large tanks, gearboxes and reservoirs. Without these, oil can drop below minimum levels, causing extreme machine and engine wear. Oil can also exceed optimum operating temperatures which causes the oil to break down, changing its viscosity and leaving deposits that can damage machine components. To help better monitor oil levels, on top of optical monitoring, norelem’s electronic components also emit warnings when either of the above scenarios occurs. To protect against oil dropping below pre-set minimum levels, norelem’s gauges are equipped with a float element with a magnetic core, creating a REED switch (an electrical switch operated by an applied magnetic field). If, after closing the electric circuit and the float drops to or below the minimum level, an electronic signal will sound. The height of the sensor can be adjusted according to requirements. Temperature levels are also monitored electronically through a bi-metal switch. When the specified temperature is reached, the sensor closes or opens the circuit, depending on the model, and emits a signal when the temperature is exceeded. “In harsh factory and machinery environments, it is not always easy for engineers to visually detect oil levels and temperatures, and it can pose huge problems not just for the machinery, but also for workers’ health and safety,” said Marcus Schneck, CEO of norelem. “That’s why our components not just use a fibreglass reinforced plastic housing to enable clear optical detection, but also works electronically to warn when dangerous situations could be happening.” Versions of the oil level gauges can be bought with either of the electronic monitoring functions or be supplied with both. They can be mounted using two M12 tapped holes or with flanged nuts through two Ø12.2mm holes and are available as a short version with a mounting hole centre distance of 127mm or as longer versions with centre distances of 300, 400 and 500mm. The display element of the short model has a fibreglass reinforced plastic housing. The longer versions have an aluminium housing. Both versions have a plastic viewing glass that has good mechanical properties and is resistant to mineral oil, petrol, lubrications, paraffin, solutions and most chemicals. Maintenance Matters Problem Solver 18 | Plant & Works Engineering www.pwemag.co.uk March 2019 Ensuring rubber compounder mills capable of operating with bulk weighing up to three tons could stop within 1/6th of a revolution and reverse to meet European EN safety standards was going to be a challenge for materials specialist Clwyd Compounders. The Wrexham, UK based company turned to Invertek Drives to see how its variable frequency drives (VFD) could help it meet the BS EN 1417:2014 Safety Standard for Rubber Mills. The need for a solution was exacerbated by a move to a new bespoke manufacturing facility close to its existing site where it was founded in 1979. Its rubber mill and mixing machines had been previously exempted from the regulations but would have to meet the standard when they were moved and recommissioned. “The EN standard is quite specific in that if a safety bar is pressed in an emergency, the mill rolls have to separate by 35mm within three seconds, and additionally the three-ton rolls must stop within 1/6th of a revolution. In addition, automatic reversal of the rolls has to occur within two seconds of the mill stopping,” said John Haywood, founder and chairman of Clwyd Compounders. “Our mills vary in size, carrying a lot of bulk with 30kw to 250kw motors operating at speeds up to 1000rpm. The rolls themselves typically operate around 30RPM depending on the material. This 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 them into reverse almost instantly. “The mills must also shut down safely if the mains power supply is lost, which is something which had proved to be an extremely challenging case to handle in the past. The drive must be capable of recovering enough energy from the mill itself to accomplish a safe stopping condition within the allowed time. “Additionally, some of the mills can go to a massive overload in short time periods and so we needed drives capable of handling this.” The company’s internal team considered the problem and then met with Invertek’s technical team that helped identify a motor control solution using its Optidrive P2 VFDs. Kes Beech, technical manager at Invertek Drives, said: “We were confident from the outset that the Fast Stop on Mains Loss feature of our Optidrive P2 along with the excellent motor control performance would ensure the machines would meet the safety standard requirements. Additionally, the Function Block programming would allow us to create a simple system for the automatic reversing. “The more efficient control of the Optidrives will provide potential energy savings of over 20% by optimising motor start-up, running and stopping while also reducing wear and tear on the motors, reducing long-term maintenance costs and downtime.” Available up to 250kW, the Optidrive P2 can also provide 150% overload for 60 seconds as standard. It also comes in IP20, IP55 and IP66 enclosures, making it ideal for industrial and heavy-duty environments, including outdoors.