Hotels, hospitals and other public facilities can now process their ownroller towels rather than send them out to commercial laundries, thanks to acomplete redesign of the necessary plant by laundry equipment OEM Ducker Engineering in Kendal. The new machines, aptly named Revolution, have proved an immediate successwith users and Ducker is building them as fast as possible to keep up with demand. They unroll, soak, wash, rinse, dry and re-roll the towels in one continuous process.
One of the keys to Revolution’s success is a comprehensive controls package, supplied by Mitsubishi Electric, which ensures all aspects of the machine are running at optimum settings to produce a quality final product. It also ensures that Revolution uses considerably less energy, water and labour thanearlier versions of the machine or conventional laundering methods.
In use the roller towels, which are typically about 30m long, are stitched together end-to-end so that the machine can operate continuously. Initially, about six or seven towels are stored in a buffer hopper, included so that continuous operation can be ensured.
From here the main drive, operating through pinch rollers, periodically pulls a 200m length of towel into a soak tank containing hot water and detergent. It stays there for a specified dwell time, as programmed into theMitsubishi FX2N PLC at the heart of the control system.
After the soak programme the main drive activates again todraw the towel through the pressure washing section, where 8 bar jets ofhigh temperature water blast away any ingrained dirt particles.
The main drive is one of six within Revolution, all of which are controlledby Mitsubishi variable speed inverters.“Sectioning the drive was one of the major decisions in the redesignprocess,” says Richard Lanagham, Ducker’s Chief Electrical Engineer. “Our original design, which dated back 25-30 years, had one big central drive. This wasn’t particularly controllable or energy efficient by modern standards and created significant issues at installation and for maintenance planning. The sectioned arrangement is better in every respect and withtoday’s inverter technology it is not a great problem to synchronise them.”
After the pressure washing a second drive pulls the towel through the rinsesection which makes sure that no residues of detergent are left. The towel then proceeds to twin, independently driven drying drums.“The towel is laced over both drums and slowly travels across them, dryingas it goes. Needless to say, it is bone-dry by the time it comes off. It is also relatively crease-free so does not need pressing.”Finally it is rewound on rewind stands not dissimilar to those found in paper mills.
“We have to be very efficient at unpicking the stitching we used to join towels at the beginning of the process and swapping to a newstand for each towel.”The FX PLC communicates constantly with the various inverters and alsocontrols process variables such as water temperature, pressure and flow,timings, detergent inflow, towel tension etc. It also drives a number of Mitsubishi HMIs located at strategic places around Revolution.
These are proving to be a great USP for Ducker, as Lanagham explains:“We did the redesign using 3D modelling software and decided that rather than file the virtual models away, we’d use them as graphics on the HMIs for local monitoring and control. We’ve had to overlay process variable readings, alarms, etc, but that was no more work than generatingconventional schematics.
Without exception, everybody who sees Revolution comments favourably on the graphics. They certainly enhance theuser-friendliness of the machine, and that is important to us because many of our potential customers have are considering the purchase of sophisticated laundry plant for the first time.”