Sorting and classifying linen is a core operation for any laundry and an essential part of the plant’s daily routine.

As Malcolm Goldie, sales manager at Kannegiesser UK, points out traceability and batching has always been an important requirement for two reasons.

First: Where laundries handle customer-owned goods as well as pool stock, these need to be identified and separated out so that the goods are returned to the correct location.

Second: Linen needs to be sorted according to the type of treatment required to ensure good results and to minimise the need for re-wash, which affects both the laundry’s productivity and its costs.

Monorail bag handling systems are well established, and, says Kannegiesser, allow laundries to classify and store linen in manageable batches, which can then be sent to the wash line as required

Honeycomb design

A variety of solutions is available for the sorting process but the company recommends a modular “honeycomb” arrangement which allows large banks of stations to be constructed, either on platforms or at floor level.

Batches of mixed categories are presented to the operators on a conveyor and they then pick out the individual items and sort them into the relevant chute. Beneath each sorting chute is a flap which opens and closes automatically so that the batch-holding bag can transfer its load without interrupting the sorting process. This reduces downtime and helps the sorting section to work at maximum efficiency. Once sorted, classified batches of laundry can be held in transit bags and stored in banks and the supporting software allows these bags to be sent to the wash-line in a sequence that matches the capacity and availability of the dryers.

The Jensen Group has a specialist division that handles its Futurail sorting and storage system.

Simon Nield, president of Jensen USA where the Futurail division is based, identifies five requirements considered when designing any sorting solution – accuracy, productivity , ergonomics, physical constraints and hygiene.

Accurate sorting is essential. If two incompatible categories of linen, such as whites and dark colours, are classified together it can increase the need for re-wash and even lead to goods being ruined. Futurail incorporates carefully designed chutes that guide products even when they are thrown from a distance. The system can also provide a display at each station and this shows a photo of the item to be classified and gives a description.

It also shows the weight of the sorted goods in each station to alert the operator when the station is reaching the pre-set weight at which goods are sent for storage. The stations also have a device to prevent overloaded batches being stored.

Tips for productivity

Sorting must not only be accurate it must also achieve a high throughput and Nield has some tips for maximising productivity.

To avoid double-sorting or stopping the belt, make sure that a sort station is always available or arrange the belts in a carousel so that items can be left on the conveyor until a station becomes available.

Avoid bottlenecks by making sure that the unloading system is at least 20% faster than the sorting system’s capacity.

Reduce gaps in sorting by making sure that the belt is loaded to the right level. Preparing work on the conveyor so that it is ready to be classified before it reaches the first sorter will also reduce the risk of gaps.

Number of operators: Employing too many operators in the sorting section can slow down the unloading system. It’s best to start with a small number and then gradually move more operators onto the line as the capacity increases.

Large items: Remove large pieces from the conveyor first so that the rest of the load is clearly visible.

All sorting operators should be working at the same rate. This can be achieved by using a series of sorting belt conveyors set to operate at gradually lower rates.

Platform height: Lowering the height of the sorting platform can also reduce the working temperature making the environment pleasanter and helping to increase a worker’s throughput.

A matter of design

Physical constraints of the building, for example low ceilings, can affect the design of a sorting section but these can usually be overcome: For example by choosing a system that can be operated from floor level, rather than on a raised platform. Both Kannegiesser and Jensen systems can incorporate this option.

The ergonomics of the system are extremely important. Sorting can be one of the laundry’s most physically demanding tasks and a poorly designed system can risk work-related injuries that will affect productivity.

Nield at Jensen recommends that the system’s design should take account of the following points:

Minimum distance: Minimise the distance

between sorting stations and operators so that it is easy to throw items into place.

Minimise effort: Systems should be designed to reduce the effort needed to place items in the right station, particularly when sorting large items. Futurail’s Tri-sort systems arranges the stations in threes with the station for large items at the front so that such items can be scooped rather than thrown.Systems can be designed so that large items are removed by suction and delivered directly to the correct station.

Minimise operator movement: Design the system so that the need for operators to turn round is kept to a minimum.

The right belt width: Make sure that the sorting belt is not too wide and that it is installed at the right height. Jensen recommends an overall belt width of 650mm and a height of 750mm.

Hygienic: A sorting system should maintain high hygiene standards, particularly in a healthcare operation. All system parts that come into contact with soiled linen should be washable and the area should be well ventilated to ensure the environment is kept as clean as possible. All Futurail systems have stainless-steel chutes, hoppers and conveyor belt valences. Air-extraction can be built-in if required.

Software counts

In any automated sorting solution it is not just the hardware – the stations, belts and chutes – that is important.

The software also contributes to a system’s efficiency in achieving optimal wash loads and making sure that loads are classified correctly. The software reduces the operator’s need to consciously work out what action to take with any particular piece. This raises the rate at which operators work while reducing the risk of mistakes.

The specialist Barcellos is experienced in designing software that meets these requirement. With its systems installed on “the soiled” side of the laundry work that needs special treatment can be easily identified as it appears on the conveyor.This allows work that may need a repair, a particular wash process or pre-treatment for difficult stains to be directed accordingly.

Called to attention

As a further aid to reducing risks of incorrect treatment, an item can be given an “attention code” so that it will signal a further “special treatment alert” later in the production line.

The software can also identify each piece by customer, so any sorting errors that might send linen to the wrong customer stand a further chance of being corrected in dispatch.

Similarly an item flagged for repair can also be coded to send out an alert so that the repair is checked to see that it has been done and is in the right place before the piece is packed for return.

The risk of sorting errors can be reduced even further by linking these checks into a bagging or rail system and indeed Barcellos has done this for customers on occasion.

Attaching RFID chips to dustmats has allowed laundries to separate the dirty mats and sort them into cages for loading into the washers.

Information can also be passed to a sub-sorting rail where it can be sorted by according to customer.