Maximising machine capacity is essential if a laundry wants to minimise its washroom costs. This means not only that each load must be weighed before it goes into the washer but also that the scales should be routinely checked for accuracy.

Scales that are used regularly can often give variable results after a time. It is well worthwhile having a standard weight that can be placed on the scales or loaded into an auto-weigh bag each week to ensure accurate readings.

Remember that certain classifications, such as towels, will be slightly damp when they are sent to the laundry. The purpose of a towel is to remove moisture so that this dampness is a consequence of normal use.

Typically, soiled towels will have 8 – 10% retained moisture when they arrive in the laundry.

Towels are probably the most expensive category to process as they have to be dried in the tumbler and drying any textile in this way often uses up to four or five times more energy than drying on the calender.

Additionally the degree of retained moisture often leads to underloading in the washer. Towels are also more difficult to fold and pack so reducing productivity in this area.

If you weigh a random load of soiled towels before washing and again after washing and tumbling till fully dry, you will find that the underloading is significant.

However, increasing the weight of towel loads in a tunnel washer beyond the compartment capacity can be disastrous as there is a risk of blocking due to overloading. This could lose a day’s production or more. Although the risk of overloading should be avoided, it does make sense to load towels right up to the compartment’s capacity mark. If operators are deliberately underloading towels because there is a problem with “wash-over” then the fault should be investigated and the dips optimised before adjusting the load weight.

One other problem often associated with towels in tunnel washers is sequencing of the work through the tunnel washer versus the production output.

A 15-stage, 50kg tunnel washer will probably operate on 100 seconds cycles with 20 seconds transfer. The machine will therefore discharge a full load every 2 minutes, so it should be processing 30 loads per hour. However, I often see situations where such a machine is only producing 20 or 25 loads per hour.

The first step is to check regularly that machines are achieving their target number of loads per hour. If not, it is essential to investigate and bring the rate up to target.

In many cases the tunnel washer will routinely go into a “holding” pattern. To the casual observer the machine appears to be working as it is still rotating backwards and forwards but in reality it has reached the end of a cycle and wants to transfer the load but cannot do so.

This can occur under one or more of the following conditions.

Waiting for a load: The washer is waiting for the next load to be discharged into the loading hopper. This might be because there is no work waiting to be loaded. Alternatively the overhead rail or step conveyor could be blocked or faulty. In this case the problem may be solved by using a long stick to prod any recalcitrant bags into action down the conveyor line.

Water level: The machine is waiting for the water to reach the correct level. Most tunnel washers have a series of sensors to detect that the correct water levels have been achieved. Incorrect levels are the single most common cause for blockages in these machines.

Water levels can be erratic if the water pressure varies considerably (especially if there are also several washer-extractors that are drawing water at the same time). Water levels can also be affected by sticky float valves, blocked valves or lint screens and weirs being blocked.

Temperature: The machine has not reached the correct temperature. Most machines will have temperature probes located at strategic points down their length and in any holding tanks – especially at the first compartment wetting-out stage. There is often a tolerance of up to 5C in the actual temperature versus the target setting but variations outside this tolerance can lead to the tunnel washer going into a holding pattern.

Membrane press is not free: This is the most common cause of tunnel washer holds. The press cannot discharge its load because it is waiting for a tumbler to unload and so the whole wash line comes to a halt.

The hold-up at the dryers may also have several causes.

The dryers may be taking a long time to produce fully dried work. Originally they may have been designed to dry a load with 50% moisture retention in about

15 minutes. However, with the passage of time, the efficiency has dropped due to leaks, or to blocked ducting or to plastic that has melted onto the inner basket. As a result of such faults, full drying now takes 20 minutes or more.

The pressure on the membrane press or the time it spends at pressure has been changed, so work leaves the press with an extra 5% or even 10% more moisture and the work will now take longer to dry.

Incorrect sequencing may be causing a bottleneck at the dryers. The operator is putting too many towel loads through one after another so all the tumblers are occupied with loads that need full drying rather than a short conditioning cycle. The tunnel washer goes on hold until a tumbler is free.

The above scenario is quite common. A tunnel washer with a design output of 30 loads per hour, can drop to 25 or even 20 loads and this reduced output not only affects the washing costs but will also reduce productivity, and therefore costs, in other departments. Sometimes the delays are so long that the laundry has to pay overtime.

All these problems can be solved quite easily and in the main the answers lie in the skills and experience of the laundry engineer.

The engineer must routinely check that the membrane press is operating at optimum conditions and producing work with no more than 50% moisture retention.

He should know how to complete a moisture retention test and adjust the membrane press to ensure consistent correct results. This test should be carried out at least once a month, more frequently if possible. Action should be taken if loads are being discharged from the press while still damp.

The engineer should also routinely and regularly check all tumblers to ensure the air is not coming in around door seals and the tumbler outer casing and that there is a good air-flow through the tumbler with all fans working and rotating in the right direction.

For steam-heated tumblers, the heater-coil should be free of any lint and regularly cleaned and the steam traps should be working correctly with rapid condensate discharge, good air-venting and tight shut-off to prevent steam leaks.

For gas fired tumblers, the correct flame and gas pressure must be consistently achieved, otherwise there is insufficient heat input and drying times become excessive.

The tunnel washer operator also plays a vital role here by ensuring that any leaks (water, steam, air) are immediately reported to the engineering department.

Any “sticky” connections on the overhead rail system that could delay or stop delivery of the bags of soiled textiles needs to be dealt with immediately. The work must be correctly sequenced. All water tanks and filters should be cleaned regularly and any restrictions in the water flow identified immediately and corrected.

All of the above actions are simple to implement and will not incur any additional expense, but they will allow production to run more smoothly and productivity to increase. Total operating costs will reduce considerably.

Visit the LCN website to read the first article in this series on managing costs