Material solutions

Controlling the wash saves costs and time

1 September 2011



Laundry managers are under pressure to cut costs but rising energy bills make this increasingly difficult. Ian Harris explains how to make significant savings by controlling wash processes


The laundry’s washroom provides the greatest potential for making significant savings without compromising finished quality. Good process control is all that is needed.

Launderers now often delegate the responsibility for setting up and designing wash processes to the detergent supplier.

However, only the best chemicals suppliers have the in-depth experience needed to optimise every program.

LTC often sees machines programmed with processes that fail to take advantage of the radical changes in chemicals over the years and of the programming flexibility that machine manufacturers now offer.

The chart below shows a typical wash program in use today. Note that the total time shown is the “card time”. It does not include the time needed to fill the machines with water to the required dip level or the time taken to reach the right temperatures. These additional times will vary considerably depending on the laundry engineer.

Program 1 charts a typical program recommended by the British Launderers’ Research Association in the 1950s, with slight modifications for the different classification – for example, wash times may be slightly extended or the temperatures raised.

This type of program can be found in many laundries today. Essentially this is the program that most launderers will use for 90% of their soiled textiles.

A closer look at this program shows several important areas where it can be altered to reduce both costs and production time.

The first question is: “Why are there two washes? The program was based on the principle that the first wash would remove all loose particulate soiling, water soluble soiling and would soften protein soiling such as blood, or tea or coffee with milk.

The theory was that there would be so much soiling that to prevent re-deposition, it would be necessary to deal with the easy-to-remove soiling bulk before discharging to the waste and moving on.

The next stage was to deal with the more difficult types of soils, removing the oils and fats as well as ingrained soiling.

This stage needed higher temperatures to swell the cotton yarns and assist emulsification.

In practice, a critical look at the soiled work coming into the laundry will show that around 90% of it is relatively lightly soiled and does not need two separate washes.

The purist may argue that skipping the first stage and starting with the higher-temperature main wash results in blood, tea and coffee stains being set into the fabric.?

That is correct, so instead of two separate washes, I suggest using a staged wash (see program 2). Start the process at 39C, then after 5 minutes, without draining, increase the temperature to 71C and continue the process for the next 8 minutes.

Essentially the textiles still have two washes but the discharge to drain is omitted so there is no need to re-fill the washers with more cold water which then has to be heated.

This staged wash saves both water and energy and in addition helps to increase productivity because the drain time between the two washes is eliminated. The time needed to heat the water after the low temperature wash is reduced because the second wash uses water that is already rather warm.

All that is needed is to raise its temperature further rather than heat a fresh intake of cold water. Less chemicals are required.

The next area to be addressed is the use of the extract process.

Virtually all modern washer-extractors use an “inter-extract” speed to remove the bulk of the excess moisture, as well as a final high-speed extract.

If the inter-extract speed is used between each rinse, then in most cases it is possible to eliminate the third rinse (see program 3).

This process will not only improve the final quality of the finished items – but will significantly

• reduce water usage;

• reduce energy consumption;

• reduce chemicals requirements;

• increase productivity.

The extent of the savings will vary from laundry to laundry but these details should give a general guide.-

Water:

Typically a low dip will be a 3:1 liquor to cloth ratio. A medium dip will be a ratio of 5:1 and a high dip will have a 7:1 ratio.

This means that a 100kg washer-extractor will use around 29litre/kg on program 1.

On program 2 the same machine will use around 26litre/kg with a saving of around 10% and program 3 will use around 19litre/kg, saving around 34%.

Steam:

Program 1: In the first wash, the energy required to heat 5litres of water from 15 – 39C = 120kcal.

In the second wash, energy is required to heat the water from 39 – 71C and also to heat 3.5 litres of fresh cold water, giving a total requirement of 232kcal.

So the total energy use for program 1 is 352kcal.

Programs 2 and 3: The staged wash uses considerably less energy. The first stage heats the water from 15 to 39C, using 120kcal.

The second stage heats 5litres from 39C to 71C using 160kcal.

So in total this staged wash uses just 280kcal, which represents an energy saving of 72kcal (20%) when compared with the two separate washes.

This move to the a staged wash rather than two separate washes is just one example of how program controls can save time, energy and money without the need for investment.




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