Special Feature

Preventing air blanketing

1 November 2011



In answer to a reader’s letter, Ian Harris explains the efficiency checks that should be carried out on multi-roll ironers


Air venting from ironer beds can cause serious problems.

When the steam is turned off at the end of the working day, the whole system rapidly cools to create a vacuum inside the steam-lines.

It is a very rare laundry that does not have any minor steam leaks and as the vacuum forms in the steam system, air is drawn into the system through such leaks.

Air is lighter than water so any air that enters the steam system will collect at the highest points. On a multi-roll ironer, these points will be the horns of the ironer bed.

Air is also an excellent insulator. The Laundry Technology Centre has recorded temperature variations across the ironer bed as high as 20C due to such air-ingress. This is sufficient to cause extensive dragging and distortion, especially to the trailing edge of finished items.

Well-designed multi-roll ironers will have a valve mechanism or similar to prevent air-ingress by automatically releasing air trapped in the horns of the ironer. However, like all electro-mechanical devices, these require maintenance and need to be periodically checked. The method for doing this should be in the ironer manual as the systems and procedures will vary from manufacturer to manufacturer.

Such maintenance will often require the removal of the ironer side panels in order to gain access to the ironer bed horns.

Roll vacuum

The purpose of the vacuum on multi-roll ironers is to draw off the evaporated water from items being fed into the ironer.

This not only improves ironer efficiency but also prevents the ironer clothing becoming water-logged, which can lead to premature clothing degradation, sweal marks and rust transfer on ironed items.

Each ironer roll should have an adjustable vent so that the airflow through the clothing can be altered to cater for the amount of moisture being evaporated by contact with the ironer bed. For example, the first roll vent may be fully opened to obtain maximum airflow whereas the last roll vent may be closed, as most of the moisture should have been removed by the preceding rolls.

The airflow through the roll clothing will be affected by a variety of factors relating to the processing environment – for example, the moisture retention (MR) percentage on washed goods, water hardness, rinse efficiency, ironer waxing procedures and the age of the clothing. There can also be localised variations across the width of the ironer roll.

This is where a vacuum gauge plays a vital role. It can accurately assess airflow (vacuum) across the ironer roll so that deficiencies can be identified and corrected.




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