Is it advisable to wash bags?

Experience shows that once bags have been used they are difficult to re-use, though this depends very much on what they have been used to filter. A water-soluble powder is not the same as one containing grease or wood particles.

It should be borne in mind that when bags are washed in an industrial washing machine, the rotation of the drum makes the internal fibres of the needle-punched felt cluster together in areas with unequal amounts of fibres. Subsequently, due to the effect of spinning, the bags in the washing machine are plastered against the drum walls, causing defects in the woven sides of the bags.

All this means that – when the bags appear to be ready for re-use – when they are fitted once more in the filter, upon starting up it will be seen that the loss of load is in fact less than with new bags. Within a short time the loss of load will gradually increase, for two reasons:

As the fibres are compacted, air does not pass through evenly, so that filtering tends to stabilise.
As the suface finish deteriorates, becoming less smooth, this encourages the appearance of a pre-layer.
In addition to these problems, which will affect performance, must be added disassembly time, transport costs involved in washing bags and assembly.

In our opinion, it is not worth washing bags. However, the market sometimes insists on this service.

Should you still be interested in washing, some of the recommended instructions are listed below:

Water-soluble powder should be washed off in cold or (50-60º) hot water in a drum or an industrial machine. It is recommended that a non-iogenic wet agent (such as Fewamat) be added to the washing water at 1-3 g/l.
Acid powder may be dissolved in the washing water at a temperature of 50ºC, adding 1-2ml of ammoniac.
Alkaline powder, such as cement for example, may be dissolved in 1-2 hours at a maximum temperature of 50ºC if acetic acid is added at 1-2 ml/l.
Contaminants such as asphalt products require washing with cold water for several hours. It is recommended that 1-10 g/l of Bayer Diadavin WTS solvent be added.