Beating dirt with High-pressure Washers

In the automotive sector they enable effective cleaning of engines, chassis and small parts as well as vehicle surfaces. You usually find pressure washers, especially the stationary type, where hygiene is of prime importance – in swimming baths, hospitals or businesses where foodstuffs and drinks are produced or stored. You also find them cleaning building facades or used in private homes and gardens.

Generally, the aim of cleaning is to apply an appropriate method to move from a specific starting situation to the desired (cleaning) goal. The starting situation is determined by the type of soiling, which may consist among other things of salts, dust, sand, oil, urine scale, protein or germs. Depending on the method chosen, four cleaning objectives can be reached, as follows:

• Optical cleanliness (no dirt visible to the eye)
• Physical cleanliness (no soiling can be identified, even with a magnifying glass or microscope)
• Chemical cleanliness (free from oxide residues or residual chemical films)
• Bacteriological cleanliness (free from living micro-organisms).

Contact pressure greatly influences cleaning outcome

It is not so much the contact power as the contact pressure, i.e. the pressure with which the jet of water impacts on the surface to be cleaned and dislodges a dirt particle. Contact pressure depends on spraying distance, angle of spray, nozzle pressure and water flow rate. The nozzle pressure is determined by the water flow rate and the nozzle diameter. The same applies to pump pressure, though this has in addition to compensate for line resistance.

The range of uses and outputs, especially of hot-water pressure washers, is impressive. This is because in addition to the dirt-dissolving properties of water, pressure and detergent, the possibility of using varied temperatures is a contributing factor. For example, you can dissolve substances such as grease, oil and similar soiling better and faster with hot water.

The steam setting (boiler temperature up to 140°C) is good for gentle cleaning of especially pressure-sensitive surfaces, since dirt that could otherwise be dislodged only by high pressure can be removed with hardly any pressure at all at extremely high temperatures. That is why the steam setting is also suitable for cleaning porous natural materials that absorb water easily.

With cold-water pressure washers, it is necessary to compensate for the insignificance of the temperature factor by increasing contact pressure, detergent use and time spent. However, cold-water pressure washers can be used with hot water up to 60°C.

If the temperature, as one cleaning factor in a hot-water pressure washer, is increased from c. 12°C to 80°C, the other factors – mechanics (= contact pressure), time and detergent – can be decreased. If the water temperature is raised to 80°C, the cleaning factor temperature results in

• a similar cleaning result at lower contact pressure
• a better cleaning result at the same contact pressure
• better softening of greasy dirt and
• a shorter cleaning time.

A final word on this subject: by using hot-water pressure washers, which in any case produce a better cleaning result, one can considerably reduce working times compared with cold-water machines. This in turn leads to faster amortisation.