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High pressure cleaning - a little extra help13th of December 2013
Many surfaces can be cleaned effectively using cold water at high pressures. But some tasks require a little extra help in the form of heat, detergent or some other agent – and manufacturers have plenty of resources up their sleeves for tackling these more challenging tasks, as Ann Laffeaty finds out.
Cold water at high pressure is recognised as being a highly effective method of cleaning dirt and grime away from building facades, patios, car parks and other surfaces. But dirt takes many forms, and cold water alone will not be capable of removing all of them. Hot water at high pressures is sometimes needed to dissolve more stubborn soiling.
However, cold water machines are still highly suitable for removing substances such as mud, dirt, sand and rust from various types of surface says Nilfisk-Advance’s senior group product manager for professional high pressure washers Andrew Caddick.
“In other words, they are ideal for use on the more organic and mineral classes of dirt,” he said. “These machines can be used on surfaces such as stone, wood or metal, and typical customer groups for cold water machines include agriculture, building/construction and certain types of contract cleaning applications.”
He admits that cold water is less effective on grease, fats and oils, however. “We estimate that hot water can save up to 40 per cent of the cleaning time when removing these substances,” he said.
“Chewing gum is also very resistant and not removable with cold water in normal conditions –and it is even very difficult to remove when using hot water. The use of cold water on chewing gum may produce results, but these will not be perfect - and will be at the expense of longer cleaning times, the use of detergent and higher pressures along with the consequent risk of damage to surfaces.”
The water temperature required when removing chewing gum, grease, oils and fats from a surface will depend on the nature of the task and the dirt type, adds Caddick. “For example for car cleaning, a temperature of 50 C would be OK but when degreasing a metal surface, up to 90 C would be better.”
According to Kärcher’s ?environmental public relations officer Linda Laipple, cold water high pressure cleaners have several advantages over hot water machines. “They are less expensive to buy and incur no water heating costs,” she said. “They also require lower service and repair costs and have fewer components.”
Other advantages include the fact irregular surfaces can be cleaned using a high pressure jet and water consumption is lower due to the reduced cross-sectional area of the nozzle, she said.
However, hot water machines offer the benefits of faster cleaning, reduced labour costs and shorter drying times.
“They also produce improved results as there is less likelihood of streaks and the cleaning surface will be left completely dry, which means it will attract new dirt less easily,” said Laipple. “The use of hot water, too, reduces the need for detergents.” Typical applications for hot water machines include vehicle washing and façade cleaning, she says.
According to IdroBase group marketing director Tommaso Gazzignato, cold water machines can tackle around 70 per cent of high pressure cleaning tasks. “However where there are oily stains present, a cold water high pressure cleaner is not the proper machine to use unless it is with a specific detergent,” he said. “In this case it is the combination that can bring successful results.”
Idrobase offers a range of professional pressure washers including hot water machines with pressures ranging from 100 to 300 bar and flow rates of 10 to 40 litres.
According to manufacturers, there are some cases where water alone will not be able to achieve the desired cleaning results. However, they have plenty of ideas up their sleeves – along with various accessories and cleaning agents – designed to allow customers to tackle these more challenging tasks.
For instance, says Gazzignato, extra cleaning power can be provided by means of a specific detergent depending on the type of dirt that needs to be removed, or by using an accessory such as a rotating nozzle or sand-blasting lance.
“Rotating nozzles are capable of removing chewing gum, for example, whereas a specific detergent in conjunction with a high pressure washer would work well when tackling graffiti on a rough surface,” he said. “However, if the surface you need to clean is more delicate - for example, when cleaning a historical monument - you would need to be careful about the type of detergent you choose. You would also need a lighter action, perhaps by using a low pressure jet.”
Nilfisk-Advance’s Andrew Caddick agrees delicate old buildings are a special case and each one needs to be considered individually. “When we cleaned a church in Copenhagen, for example, the solution we chose was simply to let the water run down the surface at lower pressure levels,” he said. “This soaked the façade and removed the dirt slowly with no risk of damaging the delicate stone surfaces.”
Other difficult tasks will call for specific solutions, says Caddick. “We have found the best method of removing chewing gum, for instance, is to use a steam cleaner with a small quantity of a special detergent and a brass bristle brush.
“Graffiti removal is another challenge. Old traditional methods such as blasting with a mix of sand and water are very abrasive and risk damaging the surface, while also presenting a problem when the debris needs to be removed.
“Newer methods use less abrasive powders such as Armex - basically a bicarbonate of soda type of powder - blasted with the water. This leads to less damage to stone and glass surfaces, and the powder is soluble and ecological which means it is easier to dispose of afterwards. However being a salt, care needs to be taken with porous surfaces.”
He adds that other technologies such as dry ice cleaning can also be used for graffiti cleaning, for removing rust from metal surfaces and for cleaning plastics. Nilfisk also offers a range of other solutions including sandblasting, softblasting and steamers.
Kärcher’s Linda Laipple advocates the use of steam for certain challenging cleaning tasks. “The steam setting of a hot water high pressure cleaner is good for the gentle cleaning of pressure-sensitive surfaces,” she said. “These extremely high temperatures used at low pressures will remove the type of dirt that could otherwise only be dislodged by high pressure. The steam setting is also suitable for use on porous, natural materials that absorb water easily.”
Sometimes a cleaning agent is required to give the high pressure washer a little extra help, she says. “These detergents will enhance the cleansing properties of water by increasing wettability, emulsification and direct chemical reactions with the constituents of the dirt,” said Laipple.
However, she adds that difficult cleaning tasks can often be solved with the use of specialist accessories rather than by changing the temperature, pressure or blasting agent. And that recent developments in fan and rotary nozzles can boost the cleaning performance of a high pressure washer by up to 125 per cent. “The choice of accessory is almost as important as the decision to buy a specific machine model,” said Laipple.
“No other method of cleaning is so flexible since with high pressure cleaning, Items and equipment can be cleaned on the inside or outside, horizontally or vertically and whether these happen to be buildings, vehicles or machinery,” she said.
And Andrew Caddick believes that the use of specialist nozzles for specific cleaning tasks will gain more importance in the future. “Special accessories can add a mechanical effect to the cleaning process, and the use of detergents is becoming more and more problematical due to legislation,” he said.