Go with the flow

01 March 2018

Most cleaning companies have a pressure washer in their fleet but many operatives are simply not trained how to use it effectively. In the wrong hands it can cause substantial damage and personal injury. With these units becoming ever more popular Nilfisk’s sales director John Brill provides guidance on how to get the best out of an extremely effective cleaning tool

Hot or cold water?

Perhaps the first and most important question. Traditionally companies would have automatically purchased a cold unit but independent tests confirm that this may not be the best option.

The Wfk – Cleaning Technology Institute located in Germany recently compared the cleaning efficiency of industrial pressure washers at different temperature levels for four applications. For all tests the bar pressure was set at 180 bar and the water flow rate at 810 litres per hour. All tests were conducted with water at cold, 60oC & 90oC degrees centigrade respectively.

The results confirmed that hot wins over cold overall as hot water was found to be much more efficient resulting in a dramatic reduction in cleaning time and associated labour and water costs. The tests confirmed overwhelmingly that it is simply not cost effective to clean at 90oC as increased fuel costs do not result in a big enough reduction in cleaning time. 

Boiler technology

Innovation across the industry has led to the development of improvements in boiler technology such as eco modes that heat water very economically to 60oC. The European Cleaning Machine Association (ECMA) rates and approves pressure washer boilers under their EUnited scheme. Some EUnited approved boilers, including Nilfisk models, are classed as >92% efficient and therefore provide big reductions in fuel consumption. In some cases saving up to 15% when compared to similar machines in their class.  

Really tough cleaning

There are some jobs where pressure washers really come into their own but the power of the hose should still be respected or short and long term damage can occur.

Cleaning out tanks and containers with traditional methods can prove fatal but a high pressure washer from a safe distance is ideal. Agricultural and construction equipment caked in dried on concrete, mud and excrement is an everyday task made easier with water at 60 degrees centigrade.

Care should be taken however when using a pressure washer on polished metalwork of any type. The key thing is not to stand too close, a minimum distance of 30cm is ideal and the flow should always be tested first by pointing the hose at the ground. A ‘turbo’ or unrestricted nozzle should never be used on paintwork of this type. Pre-spraying with a detergent liquid or foam is recommended and will reduce the amount of time that the washer is needed for. Never use the pressure washer on paintwork or signage that is flaking or rusty. Operators should also be trained to avoid engine blocks, motors or any other working components including aerial systems. 

Concreted areas, bricks & masonry

An untrained operative can get carried away when faced with cleaning large hard surface areas but the damage caused can easily run into hundreds of thousands of pounds.

Using too much water and incorrect chemicals for example on red brick will have devastating results causing efflorescence on the brick surface. The same applies to white stones such as limestone and marble, too much water saturates the stone causing brown alkaline staining. This will not be noticeable at first and may take weeks to appear. More trouble looms however as cold weather will freeze water inside the bricks and stone causing them to crack and ultimately crumble away.

High pressure washers should therefore never be used on red brick, marble, stone or cobblestone. A form of ‘soft blasting’ can be applied to porous masonry in old buildings or monuments. This involves using bicarbonate of soda instead of sand, bi-carb is soluble and environmentally friendly washing away into the regular sewer system.

Expert advice should always be obtained if expensive insurance claims are to be avoided.