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A pressure washer has many moving parts along with materials that are under a considerable amount of pressure. There are three main parts of the jet washer. An electric motor/engine, high-pressure pump and boiler are the most significant parts and the rest is peripheral.

A pump will typically have 3 pistons that are made from ceramic or stainless steel. As the pistons move out of sequence in turn water is being compressed causing it to build up pressure within the hoses and pipework that it is attached to. The high-pressure hose is made from polyurethane or the better ones are made using one or two wire braided hoses that can withstand pressure up to 400 bar.

On the outlet side of the pressure pump, a hose, trigger and lance are used to release the pressure at will. The lance nozzle has a very important job as it keeps a percentage of back pressure back, and also allows a high volume of water to pass through. The Nozzle has an orifice and an angle milled into the jet of which the water can spray. Normally it can come out at 0. 15, 25, 40, degrees. It is important that every service carried out on a pressure washer has the nozzle replaced with the correct size. You would be surprised how pressure drops are causing by a badly worn jet. This is the cheapest part to replace if pressure is down.

Should the orifice be too small the motor will struggle to push the volume of water through a small hole and therefore the pump will try and by-pass the water. This will either stop the pump or it will continue to circulate water around the pump and unloader. This bypass has to work correctly and unload the water at the correct setting. This is a serviceable area and should not be overlooked. Some bypass units have a micro switch on the bottom of the unloader. Karcher, Nilfisk Alto and a lot of the smaller domestic pressure washers have this feature so that the motor will stop the pump from moving and therefore turn the machine off when the pressure builds up.

Hot machines work with the same principle as a cold pressure washer. There is a boiler, pressure switched, level switches etc.

Fuel filters pass the clean fuel up to the burner head where a combination of moving air generated from a fan and fuel causes the flame to heat the water passing through the heat exchanger. A thermostat will regulate the heat output. The fuel jet that atomises the fuel needs regular replacement as the spread of fuel is disturbed due to dirty fuel etc. Danfoss, Stein and much more are commonly used in burners for pressure washers. Burner fuel jet will have eg 1.35 gallons per minute at 60 degrees (s) = Solid pray pattern. It’s almost like a conical shape.

In order to function properly, it is important that all parts are in good working condition. Hoses, couplings, filters or need regular servicing and checking. Pressure washers need to be serviced regularly because of the accumulation of dust and grime where they are used.

It is recommended that the pump oil in changed to. Sometimes you may find the oil emulsified as it’s mixed with water in the pump. It would be best to seek advice as the pump seals and oil seals will need replacing or at worst the piston to if it’s cracked.

Maintenance involves cleaning the nozzle, which gets clogged with dirt, causing excessive pressure to develop, distorting the spray pattern. Other parts may also develop problems and may have to be replaced from time to time

These machines are work well if inspected properly by an engineer. A degree of respect needs to be applied for these machines as 140 degrees of water at 12-21 litres a minute bursting could be fatal.

Download more information about How to size the correct nozzle for your requirements here
Download more information about How to choose the correct size nozzle here

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For Servicing Seals - Cat Pumps Model 3CP1120, 3CP1130, 3CP1140