Technical data

Aussie Pumps Bertolini Pumps Service Guidelines – July 2008
4
TYPICAL OPERATION AND REQUIREMENTS
Pressure
The pressure produced in a pressure washer
system is the result of forcing a known volume
of water through a known orifice size (spray tip).
This pressure is measured in bar or pounds per
square inch (psi).
Flow
In a pressure washer system the flow produced
is determined by the speed that the pump shaft
is rotated (rpm). The faster the shaft is rotated
the higher the output volume. This water flow is
measured in litres per minute.
Nozzle Orifice
Setting unloader valves for the required
pressure of the machine depends entirely on the
correct nozzle selection. The correct nozzle
orifice can be selected to suit any specific
pressure/flow combination using the chart on
page 5.
Operators should be conscious that nozzle wear
will create a drop in pressure and an apparent
malfunction of the machine. The abrasive nature
of water and the subsequent wear enlarges the
orifice in the nozzle. The larger the orifice, the
less pressure and the more danger of
subsequent machine malfunction through
unloader failure.
Further information on this subject is covered in
the Nozzle Selection Guide section.
Operation
The pump which is motor driven draws water in
through a series of inlet check valves as the
plungers move back. As the plungers move
forward the inlet valves close, forcing the water
to travel through a series of outlet check valves
and to the pump outlet.
When the water exits the pump the direction of
flow is controlled by means of an unloader or
regulating valve. A positive displacement pump
is always delivering a certain volume of water
whether the spray outlet is open or closed so a
device is needed to control the direction of flow.
This device allows the spray to exit through the
spray gun or redirecting (by-passing) the flow
back to the inlet of the pump if the gun is closed.
As a safety device at least one pressure relief
valve must be installed in the outbound side of
the pump to protect against component failure
and the development of dangerously high
pressure.
Note: Failure to install correct unloader valve or
regulator device could result in serious injury and
property damage.
Chemical injection
Cleaning chemicals or detergents may be
introduced into either the inbound or outbound
flow of water. An inbound chemical injector uses
the pump=s ability to draw or suck fluid in to
introduce a chemical into the water flow. An
upstream injector allows chemicals to be applied
to the surface to be cleaned at normal high water
pressures. As any chemicals introduced
upstream pass through the pump body, care must
be taken to ensure the chemicals are compatible
with the pump=s construction material and
components, such as seals.
An outbound or downstream type of chemical
injector uses the venturi system to draw chemical
into the water stream. This type of injector
requires low pressure to activate chemical flow.
Low pressure is achieved by enlarging the outlet
orifice by changing to a larger spray tip or by an
adjustable nozzle.
There are advantages to using a downstream
injector:
1. Fewer pump component parts are exposed to
the cleaning chemicals which may extend
system life.
2. The operator can control the flow of chemicals
by changing the system pressure at the
nozzle.
3. Applying the chemical at lower pressure is
more economical as less chemical bounces off
the work surface.
Hot water/steam cleaners
Heated pressure washers and steam cleaners
increase the ability of high pressure water flow to
break down dirt and grease. The cleaning action
of most detergents is also increased. Units
incorporating a boiler are very complex and
potentially more hazardous than cold water
systems. Design of these systems requires many
more additional components and should be
designed by qualified professionals with a
thorough knowledge of fuels, heat transfers, etc.
A
ussie Pumps Bertolini Pumps Service Guidelines – July 2011