Nilfisk-Advance 107146895, Service Manual, Page: 49 / 101

49
SM_MH 3M_4M Ver.1.2_May 2016
Function
D
MH 3M
The schematic drawing of the pump head below is made to get a better understanding of the function.
NOTE ! In the schematic drawing of the pump head is shown a two-way easy start valve, which is the
layout for all the single phase machines. The three phase machines are without the easy start valve.
Schematic Drawing Cylinder Head
Pressure outlet
Non-return valve
Piston
Micro switch
Water inlet
Pressure reg. valve
Control piston
Valve pressure
Valve suction
Functional description 3 ~:
Preconditions:
Machine is connected to correct power and water supply. High pressure hose and gun is
installed on the machine.
Gun is closed and machine is started on the main switch. Motor starts - the pressure is building up until it
reach the cut-off pressure. When the cut-off pressure is reached, the control piston is pushed upwards by
the higher pressure - the micro switch is activated (opens) - and the motor stops. When the motor stops,
the non-return valve is pushed back into its seat and holds the cut-off pressure in the high pressure hose,
and also in the channel going from the non-return valve to the bottom side of the control piston. Now the
trapped cut-off pressure is holding the control piston in the up position.
Starting from stand-by mode:
Press the gun. The pressure in high pressure hose, and in the channel going from the non-return valve to
the bottom side of the control piston disappears. Control piston is pushed down by the spring, and the mi-
cro switch is activated, the motor starts—and the pressure is build up.
Schematic drawing 3 ~