Function Pressure And Volume Regulation - Kärcher HDS 7/12 M Service Manual

6.31.1 Function pressure and volume regulation

Manually with a pressure regulator on the high pres-
sure pump
The pressure and volume regulation via the handle on the
high pressure pump is used to relieve the motor with most-
ly partial load operation.
Turning the spindle anticlockwise lowers the pretension of
the pressure spring.
This will lift the overflow piston with a lower pressure from
the valve seat and part of the flowing volume runs to the
suction chamber via the sleeve with the throttle bore.
The pump runs at reduced pressure.
Depending on the spindle setting, the pressure and the
water volume change.
64
English 5.906-432.0 Rev. 00 (06/15)
With the rotary regulator on the gun
The pressure and volume regulation via the rotary regula-
tor on the gun should only be used during occasional par-
tial load operation.
When the pressure is reduced via the rotary regulator, the
manual pressure and volume regulation on the pump must
always be opened all the way (direction "+" on the handle);
otherwise, the appliance will shut off prematurely.
If the rotary regulator is partially closed, the pressure in the
system will increase.
This will lift the piston off the valve seat so that a part of the
flowing volume flows back to the suction chamber via the
return.
The pump continues to run at high pressure.
Depending on the setting of the rotary regulator on the
gun, the pressure and the water volume change.
Gun closed
If the gun is closed completely, the piston will open all the
way and the entire flow volume of the pump flows to the
suction chamber via the throttle bore.
The dynamic pressure building up through the throttle bore
of the sleeve in the return actuates the pressure switch
which will in turn shut off the appliance.