ALKOTA 5305A, Service Manual, Page: 31 / 56

27
Unloader Valve
Specifications
Specifications
Maximum Flow 10.5 gal/m / 40L/m
Unloading Press
Rated
4050 psi / 280 bar
Max 4500 psi / 310 bar
Maximum
Temperature
195˚F / 88˚C
Weight 1.54 lbs / 700 G
Bypass 3/8 FNPT
Inlet 3/8 FNPT
Discharge 3/8 MNPT
Valve, Unloader
p/n C07-04504M-A
PULSAR4HPM
GENERAL PUMP
A member of the Interpump Group
Trapped Pressure Unloader Valve
DIMENSIONS
SELECTION
This product is intended to be incorporated on a finished machine. This product is to be used with clean fresh water, for use involving different or
corrosive liquids, contact the GP Customer Service Department. Appropriate filtration should be installed when using impure liquids. Choose the valve
appropriate to the working data of the pump (permissible pressure, flow and rated temperature of the system). The pressure of the pump must not
exceed the maximum pressure of the valve.
OPERATION
The valve regulates the maximum pressure of the system by varying the flow discharged by the bypass. The adjustment is made by altering, by means
of a piston, the position of a sphere which partially closes the bypass opening. The valve is sensitive to water flow. At gun opening, the water flows
through the valve which maintains the system in pressure until the gun closes, the interruption of the flow provokes the complete aperture of the
bypass which allows to discharge the flow at low pressure. At gun closure, the special mechanism of zero setting, which does not include a check
valve, keeps in connection the delivery line and the bypass line, in that way permitting to lower the pressure all around the system and not only in the
source line of the valve.
SELECTION AND OPERATION
INSTALLATION
This valve, on a system that produces hot water, must be fitted upstream from the source of heat. On a system that generates hot water, it is advisable
to use accessories that limit the accidental increase of fluid temperature. Always install a safety valve. We recommend the use of a nozzle with flow
rate which allows a regular discharge from the valve bypass of at least 5% of the flow supplied by the pump. In order to achieve a constant pressure
and easy adjustment. If the nozzle wears out, the pressure decreases. To reset pressure back to working level, it is necessary to replace the worn
nozzle. When a new nozzle is fitted, resetting of the system to its original working pressure is required.
DISCHARGE SYSTEM AND WATER ADDUCTION
The bypass discharge can be sent back to the pump intake or returned into a tank; in such cases it is advisable that the tank be fitted with baffles to
reduce eventual turbulence and air bubbles which could be harmful to the pump.
PRESSURE ADJUSTMENT/CALIBRATION
The desired working pressure must be adjusted with the system running and the gun opened. Adjust the pressure by screwing or unscrewing the
adjustment screw. The operation is easier if the correct nozzle has been chosen (see above). When screwing the adjustment screw a consequent
pressure increase must be matched. If, before reaching the desired pressure, there is no pressure increase, DO NOT FORCE. Rather, check the
correct ratio of nozzle/flow rate - pressure and, if necessary, replace with a smaller size nozzle.
ATTENTION: the nut in position 23 is a mechanical security device that limits the maximum pressure; it must absolutely NOT be removed.
Ref 300938 Rev. A
11-13