ESH150
–3PE~400V
Service manual
44/56
Ref. NR-000144-ENG
Proportioning pumps
WARNING!
Before attempting to fix any kind of malfunction, make sure the power
switch is in the OFF position and that the unit is disconnected from the power supply.
Never open the electrical console when the unit is connected to the power supply.
Proportioning pumps work under pressure. Do not release any connection or perform
repair or maintenance work on components subjected to pressure until all pressures
have been eliminated.
PROBLEMS
SOLUTIONS
The pumps lose pressure when the unit is stopped.
1
The pressure readings in the proportioning pumps are different.
1-2-3
There is cavitation in the proportioning pump.
1-2-3
The proportioning pumps do not reverse direction.
4
The proportioning pumps do not move.
4
The movement of the proportioning pumps is erratic.
4-5
SOLUTIONS
1. Pressure loss in ball valves
Observe the pressure gauges to identify which pump is losing pressure. To determine which
ball valve is faulty, check in which direction of movement the pump loses pressure. If pressure is
lost in the upward stroke, check the discharge (upper) ball valve. If pressure is lost on the
downward stroke, check the intake (lower) ball valve.
Proceed as follows to check the ball valves:
a) Disconnect the unit from the power supply and shut the stop valves controlling product
intake.
b) Depressurize the proportioning pump and dismount the faulty ball valve.
c) Pressure loss in ball valves is usually caused by foreign particles which prevent the ball
from coupling perfectly with the seat in the upper part of the closing bushing. Clean the
ball and the surface of the bushing seat and check there are no nicks, marks or
scratches on the bushing or the ball. If cleaning does not resolve the problem, or if any
defects are detected, replace the bushing and the ball.
2. Pressure reading imbalances
Pressure reading imbalances occur when an obstruction in the hose or gun prevents one of the
spray components from exiting the nozzle during spraying, or when a problem in the pumping
system prevents one of the components from reaching the gun in the required quantities.
Identifying which component is causing the imbalance is relatively easy, as the component
chemical products used in the polyurethane foam spray system are of different colours. By
observing the colour of the component coming out of the gun you can determine which
component is missing.
