ESH150
–3PE~400V
Service Manual
45/56
Ref. NR-000144-ENG
To ascertain whether the pressure imbalance is caused by an obstruction or by a problem in the
pumping system, operate the spray gun and check the reading on the pressure gauge of the
missing component. Compare this reading with the
pressure indicated on the other component’s
pressure gauge: if the pressure of the missing component is higher, the pressure imbalance is
caused by an obstruction; if it is lower, the imbalance is due to a problem in the pumping
system.
3. Cavitation
Cavitation occurs when the proportioning pump requires a greater volume of material than the
feed system is supplying, giving rise to the formation of voids in the proportioning pump. There
are three possible causes of cavitation:
a) High viscosity. Polyurethane foam spray systems normally require a minimum transfer
temperature of 12ºC: at lower temperatures, the viscosity of the component products
increases, and it is more difficult to pump them. When ambient conditions do not allow
the component products to be kept at the minimum temperature of 12ºC, auxiliary
heating equipment must be used to keep the component products at the minimum
required transfer temperature.
b) The product intake filter is clogged (see Maintenance).
c) The intake ball valve is leaking as a result of wear or defects in the ball or the closing
surface of the bushing, which causes some of the material to return to the tank.
Therefore, the volume of material delivered by the proportioning pump in the discharge
cycle is lower than required, giving rise to an incorrect product ratio.
4. Fault in the direction change sensor
The metering pump system has a plate that activates the reversing switches to carry out the
change of direction. The most common cause of the fault is the entry of a foreign body
preventing the plate from making contact with the micros.
A fault in the movement of the directional valve will cause the activation plate to pass the micro
and not make the change of direction. Proceed as follows to solve this problem:
a. Determine the direction in which the plate must move; this depends on which micro
has been passed.
b. Locate the slide for the manual override of the directional valve located on the front
of the hydraulic cylinder. Act on the side to which you want the activation plate to
move.
c. Turn the general switch ON, press the CONTROL POWER key and the MOTOR
key. With the manual valves of the coupling block open, point the gun at a waste
container.
d. Press the manual slide of the directional valve and hold it until the activation plate is
centered between the two run end micros.
e. If when pressing the slide, it moves freely, the excess run is due to an electrical
problem. Press the MOTOR key and the NORMAL key; press the run end micros
and check whether the reels are changed, and the direction indicator lights: if the
reels are not changed or the direction indicator lights fail to come on, there is an
electrical problem in the run end micro or in the reels of the directional valve.
5. Tank empty
As there is no way of visually checking the level of product in the tanks during the normal
operation of the unit, there is a risk that air will enter the circuit if the level in one tank is too low.
This will cause the pumping system to malfunction.
If this problem occurs, purge the air from the circuit as described in the corresponding section
on
p.26
(heated hoses with transformer).
