Flow, and any loss of pressure or flow outside the margins will trigger a
shut down after the pre-set delays expire. The switch will then display the
reason for the shutdown, and if configured, close the alarm relay to
trigger an optional external alarm or dialler which can text to alert the
operator of a problem. If the system recovers within the pre-set delay
period it will resume normal operation.
This method of fault detection is particularly suited to systems where the
pressure will change if there is a leak or blockage.
With a travelling irrigator on undulating terrain Auto Terrain Compensation
should be selected. The switch will then adjust itself to compensate for a
changing contour. This allows for very small over and under pressure margins
which gives a very high degree of protection against leaks or blockages.
When pumping to a hydrant or group of hydrants for the first time, once it
has been confirmed there are no leaks or blockages and the switch has
locked in a set point the operating pressure should be recorded against the
hydrant number or numbers as a group. The recorded pressure can then be
used as a useful reference for subsequent pumping to the same hydrant or
group of hydrants. If the pressure is the same as it was previously then it
can be assumed there are no leaks or blockages.
Alternatively the irrigation system should be checked visually each time the
pump is started.
DETERMINE THE PRESSURES
26
