Environmental Engineering Reference
In-Depth Information
To pump
controls
On
Off
figure 3.11 Electrode system for pump motor control.
3.3.7.3 Electrode Control Systems
The
electrode control system
uses a probe or electrode to control the
pump on and off cycle. A relatively simple control system, it consists of
two electrodes extending into the clear well, storage tank, or basin. One
electrode activates the pump starter when it is submerged in the water;
the second electrode extends deeper into the well
or tank and is designed to open the pump circuit
when the water drops below the electrode (see
Figure 3.11). The major maintenance requirement
of this system is keeping the electrodes clean.
Key Point:
Because the electrode
control system uses two separate elec-
trodes, the unit may be locked into an
on cycle or off cycle, depending on
which electrode is compromised.
3.3.7.4 Other Control Systems
Several other systems that use electrical energy are available for
control of the centrifugal pump. These include a
tube-like device
that has
several electrical contacts mounted inside (see Figure 3.12). As the water
level rises in the clear well, storage tank, or basin, the water rises in
the tube, making contact with the electrical contacts and activating the
motor starter. Again, this system can be used to activate several pumps
in series by installing several sets of contact points. As the water level
drops in the well or tank, the level in the tube drops below a second con-
tact that deactivates the motor and stops the pumping. Another control
system uses a
mercury
switch
(or a similar type of switch) enclosed in a
protective capsule. Again, two units are required per pump. One switch
activates the pump when the liquid level rises, and the second switch
shuts the pump off when the level reaches the desired minimum depth.
3.3.8 electronic systems
Several centrifugal pump control systems are available that use
electronic systems for control of pump operation. A brief description of
some of these systems is provided in the sections that follow.
