Walchem WebMaster ONE Instruction Manual page 17

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Sensor Installation
All sensors for the WebMasterONE series are provided with signal conditioning electronics, and
conductivity sensors may be located up to 250 feet (75 meters) from the controller, and pH/ORP
sensors may be located up to 1000 feet (303 meters) from the controller. It is highly recommended
that the sensors be installed within 20 feet of the controller in order to make periodic calibration
more convenient.
Sensors should be located such that they respond rapidly to a well-mixed sample of the process
water and the treatment chemicals. If they are too close to the chemical injection point, they will
see spikes in concentration and cycle on and off too frequently. If they are too far away from the
chemical injection point, they will respond too slowly to the concentration changes, and you will
overshoot the set point.
If the sensor cables need to be extended, then 24 AWG shielded low capacitance (15 pF/ft) twisted
pair cable such as Walchem P/N 102535 (Belden 9680) or equivalent should be used. Pay attention
to the integrity of the cable shield. Always route sensor cables (or any other low voltage wiring) in
conduit that is separated from any AC voltage wiring by at least 6 inches.
pH and ORP electrodes must be installed such that the measuring surfaces will always remain wet.
A U-trap provided in the manifold design should achieve this, even if the sample flow stops. These
electrodes also must be installed with the measuring surfaces pointing down; that is 5 degrees
above the horizontal, at a minimum.
If the sensors are to be submersed in the process, mount them firmly to the tank, and protect the
cable with plastic pipe, sealed at the top with a cable gland, to prevent premature failure. Place the
sensors in an area of good solution movement.
Flow Control Valve
Maximum Flow Rates in Lbs/hr
40 50 60 70
Pressure PSI
80 90 100
13
150 200 300
1/2" 150 PSI
1/2" 300 PSI
3/4" 150 PSI
3/4" 300 PSI