Cooling Tower - Low Water Cutoff 1

[Greg06]

Hi,

Does anyone have experiance using low water switch in a cooling tower basin?

I can see the advantages of shutting off the condenser water pump if there is not water in the tower basen.
On the other hand there is the potential for high maintance due to slug buildup in the tower basein.

Thank you.

 

[tombmech]

Yes, I worked in a Plant Engineering department where we regularly ripped out the ball floats on every cooling tower, and substituted electronic probes for level sensing, instead. We always included a low-level cutoff.

You are right that the probes should be selected carefully to minimize corrosion of the sensor, but it's generally more reliable than the float switch on the water makeup. Another advantage is that it automatically gives you a digital interface for alarming, etc.

Things can get busy in a hurry if a tower runs dry. It happens.

 

[quark]

I hate the capacitance or conductance type level switches as even small coating of scale on the probes result in malfunctioning of the level controller. After I started using E+H ultrasonic type transmitters life became easy. Normal switches cost me Rs 6000 (about 133 USD) where as the transmitter costed Rs 25000 (about 555USD), but it was worth investing. The hardest part of the job was to convince the old and orthodox boss.

 

[imok2]

Quark Was the "old" part necessery :>) If your lucky you might get trere too!

 

[quark]

Yes, the "old" is to complement the "orthodox", for an, otherwise, excellent guy with lots of hands on experience and good knowledge. He was always apprehensive(?) about expensive automation.

For the lucky part, with the rapid changing social scenario in India, I would rather be lucky to take a leave before I am old. The financial forecast says, if I have to spend a mere 333USD/month after I retire (thirty years from now), at the present monetary value, I have to save about USD666666, but at the present rate my total savings can't go beyond USD333333.

Pray for me:-(

 

[KenRad]

Greg06,

The low water switch you refer to - what is its function in your tower? Is it controlling makeup water, or disabling sump heaters and/or pumps on low water?

---KenRad

 

[Greg06]

KenRad,

The low water switch I an intending to refer to is a safety limit switch. The intent is to shut down the condenser water pump and chiller served by the cooling tower in the event the cooling tower runs dry.

I will not be providing sump heaters with this tower.

Thank you,
Greg

 

[quark]

Scale whether soft or hard will create problems on your probes if they are of contact type. you require to clean them often. Ultrasonic radars are cheaper of the non contact types and you can be able to record the actual levels if you want. Never gave me trouble for the past 5 years.

 

[kpntreal]

A long shot here , but what about using a float type (such as McDonnell Miller type 150)Low water cut off commonly used in steam boiler applications?
It would allow for daily flushing of debris from its float chamber, as well as provide DPDT switching for alarm or even to open a water valve for automatic emergency water feed.
Used together w/ the probe type (not w/o their own troubles w/ the probe going to ground) you may have a viable solution.