Chlorine feed question

[operatorjoe]

I work in a large water treatment facility. Chlorine is added after ozone quench/depletion. Periodically chlorine feed is disrupted. The disruption is characterized by instant loss of vacuum to chlorinator. The loss of vacuum is instantaneous and system immediately starts to recharge vacuum in pipe between chlorinator and ejector. Full recharge takes several minutes because distance between chlorinator and ejector is excessive (1/2 mile X 4 in. line). The event first causes a loss of residual then bounces high when feed is reestablished. This event may then become cyclic with a recurrence in 10 to 15 minute cycle. Although this does happen in warm months it is more frequent in cold water months. Vacuum readings on this pipe are observed to range to 23 in/Hg, (no SCADA record for that parameter). There is an approximate 30 psi drop across the ejector with 1 inch orifice. I believe that the flow across the ejector is too high. Is it possible that the ejector could continually accumulate vacuum in long line between chlorinator and ejector and reach a point where vapor pressure of water and vacuum vaporizes liquid and expansion instantly quenches production of vacuum in ejector ? We intend to measure flow with ultrasonic flow meter to verify flows across ejector.

 

[ashtree]

Are you able to give us a sketch of the layout of equipment?
Is it possible to throttle the flow of water in the line? This would test your theory on the high flow.
Is the 1/2 mile 4 inch line , up hill , downhill or level all the way? What i am thinking is perhaps the system has some sort of siphoning happening or perhaps airlocks.


Regards
Ashtree
"Any water can be made potable if you filter it through enough money"

 

[QualityTime]

I am going to take a wild guess. Does your plant suffer from unexplained nuisance alarms or unexplained equipment malfunction? Does your plant have VFD's and/or a lot of UPS's. Have you used electrical recording devices that measures the 110V power to your chlorinator? Does the value fluctuate up and down and what is the high and low readings? You need to record the instantaneous readings. If the 110V drops to 90V then comes back up etc. this is the cause of your problem. If it goes way above 110V your equipment will work but it will burn out faster. If you do not have line reactors on your VFD's you will get harmonics backfeed into your system. Another good way to check is to take voltage and amperage readings on each phase of a constant speed motor (and at the transformer). They should all be equal

 

[bimr]

Does the 1/2 pipeline have adequate capacity?