WATER TREATMENT
Volume ( cu . ft .) = p r 2 h p = 3.14 r = radius of the vessel h = height of the resin in the tank
Freeboard
Resin
Support bed ( anthracite or garnet )
Figure 2 – Softener vessel
indicate at least a 30 % saturated brine solution for a minimum of 30 minutes . A higher concentration is acceptable but is wasteful if it is much higher than 30 % or longer than 30 minutes .
Data interpretation & elution curve analysis
Plotting the data collected from the elution study and the interpretation of the results can identify irregularities and potential causes of poor softener performance . A simple review of cycle sequence timing , salometer comparisons to manufacturer data , brine tank draws down volume and review of NaCl use can provide further details on the softener operation . Brine draw evaluation is the first step in diagnosing a hard water excursion in a water softener . Small variations in cycle timing , flow rates or salt concentrations can have a significant impact on the softener output quality and can ultimately affect the operation costs of equipment requiring the soft water . Figure 1 shows some typical elution curve interpretations , with observations for each as follows : a . A good regeneration that uses a minimum of salt
b . Using more salt than necessary . Reduce the brine draw flow by installing a dole valve or decrease the slow rinse rate c . Using more salt than necessary . Reduce the brine draw flow rate d . Brine eductor draws too quickly . Check valve adjustment or replace dole valve e . Insufficient brining . Increase the brine draw time cycle f . Brine eductor draws too slowly . Check valve for blockage or adjust or replace brine valve g . Insufficient brine strength & contact time . Possible remedies are to increase brine draw time , decrease dilution water & decrease slow rinse cycle time h . Brining cycle time too short , interrupted by a premature rinse cycle
Mechanical data & calculations
Ion exchange specification data can be used to calculate performance in general terms . Below are some useful formulas and mechanical information that can help compare field results with actual operation of the ion exchange equipment ,
• Resin capacity – 5-6.4 / m 3 of resin ( older resin will have the lower capacity )
• NaCl – 96-160 m 3 of resin ( 128-144 is common )
• Service flow- 265-530 Lmin / m 3 of resin
• Backwash flow – 795 Lmin / m 3 of resin ( depending on water temperature )
• Brine draw flow – 67-134 Lmin / m 3 of resin
• Fast rinse – 200-334 Lmin / m 3 of resin
• Pressure drop – 2.25 bar / metre of resin To determine resin volume , take an actual measurement of the resin depth in the vessel and use the formula shown in Figure 2 . In lieu of physical measuring of the resin height and calculation , consult the softener manual for resin volume . The freeboard area should allow for a 50 % expansion of the resin during backflush . The softener is not completely filled with resin . Distributors for larger softeners will have a spider web design under the resin and covered with bed support material . Small water softeners may have a different distributor design . •
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Kurita America Inc .
info @ kuritaamerica . com www . kuritaamerica . com
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