Problems related to demineralization plants

efects	Causes	Remedies
Decrease in capacity between two successive regenerations	a. Increase in ionic load b. Flow recorder defective c. Insufficient chemicals used d. Resin dirty e. Plant being used intermittently f. Channelling in bed                                                                        g. Resin fouled                                                                          h. Resin deteriorated i. Resin quantity insufficient in unit	Check by analysis Check Check Give prolonged backwash Avoid this Check and ensure uniform distribution /collection If cation, give HCl wash; if anion, resin give alkaline brine treatment Check and replace charge Check and top up
Treated quality not upto the standard	a. Cation exhausted b. Anion exhausted c. Mixed bed exhausted d. MB resin not in uniform mixed state e. Some valves like backwash leaking f. Na slip from cation high g. SiO2 slip from anion high h. Unit idle i. Unit not sufficiently rinsed j. Excessive/low flow rate k. Channelling l. Resin fouled                                                                        m. Resin deteriorated	Check Check Check Repeat air mix and rinse                                                        Check Check raw water analysis; change in Na/TA and SiO2/TA ratio; use more chemicals Check raw water analysis; change in Na/TA and SiO2/TA ratio; use more chemicals Check Rinse to satisfactory quality Adjust to between unit min/max flow rate Check and ensure uniform collection/distribution Check resin and give alkaline brine/ HCL treatment Check resin and replace
Mixed bed quality not good	a. Resin not separated during backwash properly b. Air mix not proper c. Final rinse not proper d. Some valves may be leaking and contaminating the treated water	Give extended backwash after exhausting the bed Repeat Repeat Check and examine
High residual CO2 from degasser	a. It can be due to choked suction filter of degasser air blower b. Improper air flow to the degasser c. Degasser blower not in operation d. Air seal not fitted/broken resulting in short circulating of air	Check and clean filter Check damper, speed of blower, discharge pressure Check and operate blower Check and replace fitting
Unit rinse takes long time	a. Flow rate too high b. Unit exhausted c. Backwash valve passing d. Anion resin organically fouled e. MB air mix not satisfactory f. Acid/alkali pockets formed in unit	Increase flow rate Regenerate unit Check and rectify Give alkaline brine treatment Carry out air mix once again Faulty design check and rectify. Temporarily backwash (followed by air scour if MB) and rinse again
Flow rate too less	a. Choked valve and suction strainer of pump b. Cavitation in the pump c. Low inlet pressure d. Distribution or collecting system choked e. Resin trap at outlet choked f. Control valve shut due to low off-take	Check Check Check-pump Check Check and clean Increase off-take
Pressure drop across the bed increasing day by day	a. Defective valves b. Packed resin bed and resin fines present c. Collecting system choked d. Pressure gauge defective	Check Give extended backwash with open manhole and scrap off fines from top surface of the resin Check, repeat backwash Check and rectify/ replace
Flooding in degasser	a. Very high air flow rate b. Packed tower chocked due to dirt or broken packing material	Reduce air flow rate by adjusting damper Open and check
Resin being lost	a. Excessive backwash pressure b. Faulty collecting system c. Inlet strainer damaged	Check inlet pressure and reduce if necessary Examine same for breakage Check and replace
Ejector not working	a. Low power water pressure b. Air lock in the unit c. Choked or defective valves d. Ejector nozzle may be choked e. Too much back pressure from the unit f. Bulge in pipe lining	Check Backwash & open air release Examine and rectify Check Check for chokage of collecting system; passage of inlet/outlet valves Check and rectify
Incorrect reading rota-meters	a. Chocked orifice lines/orifice b. Dirty glass and float	Check and clean check and clean
Improper reading from flow recorder integrator	a. Choked impulse lines/orifice b. DP transmitter requires recalibration c. Leakage in signal tube between transmitter and panel d. Low air pressure for DP transmitter or recorder	Check and clean Recalibrate Check                                                Check
Level electrodes system for measuring and dilution tank not functioning properly	a. Improper contact between electrodes and control cabling b. Shorting of the two electrodes due to moisture or any foreign material c. Improper working of the level controllers	Check contact and rectify                                                      Check and dry the contacts of moisture and dirt Check
Leakage from acid injection/unloading/transfer pumps	a. Improper adjustment of the mechanical seal b. Low strength of sulphuric and presence of ferrous sulphate	Check and adjust Check concentration and take appropriate action
Corrosion in concentrated acid tanks and lines	a. Low concentration of sulphuric acid b. Lining of HCl tank/pipe line damaged	Check silica gel breather in acid storage tank and replace silica gel charge if exhausted Rectify
Improper opening and closing of pneumatically operated valves	a. Defective solenoid valves b. Leakage in airline from solenoid valve to the respective control valve. c. Improper contact of micro switch giving false indication to panel d. Fused mimic lamp giving false indication to the panel	Check Check                                                Check                                                Check
Improper operation of a certain regeneration cycle	a. Defective relays in the control circuit	Check and replace relays
Solid state programme not functioning properly	a. The controller can be kept in "hold" due to the reasons explained under operation b. Improper operation of the controls for the controller c. Defect in the inside of the controller	Remove conditions which cause "hold" of controller Press test switch & check the complete cycle Check the instruments thoroughly from inside. Meanwhile, operation may be continued by using bypass toggle switches