COOLING WATER TROUBLE SHOOTING

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Cooling water trouble shooting

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COOLING WATER TROUBLE SHOOTING Author Prem Baboo Sr. Manager Prod National fertilizers Ltd. India Fellow of Institution of Engineers India. An Expert for www.ureaknowhow.com prem.baboonfl.co.in pbaboohotmail.com Mob. +919425735974

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TEMPORARY TROUBLE SHOOTING In Saipem Process urea plant some cooling water Heat exchangers are lying in ground floor and some of the lying on height 5 10 15 20 meters etc. The cooling water header pressure generally running about 3.8 bars to 4.2 bars. A GROUND FLOOR HEAT C.W. HEAT EXCHANGER 1. Compressor ground floor C.W. Heat exchangers3 No 2. Turbine hot well. 3. Compressor Lube oil cooler 4. Waste water final cooler 5. Condensate cooler. B C.W. HEAT EXCHANGER ABOBE 5 METERS 1. L.P. Condenser. 2. Distillation Tower overhead condenserVertical C C.W HEAT EXCAHNGER ABOBE 10 METERS. 1. First stage vacuum condenser 2. Second stage vacuum condenser 3. Three number small condenser 4. MP condenser 5. Pre Concentrator condenser D C.W HEAT EXCHANGER ABOBE 15 20 METERS 1. M.P. Ammonia condenser 2. Inerts washing column vertical 3. L.P inerts coolervertical Trouble Shooting for Vacuum Condenser To open vent valve of outline line “U” bend and watch intensity of water and slowly close down outlet butterfly valve this valve only open about 30 as shown in the figure. Sometime the vent valve flow not sufficient due to air locking. Air locking removed with outlet line throttling valve and adjust accordingly

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1. If the flow in Heat exchanger is not sufficient then throttle all C.W outlet valves of ground floor C.W. Heat exchangers as mentioned above subjected to temperature should not be increased and minimum flow should be there to avoid sedimentation in heat exchanger cooling water side. The opening about 40-60 as shown in the figure.

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2. If the flow of C.W. in vacuum section not increases then throttle above mentioned B section valve i.e. heat exchanger above 5 meters height above ground subjected to above condition mentioned in Serial number 2. 3. Sure that Cooling water pumps discharge vale is full open and also check cooling water deck valves. 4. When charging the cooling water heat exchangers vent valves must be opened of each heat changer. 5. When cooling water header after shut down 1 st time charging the draining of dirty water including flouting material should be drained with opening of flange of ground floor heat exchanger. PERMANENT SOLUTION FOR LOW FLOW If the cooling water flow low after commissioning then one additional cell along with pump may be provided to increase the flow pressure as shown in the figures. 1. The sump along with pump of the additional cell is separated and connected through 20” pipe line. 2. One ID fan should be provided on top of the deck. 3. The Deck must be covered to avoid algae formation on the deck as the algae growth increases in the presence of sun light. 4. After installation of additional cell the pressure increases about 0.3-0.4 bar. 5. Wood is composed of 40-50 cellulose 20-35 hemi cellulose 25-35 lignin and 5-30 natural extractives. Long fibers of cellulose give wood its strength whereas lignin acts as cementing agent or binder for cellulose. The extractive is not part of structure but contributes properties such as color odor resistance to decay and density. These extractives contain chemicals like tannin poly phenolic oils fats waxes and resins. 6. The wood of the cooling water before installation must be in wet condition sprayers are provided as shown in the figure. 6. If the flow of C.W. in vacuum section not increases then throttle above mentioned B section valve i.e. heat exchanger above 5 meters height above ground subjected to above condition mentioned in Serial number 2. 7. Sure that Cooling water pumps discharge vale is full open and also check cooling water deck valves. 8. When charging the cooling water heat exchangers vent valves must be opened of each heat changer. 9. When cooling water header after shut down 1 st time charging the draining of dirty water including flouting material should be drained with opening of flange of ground floor heat exchanger.

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PERMANENT SOLUTION FOR LOW FLOW If the cooling water flow low after commissioning then one additional cell along with pump may be provided to increase the flow pressure as shown in the figures. 7. The sump along with pump of the additional cell is separated and connected through 20” pipe line. 8. One ID fan should be provided on top of the deck. 9. The Deck must be covered to avoid algae formation on the deck as the algae growth increases in the presence of sun light. 10. After installation of additional cell the pressure increases about 0.3-0.4 bar. 11. Wood is composed of 40-50 cellulose 20-35 hemi cellulose 25-35 lignin and 5-30 natural extractives. Long fibers of cellulose give wood its strength whereas lignin acts as cementing agent or binder for cellulose. The extractive is not part of structure but contributes properties such as color odor resistance to decay and density. These extractives contain chemicals like tannin poly phenolic oils fats waxes and resins. 12. The wood of the cooling water before installation must be in wet condition sprayers are provided as shown in the figure.

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Natural water is an excellent heat removal medium. Natural water contains impurities in form of dissolved gases dissolved solids and suspended solids. Natural water is either corrosive or scale forming. Untreated water in cooling water systems results in corrosion deposit formation and fouling. All the three problems are inter- related. This results in reduced operating efficiency of cooling tower and heat exchangers reduced production capacity increased maintenance cost and sometimes-significant downtime loss. Cooling water is treated to reduce above problems of corrosion of metals the formation of deposits and the growth harmful microorganism. Cooling water is treated to reduce water related problems and maintain efficient system. The desired cooling water parameters are monitored precisely. The parameters maintained are as follows: -

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Parameter Unit Normal Maximum PH -- 6.8 - 7.5 8.0 Turbidity NTU 5.0 20 Total Hardness as CaCO3 PPM 700-800 1000 Calcium Hardness as CaCO3 PPM 520 -- Magnesium Hardness as CaCO3 PPM 280 Total Dissolved Solids PPM 2200Max 3000Max Silica as SiO2 PPM 100 -- Chloride as Cl PPM 150-250 400 Total Phosphate as TPO4 PPM 4-8 4-8 Iron content as Fe PPM 1.0 1.5 Zinc as Zn PPM 1.0 1.0 Cycle of concentration 6-8 8 TBC Org/ml 100000 100000 SRB Org/ml 100 200 In order to maintain above parameters chemicals like acids alkalis oxidizing Biocides dispersants as per requirement are added. These chemicals in access quantity attacks the Timber used in Cooling Tower. The attack of chemicals affects the wood as indicted. 1. Chemical surface attack of wood caused by acids alkalis and oxidizing biocides. 2. Acids and alkalis are avoided by selecting right type of chemistry 3. Maintaining low free residual and use of non-oxidizing biocides minimizes oxidizing Biocides. 4. Leaching of preservation treatment accelerated by temperature PH and water flow. 5. Other constituent not found to contribute to wood deterioration.

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However precision control water chemistry is being maintained. Hence the chemicals normally do not influence the leaching rates of wood in normal circumstances. Extra care shall be taken in maintaining the critical parameters to reduce their effect on wood. In normal circumstances where parameters are precisely maintained our focus shall be on wood preservation and specie. During shutdown the anti-fungus chemical shall be sprayed with help of pneumatic sprayer.

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