Condenser Vac Pump[1]

GOOD PRACTICES IN INSTALLATION AND OPERATION OF VACUUM PUMPS AT SITE

PRESENTED BY: HEAT EXCHANGER ENGG. HARIDWAR

(20/04/09)

BEST PRACTICES IN SITE OPERATION VACUUM PUMPS

INTRODUCTION: 

CONDENSER AIR EVACUATION SYSTEM COMMONLY CALLED VACUUM PUMPS, ARE INSTALLED AT VARIOUS THERMAL POWER PLANTS TO - CREA CREATE TE INITIAL INITIAL VACUUM BY REMOVIN REMOVING G AIR PRESENT PRESENT IN THE SYSTEM (HOGGING MODE) - DURING OPERATION, ASSIST CONDENSER IN MAINTAINING MAINTAINING VACUUM BY REMOVING LEAKED IN AIR & NON-CONDENSIBLE GASES FROM THE SYSTEM (HOLDING MODE).

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VACUUM PUMPS ARE EFFICIENT & RUGGED UNITS AND ARE HIGHLY PREFERRED FOR HIGHER RATING SETS AS THEY PROVIDE TROUBLE FREE SERVICE. BHEL HAS SUPPLIED MORE THAN 400 VACUUM PUMPS TO VARIOUS SITES SINCE 1985 WHICH ARE OPERATING SATISFACTORILY.


INTRODUCTION (CONTD): 

REDUCED COMMISSIONING CYCLES REQUIRE RELIABLE DESIGN & MANUFACTURING, SHORTER DELIVERIES & PROPER STORAGE & PRESERVATION AT SITES.

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IN THE LAST 2 YEARS THERE HAVE BEEN SOME INSTANCES WHERE POWER STATIONS HAVE EXPERIENCED PROBLEMS DURING INITIAL START-UP OF THE PUMPS CAUSING AVOIDABLE DELAYS.

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IN VIEW OF THE ABOVE, NEED TO ADOPT “GOOD PRACTICES” DURING VARIOUS STAGES HAS BECOME NECESSARY FOR TROUBLE FREE OPERATION OF THESE CRITICAL EQUIPMENTS.


TYPICAL VACUUM PUMP ARRANGEMENT Air Leaks

CONDENSER

Cooling Water Vacuum Pump

Heat Exchanger

BEST PRACTICES IN SITE OPERATION VACUUM PUMPS VACUUM PUMP PACKAGE VIEW CHECK VALVE

SEPARATOR ROTAMETER

AIR INLET

CONTROLS MOTOR

LEVEL SWITCH

PUMP

R/C PUMP

PUMP SKID


WORKING OF LIQUID RING VACUUM PUMP


SOME COMMON PROBLEMS ENCOUNTERED AT SITES: 1.

JAMMING OF VACUUM PUMPS (NASH MODEL TC-11E, EDWARDS MODEL SHR 22500) FOUND DURING INITIAL COMMISSIONING.

2. JAMMING OF VACUUM PUMP DURING OPERATION. 3. TRIPPING OF VACUUM PUMP ON OVERLOAD. 4.

IMPELLER AND CONE CRACKING IN VACUUM PUMPS (NASH MODEL TC-11E).

5.

CONTINUOUS DISCHARGE THROUGH SEPARATOR OVERFLOW LINE (PUMP MODEL TC-11E) DURING OPERATION.

6.

DURING HOGGING, SEAL WATER POURING OUT HEAVILY FROM SEPARATOR AIR EXHAUST.


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THIS PRESENTATION FOCUSES ON THE FOLLOWING ASPECTS OF VACUUM PUMPS: 

CARE ON MATERIAL RECEIPT.

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STORAGE AND CONSERVATION.

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ERECTION / INSTALLATION.

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COMMISSIONING AND OPERATION.

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STORAGE DURING SHUT-DOWN.


MATERIAL RECEIPT: 1. VISUAL INSPECTION TO ESTABLISH RECEIPT OF PACKAGE IN GOOD CONDITION. 2. CHECK FOR COMPLETENESS OF THE PACKAGE. ANYTHING MISSING/ APPARENTLY DAMAGED MUST BE REPORTED SO THAT IT CAN BE TAKEN UP WITH VENDOR WITHIN WARRANTY PERIOD.


INITIAL STORAGE AND CONSERVATION: 1. VACUUM PACKAGES SHOULD BE PLACED ON PUCCA/ SEMI PUCCA GROUND UNDER SHED / TARPAULIN. 2. PACKAGE OPENED FOR INSPECTION SHALL BE SUBSEQUENTLY COVERED WITH TARPAULIN TO SAVE IT FROM RAIN, DUST AND PHYSICAL DAMAGE. DUST AND DIRT HARMS THE DELICATE INSTRUMENTS & FITTINGS 3. PRIOR TO SHIPMENT FROM WORKS, VACUUM PUMP IS FLUSHED WITH WATER SOLUBLE PRESERVATIVES WHICH CAN LAST ABOUT 6 MONTHS (IT CAN THEN DRY UP AND SEIZE THE PUMP); PUMP IMPELLER SHOULD THEN BE ROTATED BY 1 OR 2 TURNS MANUALLY ONCE IN 15 DAYS. THIS IS TO PREVENT ANY SEIZURE/ JAMMING OF PUMP TILL COMMISSIONING.


ERECTION/ INSTALLATION: 1. THE UNIT IS TO BE LEVELED BY SHIMMING AT THE FOUNDATION BOLTS. PUMP & MOTOR SHAFTS ARE TO BE FIELD ALLIGNED. 2. FOREIGN MATTER LIKE PIPE SCALES, SCRAP METAL, COTTON WASTE ETC. SHOULD BE REMOVED BY FLUSHING AIR INLET AND MAKE-UP WATER PIPING, BEFORE CONNECTING TO THE UNIT. 3. THE SCREEN AT THE AIR-INLET SHOULD NOT BE REMOVED FOR AT LEAST 3-MONTHS OF INITIAL OPERATION. FOREIGN MATTER CAN DAMAGE/ BREAK PUMP INTERNALS AND DAMAGE MAKE-UP WATER SOLENOID VALVE. 4. AIR & WATER PIPING SHOULD BE ERECTED SUCH THAT IT IS CONNECTED TO PUMP UNIT WITHOUT SPRINGING OR PULLING ON THE PIPING. THIS IS TO AVOID FORMATION OF ANY AIR GAPS IN PIPE JOINTS


DEBRIS ON MAKE-UP SOLENOID VALVE


OPERATION & COMMISSIONING: 1. VACUUM PUMP SHOULD NOT BE OPERATED WITHOUT ADEQUATE INITIAL PRIMING AND SEALWATER AND COOLING WATER FLOW. POOR EVACUATION CAPACITY, DAMAGED GLAND PACKINGS. 2. SEAL WATER TEMPERATURE DROP IN HEAT EXCHANGER SHOULD BE ABOUT 8 DEG. C. CHECK STRAINER, ORIFICE UNION, SPRAY NOZZLES (IF PROVIDED) FOR BLOCKAGE AND CLEAN, IF REQUIRED. CW TEMP. RISE SHOULD BE ABOUT 2-3 DEG.C.

HIGH SEAL WATER TEMPERATURE RESULTS IN CAVITATION.


OPERATION & COMMISSIONING: (CONTINUE) 3. THERE SHOULD BE A LEAKAGE OF ABOUT 60 TO 100 DROPS OF WATER PER MINUTE FROM THE GLANDS (NOT APPLICABLE FOR PUMPS WITH MECHANICAL SEALS). THIS IS TO AVOID AIR INGRESS THROUGH VACUUM PUMP. 4. DO NOT START THE PUMP IF LEVEL OF SEALING WATER IS ABOVE THE PUMP CENTRE LINE (EXCESSIVE SEAL WATER) OR LESS THAN “LOW LEVEL” (INADEQUATE SEAL WATER). EXCESSIVE SEAL WATER RESULTS IN TRIPPING OF PUMP. INADEQUATE SEAL WATER REDUCES EVACUATION CAPACITY. 5. CHECK FOR ANY BLOCKAGE OF EXHAUST CHECK VALVE OR ITS LEVER AND MAKE IT FREE.


STORAGE DURING SHUT DOWN: 1. SHORT TERM STORAGE: DRAIN PUMP OF SEAL WATER AND ONCE IN EVERY TWO WEEKS, MANUALLY ROTATE THE PUMP BY 1-2 TURNS. 2. LONG TERM STORAGE: AFTER DRAINING PUMP OF SEAL WATER, SPRAY A SUITABLECORROSION INHIBITOR (SUCH AS MOBIL-OIL) THROUGH PUMP INLET AND DISCHARGE OPENINGS. ONCE IN A MONTH, MANUALLY ROTATE THE PUMP BY 1-2 TURNS. THIS IS TO PREVENT SEIZURE/ JAMMING.


SUMMARY OF RECOMMENDATIONS/ GOOD PRACTICES FOR TROUBLEFREE OPERATION OF VACUUM PUMPS 

DURING INITIAL START-UP : - WASH AWAY INTERNAL PRESERVATIVE USING WATER, THRU’ TEMPORARY LINES, TILL CLEAR WATER DRAINS OUT. - IN CASE OF PROLONGED STORAGE, REMOVE CORROSION SCALES WITH DIESEL. DRAIN OUT DIESEL. - MANUALLY ROTATE THE IMPELLER TO ENSURE IT ROTATES FREELY. - THE SCREEN PROVIDED WITH PUMP PACKAGE AT AIR INLET IS TO BE RETAINED FOR AT LEAST 3-MONTHS AND ITS CLEANLINESS ENSURED.


SUMMARY OF RECOMMENDATIONS/GOOD PRACTICES(..contd) - DM WATER MAKE-UP LINE TO BE FLUSHED THOROUGHLY BEFORE CONNECTING TO MAKE-UP SOLENOID VALVE. - VACUUM SYSTEM SHOULD BE LEAK TIGHT TO PREVENT SUCTION OF LARGE AIR QUANTITY CONTINUOUSLY. - VACUUM PUMP TO START AFTER CHECKING WATER LEVEL IN SEPARATOR MORE THAN ‘MINIMUM’ AS INDICATED BY LOW LEVEL SWITCH. - SEAL WATER PUMP TO START SIMULTANEOUSLY AFTER CHECKING ‘MAIN MOTOR’ HAS STARTED. - THE EXHAUST CHECK VALVE SHOULD BE CHECKED FOR ITS FREE MOVEMENT AND PROPER CLOSING.


SUMMARY OF RECOMMENDATIONS/GOOD PRACTICES(..contd) - THE AIR PRESSURE TO INLET VALVE ACTUATOR SHOULD BE ENSURED TO BE MORE THAN 5 kg/sq.cm. 

DURING OPERATION / SHUT DOWN: - SHIFT OPERATION TO STAND-BY PUMP ONCE EVERY WEEK OR EARLIER. - DRAIN OUT SEAL WATER COMPLETELY FROM THE SYSTEM DURING SHUT DOWN & DRY-OUT COMPLETELY. - THE PUMP SHOULD BE ROTATED MANUALLY AT LEAST ONCE EVERY 15 DAYS TO PREVENT HARD SCALE FORMATION. - MAINTAIN DM WATER QUALITY.


SUMMARY OF RECOMMENDATIONS/GOOD PRACTICES(..contd) 

OTHER INITIATIVES: - SUPERVISION BY VENDOR DURING INITIAL COMMISSIONING. - INTRODUCTION OF PRE-COMMISSIONING LOG SHEETS.

Condenser Vac Pump[1]

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