MAINTENANCE PROCEDURES :

WARNING : IT IS ESSENTIAL THAT THE PLANT SAFETY RULES AND REGULATIONS ARE OBSERVED AT ALL TIMES DURING MAINTENANCE PROCEDURES.

Note : The Booster stage pump is an integral part of the Boiler feed pump set. The following instructions should, therefore, be read in conjunction with those for the pressure stage pump and the associated equipment.

3.1 Preparation for Maintenance :

Before commencing any maintenance procedures, the pump set must be Isolated as follows :

(1) Isolate the driving motor / turbine. Refer to manufacturer’s instructions.

(2) Isolate the electrical power supplies to all instruments.

3.2 Examining the Drive End (DE) Journal Bearing :

(1) Disconnect and remove any instruments which could interface with the dismantling procedures.

(2) Remove the drive / pump drive coupling guard.

(3) Disconnect the drive / pump coupling.

COUPLING : The top half bearing housing is located on the bottom half bearing housing by two dowel pins. Care must be taken to avoid damage to the dowel on the holes in the bottom half housing.

(4) Withdraw the dowel pins and remove the nuts from the studs securing the top of bearing housing to the bottom half bearing housing.

(5) Lift away the top half bearing housing complete with the top half oil guards.

Remove the top half journal bearing from the shaft.

(7) Take the weight of the pump shaft and rotate the bottom halves of the journal bearing and oil guards around the shaft and lift them away.

(8) Examine the journal bearing and shaft journal for signs of damage, scoring or deterioration and examine the journal bearing and the oil guards for wear. Reference should be made to the Sectional Arrangement Drawing HY-DG-188-139-0017 for the clearances of the journal bearing.

Note : Lightly smear the shaft and journal bearing surface with oil before final assembly.

(9) Rotate the bottom halves of the journal bearing and all rotating shields around the shaft and into position in the bottom half bearing housing.

Release the weight of the pump shaft.

Note : It is recommended that, at this stage, the thrust bearing axial clearance is checked and any necessary adjustments made before proceeding further.

Refer to section 3.3. in this chapter.

(10) Locate the top half journal bearing in position on the pump shaft.

(11) Lift the top half bearing housing complete with the top halves of the oil guards onto the bottom half bearing housing.

(12) Locate the top half bearing housing to the bottom half housing with the dowel pins, then secure the top half housing in position with the studs and nuts.

(13) Reconnect the drive/pump coupling.

(14) Replace the instruments and the drive/pump drive coupling guard.

3.3. Examine the non-drive End (NDE) Journal and Thrust Bearing :

(1) Disconnect and remove any instrument which could interface with the dismantling procedures.

(2) Remove the drive / pump drive coupling guard.

(3) Disconnect the drive / pump coupling.

(4) Remove the screws securing the bearing housing end cover to the top and bottom half bearing housings. Remove the cover and discard the joint.

CAUTION : The top half bearing housing is located on the bottom half bearing housing by two dowel pins. Care must be taken to avoid damage to the dowels or the holes in the bottom housing.

(5) Withdraw the dowel pins and remove the nuts from the studs securing the top half bearing housing to the bottom half bearing housing.

(6) Lift the top half bearing housing complete with the top half oil guard away.

Remove the top half journal bearing form the shaft.

(7) Unclip the spring and remove the split floating oil seal from the bearing housing.

Note : The thrust carrier ring split line is vertical to the bearing housing horizontal surface.

(8) Remove each thrust carrier ring in turn, as a complete unit, as follows : Rotate the complete carrier ring around the shaft until the half ring with the stop pin can be removed, then rotate the other half ring around the shaft until it can be lifted clear of the shaft. Repeat with the second carrier ring on the other side of the thrust collar.

(9) Take the weight of the pump shaft (i.e, support the shaft) and rotate the bottom halves of the journal bearing and the oil guard around the shaft and out of the bottom half bearing housing. Lift the halves of the bearing and guard away.

(10) Examine the journal bearing, shaft journal, thrust pads, thrust collar, split oil and oil guard for damage or deterioration. Under normal operation conditions it is not expected that any measurable wear will take place on the thrust pads other than a dulling of the white metal surfaces. It is

recommended that when this dulling has spread to more than half the surface area of the pads, they should be renewed.

Refer to the Sectional Arrangement Drawing and renew the components if necessary.

Note : Lightly smear the shaft, thrust collar faces and bearing surfaces with oil before final assembly.

(11) Support the shaft and rotate the bottom halves of the journal bearing and the oil guard around the shaft and into position in the bottom half bearing housing. Install the split floating oil seal on the pump shaft with the spring.

Release the weight of the pump shaft.

(12) Fit a new paper joint onto the end cover and secure the cover to the bottom half bearing housing with the screws.

(13) Install each thrust carrier ring in turn, as a complete until, as follows : Take the half carrier ring with out the stop pin and place it over the shaft with the pad faces touching the thrust collar and rotate it into the bottom half bearing housing, then place the other half carrier ring with the stop pin upon the first and rotate the complete carrier ring on the other side of the thrust collar.

Note : The thrust carrier ring split line is vertical to the bearing housing horizontal surface and the stop pin locates in a slot in the top half bearing housing.

(14) Check the axial clearance by moving the pump shaft towards the drive end so that the thrust collar is hard against the inner thrust pads; then, using feeler gauges between the outer thrust bearing spacer and the end cover check the clearance. Refer to the Sectional Arrangement Drawing HY-DG-188-139-0017 for the original total axial clearance. Any measurable variation should be investigated.

Note : (a) Do not insert feeler gauges between the thrust collar and the thrust pads: this may give an inaccurate reading and cause damage to the white metal pad surface.

(b) The end cover must be secured in position to check the total axial clearance.

(15) Locate the top half journal bearing in position on the pump shaft.

(16) Lift the top half bearing housing complete with the top half oil guard onto the bottom half bearing housing ensuring that the carrier ring stop pins are properly located.

(17) Locate the top half bearing housing to the bottom half bearing housing with the dowel pins, then secure the top half housing in position with the studs and nuts.

(18) Secure the bearing housing end cover to the top half housing with the screws.

(19) Install the drive/pump drive coupling spacer and element assemblies.

(20) Replace the instruments and the drive / pump drive coupling guard.

4. OVERHAUL :

The following instructions apply when the pump is due for a complete overhaul and it is necessary to dismantle it to its components parts to examine them for wear. The following procedures are intended as a guide and should be read carefully by the engineer before commencing to dismantling the pump.

WARNING : IT IS ESSENTIAL THAT THE PLANT SAFETY RULES AND REGULATIONS ARE OBSERVED AT ALL TIMES DURING MAINTENANCE PROCEDURE.

4.1 Preparation for Overhaul

Before commencing overhaul procedures, the pump set must be isolated as follows :

(1) Isolate the electrical power supplies to the pump set driving motor / turbine and the lubricating oil system (refer to manufacturer’s instructions).

(2) Isolate the electrical power supplies to all instruments.

CAUTION : The pump set pipe work and halves are not in pumps scope of supply. Reference therefore, should be made to the system instructions for the isolation of the pump set.

(3) Check that the pump set suction, discharge and leak-off isolating valves are shut.

(4) Check that the cooling water has been isolated.

(5) Open the drain and vent connections and drain the pump casing.

WARNING : BEFORE PROCEEDING WITH OVERHAUL OF THE PUMP, ENSURE THAT THERE IS NO PRESSURE WITH IN THE PUMP CASING.

(6) Disconnect and remove any instrument which could interfere with the dismantling procedures.

(7) Disconnect and remove any small bore pipe work which could interfere with the Dismantling procedures.

(8) Check that all lifting equipment and special tools are in good condition.

Note : All the shaft nuts have right hand threads.

4.2 Dismantling The Pump :

(1) Remove the drive / pump drive coupling guard.

(2) Remove the drive / pump drive coupling spacer and element assemblies.

CAUTION : The top half bearing housing is located on the bottom half bearing housing by two dowel pins. Care must be taken to avoid damage to the dowels or the holes in the bottom half housing.

(3) Withdraw the dowel pins and remove the nuts from the studs securing the drive end top half bearing housing to the bottom half bearing housing.

(4) Lift away the top half bearing housing, complete with the top halves of the oil guards. Remove the top half journal bearing form the shaft.

(5) Remove the screws securing the bearing housing end cover to the non-drive end top and bottom half bearing housings. Remove the cover and discard the joint.

CAUTION : The top half bearing housing is located on the bottom half bearing housing by two dowel pins. Care must be taken to avoid damage to the dowels or the holes in the bottom half housing.

(6) Withdraw the dowel pins and remove the nuts from the studs securing the non-drive end top half bearing housing to the bottom half bearing housing.

(7) Lift away the top half bearing housing, complete with the top half / oil guard.

Note : The thrust carrier ring split line is vertical to the bearing housing horizontal surface.

(8) Remove each thrust carrier ring in turn, as a complete unit, as follows : Rotate the complete carrier ring around the shaft until the half ring with the stop pin can be removed, then rotate the other half ring around the shaft until it can be lifted clear of the shaft. Repeat with the second carrier ring on the other side of the thrust collar.

(9) Slacken the securing socket head cap screws and rotate the mechanical seal eccentric washers to locate in the seal sleeve groove. Lock the washers in this positions.

(10) Remove the grub screws securing the seal sleeve to the shaft.

(11) Remove the socket head screws securing the seal plates to the water jackets at the drive and non-drive end of the pump casing.

(12) Remove the socket head screws securing the water jackets to the pump casing at the drive and non-drive end of the pump casing.

CAUSING : The top half pump casing is located on the bottom half casing by two dowel pins. Care must be taken to avoid damage to the dowels or the holes in the bottom half casing.

(13) Withdraw the dowel pins and remove the nuts from the studs securing the top half pump casing to the bottom half pump casing.

(14) Attach lifting equipment to the cast lugs on the top half pump casing.

(15) Use the jacking screws to break the pump casing joint, then lift the top half casing clear of the bottom half casing to expose the rotating assembly.

Discard the pump casing joint.

(16) Attach lifting equipment to the rotating assembly and lift the assembly complete with casing rings, water jackets and mechanical seals clear of the bottom half pump casing.

(17) Transport the assembly to a suitable maintenance area and support the assembly on wooden stands or trestles so that the impeller is clear of the ground.

(18) Remove the bottom halves of the journal bearings and the oil guards from the drive and non-drive end bottom half bearing housings.

(19) Slacken the coupling nut lock washer, unscrew and remove the coupling nut.

(20) Withdraw the pump half coupling from the shaft. Remove and retain the coupling key.

(21) Slide the driven end mechanical seal cartridge off the shaft. Remove and retain the sleeve key. For dismantling instructions for the mechanical seal, refer to the manufacturer’s instructions in Chapter-4.

(22) Withdraw the drive end water jackets from the shaft, then lift the casing wear ring off the impeller.

(23) Unlock the thrust collar nut lock-washer, then using the special spanner supplied, unscrew and remove the nut. Remove and retain the lock-washer.

(24) Withdraw the thrust collar from the shaft. Remove and retain the thrust collar key.

(25) Remove and retain the split floating oil seal.

(26) Slide the non-drive end mechanical seal cartridge off the shaft. Remove and retain the sleeve key. For dismantling instructions for the mechanical seal, refer to the manufacturer’s instructions in Chapter-4.

(27) Withdraw the non-drive end water jacket from the shaft, then lift the casing wear ring off the impeller.

4.3 Inspection and renewal :

The pump components should be cleaned thoroughly then inspected for any signs of wear including scoring or wiping.

All diametrical clearances should be measured with internal and external micrometers.

4.3.1 Clearances

Refer to the Sectional Arrangement Drawing for the details of the clearances. It is recommended that when the pump internal clearances have reached 1.5 times the figure quoted or are expected to do so before the next overhaul, the component or components should be renewed. The main consideration, however, is pump performance and motor power consumption.

4.3.1 (1) Examine the impeller and casing wear rings for signs of wear or damage.

Check the diametrical clearance between the impeller and casing wear rings. Compare the readings obtained with those given. If necessary, renew the wear rings.

(2) Renew the impeller wear rings as follows:

(a) Remove the grub screws securing the wear rings to the impeller.

(b) Machine the wear rings from the impeller eyes.

(c) Thoroughly clean the seating and shrink the spare wear rings onto the Impeller shrouds.

(d) Secure the wear rings to the impeller shrouds with grub screws. Lock the grub screws by light punching with a center punch at the thread junctions.

A. Machine the outside diameter of the impeller wear rings to required diameter to achieve diametrical clearance between the impeller and casing wear rings as given on the Sectional Arrangement Drawings.

4.3.3 Impeller

Examine the impeller for signs of wear or erosion, especially around the blade tips.

4.3.4 Pump Shaft ends Sleeves

(1) Examine the pump shaft for signs of damage or bowing and check for concentricity; it should be within 0.05 mm full indicator movement.

(2) Check that all threads are in good condition.

(3) Check that all keyways are free form burrs.

(4) Examine the seal sleeves for any signs of wear or damage.

4.3.5 Thrust collar and Floating oil seal

(1) Examine the thrust collar for any signs of wear or damage.

(2) Examine the floating oil seal for any wear or damage.

4.3.6 Studs, Nuts, Dowels and Keys

(1) The threads of all studs, screws and nuts must be clean, well formed and free from burrs. If the threads are damaged in any way, the component must be renewed.

(2) All keys must be good fit in their key ways and must also be flat, parallel and free from burrs. Worn or damaged keys must be renewed.

(3) All dowels must be clean and free from damage or deterioration. Worn or damaged dowels must be renewed.

4.3.7 Joints and ‘O’ Rings

All joints and ‘O’ rings should be renewed on assembly. Apply soft soap to all ‘O’ rings prior to assembly.

4.3.8 Journal Bearings

Inspect the journal for signs of wear or damage and renew as necessary.

4.3.9 Thrust Bearing

Under normal operating conditions it is not expected that nay measurable wear will take place on the thrust pads other than a dulling of the white surfaces. It is recommended that when this dulling has spread to more than half the surface area of the pads, they should be renewed. Refer to Manufacturer instructions in Chapter 4.

4.3.10 Mechanical Seals

Information on dismantling and examining the mechanical seals is given in the Manufacturer’s instructions in Chapter – 4.

4.3.11 Fitting a Spare Impeller

The impeller should only be removed from the shaft if it is found necessary to fit a spare impeller or shaft. To renew the impeller, carry out the following instructions.

CAUTION : Before removing the impeller from the pump shaft it is important to identify the correct rotating direction of impeller blades and also the position of the impeller on the pump shaft for assembly purposes.

(1) Unlock the impeller nut lock-washers, then using the special spanner provided, unscrew and remove the impeller nuts and lock-washers from each end of the pump shaft.

(2) Withdraw the impeller from the pump shaft. Removed and retain the impeller key.

(3) Check that the key fits correctly in the spare impeller or shaft key way.

(4) Fit the impeller on the shaft, ensuring the impeller key way is lined up accurately with the key.

(5) Ensure that the impeller is fitted correctly for the direction of rotation and also its original position on the shaft.

(5) Secure the impeller on the pump shaft with the impeller nuts and lock-washers.

4.4 Assembling the Pump

To assist the assembly procedure, all fittings and threads should be smeared with anti-scuffing paste.

(1) Support the pump shaft / impeller assembly on wooden trestles.

(2) Locate the casing wear rings on the impeller shrouds, then slide the water jackets, with new joints fitted, on to each end of the shaft.

(3) Ensure that a new ‘O’ ring is located in the internal groove of each seal sleeve and the groove in the seal plate face.

(4) Insert the seal sleeve keys into their keyways and slide the mechanical seal cartridges on to each end of the shaft, ensuring that the sleeve keys engage in the keyways in the bores of the sleeves.

(5) Insert the coupling key into its keyway in the shaft and install the half coupling, ensuring that the key engages in the keyway in the half coupling bore.

(6) Screw on and tighten the coupling nut and screw it in position with the lock screw.

(7) Insert the thrust collar key into its keyway in the shaft. Apply heat to the thrust collar hub until the bore of the collar is expanded sufficiently to slide the collar onto the shaft.

(8) Slide the thrust collar onto the shaft until butts against the shoulder, ensuring that the key engages in the keyway in the thrust collar bore.

(8) Slide the thrust collar onto the shaft until butts against the shoulder, ensuring that the key engages in the keyway in the thrust collar bore.

In document BFP BHEL Manual for 500MW (Page 47-59)