Prepared by

Md. Shaha Jalal Maintenance Technician

In a Largest Multinational

Company

History

The pump suction is from river water to discharge to water boxes of steam condenser. It’s

a vertical shaft, 2,100 discharge bore mixed flow pump. It’s driven by an 1650 KW

vertically mounted motor with a rated full load rpm of 372. Rated flow rate of the pump is

29,000 m3/hr.

Specification of the Equipment

Pump Specification Manufacture HHI

Model Number 1800VKNM

Type Vertical Wet Pit

Capacity 29,000 m3/h

Total differential head 14.6 m

Pump speed 372 rpm

Efficiency 86.0%

Direction of rotation from motor driven end Clock wise

Motor Specification Rated kW 1650KW

Motor Type HRQ7 806-76V

Rated Voltage 6600 V

Phase 3 ᶲ

Full load amperes 224.6

Pole 16

RPM 372

Ins. Class F

HZ 50

BRG. (DE/NDE) NU244M/AV12SNT

WT 25 Ton

Before Maintenance Equipment vibration data

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

1 2 3 4 5 6 7

H,V

,A (

mm

/s)

Data no.

Motor & Pump Base line

Motor D/E H

Allowable

Just tolerable

MOTOR D/E V

MOTOR D/E A

Motor NDE H

Motor NDE V

Motor NDE A

Pump DE H

Pump DE V

Pump DE A

Pump NDE H

Pump NDE V

Pump NDE A

Dismantling Procedure

The motor-pump assembly was disassembled with the following steps:

The stop gate was inserted into the intake basin with the help of gantry crane. 3 submergible pumps (ф4” & ф3”) were being placed inside the intake basin to

continuously pump out water.

Note: before inserting the gate, it’s important to grease the slots of the gate; the slots

will guide thru the railing inside the basin.

The pump was then stopped and motor was isolated. Pump was decoupled from the motor and lift of the pump was noted as 9.5 mm

Note: there are 6 stud bolts and 6 reamer bolts in the coupling. Space nut is screwed to

the pump shaft and pump end hub is keyed to the shaft which drops down after loosening

the coupling bolts.

Cooling water lines had been removed. The motor and motor pedestal was sequentially removed by gantry crane 3 gland packing were removed by screw driver.

Gland and upper bearing housing were removed afterward; all these were lifted using eyebolt-shackle-belt assembly of appropriate sizes.

Elbow cover was lifted (after removing tow center pins) by the crane up to when the top spider hoisted over the column pipe as it was to be supported by H-beam underneath.

Elbow cover and upper shaft tube were unfastened sequentially.

Note: There is a distance ring which rests between elbow cover and upper shaft tube

which must be handled and kept safely.

Note: There is a tapering part in every leg of the spider and this side would face the

downside while assembling.

Upper spider along with the intermediate shaft tube was then dismantled after lifting the resting assembly as long as the lower spider was supported similarly.

The upper shaft was then separated from the lower shaft by dismantling the line shaft coupling & thrust ring using special tool as seen in the figure.

Lower spider, lower enclosure tube, discharge bowl and impeller were then taken out altogether and spider-tube was dismantled in similar fashion.

Discharge bowl was separated from the impeller-shaft assembly by removing the stopper ring.

Note: Match marking is provided in every part disassembled.

Shaft was disassembled separated from the impeller using an extractor.

Note: Impeller washer must be removed first before extracting impeller from the shaft

using special tool (mechanical jacking).

Casing wear ring was pulled using hydraulic jack & a fabricated special jack with nearly 100 bar of pressure. Impeller wear ring was extracted by tapping & unscrewing it.

Dummy Inspection

Dummy inspection refers to

checking whether discharge bowl

seats in its slots after assembling

it with only shaft tubes, spiders

and elbow cover.

After assembling all these and

tightening the elbow cover on its

bolts; a gap of 3 mm found

beneath the discharge bowl on its

seating slots. It had to be

compensated. A shim of 3 mm

was ordered instantly with same

shape of distance ring from

nearby workshop of stainless

steel.

Findings

Followings were the findings on disassembly:

After dismantling the whole pump it was observed that all the Ferro form bearings and their related shaft sleeves (Upper, Upper Intermediate, Lower Intermediate and Lower) surface were damaged (out of clearance). Its gland shaft sleeve and packing was out of use. Casing and impeller wear ring surface scratched badly and clearance between them were found high and irregular

Shaft Run out

We took shaft run-out and found the reading unusually high at one point for the upper

shaft. We also checked the upper shaft reading there also found one high reading at one

point.

Final run-out reading is attached here:

Dial gauge readings corresponding to the points on lower shaft

Dial gauge readings corresponding to the points on upper shaft

Assembly

Whole assembly was just the reverse of disassembly.

Before assembling, Ferro-form bearings were taken out and replaced by new one. We also

replace 3nos of (Packing, Inter and lower sleeve) shaft sleeves. Bearing clearances after

assembly are listed below:

Dimension of Bearing

SL Description ID OD Bearing Housing ID Length

1 Feroform Bearing (Upper) 205.65 mm 250.37 mm 250.08mm 295 mm

2 Feroform Bearing (Inter) 205.69 mm 250.30 mm 250.06mm 295 mm

3 Feroform Bearing (Inter) 205.70 mm 250.40 mm 250.09mm 295 mm

4 Feroform Bearing (Lower) 205.70 mm 250.35 mm 250.07mm 295 mm

Dimension of Shaft Sleeve

SL Description ID OD

1 Packing sleeve 189.91 mm 204.99 mm

2 sleeve(Upper) No Change

3 Sleeve (Inter) No Change

4 Sleeve (Inter) 189.90 mm 204.93 mm

5 Sleeve (Lower) 189.89 mm 204.93 mm

Greasing to all spider leg sides, O-ring grooves. Plating Molykote to the bolts, studs, sleeves, thrust rings, impeller washer, shaft

coupling & all other mating surfaces etc. Tightening the bolts in a crisscross pattern like the following:

Alignment

After reinstalling motor pedestal and motor, gap between motor coupling and pump

coupling was kept 9.65 mm by turning the space nut toward the motor hub ensuring the

required gap.

A steel scale was kept stood vertically in the hub surfaces and motor jacks were adjusted

to bring the required alignment.

When the centreline of the pump & motor was confirmed, the hubs were coupled with

reamer bolts. Now the tip clearances (radial clearances of the impeller and impeller liner

in the suction bell) were recorded. The values are:

Tip clearances were judged good. Now relative position of the shaft assembly against

static elbow cover-brg housing-gland was adjusted by adjusting motor. After adjustment,

alignment readings are as follows:

POS E W N S

1 1.77 1.6 2.95 1.65

2 1.97 1.8 1.9 2.11

3 1.8 1.76 2.05 1.9

4 1.95 1.98 2.9 1.85

Test run

After test run vibration data was measured and found ok.