Water pump failures- quality
audit.
There have been four cases of water
pump failures in last two months. Details are
given below:-
|
SN
|
Loco No.
|
|
Date of
fitment
|
Date of
failure
|
Service
Life(month)
|
Cause
|
|
1
|
17955
|
|
18.11.10
|
15.4.12
|
16
|
Water
pump shaft impeller key sheared.
|
|
2
|
17745
|
|
13.3.10
|
20.4.12
|
25
|
Water
pump shaft impeller key sheared.
|
|
3
|
16681
|
|
25.5.10
|
1.5.11
|
12
|
Shaft broken near
key and sleeve end.
|
|
4
|
16640
|
|
9.11.10
|
11.5.12
|
22
|
Water
pump shaft impeller key sheared.
|
|
5
|
6272
|
|
16.11.10
|
26.8.11
|
9
|
Shaft broken.
|
|
6
|
6272
|
|
27.8.11
|
15.9.11
|
1
|
Impeller and shaft
broken.
|
|
7
|
6362
|
|
18.2.10
|
18.5.12
|
27
|
Impeller
and shaft broken.
|
Water pump had failed within 1-27
months of service due to key/key way damage.
Key and key way are not load bearing
areas and these should be treated as locking mechanism at best notwithstanding Shed’s
everlasting quest for better quality key to take care of complete load.
Water pump shaft & impeller
related failures can easily be avoided, if following points are kept in mind
and understood by concerned technicians and sectional supervisors.
1.
Avoid pressure &
intermittent thrust on key & key way- This can be done by ensuring
that load is fully shared by shaft and impeller. No relative movement however small
can be permitted.
2.
Maintain uniform
interference fit
across shaft and impeller. This can be ensured by measuring OD of shaft at four
points and ensuring no variation. Simultaneously impeller ID at 4 locations
should be measured and no Ovality should be permitted. Interference of 1.5-2
thou should be maintained.
3.
Colourmatch the
contact area
to check uniform contact. It will ensure permanent grip and distribute stress uniformly.
(contd..2)
(2)
4.
No loosening of nut
in service-
Replace the nut during overhauling. Use thread locking compound to ensure it
remains locked and does not open in service. Nut should be tightened at
175ft-lb.
5.
All
pressing must be uniform, gradual. It
should be pressed slowly under hydraulic press without any hammering. Mating
surface should be profusely filled-up with sealant to ensure perfect fit.
6.
Monitor all
measurement, interference as per check sheet to ensure desired accuracy. Use of
new impeller during every overhauling along with new shaft should be done.
Proper interference between key and keyway to be ensured. Key height should be
such that it should not bite impeller during fitment.
7.
Water seal of only approved
source should be used. Complete information regarding shop fitted Water pump parameters
like interference, make of water seal, L.oil seal should be obtained from shop.
If found inappropriate according to Shed practice, the Water pump should be
changed. Similar attention for transferred locos should be done.
8.
Quality audit of
sectional maintenance practices by deputing AME/D and ACMT should be done and
report should be sent to HQ within ten days.
Enclo: Two
Quality audit Checklist.
1.
Specification
of water pump assembly. Please check whether components are conforming to latest drawings.
1.1 Water pump shaft to drawing No. SKDP-4117
1.2 Water pump impeller to Part/Drg No.
10124664/TPE-01-0054 Alt ‘e’.
1.3 Sleeve as per Part/Drg No. 10210866/25D72053-1 Alt ‘e’.
1.4 Lock nut as per Part/Drg No. 15380166/TPE-13-0002 Alt ‘c’.
1.5 Key as per Part/Drg No. 15311090/2P78004-032.
2.
Are
components viz water pump shaft, impeller, impeller sleeve, key, washer and
lock nut procured from approved suppliers only.
3.
Replacement
criteria- Must replacement item like shaft, impeller, bearing, oil seal, water
seal etc changing frequency during M12/M24.
4.
Visual
inspection parameters of each component before fitment.
5.
Lab
testing of shaft, DPT & UST.
6.
Checking
of bearing condition and end play
7.
Measurement
of dia at various locations, limits and practices followed.
8.
Vulnerable
locations and how they are checked.
9.
Measurement
of hardness limit- practice.
10. Surface finish.
11. Sample checking of
Metallurgical composition.
12. Impeller sleeve
replacement on ID, limits followed for wear and Ovality.
13. Interference fit-
four point measurement and record of ID/OD of shaft and impeller.
14. Condition of thread.
15. Renewal and checking
of nut and its condition.
16. Use of thread
locking compound.
17. Dismantling
practices- tools and fixtures used Hydraulic Jack. Use of proper cooler
arrangement to avoid damage to shaft and impeller.
18. Assembly practices.
19. Torque value used
for the tightening of the lock nut shall be taken as 175 ft-lb.
20. Bearing condition
check
Dia check
Interference check
Fitment procedure.
21. Seal checking
Fitment
Seal spring checking and
securing with adhesive.
22. Practice of examining
released components to see sign of distress/ damage/residual life
23. Record keeping
24. Printed formatted register
exhibiting acceptable limits for each parameter.
25. ID & make of
components are being etched, recorded/not recorded.
26. Service life
recorded/analysis.
27. Calibration of gauge
28. Availability of
tools and its status.
29. Availability of test
benches, fixtures in section.
30. Skill and knowledge
gradation of each sectional staff.
Check
Sheet for Water Pump
Unit No.
:
Fitted on Loco No. : Date : Schedule
:
|
S/No.
|
Item
|
New
|
Old
|
Dimension
|
Remarks
|
|||||
|
1.
|
Impeller
|
|
|
Bore dia -
|
|
|||||
|
2.
|
a.
|
Shaft Dia at
Impeller seat
|
|
|
Std. -
|
|
||||
|
b.
|
Interference
|
0.001”-0.002”
|
|
|||||||
|
3.
|
Impeller Key
|
|
|
|
|
|||||
|
a.
|
Key dimension
|
|
|
(LXWLH)k
|
|
|||||
|
b.
|
Shaft keyway
|
|
|
(LXWLH)s
|
|
|||||
|
c.
|
Impeller keyway
|
|
|
(LXWLH)1
|
|
|||||
|
d.
|
Total height
(shaft+Impeller)
|
|
|
Hs+H1>Hk
|
|
|||||
|
Note : Key way width in impeller and
shaft to be equal so that key width will be uniform in impeller and shaft.
|
||||||||||
|
4.
|
Make
|
Mfg. Dt.
|
|
|
Water Seal
|
|
||||
|
|
|
|
||||||||
|
5.
|
Seal Plate
|
|
|
Bore dia – 2.750 /
2.75
|
|
|||||
|
6.
|
Make
|
Mfg. Dt.
|
|
|
Oil Seal
|
|
||||
|
|
|
|
||||||||
|
7.
|
Hub Slinger
|
|
|
|
|
|||||
|
8.
|
Bearing sleeve /
shaft
|
|
|
|
Std.
|
Observed
|
|
|||
|
Shaft dia
|
2.1655-2.166
|
|
||||||||
|
Sleeve ID
|
2.1644-2.165
|
|
||||||||
|
Sleeve OD
|
2.860-2.863
|
|
||||||||
|
9.
|
Bearing 6311 /
shaft
|
|
|
Bearing ID
|
2.164
|
|
|
|||
|
Make
|
Mfg.Dt.
|
Shaft OD
|
2.1655-2.166
|
|
||||||
|
|
|
Interference
|
|
|
||||||
|
Bearing OD
|
4.725
|
|
||||||||
|
10.
|
Bearing 6312 /
shaft
|
|
|
|
Std.
|
Observed
|
|
|||
|
Shaft OD
|
2.3623-2.3628
|
|
||||||||
|
|
2.361
|
|
||||||||
|
|
|
|
||||||||
|
|
5.119
|
|
||||||||
|
11.
|
Gear Key
|
|
|
Size – ½ X ½ X 2 “
|
|
|||||
|
12.
|
Gear
|
|
|
Bore dia -
|
No. of teeth
|
|||||
|
Make
|
Year
|
Gear Seat –
2.314-2.3135
|
||||||||
|
|
|
|||||||||
|
13.
|
Frame bearing
|
|
|
|
Std.
|
Observed
|
|
|||
|
Bore dia-6311
|
4.724 / 4.725
|
|
||||||||
|
Interference
|
|
|
||||||||
|
Boredia-6312
|
5.117 / 5.119
|
|
||||||||
|
Interference
|
|
|
||||||||
|
14.
|
Impeller casing
|
|
|
|
|
|||||
OVH by :
___________ Date of OVH ___________
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