Failures of EMD Power assembly in HHP locomotives of a Diesel Shed.

Large no. of power assembly failures have been observed recently in HHP locos of a Diesel Shed.

Total 13 locomotives have failed on line in last three years. Year wise failures are as follows:

Year	2010-11	2011-12	2012-13
Total	0	3	10
Loco holding	71	122	152
Cases /100 loco	0.0	2.5	6.6

Failure of power assembly year wise is given below.

Year	2010-11		2011-12		2012-13
	Shed detection	Line failure	Shed detection	Line failure	Shed detection	Line failure
	2	0	2	3	21	10
Total	2		5		31

Failures of Power assembly have shown abnormal increase in the year 2012-13.

The cause wise failures are given below:

Cause	2010-11		2011-12		2012-13		Total
	line	Shed	Line	Shed	Line	Shed
Thrust washer wear				2		2	4
Blow hole in liner/ head		1				1	2
con rod broken					3	1	4
Compression ring inline						1	1
Exhaust valve broken			1		4	3	8
Carbon deposit in valve seat and valve						5	5
Liner crack						3	3
Oil throwing						1	1
Piston crown crack			1				1
Lifting hole crack					1	1	2
Stud bolt loose			1		2	3	6
Test valve defective	1						1
Total	1	1	3	2	10	21	38

Observations:

Exhaust valve breakage (21.5%), Loosening of liner to cylinder head stud bolt (15.7%), Carbon deposition on valve (13%), Thrust washer wear (10.5%), Con rod broken (10.5%) and Liner crack (8%) are major areas of concern.

Service life wise failures are as follows:

Item	0-1 year	1-2 years	2-3 years	3-4 years	4-5 years	5-6 years	> 6 years	Total
Thrust washer			1	1	1		1	4
Blow hole in liner/ head	1		1					2
con rod broken	1					1	2	4
Compression ring inline			1					1
Exhaust valve broken				6	1		1	8
Carbon deposit in valve				1	3		1	5
Liner crack	1				1		1	3
Oil throwing	1							1
Piston crown crack			1					1
Lifting hole crack					2			2
Stud bolt loose		5		1				6
Test valve defective		1						1
Total	4	6	4	9	8	1	6	38

Observations:

·        14 (38%) power assembly failed before 3 years of service life.

·        18 power assemblies failed within 3- 6 years of service life.

·        Six failures were in loco running six yearly overdue. Now no loco is permitted to run overdue six yearly schedule.

·        23.6% failures are between 3 to 4 years of service.

·     02 cases of directly imported fully assembled power assembly failures  on test bench( prior to fitment in locomotives)

·     Loco no 12573 failed within 130 days of commissioning due to Lube oil throwing in air chamber and Loco no. 12691 failed within 123 days of commissioning due to No.15 Power Assembly  Con rod  breakage damaging Engine block and crankshaft. Failed components have been sent to DLW lab for analysis.

·      Exhaust valve breakages cases are pronounced after 3-4 years of service.

·      19 Locos are running with locally made valve lever lubricating pipe gasket.

·      17 locos are running with old upper con rod bearing shell.

·      Availability of tools and gauges as per MI has not been ensured in section.

Auditing of maintenance practice was conducted. Major discrepancies observed are:

·        Measurement and trend monitoring of Exhaust gas temperature and turbo inlet temperature monitoring is not done in running schedule.

·        Checking the working of soak back pump by opening No.16 crankcase cover is not being done in running schedule.

·        Compression pressure checking is not conducted in 90 days schedule.

·        Exhaust screen checking and piston crown checking is also not done in 90 days schedule.

·        Engine stabilization temperature, Differential temperature checking across heat exchangers  and block is not being done  in 90 days schedule.

·        Lead wire test is also not conducted in   Yearly schedule.

·        Removal of two nos. injector for testing opening pressure is also not done in yearly.

   During  3Yearly schedule following item are not attended/checked:

·        System flushing and draining

·        Bottom main bearing changing

·        Inspection of bottom gear damper.

·        Inspection of Rocker arm bushing.

·        Removal and air cleaning of inertial filter

·        Checking of Lube oil by pass valve

·        U/V light checking for fuel oil leakage.

   6yearly schedule following item are not attended/checked:

·          Removal of cam shaft and inspection.

·          Renewal of crankshaft damping device.

·          Condition basis replacement of lower liner insert

·          Checking of crankcase oil pan.

·          Keeping engine running for 24 hours without load.

·          Re-torquing of power pack fasteners at 70° C after load test.

·          Re-torquing of power pack fasteners after 100 Hrs of running.

·          Camshaft stub shaft bearing qualification.

To improve reliability and life of Power assembly following attention should be given

 Commissioning:

·        Tightness of crab nuts should be checked and retorqued. For torquing a power assembly 400 ft-lb initial torquing given to in-board crab nut and then out board nut. Crab nut is torqued to 2400 ft-lb torque by a calibrated power wrench.

·        Liner to cylinder head studs should be re-torqued in all previously commissioned locos. 15 locos have been properly commissioned and in 14 locos only six nuts were tightened. Balance 50 new locos have not been attended. 55 Old locos are also to be covered.

·        Visual checking of Valve lever mechanism for proper lubrication and unusual sound, pinching of lash adjusters should be done.

·        Proper functioning of unit injector racks.

·        Vibration Check for unusual vibration/leakages from cam gear housing. Being done

·         Exhaust gas temperature, engine stabilization temp  during load test and TRD time should be recorded.

·        Leakage checking and lab analysis of  released air filters & fuel/lube  filters should be done .

·        Conduct lead wire measurement for measuring thrust washer wear.

·        All valve lever should be removed  checked .

·        Checking unusual sound of power assembly by Electronic stethoscope

·        Valve stem length should be measured. System flushing, cleaning and draining should be done

     Running schedule:

·        Cross checking of stud tightness.

·        Cam roller rotation and visual checking for wear. Cam shaft condition to be checked in every sch.

·        Spectrograph of Lube oil sample and any variation in concentration of critical item is cause of concern and it should be attended.

·        Checking of pressure differential of filters and temperature differential of heat exchangers.

·        Exhaust gas temperature, engine stabilization temperature and TRD time should be recorded.

·        Air box and sump cover leakages to be checked.

·        Check for unusual vibration/leakages from cam gear housing & crankcase vacuum

·        Air box cleaning should be done and lab should certify cleanliness.

·        Functioning of valve lever assembly should be checked.

·        Checking unusual sound of power assembly by Electronic stethoscope.

·        Sudden notch down lub oil pressure should be checked: minimum lube oil pressure ( 1.2 kg/cm2)

·        Spectro analysis of Lube oil to be done. Case of Water contamination, fuel dilution, Governor hunting and Less LR should not be permitted.

·        Lessons learnt from past failures must be incorporated in schedule form.

     90/180 days schedule:

With above items the following items to be added.

·        Alignment of Pee pipe and tightness of fasteners. Alignment of Pee pipe with piston carrier hole to be checked by barring the piston.

·        Check exhaust screen for debris/foreign material 90 days and above.

·        Check piston crown.

·        Periodical replacement of lube oil and fuel oil filters and lab test of elements for Silicon and other contaminants level.

·        Tappet timing and rack setting done by trained artisan in 180 days sch in hot engine.

·        Torquing of connecting rod basket bolts  to be checked in 180 and above sch.

·        Kennie test to be conducted in 180 days.

    Yearly schedules:

With above items the following items to be added

·        Perform complete power assembly inspection ,including liners, pistons, piston pins, p-pipes, connecting rods, and crankshaft.

·        Check exhaust valves timing.

·        Power Pack Fasteners Torquing

·        Retorque main lube oil and piston cooling oil pump shaft nut.

·        Blow by, Conduct lead wire measurement for thrust washer and compression test.

·        Inspection of scratch mark on roller or cam lobe.

·        Cylinder Liners and piston crowns should be visually checked by one revolution check.

·        Checking and recording of Bearing temperature.

·        Valve stem height to be measured as per MI.

     3 yearly schedule:

·        Cylinder Head to be overhauled if any cylinder is having less compression pressure .

·        Renewal of  all top connecting rod bearings (No 1 to No 8)

·         Main bearing bottom changing and condition of crankshaft checking

·         Inspect crankshaft gear damper for free movement.

·         Cylinder head to liner nut torquing.

·        All air box and sump cover gasket & nylon washers changing

·        System flushing and draining

·        All bearings temperature recording after cranking. Repeat same at 10 mints before and after load test.

·        Inspect and qualify piston cooling tubes. Check rocker arms, rocker arm bushings, and

·        Inspect and qualify piston cooling tubes. Check rocker arms, rocker arm bushings, and cam followers. Renew valve bridge and lash adjuster assemblies.

·        Set MUI injector timing and rack length.

·        Overhauling of Valve lever

·        Break-in test  to be done in 3y and above schedule and whenever bearing is opened

Six yearly schedule

Remove, completely dismantle and recondition:

1. Renew or recondition crankshaft damping device.

2. Renew all exhaust manifold gaskets, Expansion joint gaskets & all hardware.

3. Renew, qualify expansion joint assemblies.

4. Install all new lower main bearing & No.6 upper main bearing thrust collars, check & record crankshaft thrust Side play should be checked after fitment.

5. If necessary change upper main bearing.

6. Renew all lower liner inserts

7. Provide all crab bolts and torque

8.  Renew all upper & lower Con-rod. Bearing & fork rod hardware’s Check, qualify, clean both engine water discharge ‘Y’ flange & renew Gaskets.

9.   Check & renew accessory drive end coupling centre bonded rubber bushes.

10. Renew accessory drive end felt seal oil.

11. Renew both side water manifold seals

12. Check, qualify water manifold brackets, straps if necessary renew strap nuts.

13. Check & ensure torque of crankcase to oil pan & engine bed bolts.

14. Check, qualify & blow piston cooling pipe manifold.

15. Renew power pack assemblies, replacement components should be new or unit exchange.

      a.  Apply new cylinder heads liners, pistons & rings.

b.  Apply new wrist pin & bearings

c.  Apply new head seat rings.

d.  Check, qualify or renew inlet tubes & piston cooling pipes.

e.  Renew all outlet elbows & seals.

16. Renew all inlet tubes, pee pipe seals & gaskets.

17. Top up fresh engine lube oil & cooling water.

18. Check, qualify, renew all hand hole covers.

19. Renew all hand hole covers gaskets & hand wheel nylon washers.

20. Keep engine in running without giving any load for 24hrs, check & record all bearing temperature.

21. Conduct load test, record FRC reading.

22. Check & record all main bearing & Con rod. Bearing temperature before & after load test

23. Re-torque all power assemblies, fasteners at engine temperature 70 degree Celsius or after load test.

24. Refit engine cover with new cushioning hose & torque the bolts

25. Re-torque the power pack fasteners after 100 hrs of running

Other instructions to be followed:

·        Highly stressed /fatigue/thermally loaded component which was removed due to failure of power assembly should not be reused.

·        Lab should certify removed items for reuse after conducting necessary testing. Without NDT test components of   power assembly should not be assembled.

·        Governor hunting & less LR should not be allowed.

·        At least two power assemblies to be renewed during Yearly schedule based on kennie and blow by test result.

·        Procurement of critical measuring items like gauges rack setting gauge and tools should be processed immediately.

Proper air filtration, adequate fuel supply, lube oil & water pressure monitoring, block water temperature differential and combustion quality should be closely monitored during every schedule.

  p.s: above measures have dramatically reduced power assembly failures.