:- Traceability of components

               Each shed shall maintain traceability record of all components sub-fitted in locomotive. Traceability of components aid failure analysis and sheds can plan corrective action by revision of maintenance practice and product development by vendors.

               Make, year of manufacturing, date of fitment, firm’s ID & shed’s/shop unique ID shall be permanently etched (electric etching/laser bar-coding) & record of the same shall be kept in section. The record must be entered in computer for immediate access & retrieval.

               Loco manufacturing shop, rebuilding & POH workshop should provide component details in locos turned out from shops. These records should be collected & complied by shed in their component master data base. No component should be accounted for in Diesel stores unless traceability requirement as laid down in IRS condition & drawing is ensured. Traceability requirement as per RDSO specification of components should be followed.

               For small components like rubber ‘O’ ring, gaskets seals etc. where etching & manufacturer ID cannot be provided. Such details should be provided in sealed packet of the component & detailing of the same should be recorded in sectional register.  Product wise, vendor wise, cause wise & age wise record of each component shall be kept & regular quality feedback to HQ & Firm should be given. 

 Wheel Root Wear.

          Wheel turning of a Diesel Loco is mostly done due to rapid generation of root wear in one of the wheels of locomotives. Pre-mature wheel turning not only results in increased ineffective, reduced outage but also causes reduction in wheel life. Intra and inter bogie wheel diameter matching requirement causes wheel turning of good unaffected wheels also.

It is important to note that development of root wear is not uniform in all wheels & in all locations clearly indicating presence of local factor(s) causing localized root wear. Wheel turning records clearly indicate that all locos or all wheels do not develop high root wear. Only a few locos at one or two locations exhibit high root wear.

Challenge before maintenance engineer is to identify the factors causing rapid root wear & take corrective measures. Unless root cause of root wear is attended, simply turning of wheel will not solve the problem & again rapid wheel root wear will take place. Factors contributing development of root wear must be understood properly to formulate an effective strategy to arrest root wear in wheels.

          Root wear can develop only when there is excessive wear on root. This excessive wear is contributed due to:

·        Rubbing of wheel root with brake blocks

·        Rubbing of wheel root with track flange.

Each factor has to be tackled separately.

Root wear due to rubbing with brake blocks.

Tell tale signs in such cases are

·     Biased wear on brake blocks: Brake block rubbing on wheel flange due to shifting

·     Asymmetrical placement of brake blocks.

·     Brake block rubbing with root in one side and projected towards tread on other side.

In such cases, during braking, brake block partially mounts/slides over root causing root wear of wheels. Had brake block been correctly applied over tread, root wear would not have taken place.

·  Play in brake hanger

·  Bent tie rod

In such cases, brake hanger brake shoe or complete brake hanger assembly keeps on swaying & during brake application sometimes mounts over wheel root causing root wear.

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Action to be taken:

1.    Ensure correct positioning of brake blocks: MS washer of 4mm thickness must be inserted in the hanger assembly to enable brake head assembly to move away from the flange.

2.    Proper fitment of brake blocks over brake heads should be ensured.

3.    Width of brake block should be measured before fitment. Wider brake blocks cause wear of wheel flange root.

4.    Alignment of brake blocks should be parallel to wheel treads with uniform clearance and without any skewness.

5.    Bent or misaligned tie bar results in brake blocks being pulled towards the flange of the wheel and riding of brake block against wheel root flange causing excessive root wear. Reinforced tie bars should be fitted in M₂₄.

6.    Pool of intermediate size wheel to be kept to obviate need of wheel turning of entire bogey/loco for root wear of one wheel.

             Root wear due to wheel rubbing with track flange

              

Wear occurs from sliding between wheel & rail typically in the flange root area.

Too high wear is cause of concern and should be monitored by monthly wheel gauging.

Wheel Rail dynamics: The wear of wheels and rails results from a complex dynamic relationship within the movement of wheel at the track with wheel spin. The kinematical properties of wheel & rail contact such as rolling radius, contact angles and wheel set roll angle vary as the wheel sets moves laterally relative to the rails.

Because of the curving of the wheels as the leading wheel sets moves outwards, the radius of the outer wheel becomes greater that the inner wheel. As both wheels are rotating at the same speed, the larger radius wheel tries to roll further than the smaller radius wheel.  Wheel set is thus steered towards a radial alignment, and it rolls smoothly around the curve. The opposite process happens on the trailing wheel sets as it moves inwards on the curve. The forces that are generated depend upon the effective conicity of the wheel set on the rail. The larger the conicity, the greater the rolling radius difference for given lateral shift. Conicity tends to increase with increasing wheel tread wear.

In practice, rotation of the wheel sets into radial alignment is resisted by vehicle suspension. The stiffer the primary yaw suspension, the larger the forces which will be required to achieve the required rotation.

Once the wheel set is unable to generate sufficient longitudinal forces to steer into radius position, the wheel sets will have an angle of attack to the track and will run in flange contact. Because of the angle of attack, both of tread contact points will be generating forces to push the wheel set into the flange, which must be resisted by flange contact force. These forces are a major cause of flange wear.

Poor curving vehicles on curvaceous routes will suffer mainly flange wear whereas good curving vehicles on relatively stringent routes will suffer mainly tread wear.

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Wheel wear is influenced by wheel rail contact angle.

How track friendly a vehicle is depends not only on its design, speed & axle load but also on its maintenance condition.

It is not uncommon for wheels of both sides of a wheel axle to degrade differently despite having the same axle load. Bogies’ dynamic curving performance by checking left & right rotation as well as bogies ability to return to a neutral tracking position is important. Leading axle is first to negotiate the curve & therefore usually have larger lateral force.

Condition monitoring of root wear:

A bogie maintenance strategy based on detection of axles that exhibit higher levels of instability (hunting) should be formulated. An exception List of locos having undergone wheel turning more than once in a year should be prepared. Look out for repeat location in same loco or of same location in different locos, An analysis based on wheel location and service type wise loco utilization should be prepared. Wheel gauging and axle box clearances checking should be done in monthly schedule and records should be kept. Information regarding health & physical status of wheels or components is key to successful maintenance planning.

Factors to be checked:

·        Check wheels and their locations which have developed root wear. Check type of wear: If wear rate is slow it is called benign. It is characterized by low wear rates, minimal plastic deformation, formation of a surface film protecting against metal to metal contact & oxide wear debris. Severe wear is characterized by high wear rates, extensive plastic deformation, transfer of material to the harder counter face and flake like metallic wear debris.

·        What is trend of root wear increase? Identify locations having highest root wear / rapid growth rate.

·        What are longitudinal and lateral clearances at those locations? Are there excessive lateral clearances between axle box & bogie pedestal. Lesser longitudinal clearance between axle boxes bogie pedestal should be attended.

·        Check condition of bogie and axle box liners, Wrong setting of axle box wear liners or bogie frame pedestal lateral wear lines

·        Check wheel profile, wheel dia variation in same axle, conicity and surface finish of wheel

·        Bogie frame rotation, condition of centre pivots, side bearer,squareness/trammeling of bogie. Mis-alignment of bogie frame. Parellelness of bogie to be checked diagonal division variation should not be more than 3mm.

·        Biased wear on all wheels. If the root wear on one side of all six wheels is high compared to other wheels in same axle. The direction of loco is apparently not getting changed and loco is running in curved section

·        Wheel load distribution,  spring pairing and use of spring of equal loaded height in same loco,check equalizing/compensating beam movement and condition of rollers

·        Centre buffer coupler angularity

All unusul values should feature in exception list of undercarriage section.

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Attention during maintenance:

1.  Before doing wheel turning, axle box clearances should be checked. Lateral & longitudinal clearances of axle boxes should be kept within prescribed limit. Lateral clearances should be brought to shop issue size (minimum value) for locations exhibiting high flange wear.

2.  Locos provided with manganese steel liners at pedestals should be checked in M₄ & above schedule to ascertain their intactness & wear. Liner gap must be uniform. Axle box liners must be renewed during M₂₄ Schedule and above.

3.  If wheel profile has worn then wheel profile should be restored with minimum cut. Surface finish of wheel should be ensured during turning.

4.  Trueness of template used in wheel turning should be periodically                    cross-checked (every 6 months). Wear adapted wheel profile to be used.

5.  Wear of all pins and bushes must be kept within 1mm. Brake riggings should be renewed during M₂₄ schedule. Worn components should be replaced out of course whenever any play is observed.

6.  Alignment of brake hanger bracket on bogie frame should be checked during M₂ schedule for ALCO and in 90 days schedule for HHP locos.

7.  Uniform load distribution: Condition of roller at the end of the equalizing beams. Should be checked for wear, flatness and free movement. Rollers should be renewed during M24 and above schedules. Load tested springs of same group should be used. Side bearer pad gap must be same both sides.

8.  Condition of centre pivot and side bearer should be checked for sign of wear and free rotation. Regular adding of lubricant in the side bearer pans for free rotation of bogie should be done.

Implementation of above instructions during POH pre-commissioning and major/medium schedules will significantly improve wheel life and reduce the need of frequent wheel turning.  A seminar has been planned in last week of November at HQ on maintenance planning of bogie for arresting root wear.

 High Pressure tube leakage.

                    Recently the failures of Diesel locos due to crack in HP tubes have been observed. Drivers were unable to cut off fuel supply by blocking control rack of affected FIP.

                    HP tubes breakages are caused due to excess vibration, crack, use of unapproved make HP tube etc.

Action to be taken:

          Maintenance of HP tube

1.    Only HP tubes of approved make are to be used, other HP tubes should be weeded out.

2.    DPT testing of HP tube should be conducted in section itself during M_24. In situ testing during M₁₂ should be carried out.

3.    Handling of HP tubes must be done extremely carefully as slight dent during handling/transportation becomes a stress notch point for propagation of crack. Suitable HP tube carrier and storage rack (wooden/rubber/plastic) should be developed.

4.    Profile checking & high pressure testing should be carried out in testing gadget in section itself.

5.    All HP tubes above 10 yrs. of age should be weeded out from main line locos, these tubes after testing can be fitted in locos working in inferior service.

6.    Grommets must be renewed during M₂₄. Condition of Grommet must be checked in every schedule & perished Grommets should be replaced.

7.    Vibration measurement of HP tube should be carried out in M₂ and above schedule. All locations showing higher vibration should be attended & vibration level should be brought down.

Checking fuel delivery at zero rack travel

Blanking of FIP in case of HP tube leakage should be done en-route.

All FIPs should be tested in section for fuel leakage when control rack is locked at zero by pump latch. It should be ensured that there is no HSD leakage when rack is locked at zero. This is an important fire prevention criterion.

“Move the control rack towards stop position and engage the latch with the slot provided in the control rack. Run the test bench at 200 RPM. There should be no delivery. ” (Ref- Page No. 11 & 12 of Instructions Manual on FIP).

It will ensure that even in case of mid-section HP tube breakage, drivers are able to complete the trip and failed HP tubes can be changed at Trouble shooting points.

Basic condition monitoring.

Ref: Implementation / Application of predictive maintenance techniques in Diesel Loco Maintenance –

Vide letter referred above, sheds were advised to introduce condition monitoring technique in diesel loco maintenance for improving loco reliability.

Identification of unusual sound in various assemblies / sub-assemblies of running locos by Supervisors & artisans by condition monitoring has still not been done in Diesel sheds. Current practice of using human ear or listening rod is grossly inadequate to identify unusual sound of various moving / rotating parts. Unusual noise is either lost or remains inaudible in cacophony of high decibel engine sound.

         

To tide over the above problem, Electronic stethoscope should be introduced in all running sections for pin pointing bearing & component noise. It includes a headset, different length probes for ease of accessibility and a pre recorded audio CD demonstrating the most common encountered troublesome engine noise. Headset allows for optimum sound quality even in very high-noise diesel loco condition.

Use of electronic stethoscope during initial & final testing of diesel locomotive, by Supervisors / artisans must be ensured for looking unusual sound especially in engine room, auxiliaries, small motors, can gear, power pack, expresser etc.

:- Failure of newly commissioned HHP loco  due to leakage in Lube oil system.

Diesel shed is experiencing problem of Lube oil leakages in various locations on newly commissioned HHP locos due to bad workmanship during manufacturing.

suitable suggestions against each item have been prepared as a corrective action for implementation at Shop floor level. These measures shall help in improving the reliability of HHP locos apart from saving precious lube oil.

The details of the lube oil leakage cases are discussed below.

1.0 1.1 1.2 1.3	Lube Oil Leakage from Turbo Housing (Right Side) No. of cases: 03 Nos.  Cause of Leakage : Improper sequence of torquing of Housing Bolt Corrective Action Required: At the time of fitment of Turbo Housing, sealing compound should be used properly and working sequence to be maintained.
2.0 2.1 2.2 2.3	Lube Oil Leakage from Scavenging Pump Header Plug  No. of case: 01  Cause of Leakage: Plug tightened, but without any compound Corrective Action Required: Use of Thread locker compound at the time of fitment
3.0 3.1 3.2 3.3	Lube Oil Leakage from OST Housing. No. of cases: 02   Causes of Leakage: Improper tightness sequence of OST Housing Bolt Corrective Action Required: Proper torquing sequence along with gasket and adhesive to be used.
4.0 4.1 4.2 4.3	Lube Oil Leakage from Turbo Housing (Left Side) No. of cases: 03  Cause of Leakage: Improper tightening sequence of Housing Bolt Corrective Action Required: Proper tightening sequence to be followed with use of thread locker compound.
5.0 5.1 5.2 5.3	Lube Oil Leakage from Hot Oil Detector Pipe Joint No. of cases: 04  Cause of Leakage: Improper alignment of steel pipe. Corrective Action Required: Proper alignment to be ensured by checking through a suitable template.
6.0 6.1 6.2 6.3	Lube Oil Leakage from TSC Plug No. of cases: 01  Cause of Leakage: Plug was not tightened properly and became loose Corrective Action Required:  Proper tightness of plugs to be ensured with use of thread locker compound.
7.0 7.1 7.2 7.3	Lube Oil Leakage from Top Deck Cover Gasket No. of cases : 01  Cause of Leakage : Improper tightness of  top deck cover back side clamp Corrective Action Required :  Back side clamp alignment and  tightness to be ensured.
8.0 8.1 8.2 8.3	Lube Oil Leakage from Lube Oil Strainer Steel Pipe thread joint  No. of cases: 01  Cause of Leakage: One end of Steel Pipe fitted to strainer housing got    loose Corrective Action Required:   Proper tightness with thread locker should be ensured.
9.0 9.1 9.2 9.3	Main Crank Case Lube Oil Drain pipe No. of cases : 7 Cause of failure- Improper Torquing of elbow, leading to leakage in majority of the locos. Corrective action required-  At the time of assembly at DLW, the elbow should be correctly torqued
10.0 10.1 10.2 10.3	Turbo soak back filter to turbo filter pipe line No. of cases: 2 Cause of Failure - Leakage from Flange to tube joint and soak back pipe gets punctured due to rubbing with either starter motor body or engine base. Corrective Action Required – Soak back pipe line should be realigned by passing it above the starter motor to avoid rubbing and facilitate easy checking and quality of Flange to Tube joint to be improved
11.0 11.1 11.2 11.3	L/oil leakage from L/oil filter drum gauge sight glass No. of cases: 1. Cause of cases: ‘O’ ring of sight glass leaks. Corrective action required-  At the time of manufacturing, the fitment   of Slight Glass should be proper and give leak-proof service of minimum three years.	gauge sight glass
12.0 12.1 12.2 12.3	Lube oil leakage from cylinder head cover frame gasket joint No. of cases: 1 Cause of failure – Improper application of gasket, sealant and incorrect torquing of hex head bolts.(EMD Pt- 454911). Leakage occurs after 2 – 3 months  of commissioning. Corrective action required-   ·      Proper application of gasket and sealant as per EMD manual. ·      Correct torquing of hex head bolts.(EMD Pt- 454911) at the time of assembly.	Leaky joints
13.0 13.1 13.2 13.3	Lube oil leakage from Armour joint. No. of cases: 9 Cause of failure – Lube oil leakage from scavenging pump to filter drum  armour joint due to misalignment during assembly. Corrective action required-  Proper alignment of mating pipelines to reduce extra stress  and dimensional accuracy of fittings should be ensured.
14.0 14.1 14.2 14.3	L/oil leakage from the sock back flange. No. of failures : 1 Cause of Failure - Leakage from Flange to tube joint due to misalignment. Corrective Action Required- Proper alignment of mating pipelines to reduce extra stress.
15.0 15.1 15.2 15.3	L/oil leakage from EMD gauge top and bottom joint . No. of cases: 2 Cause of Failure - Leakage from joint due to misalignment. Corrective Action Required- Proper alignment of mating pipelines to reduce extra  stress
16.0 16.1 16.2 16.3	Lube oil cooler adopter and elbow. No. of failures : 3 Cause of cases: Leakage from joint due to misalignment. Corrective Action Required- Proper alignment of mating pipelines to reduce extra stress.
17.0 17.1 17.2 17.3	Vent pipe at strainer to Main Lube oil Pump. No. of cases: 3 Cause of Failure - Leakage from joint due to misalignment. Corrective Action Required- Proper alignment of mating pipelines to reduce extra stress.
18.0 18.1 18.2 18.3	Lube oil leakage from filter drum pressure testing plug No. of cases: 5 Cause of Failure – Improper tightness. Corrective Action Required- Proper tightness at the time of installation and  use of thread locking compounds.