technical audit report of vcb maintenance at electric loco … · 2019. 10. 17. · in the vcb...

of 21 Issued on 25.07.2016 Report No. RDSO/2016/EL/TAR/009, Rev.0

Prepared by Checked by Issued by

lR;eso t;rs

GOVERNMENT OF INDIA MINISTRY OF RAILWAYS

Technical Audit Report of

VCB maintenance at

Electric Loco Sheds, Vadodara, Kanpur & Mughalsarai,

Report No.: RDSO/2016/EL/TAR/009. Rev ‘0’

Issue Date: July’2016

Approved by

EDSE(CO-ORD) Signature

Issued by

Electrical Directorate Research, Designs and Standards Organisation

Manak Nagar, Lucknow-226011



S. No. Date of Revision

Page No. Revision Reason for Revision



Sub: Technical Audit Report of Vacuum Circuit Breakers of Electric Locomotive.

Ref: Points noted during reliability meeting on 04-6-16 held at Railway Board.

1.0 Background: 1.1 Earlier on Conventional Electric Locomotives, apart from Air Blast Circuit Breakers,

double bottle Vacuum Circuit Breakers type 20 CB manufactured by M/s GEC Alostom (Naini Works) were used. This type of VCBs were reported with the defects like spark gap ET2 flashing while opening/closing of VCB, magnet valve coil open circuited, air leakage from magnet valve etc. In order to overcome these failures and simplify the design, single bottle VCB with indigenous Vacuum bottle design type 22 CB was developed by M/s GEC Alostom during 1998-99. This single bottle VCB had only one Vacuum Interrupter encapsulated with silicon rubber to enhance insulation level and had less no. of components and hence robust design.

1.2 33 Nos. Single bottle VCB type BVAC 25.10 of M/s Secheron make were received with imported three phase Electric Locomotives (WAP5 & WAG9) during 1995-96. The Secheron design VCB type BVAC 25.10 was introduced in 1999-2000 by M/s AAL, Noida and M/s BTIL, Vadodara under licence agreement with M/s Secheron. The initial supplies were with original design however, subsequently, these VCBs were indigenised by both the firms. Afterwards, these VCBs have been modified by firms in accordance with the need based on their field performance.

1.3 As per Railway Board guidelines circulated vide letter No. 2001/Elect(TRS)/441/10

dated 14.06.2001, only single bottle VCBs are to be used on Electric Locomotives. Presently, double bottle VCBs are less in no and are being replaced by single bottle VCB in phased manner by Zonal Railways.

1.4 The majority of population on Electric locomotives is of single bottle VCBs, this

Technical Audit Report deals with the audit of maintenance practices being followed by Electric Loco sheds for single bottle VCBs.

1.5 As the design of each make VCB is different, the reliability issues of each make VCB

differs from each other. Based on the failures reported by Zonal Railways following reliability issues have been identified in each make.

2.0 Make wise reliability issues reported in single bottle VCB:

2.1 Reliability issues of M/s AAL/Noida make VCB:

2.1.1 VCB type BVAC 25.10 of Secheron designs were provided on imported WAG9/WAP5

locomotives. The same design VCBs were also adopted on conventional tap changer locomotives being manufactured at CLW. These were introduced on conventional locomotives since 1999/2000. These VCBs were indigenously developed by M/s AAL against TOT from M/s Secheron/Switzerland.

2.1.2 Subsequently and based on reliability issues reported by Zonal Railways, the

important improvements as detailed below were undertaken by M/s AAL in the VCBs type BVAC 25.10 and modified VCB type VCBA 25.10Tr were developed.

Simplification of Command Electronics (CMDE) Use of air damping instead of hydraulic damping and shock absorption plate



Use of single 110 V coil instead of 2 coils of 12 V and 24 V. Elimination of shoulder stop screw. Use of fish bone design Auxiliary Switches.

2.1.3 Based on above, Railway Board advised Zonal Railways to upgrade the old design

VCB type BVAC 25.10 to VCBA25.10 Tr vide letter No. 2007/Elect(TRS)/441/10 dt. 06.02.08 with following line of action:

The conversion of VCBs in freight locomotives was to be undertaken during

IOH schedule; The conversion of VCBs in Passenger Locomotive was to be undertaken

during POH schedule as these locos have higher running and generally become due for POH within 5 to 5 and half-year time.; and

The VCBs lying defective at various sheds and due for rehabilitation/ IOH/POH should also to be undertaken for conversion.

As a result, up gradation of approximately 540 nos. of VCBs was to be undertaken by Zonal Railways. As per the details available with RDSO, so far only 276 Nos. of VCBs have been modified and 264 Nos. of VCBs are yet to be modified/upgraded.

2.1.4 Presently, M/s AAL is supplying VCB type VCBA25.10 Tr to Zonal Railways. Although, the reliability of VCB type VCBA25.10 Tr has improved w.r.t old design VCB, however failure has been reported in this type of VCB also. The main reliability issues reported are as follows:

i. EP valve failures; ii. Pressure regulator failures; iii. Auxiliary switch failures; iv. VST failure; and v. Pressure Switch failure

Based on the analysis of above failures following investigation and remedial actions are recommended.

2.1.4.1 EP valve failure: The main reason of failure of EP valve is moisture ingress into the valve. The moisture ingress causes deterioration of quality of rubber components leading to failures such as air leakage from EP valve and pilot valve causing VCB not closing and taking more time in closing. In order to prevent such failures it is recommended that air dryer to be properly maintained and component recommended for replacement in AOH/IOH kit to be replaced. In some cases, EP valve coil open circuit has also been reported. In order to prevent such cases, resistance of coil (1510 ohm±8%) to be measured in AOH/IOH/POH schedule.

Figure-1:EP Valve of M/s AAL



2.1.4.2 Pressure regulator failures: The failure of pressure regulator leads to pressure less, setting disturb etc. The reason of failure of pressure regulator is choking of filter element causing less air flow. In order to prevent such failures, it is recommended that draining of pressure regulator in each schedule as recommended by M/s AAL to be ensured. Also, filter cartridge with O-ring required to be replaced in every AOH/IOH as recommended in maintenance kits. In order to improve reliability further, M/s AAL has tried pressure regulator of M/s Festo make in place of M/s Bachofan make in the VCB offered for repeat type testing.

Figure-2: Pressure regulator

2.1.4.3 Auxiliary switch failures:

The failure in auxiliary switch are though less in no. in AAL make however cases of auxiliary switch cam broken, roller fixing hole worn out and auxiliary interlock mobile tips broken etc have been reported. There is no maintenance recommended during IA/IB & IC schedule however, auxiliary switch needs to be overhauled in AOH as per the recommended schedule maintenance and to be replaced in IOH and POH.

Figure-3: Auxiliary Switch

2.1.4.4 VST failures

VST is the main component of a VCB and also it the costliest part of VCB. The failures such as VST burst and VST punctured have been reported. Though, there is no schedule maintenance needed in the VST however its preventive maintenance is most important. If the RC network provided externally to VCB is not in healthy condition, surge voltage during operation shall appear at the VCB contacts which may lead to failure of VST. Presently RC

Network values (R=4.7 Ω±10% and C= 25 𝜇𝐹 ±10%) are recommended to be checked during IC schedule however few sheds are doing the checking it in each schedule. This practice may be followed by all sheds. By doing HV testing of VST (40 kV for 10 seconds) failure prone VSTs may be identified. Also the closing time and opening time also needs to be checked.

Figure-4: Vacuum Switch

Tube (VST)



2.1.4.5 Pressure Switch failures: The failure reported in pressure switch are of mainly of setting disturb. The setting may be ensured in AOH schedule and in IOH and POH pressure switch needs to be replaced.

2.1.5 The repeat type testing on VCB type VCBA25.10 Tr as per the revised CLW

specification No. CLW/ES/C-47 Alt- G has been partially completed by RDSO and

few tests to be done at NABL accredited Laboratory are under process. As per the

revised CLW specification, the mechanical endurance test for two lakh operations

has been undertaken as per IEC 60077. Also, the quality audit of the firm is being

undertaken by RDSO to overcome the above reported failures.

2.2 Reliability issues of M/s BTIPL make VCB: 2.2.1 Similar approach for modification in old design of M/s Secheron make VCBs type

BVAC 25.10 was adopted for M/s BT make VCB and M/s BT was advised by RDSO to undertake various reliability improvement measures. M/s BTIL had agreed to undertake various reliability improvements measures in two phases. In the first phase, the following improvement measures were undertaken in the VCB and modified VCB was designated as BVAC 25.10 M07 which were approved by RDSO vide letter No. EL/3.2.61/BT dt. 27.11.2006.

i. Use of distributed type Electronic Control Unit (CMDE) for better heat

dissipation; ii. Use of cam operated BBC auxiliary contacts; iii. Air damping instead of hydraulic damping; iv. Elimination of shoulder stop screw; and v. Use of Indigenous Indfos make pressure switch in place of Festo make

pressure switch.

VCBs supplied after July 2007 onwards by M/s BT are incorporated with the above modifications

2.2.2 Further, based on the performance of various make of VCBs on IR and CMDE &

Auxiliary Switch being the highest failure constituents in Secheron design VCBs, RDSO vide letter No. EL/3.2.61/Bt dt. 20.12.2007 had also advised M/s BT to eliminate CMDE & adopt fish-bone type auxiliary switch. M/s BT although initially did not agreed with this but had agreed to modify their VCBs by further simplifying the CMDE by adopting both the control coils at 110 V DC (Earlier these coils were at 12 V & 24 V DC) and adopted fish-bone type auxiliary switch. After conducting routine tests & extended mechanical endurance test for one lakh operations on such modified VCB, RDSO vide letter No. EL/3.2.61/BT dt. 30.07.09 have approved the following modifications in addition to the modifications already conveyed vide letter No. EL/3.2.61/BT dt 27.11.2006 and modified VCB was designated as BVAC 25.10 M07 (New).

i. Use of simplified Electronic Control Unit(CMDE) by eliminating 4 power

resistors(3 nos. of 50 ohms & 1 no. 68 ohm), use of electromechanical relay in place of MOSFET & R-C combination in place of OFF delay timer.

ii. Use of 110 V coils instead of 12 V and 24 V coils. iii. Use of fish bone design Auxiliary Switch similar to one’s used in DBTF type

breakers.



2.2.3 Summarizing above, M/s BTIL had implemented following modifications in their

single bottle VCBs being manufactured at their works for IR:

i. Use of simplified Electronic Control Unit(CMDE) by eliminating 4 power resistors(3 nos. of 50 ohms & 1 no. 68 ohm), use of electromechanical relay in place of MOSFET & R-C combination in place of OFF delay timer.

ii. Use of air damping instead of hydraulic dampers. iii. Use of 110 V coils instead of 12 V and 24 V coils. iv. Elimination of shoulder stop screw. v. Use of Indigenous Indfos make pressure switch in place of Festo make

pressure switch. vi. Use of fish bone design Auxiliary Switch similar to one’s used in DBTF type

breakers.

2.2.4 Thus, there are three types of VCB of M/s BT make being used detailed as below:

VCB type BVAC 25.10 [Based on original Secheron design and supplied

before July 2007]

BVAC 25.10 M07 [Modified as per para 2.3.1 above and supplied after July

2007 & before July 2008]

BVAC 25.10 M07 (New) [Modified as per para 2.3.3 and supplied after July

2008]

2.2.5 Railway Board vide letter No. 2007/Elect (TRS)/441/10 dated 06.02.08 has advised

Zonal Railways to undertake modification of these VCBs with upgraded design

VCBs. M/s BTIL had supplied approx. 594 VCBs to PUs/Railways in which 386 VCBs

were with type BVAC 25.10 and 208 VCBs were with type BVAC 25.10 M07, which

contain modifications referred in RDSO’s letter dt. 27.11.06. Thus, 208 VCBs type

BVAC 25.10 M07 needs to be modified however these modifications in 93 VCBs out

of 208 was to be carried out by M/s BTIL free of cost being in warranty. The present

status of modification is as follows:

(i) Up-gradation / modification of Single bottle VCBs, type BVAC 25.10 to VCBs,

type BVAC 25.10 M07 (New).

Total older version VCBs supplied by M/s BT to IR from 1998 to Oct, 2007 and

considered for above up-gradation/modification: 386 nos.

Status of up- gradation of older version of VCBs (BVAC 25.10):

M/s BT has received orders for up-gradation / modification: 127 nos. Number of VCBs for which order is yet to be placed by Railways: 259 nos.



(ii) Up-gradation of VCBs type BVAC 25. 10 M07 (Old) into VCBs type BVAC 25.10

M07 (New):

Total old version VCBs supplied by M/s BT to IR from July/Oct, 2007 to 2009 and considered for above up-gradation/modification: 208 nos.

Out of 208 nos., 93 VCBs were to be modified free of cost by M/s BT being in warranty which has been modified by M/s BT.

Number of VCBs to be modified on charge basis: 208-93=115 nos.

M/s BT has received orders for up-gradation / modification: 18 nos.

Number of VCBs for which order is yet to be placed by Railways: 97 nos.

2.2.6 Though the performance of upgraded VCB type BVAC 25. 10 M07 (New) is better

than the old design VCB type BVAC 25.10 however reliability issues had been

reported in modified design also hence RDSO took up the matter with M/s BT further.

2.2.7 M/s BT vide their letter dt. 21.01.2014 has submitted proposal for elimination of CMDE and provision of improved design cam in single piece for operating auxiliary switch (in which operating angle has been reduced from 30º to 15º to ensure smooth changeover of the auxiliary contact). M/s BT has proposed Coil protection unit with RC circuit which will provide protection to both closing & holding coil as well as to feed closing coil during closing of the VCB. Based on the field trial performance and report of endurance testing for more than one lakh operations of VCB (without CMDE) with coil protection unit, the proposal of M/s BTIL for providing coil protection unit and improved design operating cam have been accepted for implementation in BT make single bottle VCBs type BVAC 25.10 M07 (New) vide RDSO letter No. EL/3.2.1/BT dated 27.03.14 with following line of action:

These modifications for elimination of CMDE and improved design cam have to be implemented by M/s BT for new VCBs as well as in the VCBs coming for up-gradation of old VCBs type BVAC 25.10 into VCBs type BVAC 25.10 M07. The VCBs supplied after July’2014 are modified i.e. without CMDE and improved design cam.

Implementation of modification for elimination of CMDE and use of improved design cam in the VCBs already up-graded and warranty period has been expired will be modified on payment basis. However, already upgraded VCBs which are under warranty and reported failed will be modified for these modifications free of cost.

Implementation of this modification in the VCBs which are not covered for up-gradation will be on payment basis.

Thus, in addition to three types of VCB as explained in clause 2.2.4, the fourth type

of VCB of M/s BT being used presently is without CMDE and with improved design

cam.



2.2.8 Presently, M/s BTIPL make VCB have been reported with following type of failures:

i. Magnet valve failures; ii. Pressure regulator failures; iii. Auxiliary Switch failures; iv. CMDE failures; and v. VST failure.

2.2.9 Based on the analysis of above failures following investigation and remedial actions

are recommended.

2.2.9.1 Magnet valve failures and pressure regulator failures: The cause of failures of magnet valve and pressure regulator are similar as given in

clause 2.1.4.1 of this report for M/s AAL make and similar preventive action needs to

be taken by Zonal Railways. Additionally, Magnet Valve of M/s Rotex has been

provided by M/s BT. As a preventive action, M/s. Rotex has increased cross section

of O-ring by 0.2 mm to avoid any problem of air leakage. Magnet Valve Coil Kit is a

part of replacement in IOH Schedule. Zonal Railways to replace the same in IOH

Schedule.

2.2.9.2 Auxiliary Switch failures:

There has been no. of failure cases of auxiliary switches in BT make VCB such as

permanent deformation in contact strips, broken contact pieces, breakage of auxiliary

switch cam etc. Some of the failures are as shown in following figure.

Figure-5: Failure of auxiliary switches in BT make VCB

To overcome the failures, M/s BT has done following modifications: Aux. Switch cam profile prepared in single piece (in place to two pieces), to eliminate

cause of breakage of Aux. Switch cam mounting bolts.

For smooth changeover of the Aux. Switch contacts, profile angle of Aux. switch cam

is changed from 30 degree to 15 degree as shown on next page:



Figure-6: Existing design and modified design of Auxiliary Switch CAM

Elimination of breakage of Contacts by creating gap in the Contact Shaft of Aux.

Switch.

Preventing opening of top cover of Aux. Switch of the Shaft by providing Loctite.

RDSO has already issued instruction to use improved design operating cam vide

RDSO letter EL/3.2.61/BT dated 27-3-14 in new supplies. The modification needs to

be done by Zonal Railways as per para 2.2.7.

2.2.9.3 CMDE failures:

Based on analysis of failures, it has been decided to discontinue CMDE design and

provide Coil Protection Unit in place of CMDE. RDSO has already issued instruction

to use Coil Protection Unit vide RDSO letter EL/3.2.61/BT dated 27-3-14 in new

supplies. The modification needs to be done by Zonal Railways as per para 2.2.7.

2.2.9.4 VST failures:

The cause of failures of VST are similar as given in clause 2.1.4. 4 of this report for

M/s AAL make and similar preventive action needs to be taken by Zonal Railways.

Additionally, M/s BTIL have introduced ABB make silicone coated VSTs as shown in

figure keeping in view the failure of CGL make VSTs.

Figure-7: ABB make VST provided in place of CGL make VST

2.2.10 The VCB type BVAC 25.10 M07 (New) is taken for repeat type testing as per the revised CLW specification No. CLW/ES/C-47 Alt- G. As per the revised CLW specification, the mechanical endurance test for two lakhs operations has been undertaken as per IEC 60077. Also, the quality audit of the firm is being undertaken by RDSO.



2.3 Reliability issues of M/s Schneider make VCB:

2.3.1 The firm had earlier supplied double bottle VCB type 20 CB from GEC Alstom (Naini Works) and later on developed single bottle VCB type 22CB. After transfer of business from M/s Alstom to M/s Schneider, M/s Schneider Electric infrastructure Ltd, Vadodara is now supplying single bottle VCBs. Following major reliability issues have been reported in Schneider make single bottle VCB type 22CB.

2.3.2 Pressure Regulator failures: The cause of failures of pressure regulator are similar as given in clause 2.1.4.2 of this report for M/s AAL make and similar preventive action needs to be taken by Zonal Railways. Presently, the pressure regulator of M/s Shavo has been provided. The performance of M/s Shavo make pressure regulator is not satisfactory hence the pressure regulators of M/s Parker make have been tried in few locomotives. Also, repeat type test with Parker make pressure regulator is being taken up.

2.3.3 Magnet valve failures: The cause of failures of magnet valve are similar as given in clause 2.1.4.1 of this report for M/s AAL make and similar preventive action needs to be taken by Zonal Railways. M/s SEIL has informed that magnet valves of M/s Plasto fab make have been provided. The performance of M/s Plasto fab make magnet valve is not satisfactory. The Rotex make valves are stated to be reliable and same have been provided in few locomotives for field trial. Also, repeat type test with Rotex make magnet valve is being taken up. Same shall be cleared for regular use by RDSO after satisfactory field trial/type test.

2.3.4 Vacuum Interrupter (VI) failures: M/s Schneider has developed a new design interrupter and same is under re-type testing. Firm has informed that electrical stresses with new design Vacuum Interrupter shall be less as compared to old design. Based on satisfactory type testing new design VI shall be used in new manufactured VCBs. However, similar preventive actions as explained in clause 2.1.4.4 needs to be taken by Zonal Railways to overcome VI failures of M/s Schneider.

2.3.5 Sulphation/Rusting Problem: This problem has been reported by ELS/CNB in new supply of VCBs. Based on the discussion with firm, RDSO has issued SMI No. 285 for re-application of RTV sealant type 1080. Zonal Railways have been requested to follow the instructions contained in the SMI.

Figure-8: Rusting and sulphation inside cylinder assembly



2.3.6 Other Miscellaneous issues: Other miscellaneous issues such as driving rod uncoupled, upper insulator uncoupled and cementing from insulator uncoupled has been reported. These issues are related with product quality and have been taken up with the firm to tighten their quality process.

Figure-9: Uncoupling of driving rod of Aux switch

Apart from above, the cause of failures and preventive action related with maintenance practices are similar with other make VCBs and hence preventive maintenance practices as explained in relevant clauses of AAL and BTIPL make VCB shall be applicable with M/s Schneider make VCB also.

3.0 From the foregoing discussion, it may be concluded that VCB provided on Electric Locomotives have undergone considerable design changes in each make. The pace of the implementation of action plans decided for up gradation is also slow and still a sufficient quantity is under operation with unmodified design. Following points may be noted:

The failures in each make are still continuing. In order to improve the reliability, the maintenance practices adopted by

Electric Loco sheds also need to be analysed.

In view of above; Railway Board directed RDSO to undertake the quality audit of the maintenance practices being followed by few Electric Loco sheds. In compliance to Railway Board instructions, Quality audit of Electric Loco Shed BRC, CNB and MGS has been done by RDSO and following observations are made:

4.0 Technical Audit of ELS/BRC: 4.1 The population and failure details (FRPCPY) of year 2015-2016 of ELS/BRC is given

below:

Make M/s AAL M/s BT M/s Schneider Total

Type VBAC 25.10 Tr

BVAC 25.10 Old

BVAC 25.10 M07 (old)

BVAC 25.10 M07 (New)

22 CB

No. of failures

4 1 0 4 8 17

Pop. 37 08 07 25 145 222

FRPCPY 10.8 12.5 0 16 5.5 7.6

Table-1: Make wise failure details of single bottle VCB of ELS/BRC



4.2 Schedule Maintenance Practices being carried out by ELS/BRC: The Schedule maintenance practices carried out is mainly divided in Minor Schedule maintenance i.e. IA, IB & IC and major Schedule Maintenance i.e. AOH & IOH. The Minor maintenance schedules are being done by Schedule Inspection Wing and major schedule are being done by the E-9 section.

4.2.1 Minor Schedule Maintenance of VCB carried out by Inspection section: The staff assigned the work of doing minor schedule maintenance schedules has been discussed for the activity being done in minor maintenance schedules i.e. IA, IB & IC. The maintenance practices recommended by OEMs are generally being followed. However, the activity of tightening torque (70 NM) recommended for tightening HV connections and VCB foundation bolts is not being checked by Torque wrench though appearing on schedule Performa and only tightness is being checked by spanner. This practice needs to be introduced by shed as recommended by OEM and RDSO.

4.2.2 Major Schedule Maintenance carried out by Static Section/ E-9: The major schedule maintenance and unscheduled maintenance is being carried out by E-9 section. Following are the salient features:

4.3 Staff assigned the schedule maintenance job are conversant with the activities

specified in major schedules. All the maintenance manuals are available with the section as shown below:

Figure-10: Maintenance Manuals of different OEMs

4.4 The spares in the form of AOH and IOH kits of all make are available as recommended in RDSO SMI 236.

4.5 The test benches required for High Voltage test and test bench for testing travel characteristics of VCB was available in the Section. However, the test bench for checking travel characteristic is found defective and stated to be under repair with firm (M/s Micron, Roorkee). The shed reported that the test bench is expected to get repaired within 15 days. The pictures of High voltage test bench and travel Characteristic test bench are given on next page:



HV Chamber Control Panel

Figure-11: Test bench for High Voltage Test of VCB

Figure-12: Test Bench for testing travel Characteristics (Partly under repair)

4.6 RDSO SMIs and modification sheets were available with the shed and are being followed.

4.7 It has been noted that there is no closed room and dust free environment for doing major schedule maintenance of VCB and shed is doing major schedule maintenance on shop floor. The reliability can be further improved if maintenance is carried out in a closed room and dust free environment.



Figure-13: Schedule maintenance of VCB being carried out at shop floor (Open area and not recommended)

4.8 Other important points noted:

4.8.1 Electric Loco Shed/BRC has informed that the air dryer being supplied with VCB is

fitted only in conventional locomotives and air dryer is not being provided in three phase locomotives by CLW. VCB suppliers i.e. M/s AAL and M/s Schneider confirmed that they are supplying air dryer with new VCB to CLW. Based on the discussion held with CLW, it has been concluded that as air dryer is already fitted in three phase locomotives hence CLW is of the opinion that separate air dryer for VCB is not required.

4.8.2 Electric Loco Shed/BRC has informed that they are following two additional activities which are not included in recommended maintenance practices. The E-9 staff measures the values of RC Network in each schedule on locomotive and VCB of M/s Schneider make are blown with hot air gun as shown below inside the VCB chamber to prevent the cases of moisture entry. Other sheds can also follow these practices.

Figure-14: Hot air gun used to blow chamber of Schneider make VCB



5.0 Technical Audit of ELS/CNB: 5.1 The population and failure details (FRPCPY) of year 2015-2016 of ELS/CNB is given

below:

Make AAL BT Schneider Total

Type VBAC 25.10 Tr

BVAC 25.10 Old

BVAC 25.10 M07


22 CB 20 CB Single bottle only

No. Of failures

2 - 03 - 04 11 09

Pop. 35 - 05 - 92 85 132

FRPCPY 5.7 - 60 - 4.3 12.9 6.8

Table-2: Make wise failure details of single bottle VCB of ELS/CNB 5.2 Schedule Maintenance Practices being carried out by ELS/CNB:

The Schedule maintenance practices carried out is mainly divided in Minor Schedule maintenance i.e. IA, IB & IC and major Schedule Maintenance i.e. AOH & IOH. The Minor maintenance schedules are being done by Schedule Inspection Wing and major schedule are being done by the E-4 section.

5.2.1 Minor Schedule Maintenance of VCB carried out by Inspection section:

5.2.1.1 The maintenance practices recommended by OEMs are generally being followed. However, the activity of tightening torque (70 NM) recommended for tightening HV connections and VCB foundation bolts is not being checked by Torque wrench by ELS/CNB also. This practice needs to be introduced by shed.

5.2.1.2 The activity of draining of pressure regulator is recommended in IA, IB & IC schedule and draining of air tank is prescribed in IB & IC schedule by M/s AAL however same is not being followed at ELS/CNB. Section supervisor has informed that this activity is not required and if done shall result into over maintenance. This activity is required and needs to be followed as recommended by OEM.

5.2.1.3 The activity of weighing of air dryer (in conventional locomotives) of VCB during IC schedule is recommended and if weight is more that of 800 gm, regeneration of molecular sieves to be done. This activity is not being followed in IC schedule and is followed during AOH and IOH. This activity has been recommended by all three suppliers in IC schedule.

5.3 Major Schedule Maintenance carried out by Static Section/ E-4: The major schedule maintenance and unscheduled maintenance is being carried out by E-4 section. Following are the salient features:

5.3.1 Staff assigned the schedule maintenance job are conversant with the activities

specified in major schedules. The maintenance manuals are available with the section.

5.3.2 Presently shed is not using torque wrench for tightening as prescribed in maintenance manual. The shed need to use the proper torque wrench for the same.

5.4 The spares in the form of AOH and IOH kits are available as recommended in RDSO SMI 236. IOH kit of BT make VCB is not available however the population of BT make VCB is only five nos. ELS has informed that same is under procurement.



5.5 The test benches required for High Voltage test was not available in the shed. Section Incharge has informed that the proposal has been vetted and test bench is in advance stage of procurement. The High Voltage test bench is required to identify the failure prone VSTs and online failures of VST may be avoided. This need to be expedited.

5.5.1 The test bench for testing of travel Characteristics of VCB supplied by M/s Scope was available in the Section. However, the test bench for checking travel characteristic is capable of testing only closing time and opening time and the parameters such as contact gap, closing and opening speed and contact bounce cannot be measured. Section Incharge has informed that the proposal for a test bench including these facilities has been planned for procurement.

Figure-15: Test Bench for testing travel Characteristics

5.6 RDSO SMIs and modification sheets are available with the shed and the status of

implementation was displayed on the board as shown below. The SMI 285 issued by RDSO for reapplication of RTV 1080 sealant to avoid moisture ingress in Schneider make VCB were discussed as the SMI was issued based on the moisture ingress report from ELS/CNB. ELS/CNB has informed that they are applying the RTV sealant on the already applied sealant and not removing the already applied sealant as recommended in SMI 285. ELS have reported that cases of moisture ingress are not reported further. It was apprised to section incharge that the practice of hot air blowing of Schneider make VCB is being done by ELS/BRC and same may be adopted by ELS/CNB also to eliminate moisture ingress cases.

Figure-16: Status of SMI and MS of VCB displayed in shed




5.7.1 ELS/CNB has also informed that values of RC Network are measured in each schedule on locomotive as done by ELS/BRC.

5.7.2 ELS/CNB has informed that the shed has substantial number of double bottle VCB (85 Nos.) and failures in double bottle VCBs are more than single bottle VCB as indicated in failure summary in clause No.5.1. ELS/CNB has reported that POH/BSL is not replacing the double bottle VCB by single bottle VCB. ELS/CNB has planned for replacement of these VCBs in phased manner.

5.7.3 The maximum failure cases have been reported in BT make VCBs which are unmodified. ELS/CNB need to plan for up gradation of these VCBs as per Railway Board instructions issued vide letter No. 2007/Elect (TRS)/441/10 dated 06.02.08 based on the remaining useful life.

6.0 Technical Audit of ELS/MGS: 6.1 The population and failure details (FRPCPY) of year 2015-2016 of ELS/CNB is given

below:

Make AAL BT Schneider Total

Type VBAC 25.10 Tr

BVAC 25.10 Old

BVAC 25.10 M07


22 CB 20 CB Single bottle only

No. Of failures

03 - - 10 02 03 15

Pop. 34 - - 35 86 42 155

FRPCPY 8.8 - - 28.5 2.3 7.1 9.6

Table-3: Make wise failure details of single bottle VCB of ELS/MGS

6.2 Schedule Maintenance Practices being carried out by ELS/MGS: The Schedule maintenance practices carried out is mainly divided in Minor Schedule maintenance i.e. IA, IB & IC and major Schedule Maintenance i.e. AOH & IOH. The Minor maintenance schedules are being done by Schedule Inspection Wing and major schedule are being done by the E-4 section.

6.2.1 Minor Schedule Maintenance of VCB carried out by Inspection section: 6.2.1.1 The maintenance practices recommended by OEMs are generally being followed.

However, the activity of tightening torque (70 NM) recommended for tightening HV connections and VCB foundation bolts is not being checked by Torque wrench. This practice needs to be introduced by shed as recommended by OEM and RDSO.

6.2.1.2 The activity of draining of pressure regulator is recommended in IA, IB & IC schedule and draining of air tank is prescribed in IB & IC schedule by M/s AAL. The draining of pressure regulator is being followed at ELS/MGS however draining of air tank is not being followed.

6.2.1.3 The activity of weighing of air dryer of VCB during IC schedule and if weight is more than 800 gm, regeneration of molecular sieves to be done is not being followed in IC schedule and is followed during AOH and IOH by M5 section. This activity has been recommended by all three suppliers in IC schedule.



6.3 Major Schedule Maintenance carried out by Static Section/ E-4:

The major schedule maintenance and unscheduled maintenance is being carried out by E-4 section. Following are the salient features:

6.3.1 Staff assigned the schedule maintenance job is conversant with the activities

specified in major schedules. The maintenance manuals are available with the section. However maintenance manual of M/s AAL is of 2006 year. The latest maintenance manual of 2014 may be got from M/s AAL. RDSO SMIs and modification sheets were available with the shed except a few.

6.3.2 The spares in the form of AOH and IOH kits are available as recommended in RDSO SMI 236 for M/s Schneider make VCB. However, IOH kit of BT make VCB and AAL make VCB is not available. Section Incharge has informed that IOH kit is not available since last three years. This may be a reason for high failure rate of BT make VCB.

6.3.3 The test benches required for High Voltage test was not available in the shed. Section Incharge has informed that the proposal has been prepared for its procurement. The High Voltage test bench is required to identify the failure prone VSTs and online failures of VST may be avoided. This need to be expedited.

6.3.4 The test bench for testing of travel Characteristics of VCB supplied by M/s Micron has been newly purchased and yet to be commissioned on the proper test bench. Section Incharge has reported that there is some problem reported in the test bench and supplier has been called for remedial action as the testing machine is under warranty. This needs to be expedited so that full fledged testing of VCB may be started.


6.4.1 Electric Loco Shed/MGS has also informed that values of RC Network are measured in IC schedule on locomotive as done by ELS/BRC & ELS/CNB.

6.4.2 Electric Loco Shed/MGS has informed that the shed has substantial number of double bottle VCB (42 Nos.). ELS/MGS has reported that POH workshops are not replacing the double bottle VCB by single bottle VCB. ELS/MGS has also planned for replacement of these VCBs in phased manner and 24 Nos. has been sanctioned in RSP.

6.4.3 The maximum failure cases have been reported in BT make VCBs which are fitted with CMDE. Electric Loco shed/MGS need to plan for up gradation of these VCBs as per RDSO instructions issued vide letter No. EL/3.2.61/BT dated 27-3-14 & 6-2-15.

6.4.4 ELS/MGS has informed that there are five no. VCBs of M/s Schneider which have been failed under warranty and M/s Schneider is not responding for their replacement. RDSO needs to resolve this issue. It has been highlighted by ELS/MGS that M/s Schneider has outsourced the repairing of VCB to M/s Allied/Kolkata and response of firm is very poor. This also needs to be tackled by RDSO.



7.0 Conclusion and Recommendations:

Based on the discussion in preceding clauses, it may be concluded that a sufficient quantity of unmodified VCB of type BVAC 25.10 of M/s AAL & M/s BT and BVAC 25.10 M07 of M/s BT are still in service on I.R. The instructions for modification/upgradation of these VCBs were issued during 2008. However, due to slow pace of modification by Zonal Railways the VCBs might have already completed half of its useful life. The modification of very old VCBs having manufacturing of before 2005 may not give the desired result due to non replacement of VST in upgradation. Hence, Zonal Railways may plan for up gradation of the VCBs which have useful life of more than 8-10 years.

On the basis of failure analysis of VCB and shortcoming noticed in maintenance practices, it is recommended that following measures must be taken to improve the reliability of single bottle VCBs:

i. The test benches required for high voltage testing and travel characteristic measurement are vital and need to be procured on urgent basis wherever these are not available. The test benches should be kept in proper working order with up to date calibration.

ii. Spares in the form of AOH/IOH and POH kits are required to be available with sheds/workshops as per RDSO SMI 236.

iii. Workshops need to plan procurement of single bottle VCB to replace double bottle VCBs. Zonal Railways may also plan for replacement.

iv. The activities as given in maintenance manual of OEM should be followed by Electric Loco sheds. Tightening of torque needs to be ensured by torque wrenches only.

v. The activity of draining of pressure regulator & air tank as recommended by OEM should be followed.

vi. RDSO SMI 285 and blowing of hot air inside Schneider make VCB need to be introduced to avoid moisture ingress cases.

vii. The activity of weighing of air dryer (in conventional locomotives) of VCB during IC schedule is recommended by all OEMs and if weight is more than 800 gm, regeneration of molecular sieves to be done. This activity is not being followed in IC schedule by sheds and is followed during AOH and IOH. This activity needs to be critically examined by sheds by weighing of air dryer in few locomotives during IC Schedule and if no appreciable change in weight is observed, maintenance schedule can be revised.

viii. The working environment of test room for testing VCB needs to be improved by sheds by arranging proper lighting and fan. The maintenance being carried out in open space need to be avoided and should be done in dust free environment.

ix. RDSO has undertaken repeat prototype testing of all three suppliers and complete quality audit of the firms.

x. The service engineering of M/s Schneider is very poor and need to be tightened up.

xi. The list of various Special Maintenance Instructions and Modification Sheets issued by RDSO are given in Annexure-I. Zonal Railways are requested to follow the same.



Annexure-I

1. Special Maintenance Instructions:

S. No. SMI No. Title Date of issue

1. RDSO/2015/EL/SMI/0285(Rev.0) Re-application of RTV 1080 sealant in Schneider make VCBs fitted in conventional and 3-phase locomotives.

23.09.15

2. RDSO/2014/EL/SMI/0281(Rev.0) Use of loctite in place of RTV 1080 to seal upper and lower insulators of Schneider make single bottle VCBs type 22cb

27.06.14

3. ELRS/SMI/ 0236 Rev.1) Overhauling kits for AOH/IOH/POH of single bottle VCBs

31.12.12

4. ELRS/SMI/ 0223 (Rev.0) Replacement overhauling kit for double bottle vacuum circuit breaker type 20 CB Alstom make during AOH, IOH and POH.

31.01.01

5. RDSO/ELRS/SMI/208, Rev.1 Maintenance schedules for vacuum circuit breaker ( VCB) type 20 CB of M/S Alstom.

16.11.99

6. RDSO/ELRS/204 Remedial measures to main problems of VCB Type 20 CB of GEC Alstom make

22.05.98

7. RDSO/ELRS/SMI/162 Rev.1. Lubrication to air relay valve and main piston Of VCB

24.04.95

8. RDSO/ELRS/SMI/ 137. Maintenance of air dryer provided in pneumatic circuit breaker (VCB) type 20 CB GEC make

01.02.91

9. RDSO/ELRS/SMI/136. Instructions for testing the VCB type 20 CB for travel records

17.01.91

2. Modification Sheets:

S. No. MS No. Title Date of issue

1. RDSO/2014/EL/MS/345(Rev.1) Standradardisation of earthing switch arrangement on 3phase locomotives to make interchangeable of various makes VCB between single & 3phase locomotives

13.02.14

2. ELRS/MS/0340 Replacement of metallic corrugated steel pipe/out side steel braided flexible pipe by flexible reinforced rubber pipe connected in between VCB/Air blast circuit breaker & Air drier and main air pipe line to air drier.

29.06.05

3. ELRS/MS/302 Replacement of existing rotary auxiliary switch/conversion of existing ON LOAD fish-bone arrangement to OFF-LOAD (with inverted cam & 16 F.R.P. operation rod) on double bottle vacuum circuit breaker type 20 CB of Alstom.

10.11.2000

4. ELRS/MS/0274

Provision of rain shed on end caps at either end or horizontal insulator flange of vacuum circuit brake type 20 CB of M/s. Alsthom.(SKEL 4545 Alt.0 A4 )

09.12.99

5. RDSO/WAM4/209 Replacement of the existing latching type of fixing arrangement with bolted design of cradle cover of vacuum circuit breaker type 20 B (SKEL-4472)

29.05.98

6. RDSO/WAM4/199 Replacement of incoming steel braided flexible pipe by flexible reinforced rubber pipe connected to VCB/Air Blast circuit breaker

10.03.98

http://rdso.indianrailways.gov.in/works/uploads/File/SMI%20285%20Rev%200%20Dated%2023_09_2015.pdf

http://rdso.indianrailways.gov.in/works/uploads/File/SMI%20no.%200281%20dtd.%2027.06.2014.pdf

http://rdso.indianrailways.gov.in/works/uploads/File/SMI%20no.%200281%20dtd.%2027.06.2014.pdf

http://rdso.indianrailways.gov.in/works/uploads/File/SMI_236(5).pdf

http://rdso.indianrailways.gov.in/works/uploads/File/SMI%20223(2).pdf

http://rdso.indianrailways.gov.in/works/uploads/File/MS%20345%20Rev_1%20dtd_%2013_02_2014.pdf

http://203.176.113.182/RDSO/electrical/smi_ms_tc/serialnoswise_smi_ms_tc/ms/ms_link/MS%20340.pdf




http://rdso.indianrailways.gov.in/works/uploads/File/MS%20274(3).pdf

http://rdso.indianrailways.gov.in/works/uploads/File/WAM4%20209(3).pdf

technical audit report of vcb maintenance at electric loco … · 2019. 10. 17. · in the vcb...

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