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of 18 Issued on July 2016 Report RDSO/2016/EL/IR/0168, Rev.‘0’

1. Introduction:

Three phase locomotives have been inducted in Indian Railways in the mid-nineties of last century. There are several differences in the concept of traction as well as brake system of these locomotives as compared to earlier locomotives with conventional DC traction motor technology. The maintenance personnel of Indian Railways were used to the braking system of conventional locomotives and developed the expertise over a period of time in understanding the maintenance issues of brake system of conventional locos. The brake system of three phase locomotives is slightly complex having electronic interface with no explicit pipelines between various valves. The valves are mounted on a tri-plate panel with internal port connections doing the job of external piping. Also, the interface of brake electronics with loco electronics is software controlled. The control logics are not hard wired and there are no relays or switches.

While working with brake system of three phase locos a need is felt to provide information regarding various reliability issues faced by Zonal Railways while maintaining brake system of three phase locomotives along with the reliability action plan for solving these problems. The aim of this technical report is to illustrate various reliability and maintenance related issues faced by Zonal Railways in E-70 & CCB Brake system of three phase locomotives and its reliability action plan. Current problems are also illustrated along with action plan. This will help in better understanding of technical issues by engineers in the field for taking corrective action.

2. Pneumatic testing of 3-phase locomotives:

2.1 Air pressure built up time & test parameters:

(i) There have been few cases of MR air pressure not maintaining in 3-phase Locomotives due to failure of one compressor. Investigation revealed that other compressor was also not able to maintain MR air pressure due to its de-rated capacity. The rated free air delivery of the compressor can be verified in-situ by recording MR air pressure build up time by each compressor. MR air pressure build up time by each compressor mentioned as 12 minutes in the test specification of D & M (E-70 brake system) is very liberal, which can be achieved even with the de-rated compressor. Hence it was felt necessary to formulate pneumatic test procedure for 3-phase locomotives as deliberated during 34th MSG meeting.

(ii) Theoretical calculation for MR air pressure build up time has been done by taking into

account total permissible air leakage and total volume of reservoirs and pipe line as well. The time taken by each compressor to build up MR air pressure from 0 to 10 kg/cm2 has been theoretically calculated as about 6 minutes. Tests were carried out in Zonal Railways to find out the actual MR pressure built up time to validate the theoretical calculations. MR pressure built up time was found to be 6 & 7 minutes, which was matching with theoretical calculations.

(iii) After tests/trials, vital pneumatic test parameters of 3- phase electric Locomotives was issued as technical circular No. 0113 Rev’0’ based on D&M static test specification catalogue no. AT 371/I Part no. MM 3946 (issue no. 2) for WAG9 locomotive, catalogue no. AT 366 Part no. MM 3882 (issue no. 3) for WAP5 Locomotives. These parameters were based on CLW’s


Pneumatic & brake system check sheet no F60.812 version (2) and test reports received from Railways. MR air pressure build up time from 0 to 10 kg/cm2 by each compressor of 1750 lpm, with air dryer in isolated condition, has been specified as 07 minutes.

2.2 Cab Reversal procedure for 3-phase locomotives.

(i) Railways reported derailment of WAP-7(fitted with conventional brake rigging without provision of parking brake) in a yard during cab changing. Loco pilots reported that on removal of BL key & A-9 handle from working cab, loco started rolling and de-railed at facing point. Failure analysis pointed out that with modified (conventional type) brake rigging, when LP removed BL key from Driving (D) to Off (O), the loco brake was getting released due to leakage from D2 valve because of non-availability of parking brake.

As per the existing practice at that time for cab reversal, first BL key used to be taken out from Driving (D) to Off (O) then A-9 handle was removed at neutral position after application of brake by SA-9. It was not ensuring application of brakes through A-9 in locomotive as removal of BL key was cutting-off the air supply. Whereas in locomotives fitted with parking brakes, removal of BL key will ensure application of parking brakes automatically and ensure safety.

(ii) In view of above, it has been felt necessary to modify the cab reversal procedure due to provision of modified (conventional type) brake rigging in WAP-7 locomotives as under : (i) DBC (A-9) handle is to be moved to “Neutral” position. (ii) There after remove BL key, to ensure brake application through A-9.

The revised procedure for cab reversal in 3-phase locomotive fitted with conventional brake rigging has been issued to Railways vide RDSO’s letter no EL/3.2.19 (3 Phase) dated 04.01.2012.

2.3 Reliability Action plan for E-70 brake system: Various performance review meetings of E-70 Brake system of 3-phase locomotive were held at RDSO/Lucknow in which failure analysis and progress on implementation of reliability action plan were deliberated. Brief descriptions of the same are given as under.


Fig 1: E-70 Brake System

2.3.1. Failure of unloader circuit:

(a) Problem

Main Reservoir (MR) air pressure drop from exhaust port of unloader valves, in case of malfunctioning of unloader circuit. Also in case of failure of 01 unloader valve, it is not possible to isolate the faulty unloader valve as both unloader valves get isolated by disconnecting the electrical supply to EP valve (33) as shown in fig 2.

Fig 2: Schematic Circuit Diagram of Unloader Valve


(b) Investigation:

Unloader valves of compressors are controlled with air pressure received from electro-pneumatic valve (No. EP-33) driven by ‘O’ slot card of central electronics of locomotive. When this valve is closed, there is no air flow from the exhaust port. When the electro-pneumatic valve (EP-33) is energised it opens the exhaust port of unloader valve. Unloader valve is shown in fig. 3. It was found that exhaust port remains open even after de- energization of EP valve 33.

Fig 3: Unloader Valve (UV) in CP circuit.

(c) Action Taken:

(i) To avoid locomotive failure due to discharge of air through exhaust port of unloader, a isolating cock was provided at the exhaust port of unloader valve. Isolating cocks of size 3/4’’ with vent was provided on the threaded end of exhaust port of each unloader as shown in fig. 4.

The following precautions are to be taken for providing isolating cocks. (a) Isolating Cocks type OPL (Open Parallel to Line) should be provided on the exhaust

port of unloader valve. These are to be sealed in open position before loco leaves the Shed. Loco Pilot should be suitably advised to make entry in the log book, whenever seal is broken for operation of the cock in case of malfunctioning of unloader circuit.

(b) In case of isolation, compressor will start under back pressure. This may lead to tripping of auxiliary convertor due to high starting current drawn by the compressor motors and may have adverse effect on life of compressor motor. Therefore, unloader circuit shall be attended at the first available opportunity and the isolating cock shall be normalized after rectification of defects of unloader circuit.

RDSO had issued Modification Sheet No. RDSO/2012/EL/MS/0412 Rev.’0’ dated 22.08.2012 for provision of isolating cocks.

Unloader Valve


Fig. 4 Arrangement of isolating cocks for CP.

2.4 Failure of metal seated Non Return Valve (NRV):

(a) Problem Railways were reporting the problem of metal seated NRV’s (Disk Valve type) getting struck up in E70 brake system leading to air leakage.

Fig 5: Non Return Valve (NRV)

Non Return Valve (NRV)

Unloader Valve

Isolating

Cock

Rubber seated

NRV


(b) Investigation The reason for stuck up of NRV had been attributed to breakage of studs/spring seats and ingress of foreign particles. Carbon deposits were also causing NRV’s to struck-up.

(c) Action Taken: Metal seated type NRV was replaced by rubber seated type (Polyurethane seated). The Polyurethane rubber has excellent tear and abrasion resistant with high hardness and a low resilience. After the provision of the Polyurethane seated NRV, the problem of NRV getting stuck-up reduced substantially.

2.5 Failure of Pressure Reducing Valve (PRV):

(a) Problem Railways reported the crack/shearing of Pressure Reducing Valve body (made of Polycarbonate) provided in parking brake circuit and aux. equipment manifold of E-70 brake system.

(b) Investigation: Modified high flow Pressure Reducing Valve (PRV) was tested at firm’s premises with air leakage by providing choke of 1.2 mm to simulate the actual working condition. There was no loss of air pressure in the modified PRV. Therefore, high flow modified Pressure Reducing Valve with metallic body was adopted.

(c) Action Taken: Consequent upon satisfactory field performance of 12 numbers of indigenous high flow modified Pressure Reducing Valve of metallic body at pressure setting of 6 kg/cm2 and 8 kg/cm2 in parking brake and auxiliary equipment circuit respectively, the clearance for fitment of the same in E-70 brake panel was accorded in place of existing SMC make. The letter had been issued to all Railways vide letter No. EL/3.2.19/3-Phase dated 14.06.2013.

2.6 Failure of Driver Brake Control (DBC):

(a) Problem: When DBC Handle, is moved to Neutral position, potentiometer output was dropping to zero volts. The failure of DBC was attributed due to the play in the handle of indigenous potentiometer. However, Railways reported few cases of failures of DBC fitted with imported make potentiometers too.

(b) Investigation: Potentiometers used to be checked by ohm-meter (Resistance measurement) instead

of voltage measurement as suggested in OEM manual. There is a need to ensure proper setting of potentiometer cam switch as recommended in OEM manual on a test jig. Overhauling of DBC should be carried out after 4.5 years of service. In Neutral position of handle, normal voltage output of potentiometer should be 15V. Joint measurement carried out at ELS/GMO which indicated that in failed DBC resistance of potentiometer was recorded as open circuit instead of specified value of 2750 ± 30 ohms. In other position of DBC handles, resistance values were within the specified limit.

(c) Action Taken: (i) All indigenous potentiometers were replaced with imported make potentiometers.


(ii) Modified Cam and Stop Plate were provided in new supplies. (iii) Zonal Railways should check the healthiness of potentiometer with resistance as well

as voltage measurement method.

2.7 On application of brake BP pressure not falling down which resulted in non-application of brake without any fault massage on DDS.

(a) Problem: On application of brake, BP pressure not dropping which resulted in non-application of brake without any fault massage on DDS.

(b) Investigation: (i) It has been noticed that solder joints of signal connector pin carrying transducer signal

was found cracked and guiding strips were not intact in brake electronics rack of faulty locomotive.

(ii) Improper fitment or frequent fitment / removal of brake electronics card without ensuring intactness of card insertion guide may lead to crack of solder joint in the back plane of electronics rack. Loss of control reservoir pressure transducer voltage signal will lead to non-application of service brake through DBC.

Fig 6: Brake Electronics Rack

(c) Action taken:

(i) Thorough checking of solder joints of backplane of electronics rack by magnifying glass for any cracks, whenever rack is removed for any attention or during major schedule.

(ii) Electronic cards should be thoroughly cleaned by dry air blowing during IOH/major schedule and tightness of screw holding brake electronics card, proper fitment of card insertion guide and condition of pins are to be checked whenever cards are replaced.


(iii) For proper maintenance, RDSO issued Reliability improvement measures in the E70 brake system of 3-phase electric locomotives vide letter no. EL/3.2.19/3-phase dated 06.11.2012 for overhauling of pneumatic valves & its testing

2.8 Interchangeability of PCB card and Electronic rack for imported/indigenous versions:

(a) Problem: There are two types of brake electronics racks and cards are in service i.e. imported and indigenous rack along with imported/indigenous card. The indigenous card and indigenous rack are slightly shorter than imported ones. The indigenous cards fitted in indigenous rack work properly. However, problem may arise when indigenous cards are fitted in imported rack or imported cards are provided in indigenous rack.

(b) Investigation and action taken: (i) To address the problem of interchangeability, spacers are provided in indigenous cards

and insulation strips in the indigenous rack. With this modification, indigenous cards & racks are now completely interchangeable.

(ii) Electronic cards should be thoroughly cleaned and tightness of screws holding brake electronics rack should be checked during major maintenance schedule. Functional testing of E-70 brake system should be carried out on test bench.

2.9 Brake Electronics failures messages:

(a) Problem The failure of “Brake Electronics Failures” Spurious messages were received on DDS without brake application.

(b) Investigation: During analysis of background data, it has been noticed that most of the brake

Electronics Failure messages were not followed by S/R Interlock and brake application had not taken place. Brake Electronics Failure messages can be marked into 03 different categories as under:

(i) "Brake Electronics Failure" NOT followed by "S/R Interlock", "Speed above 2 kmph" and "Tractive effort ON"

(ii) "Brake Electronics Failure" NOT followed by "S/R Interlock", "Speed above 2 kmph" and "Tractive effort OFF"

(iii) "Brake Electronics Failure" followed by "S/R Interlock", "Speed above 2 kmph" and "Tractive effort ON. "Brake Electronics Failure" messages, as in Para (i) and (ii), do not have any influence on the operation of the loco in service.

(c) Action Taken: (i) The spurious messages were suppressed by increasing the delay time in software from

200 m sec to 1200 m sec. (ii) Action plan has been circulated vide RDSO’s letter No. EL 3.2.19/3-Phase dated 01.11.12

for increasing the delay period to 1200 ms to eliminate un-necessary fault messages appearing on screen.


2.10 Failure of Air flow Gauge (AFI): (a) Problem Zonal Railways have reported the cases of breakage of air flow indicator gauge glass.

AFI gauge is shown in fig 7.

Air Flow Gauge Fig 7: Air Flow Gauge (AFI)

(b) Investigation: Failure analysis was carried out to understand the problem and observations are listed below:

(i) The inner polycarbonate glass thickness was 8mm. (ii) The gap between the outer Polycarbonate glass and the pointer measures 1.35 mm.

When MR pressure was admitted into the HP port, the inner glass top surface was deflecting in a convex manner, resulting in a peak deflection of 2mm. Therefore at 9 bar pressure itself, the inner projected pointer was touching the inner glass which results in a continuous stress acting on the glass, consequently breaking the gauge glass.

(c) Action Taken: (i) Design modifications were carried out as under:

Thickness of polycarbonate glass increased from 8mm to 12mm.

Inside chamber size reduced from 39-49 mm to 19-20mm

The space between needle and glass is increased from 4.2mm to 5.5mm (ii) After this modification, no failure of modified AFI gauge has been reported by

Railways. This modification has been done in E-70 as well as CCB brake system.


2.11 Failure of FD1 (SA-9) and D2 Relay Valve (a) Problem:

ELS/LGD and ELS/GMO reported failures of Valve stem of D2 Relay Valve/ SA-9. This was causing heavy air leakage in valves.

(b) Investigation: (i) Stem rubber insert found shifted as shown in figure 8. (ii) A gap of up to 0.7 mm was observed as indicated in figure 9 & 10. (iii) Seating of insert found only at outer periphery of internal diameter with partial

seating at the face. (iv) Clearance between the Rubber insert and the valve stem seating surface is more,

which leads to poor bonding between the rubber insert and Valve stem.

Fig 8: Shifted rubber insert found in D2 relay valve

Fig 8. A ga Fig 9: A gap up to 0.7mm between outer seating and rubber.

valve

Fig 10. Improper seating of insert at

Periphery

Stem rubber insert

found shifted

Gap of up to 0.7mm was

observed in between Rubber

insert & Valve stem

Improper seating


(c) Action Plan: (i) Drawing of valve seating was modified and step design is removed as shown in fig 10.

All the D2 relay valves were modified.

2.12 Failures of Driver’s Brake Control (DBC) of E-70

(a) Problem: Failure of Driver’s Brake Control (DBC) of E-70 resulting in brake pipe (BP) pressure not charging and BP not increasing.

(b) Investigation: Connector pin as shown in fig 12 was found bent and has gone inside from location. Manufacturing defects caused loosening of pin in connector consequently improper matching of pins.

Fig 12: Loose and bent connector pin of DBC

(c) Action Plan: (i) Defective connector/pins were replaced.

Fig 11. Valve with modified design where step in seating is removed.

Step removed


(ii) During schedule inspection proper condition of male/female position of connector should be checked.

2.13 Failure of Drip Cup with Auto drain valve

(a) Problem: Failure of drip cup gasket causing heavy leakage of air

(b) Investigation: (i) Gasket is found cut during service due to play from body (ii) After tightening of cover, the gasket sometime slips either on bottom or core side due

to play as shown in figure 13.

Fig 13: Existing gasket profile

(c) Action Plan: (i) The inner diameter of gasket is reduced by 1.5 mm from the existing design modified

gasket as can be seen in figure 14. (ii) New die made for modified gasket profile. (iii) Cut-in date of modified gasket was May 2015. (iv) 05 nos. of modified Drip Cup Gasket provided to ELS/AQ to monitor the performance

of the modified gasket.

Fig 14: Modified gasket Inner diameter reduced by 1.5 mm


3.0 Review of Reliability Related issues of Computer Controlled Brake (CCB) system of M/s KBIL:

Fig. 15 : Computer Controlled Brake System (CCB)

3.1 Failure of Unloader Valve (M/s. KBIL make)

(a) Problem: Railways reported the failures of Unloader Valve leading to heavy air leakage and MR air

pressure drop (b) Investigation: (i) Failure of sealing rubber in the unloader valve was observed. (ii) Cap hex head size was less leading to difficulty in opening the valve during maintenance.

Fig 16: Unloader valve provided with CCB

Cap hex height increased for

proper grip


(c) Action Taken:

(i) Modified Unloader Valve with improved sealing Rubber quality (Viton rubber). (ii) Increased height of the cap hex head for proper grip for tightening. (iii) 12 loco set (24 Nos.) of modified unloader valves were already provided in the following

sheds for field trials for 4 months.

Shed No. of Valves Date of fitment

ELS/AQ 04 nos. (02 loco sets) April 2016

ELS/LGD 06 nos. (03 loco sets) May 2016

ELS/KYN 06 nos. (03 loco sets) March 2016

ELS/TKD 02 nos. (01 loco sets) May 2016

ELS/TATA 06 nos. (03 loco sets) March 2016

Based on the feedback from sheds, the modified valve will be provided in all the Locomotives. Zonal Railways were requested to monitor and submit performance report to RDSO. Performance reports are expected by July 2016.

3.2 Failure of Brake pipe Control Portion (BPCP) and NB-11:

(a) Problem:

BP pressure not building up after emergency brake application in locomotive due to air leakage from BPCP valve.

(b) Investigation: After detailed investigation it was decided to provide suitable restriction for entry of heavy foreign particles in BP pipeline circuit. During emergency brake application, there are three points from where BP is destroyed to atmosphere. These are PVEM in BPCP, NB-11 and 821 vent valve. PVEM is mostly affected due to ingress of foreign particles as shown in fig 17 & 18.

Fig 17 : Dust collected inside the valve Fig 18: Photographs of dirt/dust

ingression in BPCP valve


(c) Action Taken:

(i) Provision of mesh filter for BPCP. This was fitted in10 locos on trial basis for 04 months on WAG-9H electric Locos homed at ELS/BIA, ELS/TATA & ELS/TKD from April 2016. After successful performance, same will be implemented on regular basis.

(ii) Alternately M/s KBIL also proposed the provision of 2 way dust collector in BP circuit (as per RDSO design SKETCH No. SK-97005 deployed in BG passenger carriages) near Brake Panel. This arrangement is to be provided in 05 locos on trial basis. Performance is being monitored.

(iii) Precautions to be taken to avoid ingress of foreign particles in BP pipe line: While connecting loco with train rake, loco BP has to be kept at zero before opening BP angle cocks of locomotive and train pipe. After opening angle cocks, BP should be charged from loco. This way contamination within train pipe will be pushed towards other end of train and will not enter locomotive brake pipe easily.

3.3 Moisture drainage arrangement in Panto reservoir

(a) Problem:

No provision for moisture draining from Panto reservoir in CCB of M/s KBIL is available. This leads to accumulation of moisture which leads to malfunctioning.

(b) Investigation and Action taken:

(i) Modification has been done in ELS/RPM on loco no. 30409 in WAP-7 as shown in fig 19.

Fig 19: Drain pipe connection

(ii) RDSO to issue Modification Sheet after evaluation of performance report from ELS/RPM for regular implementation on all locomotives.

Drain pipe connected in

place of test point (TP)


3.4 Failure of “Brake Electronics” (a) Problem: The problem of “Brake electronics failed”, during power-up, “Brake Electronics Failed”

Fault was getting logged in DDS. (b) Investigation: (i) It was observed that Brake Controller (EBV-A) was taking more time for booting and

hence, CCB health signal (3008) was getting generated. (ii) Root cause was found that booting time of brake electronics was 60 sec, which is very

high. (c) Action Taken:

(i) Existing software was modified to overcome this issue by reducing the booting time of CCB to 20 sec.

(ii) This modification has been done in all locos. Firm also informed that all new locos fitted with CCB System from CLW are being turned out only with the modified software with booting time of 20 sec.

4.0 Removal of Anti-spin Valve and Auxiliary Equipment Flange Lubrication (AEFL) on E-70 &

CCB Brake System in 3-phase electric locomotives.

4.1 Removal of Anti-Spin Brake:

RDSO carried out trials in Dhanbad Division on WAG-9 locomotives to adjudge the efficacy of Anti Spin Brakes and observed the behaviour of traction control system during wheel slip. On the basis of findings of trial report no. ELRS/IR/110, it was recommended to isolate Anti Spin Brake (ASB) on WAG-9 and WAP-7/WAP-5 electric locomotives. Subsequently, it was decided to isolate the anti-spin valve, in 37th MSG meeting held in July 2015. The anti spin valve is shown in fig 20.

Fig. 20 Anti spin valve

4.2 Removal of Flange Lubrication manifold of E-70: Auxiliary Equipment Flange Lubrication (AEFL) on the E-70 brake system is also not being used. CLW is also isolating the equipment needed for these features by not providing power supply to anti-spin brake valves and isolating the cocks on AEFL manifold on the E-70 brake frame. Removal of this equipment can result in reduction of overall cost of the brake system and also improve reliability.


4.3 Action taken:

RDSO issued Modification Sheet No. RDSO/2016/EL/MS/0447 Rev.’0’ dated 21.03.16 for removal of anti spin, brake and arrangement of flange lubrication.

5.0 RDSO has issued from time to time various instructions as MS, SMI & TCs as under:

S.No. Modifications/SMI/TCs Subject

01 RDSO/2012/EL/TC/0113, Rev ‘0’ Pneumatic testing of Three Phase electric locomotives in Electric loco sheds/Workshops

02 RDSO/2012/EL/MS/0412 Rev’0’ Provision of isolating cock for unloader valves (12) in E70 brake system of 3-Phase electric locomotives.

03 RDSO/2016/EL/MS/0447 Rev’0’ Removal of Anti Slip valve of E-70 and CCB and flange lubrication manifold of E-70 from 3-Phase electric locomotives.

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