CORROSION AND ITS PREVENTION
Introduction: When metals are put into use in various forms they are exposed to environment containing liquids, gases etc. As a result of this the surface of metal starts deteriorating. This type of deterioration or destruction may be direct chemical attack or electrochemical attack.
Definition: corrosion is a chemical process of oxidation with metal to its surroundings, covering it into metal oxide, carbonates, hydroxide and sulphides. Oxidation takes place only when steel surface exposed to atmosphere or moisture. Chemical reaction is as follows:
4Fe + 3O2 --------2Fe2O3
Effect of corrosion: Corrosion of materials is liable to performance of the product; lose their strength, ductility and certain other mechanical and physical properties.
With the introduction of all steel coaches corrosion has become a major problem. Once starts it is very difficult to control it. This requires replacement of the component. This is much costlier than to save the existing part by proper and timely attention.
Corrosion in ICF coaches: Corrosion in ICF coaches is very common. Corrosion repairs to coaches are mainly carried out during POH in workshops. Corrosion repairs are also done during 102 midlife rehabilitation of coaches that are 12 to 13 years old especially at CRWS, Bhopal next POH in 24 months.
During POH all the under frame members are thoroughly inspected to locate corroded members. Corrosion is indicated by flaking of paint, flaking of metal, pitting and scale formation. Components that is not visible from both sides such as sole bar and trough floor should be examined by tapping with a spiked hammer.
Particular attention should be paid to the more vulnerable members and locations given below.
1. Sole bars, body pillars, turn under and trough floor below lavatories in all types of coaches and luggage compartments of SLRS.
2. Sole bars, body pillars, turn under and pillars above lifting pads.
3. Sole bars, body pillars behind the sliding doors of SLRS
4. Sole bars, body pillars, turn under at the door corners & near coach body bolster.
5. Headstock
Inspection of under frame member for corrosion attention should be done as per technical pamphlet no 7602(rev: 1)
Reason of corrosion in ICF Coach:
1. Accumulation of water, dust and salty discharge under luggage compartment in coaches.
2. Incorrect fitness of side panels.
3. Galvanic cell formation between steel and aluminium near window area.
4. Seepage of water at corners and ends due to water accumulation on floor.
5. In sufficient surface preparation before welding.
6. Frequent use of concentrated acids for the cleaning of toilets.
7. Leaky push cocks, flusher valves.
8. Missing/defective commode chutes resulting in splashing of toilet discharge leads to corrosion of under frame members.
9. Carrying of perishables items like fish in SLRS and Parcel vans and insufficient cleaning after unloading.
10. Entry of water through gaps in window sills.
11. Cracks in body panels and roof left unattended.
12. Painting defects left unattended.
13. Damage to under frame and trough floor due to flying ballast in dynamic condition.
14. Acid spillage from batteries.
Need of Corrosion prevention:
1. To avoid premature detachment of coaches and wagons in service.
2. Corrosion makes wagons unfit for loading. This has a bad effect on earning capacity of railways.
3. There will be a shortage of wagons fit for loading if wagons are detached for corrosion repairs.
4. Detachment of coaches for corrosion repairs has an adverse effect on the normal composition of trains.
5. In monsoon season seepage of water through corroded panels spoils the consignment and railway is forced to pay compensation for the damage.
6. Manpower material and time involved in corrosion repairs can be controlled through proper anticorrosion measures.
7. Losses of railway revenue i.e. losses to the nation.
Always Remember the Saying: - ‘A STICH IN TIME SAVES NINE’ while dealing with corrosion.
Inspection during POH:
1. Inspection of sole bars, body pillars and turn under: Examine visually and with the help of a spiked hammer from below the coach and the inspection holes in the turn under. If corrosion is suspected at places without inspection holes 100mm dia hole should be cut at the bottom of turn under for examination. If corrosion is noticed in the bottom half of the sole bar the trough floor to be cut to a width of 300mm for inspection. In case of heavy corrosion the side wall to be cut to a width of 500mm.
2. Inspection of headstock: Examine visually inner and outer headstock, stiffening behind buffers and the junction of sole bar and the headstock for corrosion. Examine the base buffer assembly carefully.
3. Trough floor: Examine trough floor adjoining the lavatories and under the luggage compartment of SLRS and Parcel vans for corrosion with the hammer.
Corrosion Repairs During POH:
1. Repairs to under frame members: Repairs to under frame members should be carried out as per RDSO pamphlet no C7602 for ICF coaches. Corrosion resistant steel sheet for trough floor, pillars, sidewalls and roof should conform to IRS M-41-97. Electrode IRS class B2 of approved brands. Paint red oxide zinc chromate primer is-2074-62. Bituminous anti corrosive solution to IRS-P30-96.
2. Repairs to Headstock: Only 8mm thick sheet is to be used headstock repairs.
3. Repairs to Sole bar: The new sole bar section to be welded from both inside and outside.
4. Repairs to Side Wall Members: For repairs to side and end wall members’ interior fittings interior panels & window frames are to be stripped. Repairs to be done as per RDSO sketch No. 76019.
5. Repairs to Trough Floor: For trough floor repairs plywood flooring to be stripped. Repairs to be done as per RDSO instructions.
6. Repairs to Roof: Special attention to be paid at locations where gutter mouldings are and where ventilators are fitted. RDSO instructions to be followed.
HOW TO MINIMIZE CORROSION
Corrosion in rolling stock cannot be eliminated altogether. Hot and humid conditions in our country are helpful for corrosion. A change in climate also has an adverse effect. However timely action during repairs and maintenance will minimize corrosion.
DURING POH
1. Thorough inspection giving extra attention to areas prone to corrosion.
2. Turn under repairs to be carried out with 5mm thick plates.
3. Only 8mm thick SS sheets to be used for head stock repairs.
4. Use stainless steel trough floor and inlays for toilets.
5. Use of 13mm comprege floor board instead of plywood.
6. Use PVC sheets for toilets and compartment floor.
7. Use stainless steel plates with drain holes in doorways.
8. Provision of tubular structure below lavatory area.
9. Corten steel is used for panel repairs.
10. Apply two coats of primer and three coats bituminous solution on all under gear members.
IN OPEN LINE
1. During pit line examination check thoroughly all under gear and under frame components, trough floor and headstock etc. for corrosion. If corrosion is noticed take proper anticorrosive measures.
2. Drain holes and drain pipes should be clear so that water stagnation is eliminated.
3. All water leakage to be arrested at the earliest.
4. Proper repairs to damaged PVC floor.
5. Gaps in window sills to be filled up.
6. Deficient/defective commode chutes to be made good.
7. Hosing of coach interior is to be avoided.
8. Avoid strong acids for toilet cleaning.
9. Body patches to be painted, carry out paint touch up where paint is peeled off.
During IOH all vulnerable areas are to be properly inspected after Cleaning of turn under holes.
How to apply anti corrosive paint in coaching stock.
I. 1st coat ------- zinc chromate
II. 2nd coat ------ zinc chromate, red oxide
III. 3rd coat ------- bituminous thin black solution
IV. 4th coat ------- Bituminous red brown solution
V. 5th coat ------- Bituminous primer thick black
VI. 6th coat ------- bituminous primer silver gray
Exterior paint schedule for coaches
At every 5th POH of a coach or if the condition of paint is not good adopt 9 days painting schedule. (A—schedule) otherwise choose 5days paint schedule.
A-schedule (9—days)
1 st day – Remove old paint
2 nd day – One coat of red oxide zinc chromate primer
3 rd day – One coat of brush filler followed by spot putty
4 th day – Filler 2nd coat (spot putty if necessary)
5 th day – Rub down with silicon carbide paper
6 th day – One coat of under coat
7 th day – Flat with silicon carbide paper. One coat of enamel finishing.
8 th day – Flat with silicon carbide paper. 2nd coat of enamel finish
9 th day – Lettering and miscellaneous work
C-Schedule
1 st day – Washing with soap solution touch up damages with primer
2 nd day – Spot putty if necessary and one coat of under coat
3 rd day – Flat with silicon carbide paper apply one coat of finishing Enamel
4 th day – Flat with silicon carbide paper apply second coat of finishing enamel.
5 th day – Lettering and miscellaneous work
Suggestions to Prevent Corrosion:
1) Supervisors involved in maintenance of rolling should be familiar with areas prone to corrosion.
2) Supervisors should educate their technicians about areas prone to corrosion.
3) Identify corrosion prone areas and inspect them thoroughly during pit line examination, sick line attention, ROH/IOH.
4) Suitable preventive measures to be adopted to save the affected component. In case of heavy corrosion replace the component.
5) Ensure painting of wagons during ROH. painting/ paint touch up during IOH and sick line attention.
6) Supervisors should educate their cleaning staff so that they follow proper cleaning technique.
7) Ensure water tightness of covered wagons.
8) Educate Shunting staff so that they perform smooth shunting without damaging the rolling stock.
9) Ensure proper cleaning of wagons by the contract staff after Unloading.
10) Electrical staff to be counselled about the corrosive effect of acids from batteries.
These small steps will go a long way in minimizing corrosion in rolling stock
BRAKE POWER CERTIFICATE (B.P.C)
This is certificate jointly signed by guard, driver and C & W supervisor prepared in triplicate by C & W supervisor after ensuring vehicle attached in train is fit to run and required amount of vacuum/pressure is maintain in engine and brake van/last vehicle. It contains train no., engine no., load, break up of load, brake power of the train, amount of vacuum/pressure in engine and brake van and first and last two vehicles number respectively.
Revised format of BPC for coaching trains was advised vide board’s letter No.98/M(C)/137/19 Pt. dated 25.08.06 S 121/2. As detailed below, certain practical situations/limitations where in the original BPC become invalid, need to look into:-
i) Two trains starting from different stations and amalgamating into one train at an en route station.
ii) Train originating from one station and disintegrating into two /more trains at an en route station
iii) Trains requiring revalidation of BPC as per provisions of RPC-4 category 3 (a) , 3(b) and 4 at terminal station or wherever train engine is changed at en route station, If no TXR staff is posted at such station.
To take care situation as above, it has been decided that.
a) For trains as in (i) above The BPCs for individual trains shall be clubbed at the intermediate amalgamating point, revalidated and the train worked up to the destination.
b) For trains under the category (ii) above, the originating station shall issue separate BPCs for all the trains which are to be formed after disintegration at any intermediate station. At the intermediate station the respective BPCs shall move along with the train after revalidation.
c) Whenever revalidation of BPC is to be carried out at NONTXR station, It is proposed that the exercise be carried out jointly by Guard and Driver as is prevalent for GDR checks of freight
For the purpose of checking brakes continuity and revalidation of BPC , whenever required , it must b ensured that the value of BP,FP in the locomotive and the rare most brake van are recorded afresh each time whenever the train engine is changed or the rake composition is altered.
There are four types of B.P.
The level of the air pressure/vacuum on the train engine and the brake van gauges as well as the percentage of operative cylinders should be recorded on a prescribed certificate and signatures of the driver and the guard of the train should be obtained by the Engineer (C&W) as per the procedure laid down 112 by each Railway. No train should be allowed to leave with an inoperative/defective Brake cylinder on any coach after pit attention. Trains which have been attended on pit line should have 100% brake power. Trains which are attended on platform or where secondary examination has been dispensed with or en route should have minimum 90% brake power.
Indian Railways Annexure 1.1
BRAKE POWER CERTIFICATE
“THIS CERTIFICATE IS VALID PROVIDED THE RAKE INTEGRITY IS NOT BROKEN OR CHANGED, OR THE TRAIN ENGINE IS NOT CHANGED . IF RAKE INTEGRITY IS BROKEN OR THE TRAIN ENGINE IS CHANGED , THIS CERTIFICATE SHOULD BE REVALIDATED BY ENGINEER (C&W) THROUGH ENDORSEMENT IN THE COLUMN PROVIDED ON REVERSE AFTER ENSURING BRAKE CONTINUITY , PROVIDED THE COACH(ES) BEING ATTACHED , IF ANY HAVE BEEN MAINTAINED AS PER EXTANT INSTRUCTION.”
Driver’s name & signature Guard’s name & signature
Engineer (C&W)
11. Driver remarks & en route endorsements by Engineer(C&W)
IMPORTANT
1. The incoming Driver shall handover the certificate to relieving Driver. If he is leaving the train without relief, it shall be deposited with the authority nominated to receive it, who will give it to the outgoing Driver.
2. The outgoing Driver & Guard will satisfy themselves from the coach nos. given in item 10 that the certificate pertains to their train.
3. It is responsibility of the Driver of train to satisfy himself that the brake power certificate is proper and valid, before working the train shall handover the certificate to relieving driver. If he is leaving the train without relief, it shall be 116 deposited with the authority nominated to receive it, who will give it to the outgoing Driver.
4. For the all types of coaches fitted with air springs in secondary suspension, all air springs should be in inflated condition. In case one or more air springs are in deflated condition, they should be isolated by isolating cock for air springs. Speed restriction of 60 kmph shall be imposed until the condition of air spring is rectified.
Brake Van Equipment:
Similarly, other brake van equipment for which Mechanical Train Examining staff is responsible to supply, should be provided according to the instructions of each Railway. As per RDSO's letter no. MC/CB/28 dt 19.5.2000, racks have to be provided in the SLRS for provision of portable control telephones, portable train lighting equipments, portable fire extinguisher, wooden wedges/skids and stretcher. Railways can modify existing emergency equipments rooms in the guard's compartment to provide racks for keeping the above mentioned items except fire extinguisher
In view of emergency use, all originating trains should be provided following items in front & rear SLRs:-
i) Fire Extinguishers DCP type -in engine (to be supplied by Loco Shed)
ii) Fire Extinguishers DCP type in AC Coach, SLR, Pantry car(to be supplied by C&W)
iii) Wooden Wedges (To be supplied by C & W )
iv) Wooden or Steel Ladder (To be supplied by operating dept.)
v) Stretcher (To be supplied by Medical dept.)
vi) First Aid Box (To be supplied by Medical dept.)
vii) Electrical Box (To be supplied by ETL dept.) 117
viii) Field Telephone Set (To be supplied by S & T dept.)
Formation Of Block Rake: For the purpose of maintaining the coaches & rakes in good condition & to avoid public complaints the Chief Mechanical Engineer in consultation with the Chief Operating Superintendent Of The Railway shall form BLOCK RAKES for each of the long distance trains & the inter railway trains & also nominate spare of coaches adequate no. of the block rakes to replace sick block rake coaches.
Destination Board: Each coach on originated rake should be provided with destination board of approved size by the Primary Maintenance Depot.
Fire Extinguisher: Approved type of Fire Extinguishers should be provided on all originating trains according to number prescribed by railways in Brake Van , Postal Van , Dining Cars AC Coaches etc. These fire extinguishers should be periodically checked after every 3 months & completely refilled after 1 year. These Fire Extinguishers should not be over due for testing & refilling.
Deficiency Rolling Stock (DRS) For Coaching Stock: Railway should devise system for detecting deficiencies. Reports of deficiencies/defects in Rolling Stock (DRS) reports in the Performa should be prepared for each mail/express/passenger originating train in duplicate by the Engineer (C & W) Electrical (TL) and should be signed jointly with the RPF representatives. Reports for mechanical deficiencies should be prepared on specified Performa and may be altered by each Railway on the basis of the items most prone to theft on their system. This should be done soon after the maintenance of the rake is complete in the sick/washing lines. In case the train starts from the platform itself, these reports should be 118 prepared by jointly by C & W and electrical department. DRS Cards should be prepared in duplicate in which original copy is kept as a record copy and carbon copy is handed over to train guard. After the coaches have been jointly checked. And DRS reports have been made, the coaches should be pad locked/key locked and the key and report should be sent to the platform Engineer *(C & W).
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