Tuesday, October 3, 2017

What can go wrong while manufacturing a locomotive?

Material kept in open for months gets rusted and laden with dust. Check this out in  shell shop. Due to lots of corrosion in the bottom, some machining will again be required before fitment.

Rust ridden bottom.

Above is the photograph of one such cab.
Following shortcomings of TM to be looked into:-
  • Less commutator slot depth.
  • Slack insulators in TMs.
 It is to be seen that commutator slot depth in   TMs is not less than standarad.

Problem of slack insulators, need to be watched out.

Rocker rings of TM should be  inspected.

Regarding unsuitable Centre Pivot of Casnub bogies : problem of blow holes may be found.

Problem of Mica getting broken in commutator need to be  inspected in the shop.

It can be seen that due to Mica getting cracked in between slots( while fixing copper bars), the gap between two slots gets reduced which makes commutator unusable.

Commutator Spider is to be inspected as there can be blow holes/ spongy castings/less material while machining.  

Dynamic seasoning plant for commutator should be  inspected. Theres is a standard RPM (say 3050) at which all plants should be working  . Less than that

may result in less seasoning. 

Thursday, September 28, 2017

What to inspect in a locomotive?

Cab AC ducts were in should be checked for shabby condition.

Make sure Inspection staff     has the fitment drawings of Cab AC ducts.
If not, Same to be collected from design office.
Problem may be reported  regarding gap between mounting brackets of transformer in three phase locos  and should be looked into.
Another problem should be noted during the inspection:-

See in above picture, you find Long nut  here and               Small nut there .

Size of the nut ( check if trade item) should be same . Some nuts can be 3 mm shorter than others in the same bracket.

If it is reported that the battery box was tag welded then  same has to be run welded in the shed.

Vertical portion

It is to be seen that not only the battery boxes are mounted on  run welded brackets only, the vertical portion on the bracket should not be left unwelded at  any place.
Battery boxes ( which are 100 % trade items ) should be   tag welded at places inside the box?
TM shop should be  visited  in order to find out condition of brush insulators and tightness of brush holder pockets.   

Complaint of   shed that CCPT 16 A fuse was being used in place of 10 A, need examination.

Sunday, September 24, 2017

About loco bearings and centre pivot

If failure of Racers occurs in WAG9 locos, procedure to mount axle should be inspected in the shop.:

G9 Racer is induction heated before fitting over the axle journal. ( two racers on each side ).

Axle box     and          Racer        Bearing in above and below snap.

Due to failure of induction heaters, gas heated racers may get the profile damaged and this may result in failure. B 
The radial clearance measurement procedure ( different for SKF and FAG racers ) should be followed with the help of NO-GO gauges.

Centre Pivot:

Castings need to be rejected during machining if there are  large number of blow holes.

Blow holes in Centre Pivot of WAP4 ( Raj ) locos loo like this:

Force fit Racer of WAP5 locos should be  examined while fitment.