Friday, October 27, 2017

Some more quality issues in Locomotives

If welding, painting are simultaneously carried out during rainwater testing rain water testing will be compromised.

In the Steel foundry(picture above)   quality issues of cast products, need to be discussed., it was told that use of Zircon sand, prevention of sand erosion and use of special refractory material at places where cross section changes   helps in improving the quality of the castings.

In some locos,  axle guide link post weld failure can occur.  Hence quality welding is required. 

 TM shop should be visited to see that Mica ( of PPCL make ) failure which results in commutator vulnerability to flashing doesnt happen.

Bogie clearances measurement procedure should be inspected in the shop  :

Above shows Gap b/w bump stop and U/F.

Above shows Vertical and  Lateral Gap between STOP and U/F .

Shown above is the Loaded height of secondary spring.
Gap between axle box and bogie frame is measured .
Ensure No loco is dispatched with outstanding NCs on bogie clearances.

Gear and wheel pressing force should be examined
Following is the picture of practical measurement method  :-

Depending upon interference between axle dia and bore dia, this force varies.
It still remains to be studied how we can increase this force .


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.