CHAPTER 6
CONVENTIONAL
CRITERIA FOR REMOVAL OF DEFECTIVE RAILS AND WELDS DETECTED BY PERIODIC
ULTRASONIC RAIL FLAW DETECTION (USFD) AND FREQUENCY OF TESTING.
6.1 Classification of rail defect
6.1.1
Since propagation of crack depends on the traffic density and speed on the
section, the various flaws and their remedial action have been classified
separately. Separate criteria for BG and NG sections have, however, been
proposed.
6.1.2
Depending on the nature and extent of internal flaws, traffic density and speed
on the section, the defects have been classified into three major categories
i.e. IMR, REM and OBS as per Annexure IV.
OBS defects have been further
classified as OBS (E) and OBS (B). An OBS defect located within fishplated zone
has been designated as OBS(E). Similarly, an OBS defect on any major bridge and
up to 100 m on its approaches has been designated as OBS(B).
6.2 Action
to be taken after detection of defects in rails
|
S. No. |
Classifi-cation of defects |
Action required to be taken |
Speed restriction etc. to be imposed if action under
column (3) is delayed. |
|
1. |
IMR |
Immediate replacement (not later than 3 days) |
Impose 30 km/h and depute a watchman till defective
part replaced. |
|
2. |
REM |
Replace within 15 days |
Impose 30 km/h if not replaced within 15 days. |
|
3. |
OBS (E) |
Replace or end crop within 15 days |
Impose 30 km/h if not replaced within 15 days. |
|
4. |
OBS (B) |
Replace within 15 days |
Impose 30 km/h if not replaced within 15 days. |
|
5. |
Other OBS |
PWI should observe with a magnifying glass each OBS
location and duly record his observation once a month, to see if the crack
has developed further in which case action as for REM defects should be
taken. PWI should maintain sleeper, fittings and ballast at such locations in
sound condition. AEN should also test-check some of the OBS locations and
record his observations during his monthly push trolley inspection of each
section. |
|
6.3 AT
weld defect classification
6.3.1 Defects
detected by 0º
and 70º
probe shall be classified in the same manner as mentioned at para 6.1.2 except
OBS (E) defects.
6.3.2 Defects
detected by 70o 2.0 MHz probe (flange testing) are classified as IMR
and OBS as per Annexure V. (Para 6.3.2 revised vide ACS
No. 10 of 2002).
6.4 Action on AT weld defects
detected
6.4.1 Following
action shall be taken in case of defects detected on welds.
6.4.2
All welds which are less than
one year old and are found to be defective during USFD, shall be replaced
within the period as stipulated in table given below and further action should
also be taken accordingly." (Para 6.4.2 revised vide ACS No. 4 of
1999)
|
S. No. |
Classifi-cation of defects |
Action required to be taken |
Speed restriction etc. to be imposed if action under column (3) is delayed |
|
1 |
IMR |
Replace within three days |
Impose 30 km/h, depute a watchman and suitably
clamp with joggled fishplate till defective' weld replaced. |
|
2. |
REM |
Replace within 15 days |
Impose 30 km/h if not replaced within 15 days. |
|
3. |
OBS (B) |
Same as IMR weld defect |
Same as IMR weld defect. |
|
4. |
OBS |
Suitably clamped with joggled fish plate PWI should observe every defective weld with a
magnifying, glass and record his observations once a month to see if the
crack has developed further in which case action as for IMR defects should be
taken. |
|
6.4.3
If the defective welds are more than one year old and if the section is not due
for renewals in the next five years, replacement of such defective welds should
be undertaken. Further, in case where the number of welds failures /defective,
welds in a year exceeds two per 100 welds, complete renewal of all the welds in
the block section should be under taken if the section is not due for rail
renewals in the next five years.
6.4.4
In all other cases where rail renewals is due in the next five years, the
defective welds shall be joggled fish plated and provided with four tight bolts
and supported on a wooden block and visually inspected every month by an
employee not lower than key man.
6.5 Flash Butt and Gas Pressure Weld defects
classification and action to be taken after detection of defects
6.5.1
Classification and action shall be same as mentioned at para 6.1.2 and 6.2
respectively.
6.6 Frequency of testing :
The guidelines for determination of periodicity and frequency of USFD
examination of rails and welds shall be as given in Annexure VI.
6.7
Marking of defects in the field: (New para 6.7 introduced vide ACS No. 1 of 1999)
The three categories of
defects shall be marked in the field, on the rails, as follows:
|
S.No. |
Classification |
Painting on both faces of
web |
|
1. |
I.M.R |
Red - 3 stars |
|
2. |
R.E.M. |
Red - 2 stars |
|
3. |
O.B.S. |
Red - 1 star |
|
4. |
OBS (B) |
Red - 1 star |
|
5. |
Other OBS |
Red - 1 star |
6.8
Check list of Ultrasonic Testing of Rail/Welds:
A check list for the officials inspecting the
quality of work being done by the Inspectors carrying out Ultrasonic Testing of
Rails/Welds is placed at Annexure-X
(New para 6.8 introduced vide ACS No. 5
of 1999)