ANNEXURE VI
PRESCRIBED
PERIODICITY OF ULTRASONIC TESTING OF RAILS FOR CONVENTIONAL TESTING
1.
According to the latest knowledge on the subject, the periodicity of ultrasonic
testing of rails should depend on the traffic density on the line in GMT, the
rail section and grade of steel and whether the threshold value in GMT (i.e. the
stipulated service life) for the particular rail has been exceeded or not, it
has also been considered logical that, except for high speed routes, no
distinction should be made between various groups of routes in determining the
frequency of ultrasonic testing.
2. Railway Board have issued following guidelines on this subject :
(i) After the initial testing of rails (in
rail manufacturing plant), the first retesting need not normally be done
until the rail has undergone 15% of its stipulated service life in GMT.
Whenever rails are not tested
in rail manufacturing plant, the test
free period shall not be applicable and the rail testing shall be done
at the periodicity given below right from the day of its laying in field. (Para 2 (i) revised vide ACS No.10 of 2002)
(ii) The frequency of testing,
after 15% of the stipulated service life and up to completion of the stipulated
service life, would vary with the rail section and grade and the traffic
density on the line. To arrive at a rational frequency of testing on any route,
the total stipulated service life of a particular rail section be divided by 8,
which will be taken as the maximum GMT to be carried between successive tests
(say 'X' GMT). Actual testing will depend upon the GMT carried by the route per
annum (say 'Y' GMT). The period in years, between successive tests could be
worked out by dividing the former by the latter (i.e., X/Y). The periodicity of
testing for different standard rail sections and grades on BG & MG for
various GMT levels are shown below for guide line. (Testing intervals have been
rounded of to the nearest multiple of three months).
(A) BROAD GAUGE
Rail section and
grade in UTS and the threshold values in GMT
|
Traffic density (GMT/year) |
90 Ib (72) (250) |
901b(90) (375) |
52 kg (72) (350) |
52 kg (90) (525) |
60 kg (72) (550) |
60 kg (90) (880) |
|
Below 10 |
3 years |
3 years |
3 years |
3 years |
3 years |
3 years |
|
10-20 |
2 years |
3 years |
2.75 years |
3 years |
3 years |
3 years |
|
20-30 |
1 year |
1.75 years |
1.75 years |
2.5 years |
2.75 years |
3 years |
|
30-40 |
9 months |
1.25 years |
1 year |
1.5 years |
'1.75 years |
2.75 years |
|
40-50 |
6 months |
1 year |
9 months |
1.25 years |
1.5 years |
2 years |
|
Over 50 |
6 months |
9 months |
9 months |
1 year |
1 25 years |
2 years |
(B) METRE GAUGE
|
Traffic density (GMT/year) |
501b (72) (100) |
601b (72) (125) |
751b(72) (150) |
75lb (90) (225) |
90lb(72) (250) |
901b(90) (375) |
|
Below 1.5 |
5 years |
5 years |
5 years |
5 years |
5 years |
5 years |
|
1.5-2.5 |
5 years |
5 years |
5 years |
5 years |
5 years |
5 years |
|
2.5-5.0 |
3 years |
4 years |
5 years |
5 years |
5 years |
5 years |
|
Over 5.0 |
2.5 years |
3 years |
3.5 years |
5 years |
5 years |
5 years |
(iii) The peiodicities given
above shall be halved when the actual traffic carried on the line has crossed
the threshold values indicated in each case.
(iv) For high speed routes,
which will be maintained to track tolerances as per
RDSO's Report No. C&M-1, the minimum frequency of testing shall be
once a year for the period after 15% service life of the rail and upto
completion of the stipulated service life. Thereafter, it shall be once in six
months.
(v) For all other routes, the
minimum frequency of testing shall be once in three years for BG and five years
for MG regardless of traffic carried.
(vi) The frequency prescribed
above for rails would equally apply to welds in the track, with the proviso
that the use of
80
probe
may be dispensed with if alumine-thermic weld failures are less than 0.5% of
the population of welds in block section since the last testing.
(vii) If the total number of
rails with IMR and REM defects detected during ultrasonic testing and/or actual
fractures exceed one per km in a block section since the last testing, the
frequency of testing shall be once in two months or after passage of 8 GMT of
traffic, whichever is earlier.
Note:
Notwithstanding what has been stipulated above, the Chief
Engineers may authorise ultrasonic testing at closer intervals, or on adhoc
basis, in case any incidence of premature failure of rails or abnormal increase
in fractures is deemed to warrant such action.