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Technical Discussions
sandeep sharma
sandeep sharma
09:19 May-17-2005
even after carrying out the magnetic particle test 350 mm dia shaft failed

dear all,
i would be highly obeliged if you can throw the light on a failure of hollow shaft of o.d. 350 mm and id. 100 mm (moc 15Cr Ni Mo4) duly heat treated . Hollow portion is for cooling water (demineralized) to keep its temp down to get better tensile and tortional strength.
This shaft was a used shaft, operator was suspecting leakage so when it was replaced it was decided to test it for cracks by using magnetic particle test. In which this shaft was found O.K. even a hydro test was carried out upto the 35 bar again we could not found the leakage so it was decided to use the shaft.
But after commisioning the shaft it failed within 10 days and at the surface of the fracture there was rusting below the surface covering at least 50 % of area.
What possibly be the mistake made by our NDT people?
Kindly throw some light if you can.

Thanks


    
 
 Reply 
 
Frank Lund
R & D,
United Kingdom, Joined Apr 2005, 219

Frank Lund

R & D,
United Kingdom,
Joined Apr 2005
219
00:33 May-18-2005
Re: even after carrying out the magnetic particle test 350 mm dia shaft failed

The fact that leakage was suspected indicated a crack reaching to the surface. In many applications to find such defects the EMA technique has been very successful. ELF in Norway switched to EMA after seeing it find defects which were revealed by grinding but not by MPI.

----------- Start Original Message -----------
: dear all,
: i would be highly obeliged if you can throw the light on a failure of hollow shaft of o.d. 350 mm and id. 100 mm (moc 15Cr Ni Mo4) duly heat treated . Hollow portion is for cooling water (demineralized) to keep its temp down to get better tensile and tortional strength.
: This shaft was a used shaft, operator was suspecting leakage so when it was replaced it was decided to test it for cracks by using magnetic particle test. In which this shaft was found O.K. even a hydro test was carried out upto the 35 bar again we could not found the leakage so it was decided to use the shaft.
: But after commisioning the shaft it failed within 10 days and at the surface of the fracture there was rusting below the surface covering at least 50 % of area.
: What possibly be the mistake made by our NDT people?
: Kindly throw some light if you can.
: Thanks
------------ End Original Message ------------




    
 
 Reply 
 
Nick Welland
Other, Quality and NDT
Aben Technical Services, Australia, Joined Oct 1999, 42

Nick Welland

Other, Quality and NDT
Aben Technical Services,
Australia,
Joined Oct 1999
42
01:14 May-18-2005
Re: even after carrying out the magnetic particle test 350 mm dia shaft failed
----------- Start Original Message -----------
: dear all,
: i would be highly obeliged if you can throw the light on a failure of hollow shaft of o.d. 350 mm and id. 100 mm (moc 15Cr Ni Mo4) duly heat treated . Hollow portion is for cooling water (demineralized) to keep its temp down to get better tensile and tortional strength.
: This shaft was a used shaft, operator was suspecting leakage so when it was replaced it was decided to test it for cracks by using magnetic particle test. In which this shaft was found O.K. even a hydro test was carried out upto the 35 bar again we could not found the leakage so it was decided to use the shaft.
: But after commisioning the shaft it failed within 10 days and at the surface of the fracture there was rusting below the surface covering at least 50 % of area.
: What possibly be the mistake made by our NDT people?
: Kindly throw some light if you can.
: Thanks
------------ End Original Message ------------

1. Was the crack propagating fromthe OD or the bore?
2. Was it a circumferential crack? If so, did it coincide with a change in section, or evident surface marks?
3. Does the corrosion on the exposed fracture surface indicate the crack was through-wall around any part of the periphery?
4. What magnetizing method did the NDT techs use?

Best regards
Nick


    
 
 Reply 
 
S.R.G.PRABHU
S.R.G.PRABHU
01:53 May-18-2005
Re: even after carrying out the magnetic particle test 350 mm dia shaft failed

I always doubt the success of MPI, as either it is done in a hurried manner or the technique and technicians are not up to the standard.Why can't we switch to other latest methods?

----------- Start Original Message -----------
: dear all,
: i would be highly obeliged if you can throw the light on a failure of hollow shaft of o.d. 350 mm and id. 100 mm (moc 15Cr Ni Mo4) duly heat treated . Hollow portion is for cooling water (demineralized) to keep its temp down to get better tensile and tortional strength.
: This shaft was a used shaft, operator was suspecting leakage so when it was replaced it was decided to test it for cracks by using magnetic particle test. In which this shaft was found O.K. even a hydro test was carried out upto the 35 bar again we could not found the leakage so it was decided to use the shaft.
: But after commisioning the shaft it failed within 10 days and at the surface of the fracture there was rusting below the surface covering at least 50 % of area.
: What possibly be the mistake made by our NDT people?
: Kindly throw some light if you can.
: Thanks
------------ End Original Message ------------




    
 
 Reply 
 
Simon Amalraja
Simon Amalraja
04:04 May-24-2005
Re: even after carrying out the magnetic particle test 350 mm dia shaft failed
----------- Start Original Message -----------
: The fact that leakage was suspected indicated a crack reaching to the surface. In many applications to find such defects the EMA technique has been very successful. ELF in Norway switched to EMA after seeing it find defects which were revealed by grinding but not by MPI.
: : dear all,
: : i would be highly obeliged if you can throw the light on a failure of hollow shaft of o.d. 350 mm and id. 100 mm (moc 15Cr Ni Mo4) duly heat treated . Hollow portion is for cooling water (demineralized) to keep its temp down to get better tensile and tortional strength.
: : This shaft was a used shaft, operator was suspecting leakage so when it was replaced it was decided to test it for cracks by using magnetic particle test. In which this shaft was found O.K. even a hydro test was carried out upto the 35 bar again we could not found the leakage so it was decided to use the shaft.
: : But after commisioning the shaft it failed within 10 days and at the surface of the fracture there was rusting below the surface covering at least 50 % of area.
: : What possibly be the mistake made by our NDT people?
: : Kindly throw some light if you can.
: : Thanks
------------ End Original Message ------------

You can also try UT Leak Detection. You need to plug both ends and try to pressurise it and look for the leak by Leak Detectors of reputed makes.

If you are in India, contact me for further details.

D.Simon Amallraja.
Mobile: 09866343309.


    
 
 Reply 
 

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