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Discussion Forums - The Hendrix Group
HomeHomeDiscussionsDiscussionsOil Refinery Co...Oil Refinery Co...Sulphuric Acid line FailureSulphuric Acid line Failure
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12/8/2009 9:00 AM
 
hi experts, We had a typical failure in our OSBL rack recently.We faced a leak from sulphuric acid line. MOC of sulphuric acid line: Carbon Steel Thickness : 8 mm Commisoned in :2005 Line is running in OSBL rack.A LP steam line (Temp 140 deg C) crosses the sulphuric acid line in (almost resting over the sulphuric acid line).LP steam line is insulated line.Leask was observed from the location where LP steam rest over sulphuric acid line. Insulation in that area is intact.Also no steam lekage observed over there. Is there any phenomenon corrosion rate of sulphuric is agrivated when the temperature is increased? please throw some light in this matter? Regards
 
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12/9/2009 9:00 AM
 
CS is suitbale only if the acid is normal to room temperature i e say around 30-35 Deg C. If the temperature reaches above 50 Deg.C you can expect severe corrosion and CS is not suitable for high temperature in that case you have to select high Chrome and high Ni steel.
 
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12/9/2009 9:00 AM
 
Dear Mr Krish, Thank you for the reply.Sulphuric acid line is of nornal temperature.But failure is due to the LP steam line tiuching the sulphuric acid line in one of the pipe rack. I would like to know any technical document how the corrosion rate of sulphuric acid increases due to increase in temperature.How corroison rate increases with increase in temperature? Regrads
 
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12/9/2009 9:00 AM
 
Carbon steel is normally used for Sulphuric Acid service for concentration 70% above and temperature upto 40Deg.C. With this temperature soft,non-adherent,non soluble iron sulfate layer is formed on the pipe inner wall.Due to high temperature(in your case the local contact area due to steam flashing)the acid will reach the bubbling temperature causing more vapor generation over liquid thus by damaging the above protective layer.Once the layer is damaged then the corrosion rate will be very severe .Further Hydrogen grooving is another phenomenon with damaged protective layer under high temperature especially for carbon steel piping wherever the velocity is increased beyond 3ft/sec. So it is better to avoid contact of high temperature steam on the acid pipeline.
 
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12/10/2009 9:00 AM
 
Dear Krish, Thank you for the reply.It was a very useful information. Regards
 
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HomeHomeDiscussionsDiscussionsOil Refinery Co...Oil Refinery Co...Sulphuric Acid line FailureSulphuric Acid line Failure


  

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