Re: Hydrogen damage analysis dear andy i have seen your reply to mr. raul about hic problem. i am working in petroleum refinery in kuwait. we have also hic related problem. can you please answer the following questions?
1. what is your action incase you suspect a hic in a pipe or elbow?
2. how do you plot the defective location?
3. what normal precations you advise for the client? 4. what is the acceptance growth rate in length of indication ( we have growth @ of 5 mm per week)?
we have one elbow found to have suspected hic in an area of 2" length in varying depth from 5mm to 17.5 mm from the OD surface. the line service is Reactor Effluent of unifiner with operating pr.about 2400 Psig and temp 140 deg F.
Thanks in advance
: dear raul
: so you have hic problems in south america! and want to find the easiest way
: of recognizing and sizing.
: first i'll start with the pipe.
: as the pipe is extruded or rolled. the outer surfaces have a work hardened
: skin and gets progressively softer towards the center. impurities migrate
: towards the middle in the forming process.
: second hydrogen
: hydrogen will pass through the pipe wall to atmosphere unless it is
: obstructed by any impurities. in this area the gas will gather and may start
: to split the pipe in a laminar direction. (hic)
: in service
: as the pressure and temperature increases the probalbility of hic increases.
: inversely the lower temp and pressure the less likelihood of hic, but the
: problem never goes away 100%.
: as a gas under pressure it will take the path of least resistance. in a
: perfect world if the pipe wall has no impurities or internal corrosion it
: will dissipate evenly around the pipe and less likely to cause a problem,
: but in the real world liquid runs along the bottom of the pipe eating away
: at the hardened surface leaving an easy path for the hydrogen.
: 0 degree 4 or 5 MHz start the scan at the bottom quarter of the pipe.
: hic will starts to show in the first third from the interior surface, it is
: not possible to call "hic" or "inclusion" when it is an isolated reflector.
: (normal inclusions are at half wall)
: hic is found at multiple depths . scan with 70 half skip 1.5mm sdh fsh. if
: the the hic has started to step (crack vertically)it will show as corner
: reflectors mid wall.
: all the best
: andy cunningham
: : Dear Forum:
: : I am working on ultrasonic spectral analysis for the detection of hydrogen damages (HIC and/or SOHIC) and I haven´t found too much literatura on this subject. Can somebody help me giving me names or leads of literature on this issue? Also, if someone has some experience, I would appreciate any comment or suggestion on how to help me with this.
: : Thanks in advance
: : Eng. Raúl Navarrete
: : Universidad Central de Venezuela.
: : Advanced ultrasonics technics laboratory
: : Venezuela.