I have come across such acid lines which are jacketed with LP steam passing through the outer pipe. I always thought this as a standard design practice.
DHURJATI SEN
Kolkata, India
Is the heater plug type? An affirmative would answer your question.
If it is not a plug type, still does it have flanges? If yes, same answer.
The Company does have an operation and maintenance code.
Even the heater OEM must have given repair procedures.
What do these say?
DHURJATI SEN
Kolkata...
Is the pressure vessel insulated?
Is it externally painted?
You can always eliminate the external corrosion and do your calculations based ONLY on internal corrosion.
As a matter of fact, the causes for external and internal corrosion are entirely different.
DHURJATI SEN
Kolkata, India
Why would you like to use such a 'not very accurate' method to ascertain the material grade?
Better consult Material Handbooks. It is tedious but highly rewarding (as well as accurate).
DHURJATI SEN
Kolkata, India
Do these chemicals auto ignite when in contact with oxygen?
Even after nitrogen blanket, why inhibition is required? (assuming the tank inside is coated)
DHURJATI SEN
Kolkata, India
Why don't you suspect the diesel?
Check the upstream units that send diesel of any probable mal operation that has been concealed.
The log books could give you a clue.
DHURJATI SEN
Kolkata, India
Why the flushing was not carried out before PWHT? That is not a good fabrication practice, irrespective of what API permits.
DHURJATI SEN
Kolkata, India
How long was the tank in service?
Is there a spare tank?
What quality control procedures were followed during tank manufacture?
Answers to the above would lead to the solution.
DHURJATI SEN
Kolkata, India
I have come across many CDUs where the top product is off-gas that is sent to flare or recovered partially as fuel gas.
Below it comes LPG & then naphtha.
DHURJATI SEN
Kolkata, India
What made you notice the thinning?
As the final structure is PVC coated, you ought not to have worried a bit regarding Galvanic corrosion!
DHURJATI SEN
Kolkata, India
You ought to have a requirement, a standard or a benchmark for comparison. Even if the unknown steel sample has received a heat treatment, still you need to know what exact heat treatment has it received.
DHURJATI SEN
Kolkata, India
You need to determine whether the corrosion is shell side, or tube side, or BOTH.
Check the tube edges (the portion that protrudes out of the tube sheet) to assess cooling water corrosion.
Pull out a failed tube to check shell side corrosion.
I will not worry much about the tie rods and the...
The expansion tank should have an inlet steam distributor that increases the temperature of the make up water before it gets into the overall system. My experience says that in most cases it is not working or damaged which leads to a temperature difference and hence fatigue failure.
DHURJATI...
Perform a visual inspection of the existing lining. Look for any physical damage.
Also, carry out holiday testing of the lining.
If both above results are satisfactory, apply the same to the new tanker.
If not, explore repair procedures for the same.
Since you have strong solid data...
How long did the carbon steel piping survive?
What piping is used for the other rolling stands?
Without a proper failure analysis, simply upgrading the material is an expensive and low technical approach, but mostly works quite well.
DHURJATI SEN
Kolkata, India
API 650 is specifically for oil storage, hence extra precautions.
Sizes and loadings are almost same in both the standards.
DHURJATI SEN
Kolkata, India
