Q & A > Question Details
In one of our CDU’s recently we had a leak on the joint between the ¾” overhead neutralizer injection line and 24” overhead vapor line of atmos column. Internal corrosion was observed on the leak area. The pipes thickness was measured at different parts around the leak area and found to be OK. It indicates localized corrosion. We are using neutralizing amine as neutralizer. We are unable to find the root cause of the failure. Are there any instances like this in other refineries? If so, what might be the probable reasons?
03/05/2016 A: Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
I am aware of similar failures at 2 different refineries. In both cases, a leak developed at the neutraliser injection nozzle in the CDU overhead line. The immediate cause of the leak was thinning and eventual perforation of the nozzle due to acid dew point corrosion. A critical factor in both cases was formation of a cold spot at the injection nozzle because the injection quill was being cooled externally by wind and internally by the flow of neutraliser. Root cause was inadequate design (no heat tracing and insulation around the nozzle/quill assembly and injection nozzle installed in the horizontal so not self-draining).
To avoid a recurrence of the failure, I would recommend installing heat tracing and insulation to maintain the nozzle/quill assembly above the acid dew point temperature and relocating the injection nozzle to 45 degrees above horizontal so the injection quill is self-draining from the isolation valve.
21/04/2016 A: NS Murthy, Suez, murthy.ns.ext@suez.com
The solution rests on understanding salt point, water dew point, wash water adequacy, right application techniques of neutralizer and filming amines, etc. Contact your nearest GE service provider to resolve this and as such OH corrosion can be eliminated.