CHART Aluminium plate type exchanger

[I2P]

Friends,
i am working in a natural gas processing plant and we have a CHART Aluminium)plate type exchanger where we are facing severe fouling in one of our passes.the exchanger has 4 passes.the choking is a build up of rust/scale/debris of the upstream piping,which is due to hurried commissioning and poor flushing of piping during the precommissioning stage.I would like to know whether anyone has encountered similar problem,and what are the methods for cleaning the same.I have heard that chemical cleaning would be best for this type of exchanger but would like to know what solvents to use,at what strengths,risk and safety factors,and detailed procedure.
Any suggestions are most welcome

 

[kenvlach]

My 1st choice would be to use an aluminum deoxidizer/desmutter solution. These are used in the metal finishing industry to clean aluminum prior to anodizing, chromate conversion coating or plating. Can safely remove rust with negligible attack of the aluminum. Use normal precautions for dilute acidic solutions (observe MSDS precautions).
Two major vendors are Chemetall Oakite and Henkel:

http://www.oakite.com/comdir/cditem.cfm?NID=179

http://www.henkelsurftechna.com/index.cfm?location=9&pageid=2&group=8&category=13

My 2nd choice would be concentrated nitric acid (67-70 wt%), used slowly & carefully. Wear facial protection, etc. (observe MSDS precautions) and watch out for the initial violent reaction which may create a backsurge. I don’t know what your aluminum alloy is (3003? clad?) but concentrated nitric has little effect on the purer alloys (clad, 1100, 3000, some 4xxx, 5xxx & 6xxx). A comparison of the effect of nitric acid on Al and other metals is shown at

http://www.pc.chemie.uni-siegen.de/pci/versuche/english/v44-24-2.html

 

[davidaver]

In this case of fouling, rust/scale/debris, it is recommended for this type of exchanger (aluminium brazed plate-fin ) to use a "puffing" procedure : blows of the exchanger in counter stream with rupture discs (low pressure is normaly sufficient) and repeat the operation if necessary. Under severe fouling this exchanger will run with maldistribution this can create high mechanical constraints due to temperature difference, leading to cracks and leaks.