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We have two Similar alfalevel packinox plate welded heat exchangers in our unit.
One has a hot end approach of 38 while the other has 52 degrees
what could possibly be the reasons of this difference?
The process are similar in both with same streams and similar feed rate
 
Answers
18/07/2018 A: Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
If the two Packinox exchangers are installed in parallel, the most likely explanation for the difference in hot approach temperature is different fouling rates, either of the spraybars (resulting in flow maldistribution within the plate pack bundle) or of the plate pack bundle itself (resulting in increased resistance to heat transfer). A comparative single point pressure survey across both exchangers and feed filters would be helpful in identifying the cause.
In the former case, if the piping arrangement to the feed filters is not symmetrical then one filter may see a higher solids loading than the other requiring more frequent bypassing of that filter for cleaning with a resultant increase in potential for blocking of the holes in the associated spraybar. Or perhaps the mesh screen in one of the filters has ruptured? Do you have facilities for on-line backflushing of the spraybars to flare using the hydrogen pressure in the exchanger shell?
In the latter case, a loss of catalyst containment in the upstream reactor can cause fouling of the plate pack bundle, especially if there is no reactor effluent strainer present or the if the strainer screen has failed. If the reactor effluent inlet piping is not symmetrical, particulate matter will preferentially flow the long way round elbows (centrifugal force) and may preferentially foul the flow channels in the plate pack bundle of the furthest exchanger away.
18/07/2018 A: sagar dandekar, Bharat petroleum, sagar.girgaon@gmail.com
Your 52 degree approach packinox may be definitely leaking from inside, try to take vacuum taste and water level taste. you can contact alfalaval for that as their engineers do this test for you and repair necessary leakages. and do it only if it is really required repairing activity can be perform during planned shutdowns.
18/07/2018 A: Mike Watson, Tube Tech International Ltd, mike.watson@tubetech.com
Tube Tech International cleans more shell/tube Texas towers globally than any other contractor using all methods regardless of Fouling severity. We find packinox plate design suffer similar issues to TT’s the only difference being - extremely difficult to clean other than with back and reverse flushing with chemicals at temperature. If that doesn’t work then replacement is the only option.
We have perfected the design of shell and tube Texas towers with major EPCs as well as the drilling, polishing and inspection technologies whereby cleaning and IRIS inspection are guaranteed.
17/07/2018 A: Jesus Perez, Alfa Laval Packinox, jesus.perez@alfalaval.com
Assuming these two units are in parallel, the 14 degrees Celsius difference could be caused by unbalanced flow distribution causing one exchanger to experience more fouling than the other one. How are the pressure drops in these two units?
If this is for two different units, any small difference in operating conditions between the two units could cause variations in performance.
17/07/2018 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
If they are in parallel with symmetrical piping, one HX may be more fouled than the other.