LIMA, As far as I remember, caustic dosing is always limited to max. 3 PTB, i.e., 10-12 ppm. This limitation has less to do with pH or caustic embrittlement problems. This is rather related to coking problems /catalyst poisioning etc. in downstream units. Overdosing of caustic does not help. It may create problems as discussed. It is going to increase fouling in Crude PT. It will increase the corrosion by H2S , as protective FeS scale may get unstable at higher pH. I am not very sure whether stoichometric balance should be maintained in case of excessive Cl-. In any case, NaOH is supposed to convert hydrolysable Chlorides of Ca & Mg which may be approx 25% of total chlorides. One does not need to bother about NaCl for O/H corrosion as max part of NaCl is expected to move out with bottom residue. 'Hope this helps. Regards

Hi alexgr7 The major contribution to the fin fan tubes corrosion is the ammonium chloride salts that create the corrosion under deposit .In order to control this please the following may help you: Mechanical change: Ask you maintenance shop to fabricate tubes insert this will help accumulation of the salt at the tubes inlet so; you will eliminate the corrosion and erosion at the tubes inlet. Process change: You know the fin-fan coolers at the over head system are cool down and condense the over head naphtha before water and hydrocarbons separate in the over head receiver. The fin-fan coolers had this tendency to foul so, the best practice is to flush them with water (with the quality) the best water source is recycled water from overhead receiver (at least wash them one hour per week). The fouling problem is due the fin fan coolers header not distribute the flow equally the farthest tubes had flow low than the nearest tubes. Corrosion Control: coating was not implemented at our plant and there is future plan to coat the fin fan coolers. Good deslter and keep the chloride level at water boot under the targets. Also, control the neutralizer pump dosing rate. Also, the over head water wash is very important to prevent the ammonium chloride salts deposit at the over head line too. At the end I am sure Mr. Lima had more to add that will be more valued to you. Have a good day

dear chakra Are you mean if I notice the high CL nothing I can do are you mean when I increas the caustic injection the cl level will not go down to the normal level You are saying the 25% of the total cl in the water boot rever to the caustic job so from where the 75% coming from. Thanks