Hi all Is there is any NACE requirement for Crude tanks.I mean if any hardness to be measured in bottom weld or shell plate or shell nozzle welds If there is any requirement by NACE how can we deviate or give concession without taking hardness as we are having very big tanks .Valuable inputs could solve our problem. NACE MR0103: Some environmental condition known to cause SCC are those containing free water in liquid phase and 1. 50 PPM dissolved H2S in the free water or 2.Free water PH 4 and some dissolved H2S present Some of the crude comes under this requirments

for oil storage tank pl. see API 650 and 653 for hardness related issue. >Hi all > >Is there is any NACE requirement for Crude tanks.I mean if >any hardness to be measured in bottom weld or shell plate or >shell nozzle welds > >If there is any requirement by NACE how can we deviate or >give concession without taking hardness as we are having >very big tanks .Valuable inputs could solve our problem. > >NACE MR0103: > >Some environmental condition known to cause SCC are those >containing free water in liquid phase and > >1. 50 PPM dissolved H2S in the free water or > >2.Free water PH 4 and some dissolved H2S present > >Some of the crude comes under this requirments

Inspector 1978 NACE MR 0103 applies to all components of equipment exposed to sour refinery environments (see para 1.3 of MR 0103) where failure by SSC would: 1. compromise the integrity of the pressure contaminated system 2. prevent the basic function of the equipment and / or 3. prevent the equipment from being restored to an operating condition while continuing to contain pressure. In other words NACE MR 0103 is strictly meant for pressure components - piping, storage vessels under pressurized operating conditions. Atmospheric storage tanks (Crude Oil) will not come under the purview of NACE MR 0103 strictly - as this is not a pressure vessel. Hardness for P 1 grade materials (C.S generally) should be within 210 BHN in welds / HAZ/Parent plate. If your tank has been specifically classified under NACE MR 0103 (though not mandatory to come under MR 0103) - as a special precautionary measure - I suggest that you take random hardness of fillet welds where accessible at bottom plates and bottom to first course shell plates and in first course shell butt welds to know the distribution of hardness at various plates used for the crude oil tank. If the hardness values are within specified limits of 210 BHN +/- 10 BHN then you do not have to worry too much from SSC problem on the crude oil tank bottom plates. Please note that a discussion forum is meant to share the experiences of professionals in the field depending on their expertise. Before giving comments on other professionals who had answered earlier , i suggest that you go thru MR 0103 applicability thoroughly. Hope this helps to solve your problem. C.V.Srinivasan Nishi Engineers Pvt Ltd India Dec 14, 2009 E-mail: nishi@vsnl.com >Hi all > i am not satisfied with the answer received .Why it is not >applicable for tankages.Also 650 stands silent in hardness >requirment.But this tanks come under the requirments >mentioned in NACE.