Vic Choices of S.S for UAN S.S. 316 L would be better than S.S 416. Ferritic S.S 416 grade will have more corrosion and will pit heavily for both ammonium nitrate and urea compositions given in your mail. S.S 316 L would be better than S.S 416. S.S 416 is not suitable for the intended service. If Chloride containing transport grade liquid fertilizer is used, with cholordes less than 500 ppm, S.S 316 may also pit over a period of time. Due to shock load /torque in transport vehiciles, S.S 316 welds may develop SCC over a period of time in 2-3 years even if it is used at 15-35 degree Celcius. You may think of Sandvik 2 RE 69 (20Cr -22 NI-2.1 Mo-1.5 Cu with Nirtogen and with low carbon) grade which will resist both UAN and also possible use of liquid fertilizer containing cholorides upto certain limits (< 500 ppm) at this temp. This material will last better than S.S 316 for the intended services with chlorides less than 500 ppm. Make sure that you do not have too much chlorides in liquid fertilizer transportation - as any austenitic S.S will tend to pit. Remember : 2 RE 69 grade material will also develop pitting over some years use pit but comparatively less than S.S 316. S.S 416 is unsuitable for all such use. Make sure that stiffeners used in road transport vehicles, amde of either S.S 316 L or Sandvik 2 RE 69 grades, are sufficient thickness so that SCC trend is minimized after a couple of yerars use . Make sure welding is done with low carbon filler wires with low heat input while welding. Also stiffners thickness for road transport vehicles should be same 316 L or 2 rE 69 grades - designed in a way to take the torque load in transport vebicles for liquid or UAN fertilizers. Trust this answers yoru querry. C.V.Srinivasan Nishi Engineers Pvt Ltd Chennai 20 India August 31, 2004 E-mail:nishi@vsnl.com /nishi@hathway.com >Hi, my name is Vic. >Could you help me please. > >I have a choice of 2 stainless steel tankers for the >transport of UAN (urea ammonium nitrate solution, >composition; 45% ammonium nitrate, 35% urea, 20% water). >One tanker is constructed form 316 and the other from 416. > >Whilst the selected tanker will cart mainly UAN, it could be >called upon to transport other liquid fwrtilisers containing >chlorides up to 10% by weight. > >Temperature would normally be in the range of 15 to 35 >degrees Celsius. > >Regards, >Vic