For a jet mixer consider a minimum jet nozzle velocity of 9 m/s. The jet mixing time can be calculated from the following equation: tm = 30*V*Dj / q*(Zl*DT)0.5 where, V = Volume of the liquid to be jet-mixed, m3 Dj = jet nozzle diameter, m q = flow rate through the jet, m3/s Zl = liquid depth in the tank, m DT = Inside diameter of tank, m http://www.cheresources.com/invision/topic/6011-design-of-jet-mixing-nozzle-forlarge-tanks/ flame arrestor Inbreathing Emptying (pump-out) and ambient cooling will lead to normal inbreathing. General equation to determine inbreathing flow : Vin,air = Vpe + CVtk0.7 Ri where Vin,air = Total inbreathing in Nm3/h (Air) Vpe = Pump-out or emptying in m3/h Vtk = Tank capacity in m3 Ri = Insulation reduction factor C = Factor subject to vapor pressure, average temperature and latitude (see Tabl e 1) Table 1 : C-factor for Inbreathing Latitude Vapor Pressure Hexane or similar Higher than hexane or unknown Average Storage Temperature (oC) < 25 >=25 < 25 >=25 Below 42o 4 6.5 6.5 42o to 58o 3 5 5 Above 58o 2.5 4 4

6.5 5 4

Find Latitude & Longitute Using GOOGLE MAP Featured Resources: Power Engineering International Provides articles on new technologies and installations as well as market report s, news, commentary and analysis.... >> Outbreathing Filling (pump-out) and ambient heating will lead to normal outbreathing. General equation to determine outbreathing flow : Vout,air = Vpf + YVtk0.9 Ri where

Vout,air = Total Outbreathing in Nm3/h (Air) Vpf = Pump-out or filling in m3/h Vtk = Tank capacity in m3 Ri = Insulation reduction factor Y = Factor subject to latitude (see Table 2) Table 2 : Y-factor for Outbreathing Latitude Y-factor Below 42o 0.32 42o to 58o 0.25 Above 58o 0.2 Special notes : i) If products contain volatile components or dissolved gases or flashing produc ts, perform flashing calculation to estimate quantity of volatile component / ga ses / vapor. This amount shall be added into outbreathing rate. ii) If products stored temperature above 40 degC or its vapor pressure higher th an 5.0 kPa, products evaporation rate shall be added into outbreathing rate. iii) Quick check on plant latitude, check out in "Find Latitude & Longitute Usin g GOOGLE MAP" Determination of Ri = Insulation reduction factor If no insulation, Ri = 1 If fully insulated including Shell and roof, Ri = Rin = (1 + h x Lin / Lamdain)-1 If partial insulated, Ri = Rinp Ri = (Ainp / ATTS).Rin + [1-(Ainp / ATTS)] Lin = Insulation thickness in m Lamdain = Insulation thermal conductivity in w/mK h =Inside heat transfer coefficient in w/m2K [4 w/m2K is commonly assumed] Ainp = Insulated surface area of tank in m2 ATTS = Total tank surface area (shell + roof) in m2 Concluding remarks The following method is the latest method used in API Std 2000, ISO 28300 & EN 1 4015. Nevertheless, API Std 2000 (6th edition) still maintaining the old method in ANNEX A as an alternative approach in determining normal venting rate. Compar ison and recommendation can be found in "Tank Venting - API Std 2000 (Nov 2009) - Revised method and Old Method in ANNEX A". In determining normal tank venting rate per ANNEX A, designer can estimate tank venting rate from a table. Siddhartha has presented an equation to predict tank venting based on simple correlation, as discussed in " Tank Normal Venting Rate Estimation Using Siddhartha Equation". JoeWong has further proposed a new correl ation as discussed in "Tank Thermal Breathing - Proposed Equation Correlate API Std 2000 Data" with better accuracy. Ref :

i) API Std 2000 "Venting Atmospheric and Low-Pressure Storage Tanks", 6th Editio n, Nov. 2009 ii) ISO 28300 "Petroleum. petrochemical and natural gas industries - Venting At mospheric and Low-Pressure Storage Tanks" iii) EN 14015 "Specification for the design and manufacture of site built, verti cal, cylindrical, flat-bottomed, above ground, welded, steel tanks for the stora ge of liquids at ambient temperature and above " ********************************** Above equations have been programmed by Ankur, an experience Chemical Engineer, share with readers of Chemical and Process Technology. You may download here.