Rectangular tank sizing Calculation Objectives
- To calculate the thickness of tank plates
- To determine the size of stiffening frame for tank - To determine dry and test weights
Assumptions
- Specific gravity of liquid is 1
- Acceleration due to gravity is 9.81 m/s2 - Density of steel is 7850 kg/m3
- Minimum Distance between stiffeners = 1.05m
References
1. UL-142, Steel Aboveground Tanks for flammable and combustible liquids, Underwriters Laboratories Inc.
2 Eugene F. Megyesy, Pressure Vessels Handbook, Pressure Vessels Publishing Inc.
3 Corus Construction and IndustrialStructural Sections to BS 4: Part 1:1993 & BS EN 10056:1999
4 ASME Boiler and Pressure Vessel Code Section II subpart D 5 Trauvay and Cauvin (2001), Piping Equipment
6 Young, W. C. & Budynas, R. G. (2002) Roark's Formulas for Stress and Strain 7th ed., McGraw-Hill. 2002
7 ASME B31.10M - 2000: Welded and Seamless Wrought Steel Pipe 8 ASME B.16.5 - 2009: Pipe Flanges and Flanged Fittings
Notes
1 A total of 10 Stiffeners were used based on a spacing of 1.05 m on the long sides (3 stiffeners on each longer side; and 2 stiffeners on each shorter side) 2 Sump Pump weight was not included in calculations
3 Weights are calculated weights. Final weights to be advised by vendor Weight calulation does not include weir.
Definition of Terms
- a Length of top plate - b Width of top plate - CA Corossion Allowance - E Modulus of Elasticity - g Gravitational acceleration - H Height of tank
- Imin Minimum Moment of inertia of top edge stiffening - L Length of tank
-
l
Spacing between vertical stiffeners -l
b Spacing of bottom plate support - R Reaction at top edge- r Radius of contact of heaviest dead weight on top tank - S Allowable stress of tank material
- t Required thickness - ta Selected thickness - w Load
- W Heaviest Dead weight on top plate
- Zmin Minimum Section Modulus of vertical stiffener
-α Factor Depending on ratio of Length to Width of top plate a/b -β Factor Depending on ratio of Height to Length H/L
ρp Density of tank material ρ Density of liquid in tank ν Poisson ratio of tank material CSA Cross-Sectional Area
Equipment Tag No. ABH 8000 Project No. No. of equipments 1 1 DESIGN DATA
Tank Material SA-516 Gr. 60
Modulus of Elasticity E = N/m2
Allowable Stress S = N/m2
Density of tank material ρp = kg/m
3 Tank Dimensions: Length L = m Width W = m Height H = m Type of Liquid Specific Gravity = Density of liquid ρ = kg/m3
Acceleration due to gravity g m/s2
No. of vertical stiffeners one side =
Maximum Distance between Stiffners l = m
Corrosion Allowance CA = mm
Height/length ratio (H/L) =
Factor for H/L β = (See Appendix)
2 SIDE PLATE THICKNESS
Required Plate Thickness = m
= mm
Thickness + Corossion Allowance = mm
Selected Plate thickness ts = mm
3 LOAD
= N/m
= N/mm
4 VERTICAL STIFFENING Minimum Section Modulus
= cm3
An equal angle L-section of dimensions 1216 1.05 0.0045733 28252.8 28.25 117.9E+06 203.4E+09 3 1000 1 Water 0.095 0.5714 3 7.57 4.57 2.4 3 4.2 7850 8 9.81 77.538 S gH l t
2
2gH
w
S Hlw Zmin 0.12845 TOP EDGE STIFFENING
Reaction at top edge = N/mm
Minimum required moment of inertia for top edge stiffening:
= mm4
= cm4
200 x 200 x 16 (moment of inertia = cm3) frame is satisfactory for vertical stiffening
BOTTOM PLATE SUPPORT SPACING
using a minimum plate thickness of mm calculated for side plates above, the maximum spacing of bottom plate supports:
= m
6 TOP PLATE THICKNESS Dimensions of top plate
Length a = m
Width b = m
Constant based on length to width ratio a/b a/b =
α = (See Appendix)
Poisson's ration
Total dead weight on tank top plate = kg (Note 2)
= N
Sum of Radii of load contacts with top plate
r = mm
Total Stress due to dead load on 4.57mm required plate thickness
= N/m2
This Stress value is < S ( N/m2) therefore required thickness for side plates is
Selected thickness = 8 mm 4.4 3.2 3195.0 4.57 -0.000125 30608563 325.69 2251.2 2342 0.3 1.375 8.48 22512126 117.9E+06 adequate 1475 0.406 gH S t lb 1.254
r b t W 2 ln 1 2 3 2w
R
0
.
3
aEt
RL
I
192
4 min
7 WEIGHT CALCULATIONS a Weight of Tank Plates
(Surface area of tank * tank thickness * Density of tank material) i- Side plates
=
ii- Bottom Plate kg
= iii- Top Plate
= Total weight of tank plates = b Weight of Stiffeners
Weight of one vertical stiffener
(CSA*Length*density of stiffener) = kg Total Weight of vertical Stiffeners = kg Weight of top edge stiffening
(CSA*Length*density of stiffener) = kg
Total weight of stiffeners = kg
c Weights of nozzles
7 Nos. 2" nozzles @ = kg
2 Nos. 4" nozzles @ = kg
2 Nos. 24" Manways @ kg/MW = kg
Total weight of nozzles = kg
d Total Empty weight of tank
(Weights of tank plates+Stiffners+nozzles) = kg Weight of water to fill tank
(Volume of tank * density of water) = kg e. Operating Weight
(Empty weight of tank + Weight of water at NLL)
NLL = m
Weight of water at NLL = kg/m3
Total Operating Weight = f. Weight of tank filled with water
(Empty weight of tank + Weight of water) = 35982.818 kg 1.06 13356 19098.818 30240 5742.818 281.22 19.06 140.6 1571.256 723.456 791.28 884.224 3845.872 3.63 kg/Nozzle 9.53 kg/Nozzle 325.69 2170.368 25.41 847.8 84.78 ) ( 2t p LHWH
p sLWt
p sabt
TANK SKETCH
Vertical Stiffener Cross-Section
Top-Edge stiffening Cross-Section
150mm
150mm
15mm
200mm
200mm
16mm
2
.4
m
Top Plate
Summary of Results
-- Tank material SA-516 Gr. 60
-- Thickness of plates
Sides = 8 mm
Bottom = 8 mm
Top = 8 mm
-- Number of vertical stiffeners = 10
-- Stiffener configuration Equal leg (L section) Stiffener Cross-section Dimensions
Vertical = 150mm x 150mm x 15mm
Top edge = 200mm x 200mm x 16mm
-- Dry weight of tank = 5742.818 kg
-- Operating weight of tank = 19098.82 kg