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Wall
Thickness Calculation of Conical Sections Under Internal Pressure
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ASME
Section VIII Div 1 paragraph UG-32
Formed Heads, and Sections, Pressure On Concave Side
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(Enter values in yellow cells for calculations and
in blue cells as information)
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DATA INPUT
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Design Conditions
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Material
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Design Pressure, Pd =
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psig
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Conical
section Material Specification
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Conical
Section Material Type
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Design Temperature, Td =
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°F
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Allowable
Stress Conical Section, S =
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psi
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Welding Efficiency, E =
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Dimensions
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Large End
Inside Diameter, Di =
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in.
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Corrosion Allowance, CA =
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in.
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Small End
Inside Diameter, di =
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in.
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Undertolerance Allowance (*), U1 =
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default value = 0
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Nominal wall
thickness, tn =
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in.
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Length of
Conical Section, Lc =
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in.
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(Large End) If tr ≤ tn acceptable
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(Small End) If tr ≤ tn acceptable
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Notes:(*)
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- As per UG-16(c)
Mill Undertolerance. Plate material shall be ordered not thinner than the
design thickness. Vessels made of plate furnished with an undertolerance of
not more than the smaller value of 0.01 in. (0.25 mm) or 6% of the ordered
thickness may be used at the full design pressure for the thickness ordered.
If the specification to which the plate is ordered allows a greater
undertolerance, the ordered thickness of the materials shall be sufficiently
greater than the design thickness so that the thickness of the material
furnished is not more than the smaller of 0.01 in. (0.25 mm) or 6% under the
design thickness.
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- As per UG-16(d)
Pipe Undertolerance. If pipe or tube is ordered by its nominal wall
thickness, the manufacturing undertolerance on wall thickness shall be taken
into account except for nozzle wall reinforcement are a requirements in
accordance with UG-37 and UG-40. The manufacturing undertolerances are given
in the several pipe and tube specifications listed in the applicable Tables
in Subsection C. After the minimum wall thickness is determined, it shall be
increased by an amount sufficient to provide the manufacturing undertolerance
allowed in the pipe or tube specification.
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- If you are
ordering a head or other such fitting that is formed from plate, such as an
elliptical, torispherical head, etc, you do not need to include the
undertolerance. You do need to account for thinning during the forming of the
head. Calculations should be done based on the minimum thickness after
forming. The vendor of such heads should provide that information.
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CALCULATIONS
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Conical Sections
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Wall Thickness [ASME UG-32(f)]
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Undertolerance thickness, U2 =
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in.
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U2 = tn*U1
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Nominal thickness adjusted for corrosion and undertolerance,
nt =
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in.
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nt = tn-CA-U2
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Large End Inside diameter with corrosion & undertolerance
removed, D =
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in.
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D = Di+2CA+2U2
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Small End Inside diameter with corrosion & undertolerance
removed, d =
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in.
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d = di+2CA+2U2
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One‐half of the included (apex) angle of the cone, α ≤ 30ᵒ =
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deg.
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α =
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arctan
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(
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0.5 (D - d)
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)
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Lc
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Minimum required thickness (Large End), tr =
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in.
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tr =
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P D
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+ CA
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Nominal wall thickness, tn =
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in.
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2 cos α (S E - 0.6 P)
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Check If tr ≤ tn (Large End)
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Minimum required thickness (Small End), tr =
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in.
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tr =
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P d
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+ CA
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Nominal wall thickness, tn =
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in.
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2 cos α (S E - 0.6 P)
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Check If tr ≤ tn (Small End)
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Maximum working pressure
[ASME UG-32(f)]
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Maximum working pressure for Conical Sections, Pc =
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psig
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P =
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2 S E nt cos α
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D + 1.2 nt cos α
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Volume inner =
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ft³
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Vi =
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1/3*π*Lc(Ri² + ri² + Riri ) / 1728
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Volume outer =
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ft³
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Vo =
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1/3*π* Lc(Ro² + ro² + Roro ) / 1728
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Weight =
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lbs
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W =
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(Vo - Vi) ρm
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RESULT
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Design Conditions
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Design Pressure, Pd =
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psig
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Design Temperature, Td =
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°F
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Material
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Conical Section Material
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Dimensions
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Large End Inside Diameter, Di =
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in.
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Small End Inside Diameter, di =
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in.
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Nominal wall thickness, tn =
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in.
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Length of Conical Section, Lc =
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in.
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Maximum working pressure =
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psig
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Volume inner =
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ft³
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Volume outer =
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ft³
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Weight =
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lbs
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