Pressure Vessel Calculator
This pressure vessel calculator gives a first estimate of the shell and head thickness of a cylindrical vessel with the ASME Section VIII Division 1 formulas. Enter the design pressure, the inside diameter, the plate material, the weld joint efficiency, and the corrosion allowance, and the pressure vessel calculator returns the required shell and head thickness, the next standard plate, its MAWP, the hydrotest pressure, and the vessel volume.
Results
The Pressure Vessel Calculator is part of our Fluids collection. Browse more fluids to size, convert, and check your work alongside this tool.
What the pressure vessel calculator does
Air receivers, boilers, separators, and storage vessels hold gas or liquid above atmospheric pressure, and the wall must be thick enough to keep the hoop stress below the allowable stress of the plate. The pressure vessel calculator applies the thin-wall formulas of ASME Section VIII Division 1 for a cylindrical shell under internal pressure and for the three common heads, adds the corrosion allowance, and checks the result against a standard plate thickness. It is a preliminary sizing tool, not a substitute for a certified design.
Pressure vessel wall thickness formulas
For a cylindrical shell under internal pressure, ASME VIII-1 UG-27 gives:
P is the design pressure, R the inside radius in the corroded condition, S the allowable stress, E the joint efficiency, and CA the corrosion allowance. The heads follow UG-32:
The shell formula is valid while P stays below 0.385 × S × E. The hydrostatic test pressure is 1.3 times the design pressure when the stress ratio is 1.
Pressure vessel design calculation example
An air receiver 1,000 mm inside diameter for 10 bar g, in SA-516 Grade 70 (S = 138 MPa), spot radiographed (E = 0.85), with 3 mm corrosion allowance and 2:1 ellipsoidal heads:
The next standard plate is 8 mm, which gives a shell MAWP of 11.6 bar. The hydrotest pressure is 13 bar, and with a 3,000 mm shell the vessel holds 2,618 L.
How to use the pressure vessel thickness calculator
Choose metric or US units and enter the design pressure, the inside diameter, and the shell length from tangent line to tangent line. Pick the plate material, which sets the allowable stress at up to 40 °C (100 °F), or enter your own allowable stress for a higher design temperature. Choose the weld joint efficiency from the radiography you plan, the corrosion allowance, and the head type. Press Calculate.
Reading the shell thickness calculation
The required thickness includes the corrosion allowance but not the mill tolerance or the thinning of heads during forming, so order heads with extra thickness. The MAWP of the chosen plate shows the margin above the design pressure. If the calculator reports that the pressure exceeds 0.385 × S × E, the vessel is thick walled and needs the Appendix 1 formulas. Nozzles, supports, external pressure, and wind or seismic loads all need their own checks.
When to use an ASME pressure vessel calculation
- Estimating plate thickness for an air receiver or buffer tank quote
- Checking the head thickness calculation of a drawing
- Comparing carbon steel and stainless steel for a vessel
- Finding the MAWP of an existing shell from its measured thickness
- Working out the hydrotest pressure and vessel volume
Common pressure vessel design calculation mistakes
- Using the room temperature stress at high temperature. Take S at the design temperature.
- Forgetting the corrosion allowance. Add it to the thickness and to the radius.
- Mixing gauge and absolute pressure. The formulas use gauge pressure.
- Ignoring forming loss. Formed heads thin out, so order extra thickness.
Tips for pressure vessel thickness
- Check the minimum thickness rules of the code as well as the formula.
- Use spot radiography to raise the joint efficiency at low cost.
- Have every pressure vessel designed and stamped by a qualified engineer.
MAWP calculation and why it differs from design pressure
The design pressure is what the process needs; the maximum allowable working pressure, MAWP, is what the finished vessel can take with the plate you use. Because plates come in standard thicknesses, the MAWP is usually higher than the design pressure. The relief valve is set at or below the MAWP. Rearranging the shell formula gives MAWP = S × E × t ÷ (R + 0.6t), with t the thickness after the corrosion allowance. The hoop stress behind this formula is simply force over area, the same idea the stress and strain calculator applies to bars and beams.
Static head and pressure vessel volume
For a vessel full of liquid, the pressure at the bottom is the design pressure plus the static head of the liquid, which the hydrostatic pressure calculator gives from the height and density. Tall vertical vessels must be checked at the bottom course. The vessel volume adds the shell cylinder to two heads: a 2:1 ellipsoidal head holds π × D³ ÷ 24, a hemispherical head π × D³ ÷ 12. For an open or atmospheric tank, the tank volume calculator is the simpler choice.
Pressure vessel thickness inputs: allowable stress of plates (up to 40 °C / 100 °F)
| Material | Allowable stress S |
|---|---|
| SA-516 Grade 70 | 138 MPa (20,000 psi) |
| SA-516 Grade 60 | 118 MPa (17,100 psi) |
| SA-285 Grade C | 108 MPa (15,700 psi) |
| SA-240 Type 304 | 138 MPa (20,000 psi) |
| SA-240 Type 316 | 138 MPa (20,000 psi) |
| SA-106 Grade B | 118 MPa (17,100 psi) |
Pressure vessel thickness, SA-516-70, E = 0.85, CA = 3 mm
| Design pressure | 600 mm ID | 1,000 mm ID | 1,500 mm ID |
|---|---|---|---|
| 5 bar g | 4.29 mm | 5.15 mm | 6.22 mm |
| 10 bar g | 5.60 mm | 7.31 mm | 9.45 mm |
| 16 bar g | 7.17 mm | 9.92 mm | 13.36 mm |
| 25 bar g | 9.54 mm | 13.86 mm | 19.26 mm |
Pressure Vessel Calculator FAQ
How do you calculate pressure vessel wall thickness?
Use t = P × R ÷ (S × E − 0.6P) plus the corrosion allowance, with the inside radius, allowable stress, and joint efficiency, as in ASME VIII-1 UG-27.
What is the hydrotest pressure of a pressure vessel?
Under ASME VIII-1 it is 1.3 times the MAWP, adjusted by the ratio of the allowable stress at test and design temperature.
What is joint efficiency in a pressure vessel?
It reflects the weld inspection: 1.0 for full radiography, 0.85 for spot radiography, and 0.70 for none, for double-welded butt joints.
Which head is thinnest?
A hemispherical head needs about half the thickness of the shell; a 2:1 ellipsoidal head about the same as the shell; a torispherical head is thicker.