Industry TemplatesFree calculatorPDF, Excel, Word exportOil and Gas

Pressure Vessel Shell and Head Thickness Calculator (ASME VIII Div 1)

Enter design pressure, diameter, allowable stress and joint efficiency to get the plate thickness for a cylindrical shell and for two common head types. Corrosion allowance and plate tolerance are added so you can quote or order material with a realistic number.

Your numbers

Design pressure

MPa

Internal gauge design pressure including static head.

Inside diameter (corroded)

Use the corroded inside diameter if you add the allowance at the end only for thickness.

Allowable stress S

MPa

From ASME II Part D at design temperature.

Joint efficiency E

Corrosion allowance

Plate under-tolerance

Typically 0.25 mm (0.01 in) for plate under ASME rules.

Your results

Shell nominal plate to order

14.8979

2:1 ellipsoidal head nominal plate

14.8237

t = P D / (2 S E - 0.2 P) for a 2:1 head, before forming thinning.

Inside radius R

900

Shell thickness, circumferential stress

11.5979

t = P R / (S E - 0.6 P), governs while P is below 0.385 S E.

Shell thickness, longitudinal stress

5.7398

t = P R / (2 S E + 0.4 P).

Hemispherical head nominal plate

9.0618

Thin shell limit 0.385 S E

45.1605

Design pressure above this needs the thick shell equations.

Simplified internal pressure formulas for preliminary sizing. Formed head thinning, nozzle reinforcement, external pressure, supports and loadings are not included. Final design must be done to the applicable code edition by a qualified designer.

Save results:

Plate to order vs design pressure

Sweeps Design pressure from 0.2 to 3, holding your other inputs fixed.

Link vessel design data to your ERP routing

Optional review of how to carry plate heats, courses and design basis into your ERP records.

Optional. The tool and every export work without this. No spam.

How to use it

Start with the design pressure and the corroded inside diameter. Pull the allowable stress at design temperature from the material table and choose the joint efficiency set by radiographic examination. The tool calculates the circumferential (hoop) thickness, which usually governs, and the longitudinal thickness, which is about half. It then gives the plate to order for the shell, the 2:1 ellipsoidal head and the hemispherical head. Compare the head result against the shell: ellipsoidal heads are usually close to the shell thickness while hemispherical heads are about half.

Formulas used

For internal pressure in a cylindrical shell the circumferential stress equation is t = P R / (S E - 0.6 P) and the longitudinal equation is t = P R / (2 S E + 0.4 P). A 2:1 semi-ellipsoidal head uses t = P D / (2 S E - 0.2 P). A hemispherical head uses t = P R / (2 S E - 0.2 P). The thin wall equations hold while P is not more than 0.385 S E for a shell. The radius R is the inside radius in the corroded condition.

E is a joint efficiency, not a quality factor from the piping code.
Seamless heads can use E of 1.0 only under specific rules.
Forming thins a head, so order more plate than the minimum.

Worked example

A 1,800 mm inside diameter separator at 1.5 MPa with S of 138 MPa and E of 0.85 gives a circumferential thickness of about 11.6 mm. Adding a 3 mm corrosion allowance and 0.3 mm tolerance means about 14.9 mm, so a 16 mm plate is the next standard step. A 2:1 head at the same conditions needs about 11.6 mm plus allowances as well, while a hemispherical head needs roughly half.

Common mistakes and ERP notes

Do not use the nominal thickness in the pressure equation: use the corroded condition. Do not forget the static liquid head on the bottom course. Do not apply these formulas to vessels operating in creep range without the right allowable stress. For manufacturers, store the design thickness, plate heat number and MTR per course so the data book and the ERP lot records agree.

Frequently Asked Questions

Which governs, circumferential or longitudinal?

For cylindrical shells with normal joint efficiency, the circumferential (hoop) equation governs because hoop stress is about twice the longitudinal stress. The calculator shows both and uses the larger value.

Why does the head need more plate than the formula?

Forming an ellipsoidal head thins the knuckle area. Heads are often ordered with extra thickness or with a minimum after forming stated on the drawing. Ask the head supplier for their forming allowance.

Can I use this for external pressure or vacuum?

No. External pressure design follows a different procedure with buckling charts. This tool covers internal pressure only, and the final design must also include nozzles, supports and wind or seismic loads.

Does it handle thick shells?

Not directly. When P exceeds 0.385 S E the thin wall formula is no longer accurate and the thick shell equations apply. The output limit row shows the pressure threshold for your inputs.

If you build vessels and track plate heats, courses and data books in an ERP, we can help connect the design calculation to the material issue and the final data book.

Talk to an Expert Explore More Free Tools

Related Tools

Industry Templates

More Industry Templates tools

See all

Back to All Tools