Calculators › Fixed Trunnion Ball Valve › Stem Strength

Fixed Trunnion Ball Valve / Practical Valve Design Manual Table 5-152 / API 6D 7.20

Fixed Trunnion Ball Valve Stem Strength

Three-section torsional verification: τN1 = M/WⅠ, τN2 = M/WⅡ, τN3 = M/WⅢ with API 6D safety factor λ < 0.67. Torque multiplier 2× for abnormal conditions.

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Reference: Qw347X 10" DIB-I / ASME B16.34 / API 6D / Valve Design Manual

Why This Calculator

📐

Three Sections

Head I-I, plain shaft II-II and double-key III-III in one check.

🔨

Keyway Correction

WⅢ = πd³/16 − b·t·(d−t)²/d exact double-key modulus.

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2× Torque Mode

Multiplier input covers abnormal/actuator stall conditions.

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API 6D Factor

Safety factor λ < 0.67 per API 6D clause 7.20.

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AISI 4140

Allowable 180 MPa preset for quenched 4140 stem.

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Auto Verdict

All six checks in a single PASS/FAIL.

How It Works

Torque Input

Enter MM and total M from torque module.

Choose Mode

Set multiplier 1 for normal, 2 for abnormal.

Section Data

Head, shaft and keyway dimensions.

Verify

Three-section stress and safety factors.

Who Is It For

Valve Design EngineersAPI 6D AuditorsQuality InspectorsFailure Analysts

Key Highlights

3 SectionsDouble KeyAPI 6D 7.202× TorqueAISI 4140

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