Trunnion Ball Valve Stem Strength

Stem torsional shear stress verification at keyway, flat key driver, plain round and ball connection sections for fixed-shaft ball valves.

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Core Formula:
τ = M / W_n

Where:
• M = total operating torque (N·mm), from stem torque module
• W_n = section modulus of torsion (mm³), varies by cross-section
• Section 1: keyway → W_n1 based on d − keyway cut
• Section 2: flat key driver → W_n2 based on flat width
• Section 3: plain round → W_n3 = πd³/16
• Section 4: ball connection → W_n4 based on connection geometry
• τ ≤ [τ] → PASS for each section

Why This Calculator

4-Section Check

Verify torsional shear at keyway, flat driver, plain round, and ball joint sections.

Section Modulus

Each section has unique Wn formula based on its specific cross-section geometry.

Auto Pass/Fail

Instant judgment for each section: tau vs. allowable shear stress.

Torque Input

Directly uses total stem torque M from the Stem Torque module.

Material Allowable

Shear allowable [tau] derived from material yield per valve design practice.

Part of Design Suite

One of 12 modules in the complete Ball Valve Design Calculation suite.

How It Works

Enter Parameters

Input total torque, stem dimensions for each section, and material allowable shear.

Compute Section Moduli

Calculate Wn for keyway, flat driver, plain round, and ball joint sections.

Calculate Shear Stress

tau = M / Wn at each critical section along the stem.

Verify All Sections

Compare each tau to [tau]; all must pass for stem integrity.

Who Is It For

Valve Design Engineers | Structural Analysts | Quality Inspectors | R&D Engineers

Key Highlights

4-Section CheckAuto JudgmentTorsional ShearMaterial-Based

Ready to Calculate?

Enter your design parameters and get instant verification results.

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