Stem thrust fundamentals
Thrust is the axial force required to unseat (lift) and reseat (lower) the gate. Contributions include:
- Pressure load on the gate face (seat area)
- Wedge mechanical advantage (seat angle)
- Packing axial friction from stem packing
- Gate & stem weight
Torque & MAST
Use thread geometry to convert axial thrust to thread torque; add packing rotational torque and friction. Compare the peak torque to MAST checks (stem shear, bearing stress, key capacity) and add a service factor for actuator sizing.
Gland flange & bolt checks
Gland flange must supply the packing normal force without exceeding bolt stress limits. Provide bolt torque, gasket area and a safety factor.
Deliverables
Produce an inputs table, calculation steps (with formulas), torque-vs-angle plot (if required) and a final actuator recommendation. V-Calc packages these automatically into Word and Excel outputs.