Calculators

MOV Actuator Torque / Thrust Calculator

Required actuator output thrust (rising-stem gate / globe) or torque (quarter-turn ball / butterfly) to stroke a motor-operated valve under design differential pressure. Sums disc-load, unbalanced stem-piston, packing-drag, lead-screw and collar-friction terms; reports actuator selection margin against rated output.

Valve type

Disc factor, VF (0.30 gate, 1.10 globe FOS, 0.90 globe FUS)

Orifice diameter, d_orif (in)

Differential pressure, ΔP (psi)

Stem diameter, d_stem (in)

Packing depth, h_pack (in)

Packing friction, μ_pk

Line pressure, P_line (psi)

Stem lead, L (in/rev)

Stem-nut friction, μ_s

Collar friction, μ_c

Collar mean diameter, d_col (in)

Actuator rated thrust (lbf)

Actuator rated torque (ft·lbf)

Method: Rising-stem total thrust F_req = F_dp + F_piston + F_pack, where F_dp = ΔP·A_orif·VF (disc factor 0.30 gate, 1.10 globe flow-over-seat, 0.90 globe flow-under-seat), F_piston = ΔP·A_stem (unbalanced stem area), F_pack = π·d_stem·h_pack·μ_pk·P_line. Stem torque: T_stem = F_req·(d_stem/2)·tan(α+φ) + F_req·μ_c·(d_col/2), with α = atan(L/(π·d_stem)), φ = atan(μ_s). Quarter-turn seating: T_seat = k·ΔP·d_port³ (BDTO coefficient k ≈ 0.10 ball, 0.45 butterfly — vendor data), plus packing torque T_pack = μ_pk·π·d_stem²·h_pack·P_line/2. EPRI MOV practice: select actuator rated ≥ 1.25× required (output) for diagnostic and degradation margin. References: EPRI NP-6160 / MPR-2524 MOV Sizing Guide; NRC Generic Letter 89-10; Limitorque SEL-10V-0197; Rotork IQ Sizing Tables; API 6D; ISA 75.01.01; AWWA C504.

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MOV Actuator Torque / Thrust Calculator

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