ISO 4051:1977

Overview

ISO 4051:1977 - "Shipbuilding - Inland vessels - Steering gear - Values of torques" is an ISO technical standard that defines nominal torque values for steering gear servomotors used on inland vessels. It applies to systems that control one or more rudders or rotating propelling nozzles. The standard gives a clear sizing reference for servomotor torque classes and includes a definition of the nominal torque characteristic, publication year (1977), and basic operational angle limits.

Key Topics

• Scope: Torque values for steering gear servomotors on inland vessels (rudders and rotating nozzles).
• Nominal torque definition: The standard defines the nominal torque as the maximum calculated torque produced by a servomotor that characterizes its size/type.
• Specified torque classes (expressed as nominal moment in MN·m):
  • 6.3 × 10⁻³
  • 10.0 × 10⁻³
  • 16.0 × 10⁻³
  • 25.0 × 10⁻³
  • 40.0 × 10⁻³
  • 63.0 × 10⁻³
  • 100.0 × 10⁻³ - applicable only to electrohydraulic servomotors
• Service angle: The standard indicates maximum service angles of 35° or 90° to each side of the mid position (as appropriate for installation/design).
• Applicability: Focused on inland navigation craft; intended to harmonize torque classification for steering equipment.

Applications

ISO 4051 is practically useful for:

• Shipbuilders and naval architects specifying steering gear requirements for inland vessels.
• Marine equipment manufacturers designing or certifying servomotors and hydraulic/electrohydraulic steering systems.
• Procurement and specification teams who need standardized torque classes for tenders and purchase orders.
• Classification societies and regulators evaluating compliance of steering systems on inland craft.
• Marine engineers and retrofit projects when assessing replacement servomotors or upgrading rudder control systems.

Using ISO 4051 torque classes helps ensure compatibility between steering gearbox, actuator and rudder/nozzle loads, simplifies component selection, and supports consistent documentation and regulatory review.

Related Standards

• Developed by ISO technical committee ISO/TC 8 (Shipbuilding).
• For complete system design, users should also consult other ISO shipbuilding and marine-steering standards, classification society rules, and local inland navigation regulations to ensure full compliance and integration.

Keywords: ISO 4051, steering gear torques, inland vessels, shipbuilding standard, servo motor torque values, rudder torque, rotating propelling nozzles, electrohydraulic servomotors.