Fluid control
Torque on valves
Valves are widely used in industrial fluid control systems to start, stop and direct flow. For the efficient and safe operation of these systems, it is of great importance to calculate the torque required when opening or closing the valves correctly. In this study, the concept of torque, the mechanisms of torque formation in valves, torque calculation methods and application examples are examined in detail.
Text and images by Kemal Comakli PhD, Mechanical
Engineering, Omer Yildiz, Mechanical Engineering, Starvalve
Process Valves and Actuator Technology Industry and
Trade inc.
Introduction
In industrial fluid control systems, valves provide operational efficiency and safety by regulating fluid flow and pressure. The rotational force required to open or close valves, i. e. valve torque, is a critical parameter that directly affects actuator selection and the overall energy efficiency of the system( ISA, 2020). Valve torque is calculated to allow for proper actuator sizing and to provide assurance that valve components can withstand the internal forces created by the flowing fluid and pressure. Pressure loss characteristics must be known to estimate torque, and system designers also use this data to calculate pump pressure requirements and evaluate energy costs associated with pressure loss across the valve in pumping applications. Cavitation is analysed to prevent unwanted noise and vibration and to prevent damage to the valve and adjacent piping. Valve manufacturers publish torque values for their products so that the actuator and mounting hardware can be properly selected. However, published torque values usually represent only the seating or opening torque of a valve at its nominal pressure. While these are important values for reference, published valve torques do not take into account actual installation and operating characteristics. In order to determine the actual operating torque for valves, it is necessary to understand the parameters of the piping systems in which they are installed. Factors such as installation
orientation, flow direction and fluid velocity of the medium all affect the actual operating torque of valves.
Torque definition and equation
Torque is the effect of a force applied to an object to rotate that object around an axis. It is also called“ moment” in engineering and is an important quantity, especially in rotating systems. Torque refers to the turning effect of force and is defined as follows:
Here:: Torque vector( Nm): Force arm vector( m): Force vector( N)
In this formula, torque is found by multiplying the perpendicular components between the force and the distance from the point of application of the force to the centre of rotation. The angle between the force and the position vector is θ:
Here: τ: Torque( Nm) R: Distance between the rotation axis and the force application point( m) F: Magnitude of force( N) θ: Angle between force vector and position vector
( degrees or rad)
42 Valve World August 2025 www. valve-world. net