Matching an electric actuator with a globe valve is not the same thing as matching an electric actuator with ball or butterfly valves. The difference is that the stem moves in a linear direction and not in a rotational motion.
If the type of actuator is selected incorrectly, the valve will either fail to function at all or wear out much quicker than expected.
The Reason Globe Valves Require Another Kind of Actuator
Whereas most valves only rotate a quarter turn from open to closed positions, globe valves use another mechanism to control flow. Globe valves operate by moving their stem either up or down while turning the handwheel.
Moving up and down like that means that it will take several full turns of the actuator’s output shaft to operate the valve. It may need from five to 30 or even more turns for larger valves.
This is why it is impossible for an electric actuator of a globe valve to be a quarter-turn actuator. A globe valve just cannot operate without a multi-turn actuator.
The multi-turn actuator works with the globe valve stem using gears to reduce speed and increase torque.
Stem Thrust vs Rotational Torque
Quarter-turn valve applications deal in rotational torque. Globe valve applications add another concept: stem thrust.
The actuator must produce enough rotational torque at the output shaft that the gearbox converts it into linear thrust to seat the plug against the seat ring.
At higher pressures, the seating force requirement increases. This is why torque data from a valve manufacturer for a globe valve looks different from data for a ball valve of the same size.
On/Off vs Modulating: Which Do You Need?
This question comes up on nearly every globe valve project. The answer depends on what the valve is being asked to do, and the two control types are not interchangeable.
On/Off Control
On/off actuators drive the valve fully open or fully closed on a binary signal. There is no intermediate position.
They suit isolation applications where the process only ever needs the valve in one of two states.
Boiler feedwater isolation, pump bypass lines, and tank inlet valves are typical examples. Simpler to specify, typically less expensive, and straightforward to maintain.
Modulating Control
Modulating actuators position the valve anywhere across its travel range. They accept a continuous control signal, typically 4-20mA or 0-10V DC, and move to the corresponding position.
A 12mA signal on a 4-20mA system positions the valve at roughly 50 percent travel.
Flow regulation, temperature control loops, and pressure modulation all call for modulating control.
A globe valve electric actuator in modulating service needs an integral positioner. The positioner compares the incoming control signal to the actual valve position and corrects any deviation.
Without it, the actuator cannot hold accurate position under changing process conditions.
HVAC systems are one of the most common environments for modulating globe valve actuators. Chilled water and hot water circuits use them to maintain room temperature setpoints by varying flow through coils.
In process plants, the same principle applies to reactor temperature control and cooling water systems.
The “AOX-M” series is designed to operate valves with 360° multi-turn rotation, such as gate valves and globe valves.
LEARN MORESizing: How Much Torque Does a Globe Valve Need?
Torque sizing for an actuator globe valve follows a specific sequence. Skipping any step risks undersizing, which leads to actuator stall, or oversizing, which wastes budget and can damage the valve packing.
Step 1: Get the Valve Manufacturer’s Torque Data
The valve manufacturer provides torque or thrust requirements for the specific valve size, pressure class, and packing type. This is the only reliable starting point.
Generic tables from actuator catalogues are not a substitute. The actual valve datasheet accounts for seat seating force, packing friction, and stem thread efficiency in ways that general estimates cannot.
Step 2: Identify the Worst-Case Operating Condition
Globe valve torque requirements are not constant. They typically peak at two points: opening from the fully seated position, and final seating at closure. Both must be checked. The higher value governs the actuator selection.
Temperature affects this too. PTFE packing compresses differently at elevated temperatures. Valves in steam or high-temperature liquid service may show significantly higher breakaway torque than similar valves in ambient service at the same pressure rating.
Step 3: Apply the Safety Margin and Check Travel Time
A safety factor of 1.25 to 1.5 is standard for most industrial applications. Multiply the worst-case valve torque by the safety factor to get the minimum actuator output torque required.
For modulating service, leaning toward 1.5 makes sense. Modulating actuators cycle continuously and experience more cumulative wear than on/off units.
Some applications also specify a maximum travel time. A steam turbine bypass valve may need to close in 15 seconds to protect downstream equipment.
The actuator’s output speed, measured in stem turns per minute, must match the required travel time.
AOX multi-turn electric actuators cover output torques from 30 Nm to 6,000 Nm, with adjustable running time settings that allow travel speed to be matched to process requirements.
Common Mistakes When Pairing Actuators with Globe Valves
Most pairing problems trace back to a small number of recurring errors.
Using Torque Data from the Wrong Valve Size
Torque requirements scale with valve size. A 2-inch globe valve and a 4-inch globe valve at the same pressure rating do not have similar torque requirements.
Always use the datasheet for the specific valve size being installed, not a neighboring size from the same product family.
Overlooking Packing Type
Graphite packing produces significantly more friction than PTFE at the same stem size.
An actuator sized for PTFE packing may stall on a valve with graphite packing if no additional margin was built in.
Packing type needs to be confirmed before finalizing the selection, not discovered after commissioning.
Packing Friction & Stem Thrust — PTFE vs Flexible Graphite
Flexible graphite packing can generate up to 2.5× higher stem friction than standard PTFE packing at elevated temperatures. The difference grows sharply above 180 °C (350 °F), where PTFE begins to soften while graphite packing friction increases.
When specifying a multi-turn electric actuator for high-pressure steam globe valves or any graphite-packed service, always add a minimum Safety Factor ≥ 1.5× to the valve manufacturer’s rated breakaway thrust — not the nominal running torque — to prevent actuator stall on cold start-up.
Steam / Graphite-packed globe → Actuator Thrustmin = Rated Breakaway Thrust × 1.5 (use 1.25 for PTFE-packed ambient service only)Send Your Valve Datasheet for a Free AOX Thrust & Packing-Friction Sizing
Upload valve size, class, packing type & fluid temp — we return the exact AOX multi-turn model, required Nm, and travel time within 1 business day.
Assuming the Actuator Handles Modulating Control Without a Positioner
A globe valve with electric actuators in modulating service needs a positioner. Some actuators include one as standard. Others require an external unit.
Assuming modulating capability without confirming positioner inclusion is a common and avoidable specification error, and one that usually surfaces during loop commissioning at the worst possible time.
Selecting on Voltage Compatibility Alone
Voltage compatibility gets most of the attention in procurement. Torque output, travel time, control signal type, and enclosure rating often get less scrutiny.
All of them matter. An actuator with the right voltage but wrong torque will not operate the valve correctly regardless of the electrical connection.
Electric Globe Valve Actuator: FAQs
Q1. Can a quarter-turn actuator be used on a globe valve?
No. Quarter-turn actuators produce 90 degrees of rotation between open and closed. Globe valve stems require multiple full revolutions of travel.
Physically connecting a quarter-turn actuator to a globe valve stem will not produce the required stem movement and may damage the actuator gearbox. Multi-turn actuation is a hard requirement, not a preference.
Q2. What is the difference between on/off and modulating actuators?
On/off actuators move the valve to fully open or fully closed on a binary signal. There is no in-between position. Modulating actuators accept a continuous control signal and position the valve at any point across its travel range.
Modulating units require a positioner to maintain accurate position under changing process conditions. On/off units do not.
Q3. How much torque margin should be left above the valve’s rated requirement?
The accepted standard is a safety factor of 1.25 to 1.5 times the worst-case valve torque. For modulating service, the higher end of that range is more appropriate.
For valves with graphite packing or in high-temperature service, additional margin beyond 1.5 may be justified. Always base the calculation on the valve manufacturer’s actual data, not estimated figures from generic tables.
