EnglishISO 5211 Butterfly Valve Actuator Mounting and Selection Guide
ISO 5211 specifies the mechanical interface between actuators and part-turn valves, including butterfly, ball, and plug valves. When selecting an actuator, check the flange designation, mounting dimensions, bolt-hole pattern, and interface torque rating. You should also confirm the valve stem dimensions, drive socket, mounting height, and actual operating torque.
The same F-series flange designation only indicates that the basic mounting interfaces are compatible. It does not necessarily mean that the valve and actuator can be connected directly.
What Is ISO 5211?
ISO 5211 is the international standard for mounting interfaces used with part-turn actuators on industrial valves. This interface can be used with electric, pneumatic, hydraulic, and gearbox-operated part-turn actuators.
The standard mainly specifies:
- Mounting flange dimensions, bolt circle diameter, and bolt-hole layout
- Number and size of fasteners
- Connection between the valve stem and the actuator drive component
- Maximum flange torque that the mounting interface can transmit
ISO 5211 only covers the mechanical mounting interface. It does not specify the actuator’s power supply, control signals, enclosure rating, or overall dimensions. The current international edition is ISO 5211:2026.
Flange Designations, Maximum Torque, and Mounting Dimensions
ISO 5211 uses designations such as F03, F05, F07, and F10 to identify different mounting flange sizes. Each designation corresponds to a specific locating diameter, bolt circle diameter, fastener size, and interface torque rating.
| Flange Designation | Maximum Flange Torque (N·m) | d1 min. (mm) | d2 f8 (mm) | d3 PCD (mm) | d4 | Number of Holes n |
|---|---|---|---|---|---|---|
| F03 | 32 | Ø46 | Ø25 | Ø36 | M5 | 4 |
| F04 | 63 | Ø54 | Ø30 | Ø42 | M5 | 4 |
| F05 | 125 | Ø65 | Ø35 | Ø50 | M6 | 4 |
| F07 | 250 | Ø90 | Ø55 | Ø70 | M8 | 4 |
| F10 | 500 | Ø125 | Ø70 | Ø102 | M10 | 4 |
| F12 | 1,000 | Ø150 | Ø85 | Ø125 | M12 | 4 |
| F14 | 2,000 | Ø175 | Ø100 | Ø140 | M16 | 4 |
| F16 | 4,000 | Ø210 | Ø130 | Ø165 | M20 | 4 |
| F25 | 8,000 | Ø300 | Ø200 | Ø254 | M16 | 8 |
| F30 | 16,000 | Ø350 | Ø230 | Ø298 | M20 | 8 |
| F35 | 32,000 | Ø415 | Ø260 | Ø356 | M30 | 8 |
| F40 | 63,000 | Ø475 | Ø300 | Ø406 | M36 | 8 |
| F48 | 125,000 | Ø560 | Ø370 | Ø483 | M36 | 12 |
| F60 | 250,000 | Ø686 | Ø470 | Ø603 | M36 | 20 |
| F80 | 500,000 | Ø900 | Ø670 | Ø813 | M42 | 20 |
| F100 | 1,000,000 | Ø1,200 | Ø870 | Ø1,042 | M42 | 32 |
- d1 min. is the minimum outside dimension of the load-bearing flange;
- d2 is the locating diameter;
- d3 is the bolt circle diameter, also known as the PCD;
- d4 is the nominal thread size of the fasteners.
The maximum flange torque is the highest torque that the mounting interface can transmit under the conditions specified by the standard. It is not the valve’s actual operating torque or the actuator’s recommended output torque.
This table is intended for preliminary matching only and does not replace the complete standard or the manufacturer’s drawings.
Mounting Hole Positions and Angles
The mounting holes are evenly spaced around the d3 bolt circle. The angle α between adjacent holes is determined by the number of mounting holes n: α = 360° / n. The hole nearest the reference centerline is offset from that centerline by α/2.
ISO 5211 Mounting Hole Arrangement
| Flange Range | Number of Holes n | Angle Between Adjacent Holes α | Hole Pattern Offset Angle α/2 |
|---|---|---|---|
| F03–F16 | 4 | 90° | 45° |
| F25–F40 | 8 | 45° | 22.5° |
| F48 | 12 | 30° | 15° |
| F60–F80 | 20 | 18° | 9° |
| F100 | 32 | 11.25° | 5.625° |
For example, the F10 flange has four mounting holes with an angle of 90° between adjacent holes. The entire hole pattern is offset by 45° from the horizontal or vertical reference centerline.
How to Match an Actuator to a Butterfly Valve
Step 1: Confirm the Valve Operating Torque
Determine the valve’s actual operating torque under the specified service conditions. Consider:
- Valve size and pressure rating;
- Maximum differential pressure;
- Seat material;
- Process medium and temperature;
- Operating frequency;
- Long periods of inactivity.
Do not select the actuator based on the valve’s DN size alone.
Step 2: Allow an Appropriate Torque Margin
The actuator’s rated output torque should be higher than the valve’s actual operating torque. This additional capacity allows for:
- Changes in operating conditions;
- Increased friction or resistance over time;
- Other factors specified by the project.
The required torque margin should be confirmed by the valve manufacturer, actuator manufacturer, or project specification.
Step 3: Check the Mounting Flange
First, confirm that the valve and actuator have the same ISO 5211 flange designation. Then check:
- d2 locating diameter;
- d3 bolt circle diameter;
- d4 fastener size;
- Number of mounting holes;
- Hole pattern orientation.
The same flange designation does not automatically guarantee direct compatibility.
Step 4: Check the Valve Stem and Drive Socket
The valve stem must match the actuator drive socket in both shape and size. Common connection types include:
- Parallel square stem;
- 45°-oriented square stem;
- Double-D stem;
- Keyed round stem;
- Splined stem.
Different stem dimensions or drive configurations may require a coupling or adapter.
Step 5: Check the Mounting Height
Confirm the following dimensions:
- Valve stem projection;
- Actuator drive socket depth;
- Effective engagement length;
- Coupling dimensions.
Also make sure the actuator does not interfere with the valve body, piping, or insulation.
Step 6: Confirm the Control Requirements
Check all electrical, control, and environmental requirements, including:
- On/off or modulating operation;
- Supply voltage;
- Control and feedback signals;
- Operating time;
- Fail position on power loss;
- Enclosure rating;
- Explosion-protection rating;
- Ambient temperature;
- Manual operation requirements.
Parameters to Check Even with the Same F-Series Flange
An F-series flange primarily defines the mounting hole pattern and the load capacity of the interface. Even if both the valve and actuator are marked ISO 5211 F10, they may not connect directly. Common reasons include:
- Different valve stem shapes, dimensions, or square-stem orientations
- Different valve stem heights or actuator drive socket depths
- Different coupling designs or effective engagement lengths
- Interference between the actuator housing and the valve body, piping, or insulation
- Actuator output torque exceeding the valve’s maximum allowable input torque
The F-series flange designation should therefore be used only as an initial matching criterion. It does not replace a complete dimensional and torque check.
Why the Same F-Flange Does Not Guarantee Compatibility
An F-series flange primarily defines the mounting hole pattern and the load capacity of the interface. Even if both the valve and actuator are marked ISO 5211 F10, they may not connect directly. Common reasons include:
- Different valve stem shapes or dimensions;
- Different square-stem orientations;
- Different valve stem heights;
- Different drive socket depths;
- Different coupling designs;
- Interference between the actuator housing and the valve body or piping;
- Actuator output torque exceeding the valve’s maximum allowable input torque.
The F-series flange designation should therefore be used only as an initial matching criterion. It does not replace a complete dimensional and torque check.
Direct Mounting vs. Bracket and Coupling Mounting
Direct Mounting
Direct mounting means that the actuator is installed directly on the valve’s top flange. The valve stem engages directly with the actuator drive socket or a replaceable drive insert.
Bracket and Coupling Mounting
A bracket and coupling can be used when:
- The valve stem does not match the actuator drive socket;
- The stem projection is too short;
- Additional clearance is needed for piping or insulation;
- Heat transfer from a high-temperature valve must be reduced.
The connecting components must:
- Keep the valve stem and actuator output shaft concentric;
- Be capable of transmitting the actuator’s maximum output torque.
| Comparison Item | Direct Mounting | Bracket and Coupling Mounting |
|---|---|---|
| Structure | Compact | Greater mounting height |
| Number of Parts | Fewer | More |
| Interface Requirements | Flange and drive components must match directly | Differences can be accommodated with connecting components |
| Drivetrain Backlash | Lower | Depends on the coupling design |
| High-Temperature Isolation | Limited | Easier to achieve |
| Maintenance Focus | Check fastener tightness | Also check alignment and the coupling |
Information Required for Actuator Selection
The final actuator configuration must be determined based on the specific inquiry and operating conditions. Providing the following information will help the supplier accurately verify the torque requirements, mounting interface, and control configuration.
| Information Category | Required Parameters |
|---|---|
| Valve | Type, size, pressure rating, connection type |
| Operating Conditions | Medium, temperature, operating pressure, maximum differential pressure, operating frequency |
| Valve Seat | EPDM, NBR, FKM, PTFE, or other materials |
| Mounting Interface | ISO 5211 flange designation, PCD, number of holes, fastener size |
| Valve Stem | Type, dimensions, orientation, projection height |
| Control | On/off or modulating service, power supply, control signal, feedback signal |
| Environment | Enclosure rating, explosion-protection rating, ambient temperature, corrosive conditions |
| Fail Position | Stay in place, fail open, or fail closed on power loss |
Get Technical Drawings and a Project Quotation
If you are unsure whether a butterfly valve and actuator can be connected directly, send Union Valve the valve size, pressure rating, medium, temperature, maximum differential pressure, valve stem dimensions, and control requirements.
Our engineering team can help verify the ISO 5211 interface, operating torque, and mounting arrangement. We can also provide a suitable actuator configuration, detailed dimensional drawings, and a formal quotation to help reduce selection errors and on-site installation problems.
Contact Union Valve and submit your operating parameters to receive selection advice, technical drawings, and a project quotation.
FAQ
What Does F10 Mean?
F10 is an ISO 5211 mounting flange designation. It corresponds to specific locating dimensions, bolt circle diameter, fastener size, and maximum flange torque. It does not indicate the valve size or pressure rating.
Is There a Fixed Relationship Between an F-Series Flange and a Butterfly Valve’s DN Size?
No. Butterfly valves with the same DN size may use different F-series flanges because of differences in design, pressure rating, valve stem, and operating torque.
Can an F07 Actuator Be Installed on an F10 Butterfly Valve?
Normally, it cannot be installed directly. If the torque and structural requirements allow, a suitable adapter bracket and coupling can be designed. However, the load capacity, alignment, and effective engagement length must all be checked.
Related Articles:
