The ISO 5211 standard defines the mechanical interface between part-turn valve actuators and industrial valves such as butterfly valves, ball valves, and plug valves. Published by the International Organization for Standardization, it ensures that actuators and valves from different manufacturers can be mounted together without custom adapters, reducing engineering lead time and simplifying procurement across global supply chains.
ISO 5211 is a multi-part international standard titled Industrial valves — Part-turn actuator attachments. It specifies the dimensions and tolerances for the mounting flanges and drive couplings that connect a part-turn (quarter-turn) actuator to the valve stem and body. The standard is referenced by valve OEMs, automation engineers, and procurement teams to guarantee mechanical interchangeability.
The standard is divided into two parts:
ISO 5211 classifies mounting flanges by a letter-and-number code. The letter F stands for Flange, and the number indicates the bolt-hole circle diameter in millimetres divided by 10, rounded to a standard designation. For example, an F07 flange has a bolt circle diameter of 70 mm, and an F12 flange has a bolt circle of 125 mm.
The full range of ISO 5211 flange designations is:
| Flange Code | Bolt Circle Ø (mm) | Number of Bolts | Bolt Thread Size | Spigot Ø (mm) | Typical Torque Range (Nm) |
|---|---|---|---|---|---|
| F03 | 36 | 4 | M5 | 25 | Up to 32 |
| F04 | 42 | 4 | M5 | 30 | Up to 63 |
| F05 | 50 | 4 | M6 | 35 | Up to 125 |
| F07 | 70 | 4 | M8 | 55 | Up to 500 |
| F10 | 102 | 4 | M10 | 70 | Up to 1,000 |
| F12 | 125 | 4 | M12 | 85 | Up to 2,000 |
| F14 | 140 | 4 | M16 | 100 | Up to 4,000 |
| F16 | 165 | 4 | M20 | 130 | Up to 8,000 |
| F25 | 254 | 8 | M16 | 200 | Up to 16,000 |
| F30 | 298 | 8 | M20 | 230 | Up to 32,000 |
| F35 | 356 | 8 | M30 | 260 | Up to 63,000 |
| F40 | 406 | 8 | M36 | 300 | Up to 125,000 |
These compact flanges are typically found on small quarter-turn pneumatic and electric actuators used for DN15–DN50 ball valves and small butterfly valves.
| Item | F03 | F04 | F05 |
|---|---|---|---|
| Flange outer diameter (max) | 50 mm | 58 mm | 68 mm |
| Bolt circle diameter | 36 mm | 42 mm | 50 mm |
| Number of bolts | 4 | 4 | 4 |
| Bolt hole diameter | 5.5 mm | 5.5 mm | 6.5 mm |
| Bolt thread | M5 | M5 | M6 |
| Spigot (male) diameter | 25 h8 | 30 h8 | 35 h8 |
| Spigot height (min) | 3 mm | 3 mm | 4 mm |
| Flange thickness (min) | 6 mm | 6 mm | 8 mm |
These are the most commonly specified flanges in process automation, covering the majority of actuated ball and butterfly valves from DN50 to DN300.
| Item | F07 | F10 | F12 | F14 |
|---|---|---|---|---|
| Flange outer diameter (max) | 90 mm | 125 mm | 150 mm | 175 mm |
| Bolt circle diameter | 70 mm | 102 mm | 125 mm | 140 mm |
| Number of bolts | 4 | 4 | 4 | 4 |
| Bolt hole diameter | 9 mm | 11 mm | 14 mm | 18 mm |
| Bolt thread | M8 | M10 | M12 | M16 |
| Spigot (male) diameter | 55 h8 | 70 h8 | 85 h8 | 100 h8 |
| Spigot height (min) | 5 mm | 6 mm | 6 mm | 6 mm |
| Flange thickness (min) | 10 mm | 12 mm | 14 mm | 16 mm |
Used for heavy-duty applications such as large-diameter butterfly valves (DN350+), high-pressure ball valves, and damper drives in power plants and water treatment facilities.
| Parameter | F16 | F25 | F30 | F35 | F40 |
|---|---|---|---|---|---|
| Flange outer diameter (max) | 210 mm | 300 mm | 350 mm | 415 mm | 470 mm |
| Bolt circle diameter | 165 mm | 254 mm | 298 mm | 356 mm | 406 mm |
| Number of bolts | 4 | 8 | 8 | 8 | 8 |
| Bolt hole diameter | 22 mm | 18 mm | 22 mm | 33 mm | 39 mm |
| Bolt thread | M20 | M16 | M20 | M30 | M36 |
| Spigot (male) diameter | 130 h8 | 200 h8 | 230 h8 | 260 h8 | 300 h8 |
| Spigot height (min) | 8 mm | 10 mm | 12 mm | 14 mm | 16 mm |
| Flange thickness (min) | 20 mm | 25 mm | 30 mm | 35 mm | 40 mm |
The drive coupling transmits torque from the actuator output shaft to the valve stem. ISO 5211-2 specifies three primary coupling types, each suited to different application requirements:
The most common coupling for small to medium actuators. The actuator output is a female square socket that mates with the valve stem's male square end. Square drives are economical and tolerate minor misalignment. Standard square drive sizes include 9 mm, 11 mm, 14 mm, 17 mm, 22 mm, 27 mm, and 36 mm across flats.
Also called a double-flat or parallel-flat drive. Two parallel flats transfer torque while eliminating the stress concentrations found at square corners. Preferred for medium to high torque applications where square drives may gall or deform under repeated cycling. Common flat widths: 11 mm, 14 mm, 19 mm, 22 mm.
A cylindrical bore with a keyway, secured by a key per ISO 773 or DIN 6885. This is the standard for large and high-torque actuators (F16 and above), where a square or flat drive would be impractical. Keyed connections allow disassembly for maintenance without damaging the shaft. Bore diameters follow preferred number series: 20 mm, 25 mm, 30 mm, 40 mm, 50 mm, 60 mm, 80 mm.
While ISO 5211 does not specify mandatory torque limits, industry practice correlates flange sizes with safe operating torque ranges. Selecting an undersized flange for the required torque can cause bolt fatigue, spigot fretting, and eventual mounting failure.
| Flange Code | Recommended Max Torque (Nm) | Typical Valve Application |
|---|---|---|
| F03 | 32 | DN15–DN25 ball valves, small needle valves |
| F04 | 63 | DN25–DN32 ball valves, DN40 butterfly valves |
| F05 | 125 | DN40–DN50 ball valves, DN50–DN65 butterfly valves |
| F07 | 500 | DN65–DN100 ball valves, DN80–DN125 butterfly valves |
| F10 | 1,000 | DN100–DN150 ball valves, DN150–DN200 butterfly valves |
| F12 | 2,000 | DN150–DN200 ball valves, DN200–DN300 butterfly valves |
| F14 | 4,000 | DN250–DN350 butterfly valves, plug valves |
| F16 | 8,000 | DN350–DN500 butterfly valves, high-pressure ball valves |
| F25 | 16,000 | DN600–DN800 butterfly valves, damper drives |
| F30 | 32,000 | DN900–DN1200 butterfly valves |
| F35 | 63,000 | DN1400–DN1600 large bore valves |
| F40 | 125,000 | DN1800+ and custom large-diameter dampers |
Selecting the correct ISO 5211 interface involves four sequential checks:
| Standard | Scope | Valve Type | Mounting Interface |
|---|---|---|---|
| ISO 5211 | Part-turn actuator mounting | Ball, butterfly, plug valves | Flange + drive coupling |
| ISO 5210 | Multi-turn actuator mounting | Gate, globe, sluice valves | Flange + thrust base |
| NAMUR VDI/VDE 3845 | Pneumatic actuator accessory mounting | Solenoid valves, positioners, limit switches | Top-mount accessory pattern (80 mm × 30 mm) |
| DIN 3337 | Part-turn actuator (German predecessor) | Ball, butterfly valves | Largely superseded by ISO 5211, still found on legacy equipment |
| MSS SP-101 | Part-turn actuator (US practice) | Ball, butterfly valves | Functionally compatible with ISO 5211 for common sizes |
In practice, ISO 5211 has become the global default. Most valve and actuator manufacturers in Asia, Europe, and the Americas design their mounting interfaces to conform to ISO 5211, often dual-marking products as conforming to both ISO 5211 and the legacy DIN or MSS standard where overlap exists.
Yes, using a mounting bracket with a stepped or reducing adapter plate. However, this adds stack height and may introduce alignment errors. Always confirm that the bolt pattern on both sides can be accommodated in the adapter design.
The standard does not mandate a material. Actuator flanges are typically cast aluminium (EN AC-46100 or similar) for F03–F12, ductile iron (EN-GJS-400-15) for F14–F25, and cast steel (EN 1.0619 / WCB) for F30 and above. Valve top flanges follow the valve body material, often cast iron, ductile iron, carbon steel, or stainless steel.
They are separate standards for different interfaces. ISO 5211 governs the valve-to-actuator mechanical connection; NAMUR VDI/VDE 3845 governs the actuator-to-accessory pneumatic/electrical interface (solenoid valves, limit switch boxes, positioners). A fully automated valve assembly typically conforms to both standards simultaneously.
Measure four parameters with a vernier caliper: (1) bolt circle diameter (centre-to-centre of opposing bolt holes or bolt-to-centre doubled), (2) number of bolt holes, (3) bolt hole diameter, and (4) spigot outer diameter. Cross-reference these measurements against the dimension tables above. The bolt circle diameter is the most reliable single identifier.
No. ISO 5211 is purely a dimensional interface standard. Functional safety requirements for actuated valves fall under IEC 61508 / IEC 61511 (safety integrity levels) and application-specific standards such as ISO 12490 for pipeline valves in petroleum and natural gas industries.
