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What does NAMUR mean on a valve actuator specification?
On a pneumatic valve actuator, NAMUR usually means the standard mounting interface defined in VDI/VDE 3845, so that a solenoid valve, a limit switch box or another accessory from any maker fits the actuator without a custom bracket. A line such as "pneumatic actuator, NAMUR solenoid, NAMUR switch box" asks for exactly that.
The name comes from an association, not a product. The Wikipedia entry on NAMUR describes it as an international association for users of automation technology in the process industries, established in 1949, whose work results "are published in the form of NAMUR recommendations and worksheets and submitted to national and international standardization bodies as proposed standards". The same entry lists among its work "NAMUR sensors (e.g., IEC 60947-5-6)" and "NAMUR solenoid mounting plates (VDI/VDE 3845, ISO 5211)".
How do ISO 5211 and VDI/VDE 3845 differ?
ISO 5211 and the NAMUR interface, VDI/VDE 3845, join different things on the same valve package. ISO 5211 is the mounting flange and drive between the valve and the actuator, under the actuator. VDI/VDE 3845 is the interface between the actuator and its accessories, the solenoid valve on its side and the switch box on top. A quarter-turn package therefore usually names both.
| Interface | Joins | Where it sits | What it fixes |
|---|---|---|---|
| ISO 5211 | Valve to actuator | Under the actuator | The mounting flange and the drive to the valve stem |
| VDI/VDE 3845 (NAMUR), side | Solenoid valve to actuator | On the actuator's air port face | The hole pattern and air ports for a valve that mounts flat |
| VDI/VDE 3845 (NAMUR), top | Limit switch box to actuator | On top, on a bracket | The bracket holes and the shaft that drives the box |
Festo's SRBC sensor box datasheet, for example, says the box is mounted "on quarter turn actuators with a hole pattern to VDI/VDE 3845 using mounting adapters". Our guide to ISO 5211 actuator mounting flanges covers the valve side, and our valve selection by standard guide sets both in context.
How does a NAMUR solenoid valve mount on an actuator?
A NAMUR solenoid valve bolts flat onto the NAMUR face of a pneumatic actuator, with its mounting holes and air ports lined up with the actuator's, so a valve from one maker fits an actuator from another without a custom bracket. Tameson's technical guide explains that the NAMUR standard "specifies the dimensions and hole patterns for mounting directional control valves to pneumatic actuators", and gives two sizes, a NAMUR 1/4" and a NAMUR 1/2" interface.
Tameson's NAMUR guide lists the mounting steps: depressurise first, clean the interface, check the O-rings around the valve's air ports, line up the holes and the air ports, fit and tighten the screws, then connect the air and the solenoid wiring and test for leaks. Tameson describes the gain plainly: the interface makes mounting "simple" and ensures "compatibility and ease of installation across different manufacturers".
A specification still has to say which size of interface the actuator carries and what the solenoid must do: for example, which function it performs and its coil voltage.
How does a limit switch box mount on a NAMUR actuator?
A limit switch box sits on top of the actuator on a NAMUR bracket, and the actuator's shaft turns a cam inside the box that trips a switch at the open and the closed position. Tameson's guide to limit switch boxes notes they "can be directly mounted to pneumatic actuators via standardized interfaces (e.g., NAMUR VDI/VDE 3845)", and that the cam "engages the limit switches at designated positions, which are typically the 0° and 90° positions".
Makers' switch boxes follow the same pattern. Rotork's RCE4L and RCE4 boxes "are mounted on the RC200-series according to VDI/VDE 3845, NAMUR on the top side of the actuator and are operated by its shaft", with "two microswitches which are effected by two independently adjustable cams". Festo's SRBC box comes with a "Pre-assembled stainless steel mounting adapter 80x30 H20", and Festo also lists an adapter for a 30 x 130 mm hole pattern; Tameson notes its boxes fit "hole patterns of 80 x 30 mm and 130 x 30 mm". Brackets come in more than one size, so check the bracket against the actuator's datasheet.
What is a NAMUR sensor, and how is it different?
A NAMUR sensor is an inductive proximity sensor that follows a signal standard, IEC 60947-5-6, rather than the VDI/VDE 3845 mounting standard. In a limit switch box it is one of the switch options, alongside mechanical microswitches and magnetic reed switches.
Festo's SRBC datasheet lists, for example, an inductive variant with an "8.2 V DC NAMUR N/C contact" next to mechanical and magnetic reed versions, and an ATEX version. Tameson's guide lists "NAMUR inductive sensors (ATEX)" among the switch options for two of the box series it compares. So "NAMUR" on a switch box line can mean the mounting, the sensor, or both: write each out.
What should a NAMUR line on a valve package state?
A NAMUR line on a valve package should state the actuator and each accessory separately, and say for each which NAMUR it means: the VDI/VDE 3845 mounting interface, the IEC 60947-5-6 sensor signal, or both. Without that, two suppliers can quote two different packages against the same line. A complete line covers:
- The actuator: double acting or spring return, its size, and the ISO 5211 flange it carries.
- The solenoid valve: NAMUR mounted, the interface size, its function, coil voltage and any hazardous-area rating.
- The limit switch box: NAMUR mounted, the bracket for that actuator size, the switch type (mechanical, inductive or NAMUR sensor) and the number of switches.
- Ingress and hazardous-area ratings for the accessories, as for the actuator. Our guides to actuator IP ratings and explosion-proof actuators cover those.
- Whether the package is supplied assembled and tested, or as loose parts.
Send the line to enquiry@flowsynergy.ae for valve selection and technical support, or see our actuators, dampers and fittings page.
Frequently asked questions
Is a NAMUR solenoid valve the same as any solenoid valve?
No. A NAMUR solenoid valve has the standard NAMUR mounting face, so it bolts directly onto a pneumatic actuator's NAMUR interface. Tameson defines a NAMUR solenoid valve as one "designed to be mounted on pneumatic actuators using the standardized NAMUR interface".
Does a NAMUR actuator still need ISO 5211?
Yes, if it drives a quarter-turn valve. The NAMUR interface carries the accessories, and the ISO 5211 flange and drive connect the actuator to the valve, so a complete package names both.
Can a switch box from one maker fit an actuator from another?
Usually, if both follow VDI/VDE 3845; that is the point of the interface. Check that the bracket matches the actuator's size and shaft height, because brackets come in more than one size.
Does a NAMUR sensor need a NAMUR interface?
No. The NAMUR sensor is a signal standard (IEC 60947-5-6), and the NAMUR interface is a mounting standard (VDI/VDE 3845). A switch box can have one, the other or both, so state each on the line.
Sources quoted on this page
Read 11 November 2026. Confirm every detail against the current edition of any standard named and the maker's datasheet for the exact actuator and accessory.
- Wikipedia, NAMUR: the association, its recommendations and the standards it helped develop.
- Tameson, NAMUR interface for solenoid valves and Limit switch boxes for pneumatic quarter-turn valves: mounting, interface sizes, how a switch box works, switch options.
- Festo, Sensor boxes SRBC datasheet: mounting to VDI/VDE 3845, adapter, switch variants.
- Rotork, RCE4L limit switch box: mounting according to VDI/VDE 3845.
No clause, table or dimension from VDI/VDE 3845, ISO 5211 or IEC 60947-5-6 is reproduced here; the interfaces are summarised from published maker and reference pages. Products named are published examples, not a statement of what Flowsynergy supplies.