Valve position feedback · Switch and sensor types, NAMUR mounting, visual indicators, enclosure and proof testing
A valve position indicator, built as a limit switch box in the products cited here, sits on top of a quarter-turn actuator, turns with the actuator shaft and tells both the operator and the control system whether the valve is open or closed. A dome or flag shows the position locally, and cams inside trip switches or sensors at each end of travel. Ask three things first: which switch or sensor type matches your control input, how it mounts and is set on your actuator, and which enclosure rating and approvals the site needs.
Position indicators and limit switch boxes for automated quarter-turn process valves, including versions with 4–20 mA position transmitters. Panel indicator lamps for switchgear, medical sleep-position devices and the valve actuators themselves are outside this page.
CNFX editorial research · Sources checked October 12, 2026 · 4 sources
Choose the switch or sensor type for your control input
Rotork's limit switch box brochure lists mechanical, magnetic and inductive options. A silver-plated SPDT snap-action switch is rated up to 5 A at 250 VAC or 3 A at 24 VDC, while a gold-plated SPDT switch is rated up to 0.1 mA at 250 VAC or 0.5 mA at 30 VDC, both for −40 to +125 °C. Hermetically sealed NOVA magnetic proximity switches are rated up to 5 A at 250 VAC, and sealed reed switches up to 1 A at 24 VDC. [1]
For intrinsically safe circuits the brochure lists inductive NAMUR sensors with a nominal 8 VDC supply drawing 1 mA when the target is detected and 3 mA when it is not, and amplified PNP or 2-wire sensors for 5–60 VDC or 10–30 VDC inputs. [1]
Where open/closed is not enough, a 4–20 mA position transmitter inside the box represents 0–100% of travel, with ±0.5% linearity on full scale and a 13–30 VDC supply; HART versions list a 10 ms update time and a 70 ms response time. [1] Editorial note: match the switch to the input card it drives, because a gold contact is chosen for low-current signals and a NAMUR sensor needs a matching isolating amplifier or barrier.
A second maker's sensor shows the same NAMUR interface from the sensor side. Pepperl+Fuchs's data for its NCN3-F25-N4-V1, a dual inductive sensor for direct mounting on standard actuators, lists two normally closed NAMUR outputs, 2-wire, at a nominal 8.2 V (internal resistance about 1 kΩ), drawing at least 3 mA when the measuring plate is not detected and no more than 1 mA when it is, with conformity to EN 60947-5-6:2000 / IEC 60947-5-6:1999 and NE 21:2007. It gives a rated operating distance of 3 mm, an assured operating distance of 0–2.43 mm, switching frequency up to 1,500 Hz, hysteresis of 5% (typ.), IP67, −25 to 100 °C operation, a PBT housing, 45 g mass, MTTFd of 1,010 years with a 20-year mission time and 0% diagnostic coverage, and IECEx approval for equipment protection levels Ga and Gb. [4] The sensing distance falls with the target metal: reduction factors are 1 for St37 steel, 0.86 for 304 stainless, 0.54 for brass, 0.52 for aluminium and 0.43 for copper. Pepperl+Fuchs states that NAMUR sensors must be operated with approved switch amplifiers. [4]
Editorial calculation: with a 3 mm rated distance, an aluminium cam or target gives about 3 × 0.52 ≈ 1.6 mm and a 304 stainless one about 2.6 mm, so the target material in the switch box sets how close the cam must run to the sensor. The 1 mA / 3 mA levels match those Rotork lists for its NAMUR sensors. Ask the supplier which target material the box uses and for the sensor's rated distance with that target. [4][1]
Give the supplier the actuator make, model and NAMUR pattern, valve rotation (90°, 180° or three-way), the switch or sensor type and quantity, the control input it connects to, any solenoid valve wiring, cable entry size, enclosure material and IP rating, hazardous-area approvals, SIL requirement, ambient temperature range and the indicator colours or shape.
02
Mount, indicate and set it on the actuator
Rotork's KN and KNC mounting kits, made from AISI 304 stainless steel, fit an ISO F05-drilled device to a NAMUR-pattern actuator to VDI/VDE 3845. The kit is chosen by the actuator's pattern and pinion height: 30 × 80 with 20, 30 or 40 mm pinions, 30 × 130 with 30, 40 or 50 mm, and, for one kit, 25 × 50 with 20 mm. [1]
The brochure's visual indicator codes include a 3D 90° red and green dome, a yellow and black open-close version, 3D 180° indicators, indicators for three-way L and T port valves, a 60° version, a 316 stainless steel dome, and rigid 150 mm or 300 mm and flexible 500 mm extensions. [1] Its twin shaft design fixes the indicator permanently to the top shaft so it stays aligned after reassembly. [1]
Rotork's SF-SS installation manual sets each cam by driving the actuator to the end position, lifting the cam off its splined sleeve, turning it until the switch operates and re-engaging it, and warns that an inductive sensor must not touch its cam. [2] Editorial note: after setting, stroke the valve fully and confirm that the indicator and both signals agree with the actual valve position.
03
Check enclosure, approvals and proof testing
Rotork's SF-SS series is offered in copper-free aluminium or 316 stainless steel, rated IP66/67 with NEMA 4/4X on request, for −40 to +80 °C as standard and −60 to +105 °C on request, with ATEX, IECEx, UL and other approvals and a TÜV SIL certificate up to SIL 3; the aluminium version has C5-M painting as standard. [1]
Rotork's safety manual says the proof test should be performed at least once a year, during the testing of the actuator-valve assembly, and that for its Type A devices the proof test corresponds to a full stroke test of the actuator-valve assembly. It adds that the user should not repair the equipment and must respect the electrical ratings on the nameplate, otherwise the SIL grade is not guaranteed. [3]
The SF-SS manual states that below −10 °C or above 70 °C ambient, cables rated for the minimum and maximum ambient should be used, with a working temperature 11 °C above ambient. [2]
04
One visible supplier, sold with valves and actuators
Heyue Valve Actuator is the company shown below; its page lists a position indicator limit switch box.
The supplier reviewed also makes pneumatic valves and actuators; ask for the switch type, enclosure rating, mounting kit and any approvals for the exact box.
05
Dome, shaft, cams, switches, transmitter, terminals and kit
The parts follow Rotork's Soldo documents; another maker's box may combine or omit some of them, such as the optional transmitter.
Signal, enclosure, mounting and indication values for the quotation
Actuator pattern, input card and site approvals come from your plant. Rotork figures appear in the middle column as examples; the operating-pressure row belongs to the actuator, not the indicator.
Field
What it means and published values
Ask the supplier for
Operating Pressure (MPa)
Relates to the actuator air supply, not the indicator.
Actuator supply pressure.
Operating Temperature (°C)
SF-SS: −40 to +80 °C standard; −60 to +105 °C on request. [1]
1 company lists this product among what they make. Company figures are quoted from each
company's own website; every card states where the relationship came from.
HEYUE Valve Actuator
Manufacturing site to be confirmed for the order
Lists a position indicator limit switch box with pneumatic valves and actuators.
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
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Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
What is the difference between silver and gold contacts in a limit switch box?
In Rotork's range, silver contacts are rated up to 5 A at 250 VAC, while gold contacts are for low-current signals of 0.1 mA at 250 VAC. [1]
How does a position indicator mount on an actuator?
Through a NAMUR VDI/VDE 3845 mounting kit chosen by the actuator pattern (30 × 80 or 30 × 130) and pinion height. [1]
How often should a limit switch box be proof-tested?
Rotork's safety manual says at least once a year, during the testing of the actuator-valve assembly it is mounted on. [3]
What current does a NAMUR valve position sensor draw?
Pepperl+Fuchs's NCN3-F25-N4-V1, to IEC 60947-5-6, draws at least 3 mA with the target not detected and no more than 1 mA when detected, at a nominal 8.2 V. [4]
Sources and what still needs a direct check
Sources checked 2026-10-12. Three sources are Rotork documents for its own Soldo limit switch boxes; Pepperl+Fuchs's data covers its own dual NAMUR sensor for actuators. Another maker's ratings must come from its own data sheet and certificates.
