Frequently Asked Questions
Everything importers, integrators and resellers ask before ordering — sizing, mounting standards, air supply, OEM/ODM and quality.
Actuator Basics
What is the difference between double-acting and spring-return pneumatic actuators?
Double-acting actuators use air pressure to drive rotation in both directions — pressurized air opens and pressurized air closes — and hold position only while air is applied. Spring-return (single-acting) actuators use air to compress a spring bank in one direction, and the spring drives the return stroke when air is vented, which gives a defined fail-safe position on loss of supply. Spring-return units are the common choice for emergency shutdown duty; double-acting suits applications where air is continuously available and no spring force is needed.
How does a spring-return actuator work?
A spring-return actuator contains a spring cartridge (or multiple springs) that is compressed as the actuator strokes on air pressure. When the air supply is vented or lost, the stored spring energy drives the output shaft back to the preset fail position. Output torque on the spring end is typically lower than on the air end, so sizing must be checked against the spring-end curve, not the air-end figure. On many rack and pinion models, spring cartridges can be swapped to change the fail torque range.
What do fail-closed (FC) and fail-open (FO) mean, and how do I choose?
FC (fail closed) means the actuator drives the valve closed when air is lost — used to isolate flow or protect downstream equipment, common on burners and process lines. FO (fail open) means the valve opens on air failure, typical for cooling water and venting duties. Selection depends on your process safety requirement: decide what the valve must do when the plant loses air, then specify FC or FO. The spring direction is set at the factory and cannot be changed in the field without reconfiguration.
How do I select the right actuator torque?
Start with the valve's maximum required torque at the worst-case differential pressure, then add a safety margin — commonly 25–30% for double-acting units and more for spring-return, because spring output varies across the stroke. Provide valve type, size, differential pressure, media and operating temperature, and we size the actuator from our 8–200,000 Nm range. Under-sized actuators cause slow or incomplete stroking; oversized ones raise cost and air consumption, so the margin should be calculated, not guessed.
Mounting & Compatibility
What is the ISO 5211 standard?
ISO 5211 defines the mounting pad, bolt circle and drive coupling for valve actuators, covering sizes from F03 (36 mm bolt circle) up to F25 (254 mm) and beyond. A compliant actuator bolts directly onto an ISO 5211 valve top flange without adapters, with interchangeable drive inserts (square, double square, female or keyed) matched to the valve stem. When ordering, confirm the valve's ISO 5211 size and stem dimensions so the drive insert matches.
What is a NAMUR interface?
NAMUR refers to the VDI/VDE 3845 interface: a standardized mounting pattern for solenoid valves and positioners on the actuator, using a 30×80 mm hole pattern with the valve center 130 mm from the actuator shaft axis. It lets you mount a 5/2 or 5/3 solenoid directly on the actuator top or side pad without brackets or tubing, reducing leak points. If you already have a NAMUR solenoid or positioner, tell us the make and model and we confirm compatibility.
How do I match an actuator to my valve?
Send valve type, size, end connections, maximum differential pressure, required rotation (90° or multi-turn), media and fail position. We cross-check the valve torque at break, running and end-of-stroke against our output curves and recommend a model with the correct ISO 5211 size and drive coupling. For retrofits, also measure the existing stem length, keyway and any obstruction above the bonnet.
What air supply do pneumatic actuators need?
Standard operating pressure is 4–8 bar, with most models rated to 10 bar maximum. Air should be filtered to 5 µm or better, dry (dew point below the lowest ambient temperature to avoid freezing), and can be used lubricated or non-lubricated; if lubricated, use a compatible oil such as ISO VG32. Air consumption is specified per model in liters per cycle — from roughly 0.1 L/cycle on small units to tens of liters on large scotch yoke units — so the compressor and piping should be sized accordingly.
What temperature range do your actuators cover?
The standard build with NBR seals covers about -20°C to +80°C, which fits most indoor and mild-outdoor installations. With alternative seal materials (FKM for high temperature, silicone or special compounds for low temperature), ranges of -40°C to +150°C can be provided. Confirm the minimum and maximum ambient and media temperatures, plus any condensation or washdown exposure, so the seal and coating spec can be matched to the site.
Orders, OEM & Compliance
Do you offer ATEX-rated actuators for hazardous areas?
ATEX-certified versions are available as an option for explosive atmospheres; the certification class depends on the zone, gas group and temperature class at your site. Confirm the area classification (zone, group, T-class) and whether you need the valve and accessories certified as a set, and we quote the correct build. Standard units are not rated for hazardous areas and should not be installed there without the ATEX option.
What are your MOQ and lead times?
MOQ is 1 unit for samples so you can test torque, mounting and finish in your own application before committing to volume. For production orders the typical MOQ is 10 units per model; lead time for standard configurations is about 15–30 days, with sample orders typically 7–15 days. Lead times depend on the spring configuration, seal material and any custom options, and are confirmed in writing at quotation.
Can you manufacture under my brand (OEM/ODM)?
Yes. OEM covers private labeling: your brand, nameplate, color/coating, packaging and manuals on existing models. ODM goes further: we develop or modify the actuator to your spec — torque curve, stroke angle, port types (G, NPT), special seals, limit switch boxes and mounting options. Custom torque ranges, non-standard travel stops and special coatings (marine, chemical) are common ODM requests. A pre-production sample is provided for approval before mass production.
Do you provide samples, and what does the sample process look like?
Samples are available for most models before bulk orders. The typical flow is: send your valve data and torque requirement → we confirm the model and specification → the sample ships within 7–15 days → you test torque, mounting and cycle performance → approval for mass production. Sample cost is deducted or credited on many production orders — confirm the policy at quotation.
What is your warranty and after-sales policy?
The baseline warranty is 12–24 months depending on model and agreement, with a documented RMA process for returns. We keep spare seal kits, springs and accessories in stock for common models, and our engineers support sizing, troubleshooting and commissioning by email or video call. Warranty covers manufacturing defects; damage from overpressure, contaminated air or misapplication is handled on a case-by-case basis.
Installation, Maintenance & Support
How do I install and commission the actuator?
Mount the actuator on the ISO 5211 flange with the drive insert aligned to the valve stem, and cycle the valve by hand or slowly at low pressure to confirm stroke direction before full operation. Then set the travel stops to the exact open/closed position, connect the air lines (5 µm filtered air recommended), and stroke several times while checking for binding and correct fail behavior when supply is vented. For spring-return units, verify the fail position before pressurizing. Our installation sheet gives flange bolt torque values and travel-stop adjustment procedures per model.
How often does an actuator need maintenance, and what is its service life?
Rack and pinion actuators commonly exceed 500,000 cycles in testing with correct air quality and periodic lubrication; scotch yoke units on slow large-valve duty typically run longer in calendar terms. Practical guidance: inspect annually or every 200,000–500,000 cycles, whichever occurs sooner — check for air leaks, corrosion and travel-stop drift, and re-lubricate per the datasheet. Seal kits are replaced when leakage or stiffness appears; keep one kit per site per model. Actual life depends on air quality, cycle rate, temperature and media exposure.
What is the difference between rack and pinion and scotch yoke actuators?
Rack and pinion actuators provide near-constant torque through the stroke and are compact and economical from about 8 Nm up to several thousand Nm — the typical choice for 90° ball and butterfly valves. Scotch yoke actuators generate higher torque at the ends of the stroke through a camming effect, which matches the peak break torque of large ball and butterfly valves; they cover the higher end of our range up to 200,000 Nm and are common on large isolation valves. If your valve breaks at high torque but runs at low torque, a scotch yoke often matches the duty more closely; for constant-load duty a rack and pinion is usually the simpler solution.
Can you help with sizing and technical support?
Yes. Send the valve datasheet or the parameters listed above, and our engineers respond with a model recommendation, torque calculation sheet and air consumption figure — usually within one working day. Support is included with every order, and we also provide spare parts lists, installation sheets and commissioning checklists for your installers.
Still Have Questions?
Send us your valve spec and our engineers will answer within 24 hours — factory-direct, no middlemen.