Most positioners sold today either use a nozzle-flapper I/P converter or a piezo-electric pilot. The two behave very differently once plant air is not perfectly clean and the ambient temperature swings. We build on nozzle-flapper — the route Fisher, Samson, ABB and Azbil also use — for one practical reason: it forgives your air supply.
Five stages, no digital trick in between. Knowing this is what lets you troubleshoot a loop in ten minutes instead of swapping parts.
The 4–20 mA signal drives a coil. Current in, magnetic force out — no motor, no gear train, nothing to wear into backlash.
A flapper is pulled toward a nozzle. The closer it sits, the higher the pressure behind the nozzle. This is the only measuring point in the loop.
A pneumatic relay amplifies that small back-pressure into the flow your actuator needs on OUT1 or OUT2, then the position sensor closes the loop.
Both work on a bench with clean, dry, constant-temperature air. The difference shows up in month eighteen, on a plant air header everyone has stopped caring about.
If your plant air is instrument-grade and you are designing a battery or loop-powered device, a piezo pilot is a legitimate choice. If you are specifying for a refinery, a chemical plant or a steel mill where the air header is shared with everything else, the nozzle-flapper route is the one that survives.
A positioner that bleeds continuously is a compressor load that runs 8,760 hours a year. On a large site this line item is bigger than the purchase price.
| Positioner | Steady-state air |
|---|---|
| TORLEO TOP-5879F1 | 36 L/h |
| ABB TZID-C | 24 L/h |
| Masonelian SVI II AP | 36 L/h |
| Metso ND9000 | 104 L/h |
| Samson 373X | 110 L/h |
| Azbil SVP302 | 210 L/h |
| Flowserve PMV-D3 | 490 L/h |
| Fisher DVC6200 | 537 L/h |
| Foxboro SRD960 | 1000 L/h |
Published steady-state consumption, no valve movement. This table is not a claim of overall superiority: two competitors sit in the same low-consumption class, and the rest of the installed base is 3–15× higher. It exists because nobody puts this number on a tender document, and then everyone is surprised by the compressor bill.
Every one of these is normally an accessory line on the same purchase order. We moved them into the housing.
The P/I air path closes automatically on loss of signal, air or power. Hold the valve where it is with one external air-lock valve and nothing else.
Upper and lower position contacts are available as a built-in module. Wire the DCS interlock straight to the terminal block.
Copy four parameters into the spare, swap the housing, done — no full auto-calibration on a live loop. Full auto-calibration itself takes 3–5 minutes on a normal actuator.
The failure mode nobody catches in a DCS trend: an emergency shutdown valve that has not moved in two years and no longer will.
Built-in TSP strokes the ESD valve part of its travel from the fully open position, on a schedule, and returns it. The line keeps running.
The position feedback confirms travel, not just an output signal. A stuck stem shows up as a failed test instead of a failed trip.
Results support the proof-test interval your SLS logic expects, without a full shutdown stroke. Standard on the C-series electronics.
Taken from the published datasheet. Ask us for the test report on any line item.
| Parameter | Value | Basis |
|---|---|---|
| Control accuracy | 0.1–0.3 % F.S. | Auto-calibrated, typical actuator |
| Repeatability | 0.2 % F.S. | Datasheet |
| Linearity | 0.3 % F.S. | Datasheet |
| Hysteresis | 0.2 % F.S. | Datasheet |
| Sensitivity | 0.2 % F.S. | Datasheet |
| Steady-state air | 36 L/h | 1.4 bar supply, no movement |
| Air supply | 1.4–6 bar | Oil-free, dry, filtered |
| Stroke range | 10–150 mm linear · 0–120° rotary | Direct or lever feedback |
| Ambient | −30…+70 °C (T4) · low-temp −40…+60 °C | Model dependent |
| Enclosure | IP66 | IEC 60529 |
| Safety | SIL3 capable | TÜV SÜD certificate |
| Housing | Die-cast aluminium, epoxy coated · 316L stainless | Model dependent |
Weight: 3.5 kg aluminium / 5.2 kg stainless (C41). Enclosure 130 × 128 × 153 mm (C41) · 155 × 128 × 145 mm (C45).
Valve type, size, actuator, air supply, area classification and what has been failing. We will tell you which configuration fits — and which accessory you can drop.