Product Overview
The EEI 585.C (also referenced in literature as 585-C-EEI, 585C-EEI or EEI 585 C) is a heavy-duty, double-acting quarter-turn rotary actuator developed by EEI – Elettromeccanica Industrial of Italy for the reliable automation of ball valves, butterfly valves, plug valves and dampers in demanding process industries. Belonging to the mature 580/585 series of symmetrical twin-piston rack-and-pinion actuators, the EEI 585.C converts pneumatic or hydraulic pressure into a precise 90° rotary output (180° versions available by variant) through two opposing pistons whose precision-machined rack teeth mesh a central, hardened alloy-steel pinion.
The defining mechanical advantage of the EEI 585.C is the symmetry of its rack-and-pinion geometry. Unlike scotch-yoke actuators, which exhibit pronounced torque variation near the end positions, the twin-piston layout of the EEI 585.C produces essentially constant torque throughout the full sweep. In practical terms, this means a valve cannot jam at an angle where the actuator has gone weak — a common failure mode with yoke-type units in slurry, coking and deposit-prone services. The “double-acting” designation is equally important: with no spring-return bias, the EEI 585.C develops equal, substantial torque in both directions and, crucially, stays exactly where it is on loss of air supply — a fail-in-place characteristic that is highly desirable in modulating control loops and, when paired with a monitored trip solenoid and partial-stroke test valve, integrates cleanly into SIL-rated emergency shutdown architectures.
Engineered for continuous-duty process service, the EEI 585.C features a hard-anodized extruded aluminum body, stainless-steel fasteners, PTFE piston wear bands that eliminate metal-on-metal sliding, externally accessible travel limit screws and an integral visual position indicator. Both side faces carry NAMUR-standard accessory pads, allowing a 5/2 or 3/2 Namur pilot solenoid, smart positioner, or inductive limit switch box to bolt directly without adapter plates. The EEI 585.C shares ISO 5211 flange patterns, bolt circles and dimensional envelopes with the legacy Biffi / Flowserve 580-series, making it a genuine drop-in spare for plant lifecycle refresh programmes without re-machining valve adapters or fabricating custom brackets.
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | EEI 585.C (585-C-EEI / 585C-EEI / EEI 585 C) |
| Manufacturer | EEI – Elettromeccanica Industrial (Italy) |
| Product Type | Double-acting rack & pinion quarter-turn rotary actuator |
| Series / Platform | 580 / 585 series symmetrical twin-piston family |
| Action Type | Double acting (air-to-open / air-to-close); fail-in-place on air loss |
| Output Motion | 90° standard (mechanically adjustable ±5°); 180° versions by variant |
| Nominal Output Torque | 60 – 6000 Nm across the size range, referenced at 5.5 bar supply |
| Operating Pressure (Pneumatic) | 3 bar minimum – 8 bar standard maximum; some frame sizes rated to 10 bar |
| Hydraulic Service Pressure | Up to 30 – 80 bar depending on frame size and variant |
| Air Supply Port | G 1/4″ or G 1/2″ BSP / NPT depending on frame size; NAMUR interface optional |
| Mounting Flange | ISO 5211 — F03, F04, F05, F07, F10, F12, F14, F16 depending on frame size |
| Output Drive | Through-bored square drive sleeve per ISO 5211 / DIN 3337; keyed option for heavy duty |
| Body Material | Extruded aluminum alloy, hard anodized as standard; epoxy-polyester coating optional |
| Pistons / Rack | Aluminum alloy with PTFE-based wear strips |
| Pinion | Hardened alloy steel, precision machined and heat treated |
| Seals / O-Rings | NBR (nitrile) standard: -20 °C to +80 °C; FKM (Viton) optional: -30 °C to +150 °C |
| Adjustable Travel Stops | External hex-head screws, independently adjustable open and close ends |
| Position Indicator | Molded polyamide visual pointer with OPEN / CLOSED dial |
| NAMUR Accessory Pads | Yes — both sides, for Namur solenoid, positioner and limit switch box |
| Ambient Operating Temperature | -20 °C to +80 °C (NBR); -30 °C to +150 °C (FKM option) |
| Ingress Protection | IP65 standard; IP67 optional with sealed accessory covers |
| Typical Weight | 2.5 kg (smallest frame) to 120+ kg (largest bore frame) |
| Lubrication | Factory pre-lubricated; no external greasing required in normal service |
