Scotch yoke pneumatic actuators

Scotch yoke pneumatic actuators engineering

Elfor Controls Quarter Turn Scotch Yoke Pneumatic Actuators EC SERIES are designed and engineered to act all ¼ turn valves, to provide an output torque curve which covers the most common on-off or modulating valves torque requirement.

EC Series valve actuators can be supplied with either symmetrical, or canted yokes to optimize actuator sizing.

Main features

  • Totally weatherproof .
  • Carbon Steel and Stainless Steel Single or Double acting.
  • Heavy duty Scotch yoke mechanism design, symmetric or canted execution.
  • Flange connection according to ISO 5211.
  • Adjustable end stoppers, to ensure accurate angular stroke adjustment (standard execution 90° +/-5°).
  • Emergency manual override available on request
  • Modular design
  • Operating pressure up to 12 barg (174 psi)
  • Power supply air or sweet gas
  • Temperature range -60 to 100°C (-76 to 212°F)

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1. PISTON GUIDE O-RING: installed in the appropriate housing seat in order to be compressed during assembly of two parts, creating a sealing gasket. It is a dynamic seal with defined dimensions according to standard DIN3771. Low friction, permanently lubricated.

2. O-RING ON PISTON AND LOCKING FERRULE: a static seal to prevent leakage / bypass in the pressure cylinder.

3. EXTERNAL TIE ROD: for pressure cylinder, sized according to UNI EN 14359.

4. O-RING ON CYLINDER HEAD: for static sealing.

5. SLIDING BUSH AND O-RING SEAL ON SCOTCH-YOKE: bronze bushing to ensure the anti-static nature of the system; self-lubrication to reduce friction and O-RING to ensure central body's sealing, high performance guarantee and low coefficients of friction.

6. BEARINGS 18NiCrMo5 alloy material, hardened 60 HRC, high resistance in order to slip on the scotch-yoke's guide slot; they ensure perfect alignment between scotch-yoke and cylinder rod during the conversion from translational motion to rotary one.

7. THREADED COUPLING with fixing grain provides better resistance to tension and compression between the chrome piston rod and the scotch yoke's hub.
8. GUIDE RAIL on the central body adequately machined with the lowest tolerances to ensure scotch-yoke perfect motion.

9. ADJUSTABLE LIMIT SWITCHES allow the scotch-yoke stroke adjustment of + - 5°. IP 67 System protection is ensured by an O-ring sealing. O-ring position is motionless thanks to screws and nuts fixing solution.

10. SELF-LUBRICATING SINTERED BRONZE BUSH AND CHROME BAR SLIDING SYSTEM allows high levels of performance, high operating speed and components wear resistance. O-ring fixed on the cylinder prevents working fluid's leakage.

11. CYLINDER is machined with the lowest tolerance and it shows a lapped finish in order to guarantee piston's O-ring sealing and a fluid motion. Surface finish treatment allows protection against aggressive corrosion. (All Actuators are certified to work with air or sour gas).

12. POSITION INDICATOR with high visibility, designed according to ISO 5211 is ready for accessories installation, such as Limit Switch and positioner.

13. SEAL between the cover and the central body ensures IP67 protection system.

14. FLANGE actuator is designed to meet all requirements of ISO 5211,for direct or coupling joint connection.

Standard and certifications

Elfor Controls actuators are designed to meet SIL 3 as a “single device”. Elfor Controls offers SIL features according to the IEC61508 and IEC61511 standards. Elfor Controls EC series pneumatic actuators are certified SIL 3 without partial stroke system and SIL 3 with periodic proof testing system.
  • PED 2014/68/EU
  • ATEX 2014/34/EU
  • EAC TR TS 012/2011
  • IP66/67M according to IEC/EN 60529
  • SIL3 certified (EC61508 and IEC61511) as a “single device”
  • Designed and tested in accordance with EN 15714-3
  • Further certifications are available, please contact Elfor Controls for updated list.

Elfor Controls Srl
Via Bastone 148/150 - 24044 - Dalmine (BG) Italy
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