Scotch yoke hydraulic actuators

Scotch yoke hydraulic actuators engineering

Elfor Controls Quarter Turn Scotch Yoke Hydraulic 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 350 barg (5000 psi)
  • Power supply Oil
  • Temperature range -60 to 100°C (-76 to 212°F)

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1. O-RING COUPLED WITH THE SEALING RING guarantees a double-sealing effect, used for dynamic applications in hydraulic cylinders. Low friction, absence of phenomena of STICK-SLIP (stop and sliding) and good abrasion resistance are the main features.

2. BAND DRIVING prevents metal to metal contact between piston / cylinder and guide rod / piston, supports radial loads and reduce vibrations.

3. This type of DOUBLE SEAL guarantees high system reliability level and it's accurately designed for high pressure applications.

4. On the body side, in addition to the double sealing system, a BIDIRECTIONAL SCRAPER RING is installed in order to:

  • 4a. prevent the introduction of dust, dirt, foreign matter into the sealing system. This is achieved thanks to a special scraper lip which produces an effective self-cleaning action: preventing slugs development and protecting the guiding parts extending seals service life.

  • 4b. retain the oil film to keep rod seal lubricated. The asymmetric lips are designed to differentiate the sealing action on both static and dynamic conditions: the static lip side is flexible, more sensitive to pressure variations and ensures a wide contact surface; the dynamic one is shorter and stronger in order to concentrate load on the surface in motion.

  • 4c. provide excellent wear resistance and long life working.

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°.

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

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

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

13. O-RING SEALING on limit switches ensures IP67 System protection. O-ring position is motionless thanks to screws and nuts fixing solution.

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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