Self-Contained Electro-Hydraulic Actuator EHC-AA E 2.163.0/07.13 E 2.800.2/04.11 4 Self-Contained Electro-Hydraulic Actuator EHC-AA Innovative drive concept Electro-hydraulic actuators are used on process valves with strict requirements for dynamics, positioning forces and safety. On conventional actuators with a mechanical spring, the drive has to be designed and manufactured according to the particular requirements of each individual process valve. Subsequent adaptation of the drive to a different valve is not possible, leading eventually to a considerable number of models. The basis of the innovative drive concept is a hydraulic accumulator which replaces the mechanical spring. Its spring characteristics can be altered very simply by adjusting the operating pressure of the piston accumulator. This drive concept has the effect of reducing the variety of models to a few basic types. The use of the piston accumulator as a standard component also contributes to the cost reduction. Similarly, given the capability to adjust its characteristics, common parts can be used, thus supporting the modularisation of the valve actuators. It is possible to monitor the piston accumulator easily during operation. The drive concept on this basis complies with the requirements of Safety Integrity Level 2. Safety Integrity Level 3 is achieved when a shut-off valve operated by an on/off-actuator is configured in series with a control valve operated by a servo-actuator. This innovative actuator contains all the components necessary for operation and does not require a separate oil supply unit.
EHS Axial piston pump Electric motor
Pressure filter
Hydraulic accumulator
Pressure transmitter
Proportional valve with positioning module I I I p T s Pressure control device
Hydraulic cylinder
pressure Limit switch control device Position transmitter I p Temperature transmitter Pressure transmitter
Hydraulic accumulator
M Safety control EHS Cooler unit
Terminal box
Note: The information in this brochure relates to the operating conditions and applications described. For applications and operating conditions not described, please contact the relevant technical department.
E 2.163.0/07.13 Subject to technical modifications. 2 Functional description Cylinder Piston accumulator A key component of the compact drive is a hydraulic linear as hydropneumatic spring cylinder with piston rod and flange on the rod-side end (8). The piston side of the cylinder is linked to the pressurised oil side of the piston accumulator (13). The rod is extended using a hydropneumatic spring. Retraction is possible by filling the rod side with pressurised oil. The pressurised oil is supported by the gas volume To do this, the rod side must be actively closed using of the accumulator. The oil pressure corresponds a safety device (14). to the gas pressure. During operation, the oil is pre-charged by the pressure control device to a minimum pressure (7). In the case of the servo-actuator, the stroke of the piston rod is It corresponds to the minimum required positioning force adjusted continuously by a proportional valve. In the case of the actuator when the piston rod is extended. of the on / off-actuator, the rod side is supplied with pressurised oil by the control valve and the cylinder rod is retracted (100% When the piston rod retracts, the pressure rises stroke). on the piston side of the cylinder.
The cylinder stroke is measured using an integrated position The cylinder position is already measured for position sensor (10). The limits of the cylinder can be monitored control (10). Oil pressure and oil temperature are recorded by contactless limit switches (9) as an option. using integrated sensors (11, 12). These variables are evaluated for condition monitoring of the actuator.
Self-contained electro-hydraulic Preferred actuator EHC-AA models 50 63 80 100 125 140 160
Piston diameter D mm 50.00 63.00 80.00 100.00 125.00 140.00 160.00
Rod diameter D mm 25.00 28.00 36.00 45.00 50.00 56.00 63.00
Static force 210 bar Fn kN 41.23 65.46 105.56 164.93 257.71 323.27 422.23
Front view Rear view E 2.163.0/07.13 3 Oil supply unit Cooling systems To supply the pressurised oil, actuators have The cylinder and the hydraulic oil are cooled using an oil/ an axial piston pump with adjustable swash plate (1). air heat exchanger (15). This means that the external heat Its supply pressure is maintained at a constant value. transfer from the process into the oil system is reduced A hydraulic accumulator is connected to the pump (4). right from the point of entry. The volume stored there corresponds to at least one reserve stroke of the drive. Reliability Within a position control circuit, a proportional valve (6) is actuated and the piston rod is moved. Tried and tested components are used which If there is a sudden requirement for oil, the accumulator can be configured to be redundant as an option. buffers the flow of the pump. The hydropneumatic spring can also be designed When holding the position of the actuator, this concept to be redundant. minimises the energy consumption by cutting back The innovative drive concept with hydropneumatic the supply to almost zero. The oil is stored spring guarantees a high level of reliability in operation. in a tank which is optimised through the use of flow simulations. Below the tank is a drip tray with a monitoring Safety control for shut-off contact. The oil temperature and oil level in the tank are The safety control (14) acts independently. also monitored. It relieves the rod side of the cylinder when de-energized. When triggered, the piston rod extends and closes the process valve. As an option, the actuator can be equipped with a 2-out-of-3 logic.
Terminal box All sensors and solenoid valves are connected to a terminal Simulation strip in a terminal box (16). This also contains the electronic of the tank flow positioning module.
Model code
EHC-AA – XXX – D – G – E – X
Electro Hydraulic Control Actuator Autarchic
Piston diameter XXX = mm
Cylinder type D = Differential cylinder
Type of spring G = Gas spring
Direction of movement with spring assistance E = Extension R = Retraction
Measurement technology (redundant versions available) W = Position transmitter E = Limit switch P = Pressure transmitter T = Temperature transmitter E 2.163.0/07.13 4 Features Safety control High degree of modularity and adaptability The patented electro-hydraulic safety control EHS due to the hydropneumatic spring from HYDAC complies with the requirements of IEC 61508 and IEC 61511. Low number of actuator variants many common parts
Possibility to increase the availability due to redundancy
High level of flexibility since force level and, if necessary, any force characteristics can be adapted during operation
One actuator suitable for use on different process valves
Continuous monitoring of the availability of the closing force during the motion EHS 1oo1 EHS 2oo2
Energy saving pressure supply with pressure The safety integrity level SIL of the system controlled variable displacement or fixed displacement is determined by the risk assessment. As part of the pumps with accumulator charging circuit control chain, on the one hand the hydraulic control Safety function is performed reliably elements and their circuitry must satisfy the requirements. thanks to proven technology On the other hand, the highest possible reliability is expected, so the system must therefore have maximum Modular safety logic selectable availability and must also be easy to maintain. for example in a 1-out-of-2 or 2-out-of-3 voting The electro-hydraulic safety control using Partial stroke test can be carried out SIL-compliant control modules takes account of these factors and, with the choice of different logic SIL 2 for individual drive, SIL 3 for series circuit modules, enhances the reliability of the safety control.
Technical specifications Nominal pressure 210 bar ISO VG 32, ISO VG 46, mineral oil to DIN 51 524, HFD-U Operating fluids HFD-R fire-resistant ISO 6743-4 – others on request Temperature range of environment -5 °C to +60 °C Atmosphere Dusty industrial environment, potentially explosive according to ATEX Directive (optional) Relative air humidity up to 90 % Electrical specifications Control voltage 24 V DC Power supply 400 V, 3 phase, 50 Hz – other on request Nominal current of coil 1.45 A for 24 V DC (standard coil), 0.55 A for 24 V DC (ATEX) Protection class IP54 (standard) – others on request Nominal current for positioning module < 100 mA Target position 0 - 100% 4 – 20 mA Actual position 0 - 100% 4 – 20 mA Positioning Positioning accuracy < 1 % Repeatability < 0.1 % Hysteresis < 0.1 % Actuating times Control operation 3 s – 60 s Controlled Open / Close 1 s – 30 s Safety stroke Open / Close 0.04 s – 2.5 s E 2.163.0/07.13 5 Cooling Systems 5.700 Electronics 180.000 Accessories 61.000 Compact Hydraulics 53.000 Filter Systems 79.000 Process Technology 77.000 Filter Technology 70.000 Accumulator Technology 30.000 www.hydac.com Local Expertise. Global Presence. HYDAC SalesandServicePartners HYDAC Companies HYDAC HeadOffice HYDAC SYSTEMGMBH Head Office Internet: www.hydac.comInternet: E-mail: [email protected] Fax: Tel.: Germany 66280 Sulzbach/Saar Industriegebiet +49 6897509-577 +49 6897509-01
E 2.163.0/07.13