DE202011109158U1 - Electrohydraulic safety control - Google Patents

Abstract

Electrohydraulic safety control, which changes an end position for a hydraulic actuator (2), with a safety criterion that is redundantly monitored by at least three sensors G1, G2, G3, which is monitored in a 2 of 3 selection, which in the event of activation on a hydraulic actuator (1st ), characterized in that the sensors G1, G2, G3 act independently of one another via evaluation units S1, S2, S3 on solenoid valves V1, V2, V3, which are interconnected in a hydraulic 2 of 3 selection and open in the event of a power failure and a first Connect the line (16a, 16b) to a pressureless tank (5) in order to release a piston (21) for its actuation by a spring (19) via connecting lines (26) to the actuator (1) by lowering the pressure, so that the evaluation units S1, S2, S3 are interconnected to form an electronic 2-of-3 selection (81) which, in the event of activation, a solenoid valve V6 in a second St rang (17a, 17b) to open with current controls to also via the second branch (17a, 17b) ...

Description

The invention relates to an electro-hydraulic safety control, which changes an end position in a hydraulic actuator with a redundant monitored by at least three sensors G1, G2, G3 safety criterion, which is monitored in a 2von3 selection, which in case of activation on a hydraulic actuator acts.

Safety controllers should generally meet two criteria: they should retain their safety function under all operating conditions and should be fast in order to prevent major damage. Electrohydraulic safety controls are used on mass flow valves, such as quick-acting valves at the inlet of steam turbines, blow-off valves at the outlet of gas turbines, or blocking mass flows in process and process engineering. However, hydraulic actuators in a safety control can also be used for the beam deflection in a Pelton turbine.

If a steam turbine is coupled to a generator and is not ensured with the normal control organs that excessive overloading occur during load shedding of the generator, the speed of the steam turbine is monitored for reaching a limit speed, when it enters the safety control with the hydraulic actuator a quick-closing valve on Inlet of the steam turbine closes.

Hydraulic actuators with a valve, which influences large mass flows, are usually piloted internally via an additional control piston to achieve a short positioning time.

The DE 4330038 A1 disclosed ( 1 and 2 ) a known hydraulic 2von3 selection, which is interconnected in hydraulic blocks. Hydraulic solenoid valves in which a solenoid operates against a spring, inevitably bring with the solenoid greater displacement than with the spring. Therefore, if one energizes the valves for hydraulic 2-out-of-3 selection, one has somewhat greater security against "snagging," but no information at the time a wire break occurs. If a wire break has occurred while the system is running and another wire break occurs or one of the other two valves gets stuck, there is no shutdown. Thus, when the system is running, it is only necessary to test the three valves one after the other in a manner that is not too long in time, by triggering them with electricity for wire breakage and snagging. If a wire break or a defective spool is detected, this can be corrected and checked even while the system is running. When stuck in the closed state, a shutdown can be done by the other two valves. When stuck in the open state, for example in a functional test of the valve, an opening on another valve already leads to a shutdown. The replacement of a complete valve can only be done when the system is switched off.

The safety control according to the invention has the task of maintaining its safety function in case of failure of components. This is achieved with the features of the protection claim 1. The invention has the advantage that, with a minimum of valves during operation, wire breakage on a hydraulic 2-by-3 selection is instantly indicated, and with a single switch, components such as whole solenoid valves are interchangeable without having to dispense with 2-by-3 selection. Furthermore, the invention allows for true 2-by-3 triggering during operation for control of all hydraulic 2-by-3 shift states. The risk of error during maintenance work on the safety control during operation is drastically reduced. To control all 2 of 3 choices, only one switching device needs to be operated. All pressure losses that result from the control circuits are inevitably compensated by needle valves V4, V5, which must be closed during operation in each strand only for the replacement of components. So that after replacing components in an isolated first or second strand no pressure drops occur when restarting, the needle valves V4, V5 must each be previously opened again to completely fill the strand with liquid. Dependent claims 2 to 11 show further improvements of the present invention.

Interventions become even more secure if the possibilities for, for example, manual isolation of one of the two strands from an open position to an isolated position are possible only from an open position of both strands, since the applicable blocking positions are locked against one another. Forced mechanical locking on site provides additional security. This can be achieved by two mechanically mutually locked 2/2-way valves V4, V5 or by a 3-position valve V11, which releases both strands in a neutral center position, while locked in one of the two end positions a strand is and the other strand can not be closed. For security against switching from an open position for both strands by unauthorized persons, this position can be secured with a key switch.

In addition, the arrangement allows regular functional check of the valves in each of the two strands, after it has been isolated - apart from the needle valves V7, V8 -:
A regular function check of the valves V1, V2, V3 for the hydraulic 2von3 selection in the first line can be done by short-term power interruption to the valve and control of the associated end position and also be monitored from a control room. In an isolated first strand but also allows any hydraulic 2von3 selection while the system is running by interrupting the electrical current to simulate the valves and also recognize in a wait at the valve positions.

For bidirectionally position-monitored valves V1, V2, V3 ( 1a ) this is a simple solution. Lower costs arise when the valves V1, V2, V3 ( 1b ) are position-monitored and in the first strand additional pressure switches P1, P2, P3 are mounted, which provide information about the valve positions for the position not monitored end positions.

The costs are even lower when the solenoid valves V1, V2, V3 ( 1c ) are equipped without limit switches and additional restrictors R4, R5, R6 and additional pressure switches P5 are fitted to check the valve positions in a functional check.

Periodic functional check of valve V6 of the second-stream 2-D electronic trip can be checked by isolating the second train and momentarily "energizing" valve V6 and followed from a standby when pressure monitoring is connected in the second train. A pressure drop then indicates the open position of valve V6. After blocking the second line with the switching device V4, V5, V11, this functional check can also be carried out with a simple, predetermined sequence while maintaining the safety on site.

The most common failure in such a safety control is the "snagging" of valves when they remain in the same position over long periods of operation of the equipment. A regular function check during these operating periods largely prevents a slow settling and is therefore also a prerequisite for the function of a strand, if the other strand is to be isolated, for example, for the replacement of a defective valve during operation of the system.

In general, however, can also be an actuator to be switched "stuck" when a piston or a piston rod jammed. In an example, internally pilot-controlled actuator can be with an additional needle throttle and a solenoid valve, the pressure in the cylinder lower enough that the spring generates a partial stroke, which is controlled by limit switches, a distance measurement or even by eye. The triggering of a partial lift can be triggered on site or from a control room. A reduction of the planned partial lift can be regarded here as an impending disturbance and be scheduled for a check at the next possible shutdown of the system.

The present electro-hydraulic safety controller can also be combined with additional safety criteria. For the 2-by-3 disconnection, contacts of the additional disconnection criteria are connected in parallel to the contacts of the speed monitoring, for the disconnection of the individual valve V6 in parallel.

It will be understood that the present invention is applicable to high pressure and low pressure hydraulics.

The invention is described below on the basis of exemplary embodiments. Show it:

1a schematically a block diagram of an electro-hydraulic safety control according to the invention for a hydraulic actuator with the possibility for a functional check of both strands during operation and the possibility for replacing the stroke introducing electromagnetic valves V1, V2, V3 and V6 during operation of the system;

1b schematically a block diagram analogous to FIG 1a in which the switching device is realized by a three-position valve V11 and the solenoid valves V1, V2, V3 are endlagenüberwacht only one side, but in addition pressure monitor P1, P2, P3 are installed to control the not position monitored end positions;

1c schematically a hydraulic block as in 1b with a three-position valve V11, wherein the end positions of the solenoid valves V1, V2, V3 are monitored indirectly by additional pressure monitor P5 and other relief reactors R4, R5, R6; and

2 : schematically, as at the safety control according to the invention in 1a . 1b or 1c Control circuits are possible.

In the figures, the same reference numerals are used for the same elements.

In 1a is the control of a quick-closing valve 2 via a hydraulic actuator 1 shown. actuators 1 are often internally piloted to achieve a short positioning time. In the present example 1a is such an actuator 1 with internal pilot control shown only schematically, since the internal pilot control is included with the valve manufacturer.

Control oil is supplied by a pump 39 a hydraulic block 7a at an infeed 15 supplied at system pressure and via drain lines 23 . 24 in a tank 5 recycled. The same system pressure acts via a throttle R2 on a piston 21 at the hydraulic actuator 1 to a spring 19 to keep biased in a lower end position. An opening 28 on the piston 21 is from a differential piston 20 which is the piston 21 can follow, closed. On top of the differential piston 20 acts via a connection line 26 one in the hydraulic block 7a at a junction 22 worn pressure. Aperture R1 is dimensioned such that, on the one hand, the pressure during operation is equal to the system pressure, but immediately drops when the control is activated, without influencing the pressure in the system. As soon as this pressure falls to a quick release release pressure and lower, the differential piston separates 20 from the piston 21 and gives the opening 28 free. The feather 19 can now suddenly the oil in the cylinder 18 over the opening 28 squeeze out without too much oil flows through the throttle R2. That in the room of the spring 19 Squeezed oil flows through a drain line 25 in the tank 5 back. The one from the spring 19 Triggered stroke acts on the quick-acting valve via a piston rod 2 at the inlet 27 to a steam turbine 3 which, for example, about their wave 4a drives a generator (not shown). Quick closure is necessary, for example, when a load shedding on the generator is not sufficiently regulated and overspeed, which can lead to the destruction of components, must be prevented by means of speed monitoring.

From a pulser wheel 4b on the shaft of the steam turbine, the speed is detected by means of 3 sensors G1, G2, G3 and in a control part 6 of evaluation S1, S2, S3 monitored for exceeding a limit speed. The limit contacts generated by the evaluation units S1, S2, S3 are available both as closing contacts and as opening contacts.

A hydraulic 4/2-way solenoid valve V1, V2, V3 is actuated via the contacts of the evaluation units S1, S2, S3, with the end positions of the valves with limit switches 9 . 10 are monitored and the valves are permanently energized to open at overspeed or wire breakage.

The valves V1, V2, V3 are in a hydraulic block 7a housed and delivered to a 2-by-3 selection hydraulically in a first strand 16b connected in the event of a 2von3 release by means of pressure reduction in the first strand 16a and in the connection line 26 the actuator 1 adjusted by spring. A reduction in pressure is therefore possible because before the diversion 22 in the first strand 16a and a second strand 17a a throttle R1 is attached, on the one hand with certainty so much fluid through that all leaks in both strands are covered, but on the other hand, with its resistance ensures that the pressure in the first strand 16a . 16b really drops when two of the solenoid valves V1, V2, V3 are open, or the pressure in the second strand 17a . 17b really drops when solenoid valve V6 is open.

Of the contacts of the evaluations S1, S2, S3 electronically finds a 2von3 evaluation 8th instead, which drives a 2/2-way solenoid valve V6 with current at overspeed and opens, the latter in the second strand 17b is arranged, which also branches off behind the throttle R1, to analog by means of pressure reduction, the actuator 1 adjusted by spring. In this way, both an electric and a hydraulic 2von3 selection are present, which independently of each other on the actuator 1 act. The safety aspects for a 2von3 electronic selection are in the Standard DIN EN 6261 . VDE 0113-50 listed.

In the first strand 16a . 16b and in the second strand 17a . 17b Block valves V4, V5 are installed in the form of mutually lockable, manually operated ball valves. A mechanical lock 11 . 12 however, only allows one of the two ball valves to be closed from a common open position can be. In the present case, the lock is made by interpenetrating circular discs 11 . 12 achieved, each having a recess 37 having the size of the interpenetration. The end positions of the ball valves V4, V5 are with switches 13 . 14 displayed for remote monitoring. For the maintenance of the system shown, there are several advantages. First, during operation, a defect such as broken wire or defective coil on individual solenoid valves V1, V2, V3 can be detected and displayed immediately if the end position does not match the desired state. Furthermore, a completely simulated function control of all 2von3 selection options for the solenoid valves can be carried out at any time during operation, which on the one hand includes the detection of "sticking" of a valve and on the other hand prevented by regularly simulated actuation deposits in the sealing gaps.

During operation, the needle valves V7, V8 can remain open because they allow only small quantities and the pressure at the branch 22 only marginally influence.

When the valve V7 is open can in the first strand 16b provided that it passes through valve V4 ( 1a ) or V11 ( 1b and 1c ), while the system is running, any hydraulic 2-by-3 selection under system pressure can be simulated and visualized.

When the valve V8 is open can in the second strand 17b provided that this is controlled by valve V5 ( 1a ) or V11 ( 1b and 1c ) is simulated while the system is running, a function check of the valve V6 at system pressure simulated and visualized by a pressure monitor P4 by the valve V6 is energized. The needle valves V7, V8 must be closed if components such as valves or pressure switches are replaced while the system is running on the corresponding line. A functional check of the first strand 16a . 16b according to 1a can be made in individual steps, with only one of the valves V1, V2, V3 is always switched. debit position end position selection V1 V2 V3 V1 V2 V3 Closed. Closed. Closed. to to to 0 out of 3 open Closed. Closed. on to to 1 of 3 open open Closed. on on to 2 of 3 Closed. open Closed. to on to 1 of 3 Closed. open open to on on 2 of 3 Closed. Closed. open to to on 1 of 3 open Closed. open on to on 2 of 3 open open open on on on 3 of 3

In the example of 1b is only the hydraulic block 7b opposite the hydraulic block 7a in 1a amended. In the hydraulic block 7b the throttle R1 is also designed so that even the outflow of only 2 of the valves V1, V2, V3 and by the 3-position valve V11 sufficient pressure reduction in the first strand 16a and in the connection line 26 causes. The same applies to a sufficient pressure reduction in the second strand 17a . 17b for the flow rate of valves V6 and V11 in the open state. The 3-position valve V11 replaces the two mechanically interlocked ball valves V4 and V5 in 1a , The valve V11 is constructed so that in a neutral center position access to both strands 16b . 17b is open, while one strand remains open in one end position and the other strand is locked. The end positions for blocking are with limit switches 13 . 14 supervised. In addition, pressure switches P1 are installed in front of the solenoid valve V1 and pressure switches P2, P3 on the two outlet lines of solenoid valve V1.

A functional check of the first strand 16a . 16b according to 1b This can be done in single steps, whereby the "closed positions", which are not monitored with limit switches, are visible and can be evaluated by the combination of the values displayed on the pressure switches. Debit position / end position (Endl.) pressure indicator selection V1 / Endl. V2 / Endl. V3 / Endl. P1 P2 P3 active active active high* undetermined undetermined 0 out of 3 inactive / to * active active high high* high* 1 of 3 inactive / to * inactive / to * active deep deep deep 2 of 3 active inactive / to * active high* deep* undetermined 1 of 3 active inactive / to * inactive / to * deep deep deep 2 of 3 active active inactive / to * high* undetermined high* 1 of 3 inactive / to * active inactive / to * deep deep deep 2 of 3 inactive / to * inactive / to * inactive / to * deep deep deep 3 of 3

• • Gestartet wird aus einer Null-Lage, in der die Magnetventile geschlossen sind.
• • Wenn im ersten Schritt P2 und P3 „hoch” anzeigen, dann müssen die nicht mit Endschaltern überwachten Positionen der Magnetventile V2 und V3 die Funktion „geschlossen” erfüllen.
• • Wenn im dritten Schritt P1 „hoch” und P2 „tief” anzeigen, dann müssen die nicht mit Endschaltern überwachten Positionen der Magnetventile V1 und V3 die Funktion „geschlossen” erfüllen.
• • Wenn im fünften Schritt P1 „hoch” und P3 „tief” anzeigen, dann müssen die nicht mit Endschaltern überwachten Positionen der Magnetventile V1 und V2 die Funktion „geschlossen” erfüllen.

For an arrangement with one-sided monitored end positions of the solenoid valves V1, V2, V3 according to 1b the switching sequence is selected such that only one valve is switched per step in order to limit malfunctions more precisely, since only the pressure monitors P1, P2, P3 allow a statement about the unmonitored positions of the other two valves. For each subsequent step, the pressure values and end position displays marked with an asterisk (*) must be taken into consideration for an evaluation:

• • Starting is from a zero position, in which the solenoid valves are closed.
• • If P2 and P3 indicate "high" in the first step, the positions of solenoid valves V2 and V3, which are not monitored by limit switches, must fulfill the "closed" function.
• • If in step P1 "high" and P2 indicate "low" then the positions of solenoid valves V1 and V3, which are not monitored by limit switches, must fulfill the function "closed".
• • If, in the fifth step P1, "high" and P3 indicate "low", then the positions of the solenoid valves V1 and V2, which are not monitored by limit switches, must fulfill the "closed" function.

That is, also a cheaper version for the solenoid valves according to 1b Fulfills the condition of full function control by installing three additional pressure monitors P1, P2, P3 and dividing the simulation into individual steps as shown. The function of the 2-by-3 selection is still using limit switches 9 demonstrated.

The valve V11 is manually operated in a first embodiment 30 on site and with a key switch 33 secured in the neutral middle position so that only authorized personnel can block a strand 16a . 17a by making a change by hand on valve V11. The valve V11 is constructed so that when switching to block a strand of the other strand is inevitably open. A magnetic operation 31 for functional checks is conceivable. However, this depends on the concept and safety of the overall control.

But it is also possible to monitor the valve functions of the solenoid valves V1, V2, V3 in the first strand 16b without limit switch. In 1c are the solenoid valves V1, V2, V3 executed without end position monitoring. The end positions are monitored indirectly in a switching sequence. For that are opposite 1b additional restrictors R4, R5, R6 with small flow rate and a pressure switch P5 attached. The throttle point R5 bridges an input of the solenoid valve V2 to the drain line 23 and the throttle point R6 bridges an input of the solenoid valve V3 to the drain line 23 , In addition, the output of the valve V1, which is connected to an input of the valve V3, connected to a throttle point R6 to the input of the valve V1. When solenoid valves V1 and V2 are closed, the pressure at P2 drops to zero. When valves V2 and V3 are closed, the pressure at P6 drops to zero. The pressure reading at P3 will always be "high" as long as valves V1 and V3 are closed. debit position pressure indicator selection V1 V2 V3 P1 P2 P3 P5 Closed. Closed. Closed. high deep high deep 0 out of 3 open Closed. Closed. high high high deep 1 of 3 open open Closed. deep deep high high 2 of 3 Closed. open Closed. high deep high high 1 of 3 Closed. open open deep deep deep deep 2 of 3 Closed. Closed. open high deep deep deep 1 of 3 open Closed. open deep deep deep deep 2 of 3 open open open deep deep deep deep 3 of 3

It is understood that, for example, the throttle point R4 has such a small throughput that the pressure P1 does not noticeably drop when, in a 1 of 3 selection, the solenoid valve V3 is open and the solenoid valves V1 and V2 are closed. This is achieved, for example, if the throttle points R4, R5, R6 consist of diaphragms with a diameter of 0.5 mm and the throttle R1 as a diaphragm has a diameter of 6 to 7 mm. This also results in a sequence of test steps in which only one valve is always switched, while the target position to be reached on the combination of the pressure displays P1, P2, P3, P5 can be controlled.

In the 1a . 1b . 1c the pressure monitors P1, P2, P3, P4, P5 are shown as pressure transducers, which pass on a pressure signal as an analog current signal, for example in the range between 4 and 20 mA and enable an evaluation in a local control or a control room. Likewise, of course, the limit switches 9 . 10 . 13 . 14 connected to a controller (not shown here) for evaluation.

A functional check of the second strand 17a . 17b is for the examples of figures 1a . 1b and 1c equally feasible.

In a first step, the strand becomes 17b isolated with the valve V5 or with the valve V11, the valve position with the limit switch 14 is verifiable. The needle valve V8 remains open so that there is no pressure drop due to leakage. In a second step, the solenoid valve V6 is energized (key T4 in FIG 2 ) and opened, with the control for the opening of the pressure in the pressure monitor P4 must drop. In a third step, the valve V6 is closed again by removing the test current, wherein the control pressure of the pressure monitor P4 must again correspond to the system pressure. If a defect is detected at the valve V6 which requires a replacement, the needle valve V8 is closed, the replacement is made and the needle valve V8 is opened, so that the strand is refilled.

In 2 is shown as the controller 6 through a functional check 6a can be supplemented. The valves V1, V2, V3, V6 can be operated via a +24 volt power supply. With the speed monitoring 6 the NC contacts K1, K2, K3 for the first strand and the closing contact K4 for the second strand are activated. In the middle position of the switching device V11, the keys T1, T2, T3, T4 are ineffective. The keys T1, T2, T3 could also cause a power failure via normally closed contacts L1, L2, L3 for the solenoid valves V1, V2, V3 and would trigger a true shutdown. They may therefore only be effective as long as the first strand 16b via the switching device V4 or V11 in its end position 13 is locked and locked. Similarly, the key T4 with closing contact L4 through the switching device V5 or V11 in its function for the second strand 17b and the solenoid valve V6 only effective as long as the second strand 17b , in the final position 14 valve V5 or V11 is locked and locked.

The sequence of functional checks can be done manually with the keys T1, T2, T3 for the first strand 16b and with the T4 key for the second strand 17b respectively. It is essential that the monitored end positions of the valves V1, V2, V3 and the pressure displays P1, P2, P3 and P4 and the blocking positions 13 and 14 be controlled at the same time. In other words, with a little extra effort in the control, the subsequent steps of a function check can also be logged in a control room and / or automated in the respective blocking position.

On an actuator 1 according to 1a and 1b is quite generally, so even without a 2von3 selection, a safety improvement possible, which allows a functional check by means of partial stroke. The cylinder has this 18 a departure line 29 on a hydraulic block 32 with an adjustable needle throttle R3 and with a downstream shut-off valve V9 leads. The needle throttle R3 is set, for example during commissioning, so that the pressure on the piston 21 drops by about 5% to 10% under closing pressure and the spring 19 shifts the piston by a corresponding amount. This allows a sporadic function control of actuator 1 during operation. If the actuator 1 has an analog position control, can be changes such as increased friction in the sealing gap of the piston 21 due to precipitated oil products or a clamping piston rod during operation due to the lack of displacement of the piston 21 determine. Such a test is made possible, for example, with a quick-closing valve 2 in that this is part of a safety chain and that the actual determination of the flow rate passes through a control, which compensates for the change in the flow rate, by a partial lift of the quick-closing valve 1 would arise. Another possibility is the partial stroke on the actuator 2 to restrict to an ineffective for the closure flow line.

LIST OF REFERENCE NUMBERS

1

hydraulic actuator

2

actuator

3

steam turbine

4a

wave

4b

impulse generator

5

tank

6

control part

6a

function control

7a, 7b

hydraulic block

8th

Electronic 2 of 3 selection

9

End position

10

End position

11

mechanical locking

12

mechanical locking

13

End position

14

End position

15

feed

16a, 16b

first strand

17a, 17b

second strand

18

cylinder

19

feather

20

differential piston

21

piston

22

diversion

23

drain line

24

drain line

26

connecting line

27

inlet

28

opening

29

drain line

30

manual operation

31

solenoid Operated

32

Part lifting device

33

key switch

36

Flow direction

37

recess

39

pump

41

ventilation valves

G1; G2; G3

sensors

K1; K2; K3

NC contacts

K4

Closing contact

L1; L2; L3

NC contacts

L4

make contact

P1; ...; P5

pressure monitoring

R1; ...; R6

throttle

S1; S2; S3

Processors

T1; ...; T4

Keys

V1

4/2-way solenoid valve

V2

4/2-way solenoid valve

V3

4/2-way solenoid valve

V4

Shut-off valve, ball valve to switching device

V5

Shut-off valve, ball valve to switching device

V6

2/2-way solenoid valve

V7

needle valve

V8

needle valve

V9

2/2-way solenoid valve

V11

3-position valve to switching device

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4330038 A1 [0005]

Cited non-patent literature

• Standard DIN EN 6261 [0027]
• VDE 0113-50 [0027]

Claims (11)

Electrohydraulic safety control, which in the case of a hydraulic actuator ( 2 ) changes an end position, with a redundantly monitored by at least three sensors G1, G2, G3 safety criterion, which is monitored in a 2von3 selection, which in case of activation to a hydraulic actuator ( 1 ), characterized in that the sensors G1, G2, G3 act independently of one another via evaluation units S1, S2, S3 on solenoid valves V1, V2, V3, which are interconnected in a hydraulic 2von3 selection and open when power drops and a first Strand ( 16a . 16b ) to a pressureless tank ( 5 ) to connect via connecting cables ( 26 ) to the actuator ( 1 ) by lowering the pressure of a piston ( 21 ) for its operation by a spring ( 19 ), that in the further evaluation units S1, S2, S3 to an electronic 2von3 selection ( 81 ), which in the case of activation, a solenoid valve V6 in a second strand ( 17a . 17b ) is energized to open so as to also pass through the second strand ( 17a . 17b ) to the pressureless tank ( 5 ) and via a resulting pressure drop in the connecting lines ( 26 ) the actuator ( 1 ), and that during operation, optionally, the first strand ( 16b ) or the second strand ( 17b ) in each case by a switching device V4, V5, V11 of the connecting line ( 26 ) is separable in order to allow functional checks and / or a complete replacement of valves in the corded off, the blocking to the first strand ( 16b ) through a needle valve V7 and the blocking to the second strand ( 17b ) can be bridged by a needle valve V8, and wherein the needle valves before a first throttle R1 branch off at system pressure from the control oil system and remain open during functional checks and shutdowns, however, for repairs to the respective strand ( 16b . 17b ) are closed in order to fill this back to system pressure after a repair, before the associated switch to blocking is canceled. Electrohydraulic safety controller according to claim 1, characterized in that the two strands ( 16b . 17b ) are locked against each other so that the valves V4, V5 and V11 shut off from an open position for both strands only one strand and at the same time block the other strand in the open position. Electrohydraulic safety controller according to claim 2, characterized in that the locking of the two strands ( 16b . 17b ) Forcibly mechanically through the valves V4, V5 and V11. Electrohydraulic safety controller according to one of claims 1 to 3, characterized in that solenoid valves V1, V2, V3 are position monitored on both sides or have a position feedback to detect a "snagging" in intermediate positions. Electrohydraulic safety controller according to one of claims 1 to 3, characterized in that the solenoid valves V1, V2, V3 are position-monitored and that in the first strand ( 16b ) Pressure monitor P1, P2, P3 are mounted, which allow a statement about the not position monitored end positions of the solenoid valves V1, V2, V3. Electrohydraulic safety controller according to one of claims 1 to 3, characterized in that the solenoid valves V1, V2, V3 have no limit switches, but that the valve positions indirectly through the installation of relief chokes R4, R5, R6 and by pressure monitors P1, P2, P3, P5 are shown. Electrohydraulic safety controller according to claim 4 to 6, characterized in that the solenoid valves V1, V2, V3 are controlled for function control in a sequence to obtain from the pressure readings confirmation of the function of the other two valves. Electrohydraulic safety controller according to one of claims 1 to 7, characterized in that the function control of the solenoid valves V1, V2, V3 is carried out with respect to a 2von3 triggering in a switching sequence in which only one valve is connected to each subsequent step to check its effect , Electrohydraulic safety controller according to one of claims 1 to 8, characterized in that on the second strand ( 17b ), a pressure monitor (P4), for example, connected via a pressure transmitter to allow in the locked state, a function control of the 2/2-way valve V6 and, for example, "sticking" or wire break detect. Electrohydraulic safety controller according to claim 6, characterized in that the blocking position of the first strand ( 16b ) only by hand ( 30 ), for example with a key switch ( 32 ) can be achieved simultaneously triggering a function test, for example, at the push of a button T4 automated function in the second strand ( 17b ) is prevented at the valve V6. Electrohydraulic safety controller according to one of claims 1 to 10, characterized in that the cylinder ( 18 ) of a hydraulic actuator ( 1 ) with piston ( 21 ) and return spring ( 19 ) is fed on its pressure side via a throttle R2 with liquid and behind the throttle R2 with a drain line 29 in which an adjustable needle throttle R3 and a check valve V9 are arranged, which with the opening of the check valve V9 from a standby position during operation by a predetermined pressure reduction on the piston 21 to check the function of a partial stroke of the spring 19 allow, without the actual function is achieved by a total lift.

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