NL2002025C

NL2002025C - Hydraulic system, and a method to thermally condition a valve.

Info

Publication number: NL2002025C
Application number: NL2002025A
Authority: NL
Inventors: Johannes Adrianus Maria Overgaag
Original assignee: Thomassen Turbine Systems B V
Priority date: 2008-09-26
Filing date: 2008-09-26
Publication date: 2010-03-29
Also published as: US20110240152A1; EP2329152A1; WO2010034804A1

Description

P85647NL00

Title: Hydraulic system, and a method to thermally condition a valve

The present invention relates to a hydraulic system comprising: -at least one hydraulic apparatus, controllable by hydraulic fluid; -at least one valve, arranged to control the apparatus utilizing the hydraulic fluid, the valve having a housing, being provided with at least one 5 first fluid port and at least one second fluid port; and -a valve controller, configured to adjust the valve.

Such a system is known from the prior art. For example the hydraulic apparatus can be a turbine, for example a gas turbine, or an actuator, for example a cylinder/piston-type actuator, or a different 10 hydraulic apparatus. The valve can be, for example, a servo valve.

Typically, the valve can have four ports: two first ports named oil supply (P) and oil drain (T), and two second ports (A, B) for connection to respective sides of the hydraulic apparatus. After assembly, the first two ports (P, T) are in fluid communication with a respective oil supply (for 15 example a hydraulic fluid reservoir, a hydraulic pump), and a respective hydraulic fluid discharge line, or drain. Also, after assembly, the latter two ports (A, B) are usually in fluid communication with the hydraulic apparatus, to be controlled.

A problem of known systems is a relatively low reliability of valve 20 operation, leading to relatively high maintenance costs. Contaminants, for example sludge and varnish, can affect sensitive and critical valve components of the system. This will lead to oil flow problems and seizure of the (servo) valve, causing trips or fail to start, leading to decreasing unit availability, hence increased operational and maintenance costs.

25 For example, a gas turbine unit which is affected by sludge and varnish may show increasing costs due to trips or other operational disturbances. The problem is considerable for power plants, for example 2 large power producers operating several Frame 7FA generator units in peaking mode. In such a case, units lube oil may become contaminated with sludge and varnish, leading to malfunction of servo valves that hydraulically control generator operation. Oil cleaning methods have been 5 tried to solve the problem, however, so far, they were not always effective.

The present invention aims to solve the above-mentioned problems. Particularly, the invention aims to improve the hydraulic system, and to reduce chances of system malfunction.

According to an embodiment, this can be achieved by the features 10 of claim 1.

The system is characterized by a fluid bypass-device which is configured to allow a fluid bypass-connection between at least one first port and a second port.

It has been found that contaminants can precipitate under specific 15 operating conditions whereby their molecules will agglomerate into a gooey type polar substance that will stick to other materials (metal surfaces), and that those conditions can be avoided by application of the fluid bypass-connection. In this way, hydraulic fluid flow problems and seizure of the (servo) valve can be prevented, leading to considerably improved system 20 availability, and relatively low operational and maintenance costs, compared to the prior art systems.

Particularly, application of the fluid bypass-device can lead to a thermal conditioning of critical valve components, such, that those components can be maintained in or near a temperature to avoid 25 contaminant precipitation and/or deposition. Very good results have already been obtained by application of the present invention.

For example, the invention can solve the problem of malfunctioning hydraulic control systems caused by sticking servo valves and solenoid valves, affected by sludge and varnish contaminants within the hydraulic 30 fluid (for example oil).

3

The valve can be servo valve, for example applied on turbo machinery, for example gas turbines. Depending on the specific type of gas turbine, the number and type of applied servo valves may vary. Most turbine units have servo valves installed on hydraulic actuated gas fuel 5 valves, liquid fuel valves and variable inlet guide vane actuators.

Also, an aspect of the invention provides a method to thermally condition a valve, the valve being arranged to feed hydraulic fluid to a hydraulic apparatus, the valve having a housing, the housing being provided with first fluid ports and second fluid ports, wherein a valve 10 controller adjust the valve depending on one or more signals relating to a working condition of the hydraulic apparatus, characterized by allowing a fluid bypass-connection between at least one first port and a second port, to thermally condition the valve using a hydraulic bypass fluid flow.

An aspect of the invention provides a method to thermally 15 condition a servo valve, for example the an afore-mentioned method, the servo valve being arranged to feed hydraulic fluid to a hydraulic apparatus, the valve having a housing, the housing being provided with first fluid ports and second fluid ports, wherein the valve housing comprises a valve mechanism that is adjustable between a neutral state to block fluid 20 connections between the first ports and second ports, and at least one fluid transmission state to allow fluid connections between the first ports and second ports, wherein a valve controller adjust the valve mechanism depending on one or more signals relating to a working condition of the hydraulic apparatus, characterized by supplying heat to the valve when the 25 valve is in the neutral state.

Further advantageous embodiments are described in the dependent claims. Non-limiting examples of the invention will be described in the following, with reference to the drawings.

Figure 1 schematically shows a non-limiting embodiment of the 30 invention; 4

Figure 2 shows the embodiment of Fig. 1, during a thermally conditioning state; and

Figures 3A, 3B, 3C show a bottom view, top view and side view of an example of a bypass-device.

5 Similar or corresponding features are denoted by similar or corresponding reference signs in the present patent application.

Figure 1 schematically shows an example of a hydraulic system. The system comprises a hydraulic apparatus H, controllable by hydraulic fluid (i.e. a hydraulic working medium). The apparatus H can be configured 10 in many different ways, and can for example include a hydraulic actuator, a piston/cylinder type device, it can be part of a generator system, a turbine system, and/or a different apparatus. Particularly, the apparatus H can be pressure controlled, wherein an operating state of the apparatus H can be set or changed by (for example, temporally) adjusting pressure of hydraulic 15 fluid that is fed to respective control ports AH, BH of the apparatus H.

The system also comprises a valve 10, to hydraulically control the apparatus H. The valve 10 is arranged to feed hydraulic fluid to the hydraulic apparatus H, and to receive hydraulic fluid from the apparatus H, via respective fluid lines L, for hydraulically controlling the apparatus H.

20 The present valve 10 comprises a housing 11, the housing 11 being provided with first fluid ports, including a supply port P and return (drain) port T, and second fluid ports A, B, The present embodiment only has two first ports P, T and two second ports A, B. Alternatively, the valve 10 can include a different number of first and/or second ports.

25 The system can include a valve controller C, configured to adjust a valve mechanism 13 of the valve 10, for example based on one or more signals relating to an operating condition of the hydraulic apparatus H. The controller C can be configured in different ways, for example including suitable hardware and/or software, a microcontroller, computer, or in a 30 different manner. For example, the valve 10 can include one or more 5 controllable valve adjusters Q, for example an actuator or a servo, that can adjust the operating state of the valve 10, the adjuster Q being (for example electronically) controllable by the controller C. In the present embodiment, the controller C and adjuster Q are depicted as being separate components 5 (the controller C being located external of the valve housing 11, and the adjuster being included in the housing 11); alternatively, controller and adjuster can be integrated with each other.

Also, for example, the valve controller C can be configured to adjust the valve 10 (i.e, to adjust the valve mechanism 13), to set the apparatus H 10 to a predetermined, for example desired, operating state. To that aim, for example, valve controller C can be configured to control the valve 10, depending on one or more apparatus related signal, relating to a working condition of the hydraulic apparatus H. The apparatus related signal can include various types of signals, for example a control signal, sensor signal, 15 a linear position transducer signal, a feedback signal, a signal relating to a detected functioning of the hydraulic apparatus H, and/or a different type of signal. For example, the hydraulic apparatus can include or be associated with a monitoring device MH that can monitor a condition of, or relating to, the functioning hydraulic apparatus H. During operation, the monitoring 20 device can provide the controller C with the apparatus related signal. As an example only, the signal can relate to a piston position in case the apparatus H is a piston/cylinder type device, or a parameter that relates to the piston position. Similarly, it can relate to a turbine power output parameter in case the apparatus H is part of a turbine generator system. In the present 25 embodiment, the controller C and monitoring device MH are depicted as being separate components; alternatively, controller C and device MH can be integrated with each other.

For example, in the present embodiment, the valve housing 11 comprises a valve mechanism 13 that can be set to a neutral state to block 30 fluid connections between the first ports P, T and second ports A, B. Such a 6 neutral state is shown in Fig. 1. The present valve mechanism 13 can be adjusted, from the neutral state, to at least one fluid transmission state to allow fluid connections between the first ports P, T and second ports A. B. Figure 2 shows one fluid transmission state, wherein the supply port P is in 5 fluid connection with port B, and wherein return (drain) port T is in fluid connection with port A. In an alternative fluid transmission state (not shown), supply port P can be in fluid connection with supply port A, and return port T in fluid connection with port B.

Particularly, as follows from the drawings, the second fluid ports A, 10 B of the valve are (indirectly) in fluid connection with respective ports AH, BH of the hydraulic apparatus H. Also, the valve’s first fluid ports P, T are in fluid connection with a fluid supply S and a fluid drain D, via respective hydraulic fluid connections.

The hydraulic fluid supply S can be configured in various ways, 15 and may for example include one or more fluid transport lines (i.e., fluid ducts, conduits), one or more fluid pumps, one or more fluid reservoirs, one or more fluid treatment devices, a filter system for filtering the hydraulic fluid, a fluid heating system to heat the fluid to a desired fluid temperature. The same holds for the fluid drain D. Besides, the supply system S and 20 drain system D can be integrated in a fluid circulation system.

Advantageously, the hydraulic system is provided with a fluid bypass-device (bypass-unit) 20 which is configured to allow fluid bypass-connection between at least one first port P, T and a second port A, B, particularly during operation of the valve 10 (that is, when the valve 10 is 25 being controlled by controller C to control the apparatus H, or in other words: when the valve controlled apparatus H is performing a desired apparatus function). In this way, the valve 10 can be (thermally) conditioned in a relatively simple, economical and efficient manner, to prevent or diminish sludge and varnish formation in (and near) the valve 10.

7

In the present embodiment, the fluid bypass-device 20 is arranged to provide a fluid bypass-connection in at least one of the fluid connections between the valve 10 on one hand, and the hydraulic apparatus H, source S and drain D on the other hand. Particularly, the present bypass-device 20 5 can provide a first fluid bypass-connection, between one of the second ports A and the return port T that is connected to the return line dl. Also, the device 20 can provide a second bypass-connection 33b, between the other of the second ports B and the return port T (via the return line dl).

The bypass-device 20 can be configured in different ways.

10 Preferably, the fluid bypass-device 20 has a housing 21 that is separate from the valve housing 11. The fluid bypass-device 20 is preferably configured to be detachably connected to the valve housing 11 (for example between the valve housing 11 and an optional fluid line connector plug 45 -depicted by a dashed lines 45- that may have end ports of the four fluid lines 15 si, d2, L leading to the source S, drain D and apparatus H).

A connection between the device 20 and a valve housing (and optional plug 45) can be achieved in various ways, for example using one or more attachment devices, clamping devices, and/or suitable interconnection means. The present embodiment is provided with a number of bolts 41, for 20 bolting the device housing 21 to the valve housing 11. To this aim, the valve housing can be provided with bolt receivers 42 (configured to cooperate with bolt ends), and device housing 21 can include bores 46 to lead the bolts 41 via the device housing 21 to the valve 10. In the depicted operating position (see Fig. 1-2), the device 20 is connected to the valve housing 11, and can 25 provide a fluid connection between drain port T and at least one of the second port A, B. In yet a further embodiment, the bolts 41 can be used to connect the optional fluid line connector plug to the bypass-device 20, as well, using respective bores of the plug.

Figures 3A-3C show a non-limiting example of the bypass-device 30 20. Optionally, the housing 21 of the fluid bypass-device 20 and the valve 8 housing 11 can be configured to exchange heat with each other, particularly for thermally conditioning the valve housing 11. Also, optionally, the fluid bypass-device 20 can be configured to be thermally conditioned by a respective bypass-fluid flowing through the fluid bypass-device 20. The 5 bypass-device’s housing 21 can be made of a material having a high thermal conductivity, for example a metal or an alloy. Also, the fluid bypass-device 20 can comprises a temperature conditioning surface 71 that is substantially in thermal contact with an opposite surface 72 of the valve housing 11 when the device 20 is connected to the valve housing 11, to exchange heat with the 10 valve housing (particularly via heat conduction).

As follows from Figures 1-2, the present bypass device 20 comprises two first fluid channels 31p, 31t, (particularly bores), including a source channel 31p and return channel 3 It, that are connected with respective first fluid ports P, T of the valve 10 after assembly. The device 20 also includes 15 two second fluid channels 32a, 32b (particularly bores), connected to respective second fluid ports A, B of the valve 10. In the embodiment, the first and second channels 31, 32 of the bypass device 20 all extend in parallel, particularly extending normally with respect to two outer surfaces 71, 72 of the housing (see Fig. 3).

20 The present bypass-device 20 comprises four first ports pi, tl, al, bl (located in the first housing surface 71) facing the valve housing 11 after mounting, and second ports p2, t2, a2, b2 (locates in the second housing surface 72) facing away from the valve housing 11.

Particularly, first ends of the fluid channels 31, 32 of the bypass-25 device 20 provide a first source port pi, a first return port tl, and two first apparatus ports al, bl, which are connected to respective opposite ports P, T, A, B of the valve, after mounting. Preferably (see Fig. 3C), the hydraulic system (for example the bypass-device 20) is provided with sealing means, for example resilient seals, for example O-rings 29, the provide sealed 9 hydraulic connections between the first ports pi, tl, al, bl of the bypass-unit 20 and the respective valve ports P, T, A, B.

In the embodiment, the first ports pi, tl, al, bl of the bypass-unit 20 are arranged to be in precise alignment with the respective valve ports P, 5 T, A, B, when the device’s housing 21 is mounted onto the valve housing 11. As follows from Fig. 3C, for example, the first ports pi, tl, al, bl can be located at the corners of a substantially square pattern (the apparatus ports al, bl being located diametrically with respect to each other, and the source and drain port pi, tl being located diametrically with respect to each other), 10 in case the valves ports P, T, A, B are be located in such a configuration.

Also, as follows from the drawing, second ends of the channels 31, 23 of the bypass-device 20 provide a second source port p2, a second return port t2, and two second apparatus ports a2, b2, which are connected to respective fluid lines si, dl, L of the system after assembly. In the present 15 embodiment, this connection can be achieved via the optional plug 45 that is provided with end ports of all the (four) fluid lines si, d2, L leading to the source S, drain D and apparatus H. Alternatively, the fluid lines si, d2, L can be connected directly to the second ports pi, tl, a2, b2 of the by-pass device 20, using suitable fluid line connectors.

20 As follows from Figures 3A, 3B, for example, the second ports p2, t2, a2, b2 of the bypass-unit 20 are arranged to be in precise alignment (i.e. are located in a straight lines with respect to each other) with the respective first ports pi, tl, al, bl of the device 20.

In the present embodiment, the bypass-device 20 is arranged such, 25 that a bypass fluid flow through the device 20 can lead to a respective fluid flow (leakage flow) through the valve housing 11. Particularly (see the drawings), the present bypass-device 20 can be mounted onto the valve ports P, T, A, B to provide fluid communication between those valve ports and respective first device ports pi, tl, al, bl; after mounting, the bypass-30 device 20 provides external device ports p2, t2, a2, b2 that effectively 10 ‘replace’ the valve ports P, T, A, B, for example to receive fluid line connectors or the fluid line connector plug 45.

Particularly the housing 21 of the fluid bypass-device 20 comprises a first fluid bypass channel 33a to connect one of the second fluid channels 5 32a (associated with apparatus ports al, a2) to the return channel 31t (and therefore to the return ports 31a, tl, t2, valve return port T and return line dl).

Also, the housing 21 of the fluid bypass-device 20 comprises a second fluid bypass channel 33b to connect the other of the second fluid 10 channels 32b (associated with the other apparatus ports bl, b2) to the return channel 31t (and therefore to the return ports 31a, tl, t2, valve return port T and return line dl).

For example, the fluid bypass-channels 33a, 33b can extend substantially laterally between the respective fluid channels 31, 32 (see Fig. 15 1-2), of in a different direction. Preferably, the bypass device 20 is controllable to adjust a flow rate of bypass fluid flowing through a respective fluid bypass connection 33a, 33b. Preferably, the flow rate can be adjusted over a desired range, for example from zero flow rate to a certain maximum bypass fluid flow rate. In the present embodiment, a channel width or 20 diameter of each bypass channel 33a, 33b is adjustable (preferably in a range from zero to a maximum channel width or diameter), to set a respective bypass-flow. For example, the bypass-device 20 can include a bypass-control mechanism 25, operable to adjust bypass flows during operation.

25 In an embodiment, the bypass-control mechanism 25 can be automatically and/or remotely (for example electronically) controllable, for example by the controller C. In the present embodiment, the bypass-control mechanism 25 is manually controllable, and includes two manually controllable needle valve devices 25a, 25b, to control the flow rate through 30 the two bypass-channels 33a, 33b. Each needle valve device 25a, 25b can be 11 set to a bypass-channel blocking state to close the respective bypass-channel 33a, 33b. Each needle valve device 25a, 25b can be set to a respective opening state, allowing fluid flow via the respective bypass-channel, 33a, 33b, preferably such that the flow rate of the fluid flow can be set finely and 5 accurately.

According to a further embodiment, the housing 21 of the bypass-device 20 can be a substantially solid body 21, containing the internal channels to provide the port channels 31, 32 and bypass-channels 33, as well as containing the respective bypass flow adjuster(s) 25a, 25b.

10 In a further embodiment, the bypass-device 20 is provided with a protecting mechanism, configured to prevent unauthorized control over the bypass-control mechanism 25. For example, the protecting mechanism can include a blocking mechanism that can block operation of the control parts 25, or a covering that can be locked onto the bypass-device 20 to prevent 15 handling of the control parts 25.

Operation of the embodiment can include a method to thermally condition the valve 10. During operation of the present hydraulic system, the pressure of hydraulic fluid in a supply line si (of the fluid supply S) that is upstream with respect to the valve 10 (and bypass-device 20), is higher 20 than the pressure of hydraulic fluid in a downstream return line dl that leads (from return port t2 of bypass-device 20) to the drain D.

During operation, the valve controller C can adjust the valve mechanism 13 depending on one or more signals relating to a working condition of the hydraulic apparatus. When the two bypass-channels 33a, 25 33b of the bypass-device 20 are closed, the bypass-device will not allow respective bypass-flows flowing to the return line dl. In that case, control of the apparatus H will be generally the same as a situation without application of the bypass-device 20. For example, controller C can set the valve 10 to a fluid transmission state to allow fluid connections between the 30 first ports P, T and second ports A, B to hydraulically control the apparatus 12 H, depending for example on feedback signals received from the apparatus monitoring device MH, until the apparatus H has reached a desired apparatus state. When the desired apparatus state has been reached, the valve 10 can be set into its neutral state (see Fig. 1), thus blocking any 5 further fluid transmission from the fluid supply S to the apparatus H. In that case, no fluid will flow through the valve 10. When the desired apparatus operating state has been reached and after the valve 10 has been set to the neutral state, fluid pressures in the two respective apparatus fluid control lines L will remain stationary (depending on the apparatus and its 10 operating conditions, these pressures can be the same, or they can be different pressures).

Advantageously, during operation, at least one of the bypass-channels 33a, 33b of the bypass-device is open. This can be achieved in the present embodiment, by opening a respective control valve 25a, 25b, for 15 example the second control valve 25b (see Fig. 2). As a result, a fluid connection is available between a respective second fluid channels 32b (and therefore respective apparatus ports bl, b2, and respective valve port B) on one hand, and the return channel 3 It (and therefore to the return ports 31a, tl, t2, valve return port T and return line dl) on the other hand. This will 20 generally lead to a (temporal) change of hydraulic fluid pressures at the apparatus H (i.e. in the control lines L) with respect to the above-mentioned situation where both bj^pass-channels 33a, 33b were closed. For example, due to the opening of the second fluid bypass channel 33b, fluid will tend to flow from the apparatus H to that bypass channel 33b via a fluid line L, 25 respective second channel 32b (as is indicated by an arrow X).

The resulting bypass-fluid induced change of fluid pressures will lead to the apparatus H tending to change its operating state. The tendency of the apparatus to change its operating state will be automatically counteracted by the control C, by setting the valve 10 into a respective fluid 30 transmission mode (as in Fig. 2), such, that high pressure fluid from the 13 source S cancels (and even temporarily reverses) a fluid pressure drop experienced at the apparatus due to the fluid bypass. Particularly, the valve 10 is controlled such that pressures in the apparatus control lines L are restored to stationary pressure values that provide the desired (for example 5 predetermined) apparatus working state.

As a result, the system can experience a continuous fluid bypass-flow (indicated by arrows Y in Fig. 2), flowing through the valve 10 and bypass-device, when the apparatus H is in a desired (for example stationary) operating condition to perform a respective apparatus function, 10 without the valve 10 being in a neutral state. The bypass flow flows through the valve 10, and bypasses the apparatus H (i.e. the bypass flow does not particularly flow to and from the apparatus’ fluid ports AH, BH).

Thus, advantageously, operation of the system can involve a method of allowing a fluid bypass-connection between the fluid drain port T 15 and at least one of the second ports A, B of the valve 10, to thermally condition the valve 10 using hydraulic bypass fluid flow. For example, to that aim, a temperature of the hydraulic bypass fluid (supplied from the source S) can be higher than 40 °C, particularly higher than 50 °C.

Besides, as in the present embodiment where the valve mechanism 20 13 is adjustable between a neutral state and one or more fluid transmission states, the bypass fluid flow can lead to the valve mechanism 13 being in a fluid transmission state during a predetermined (for example stationary) operating state of the hydraulic apparatus.

In the present embodiment, heat is supplied to the valve utilizing 25 warm hydraulic fluid, particularly by setting the valve in a fluid transmission state. Also, as follows from the above, in case the valve 10 is a servo valve, operation of the system can include a method to thermally condition a servo valve. For example, the valve controller C can adjust the valve mechanism of the servo valve depending on one or more signals 30 relating to a working condition of the hydraulic apparatus H. Alternatively, 14 according to an aspect of the invention, operation can then include supplying heat to the valve when the valve is in its neutral valve state. For example, heat can be supplied utilizing dedicated heating means, for example one or more electrical heating devices (not shown) integrated with 5 or mounted on the valve housing 11. For example, the heater can be configured to heat the valve housing to a temperature higher than 40 °C, for example at least 50 °C.

The present bypass-device 20 can create a defined hydraulic fluid flow through the valve component 10 and the associated hydraulic system 10 under various operating conditions. For example, the hydraulic fluid flow can thermally condition various components of the system, specifically in case the system is controlled to operate discontinuously (for example, in case the valve controller C controls the valve 10 to maintain a certain valve state during a substantial part of an operating period). According to a further 15 embodiment, during operation, the valve 10 is controlled to maintain a certain valve state during a large operational period of at least one hour, particularly at least several hours, more particularly at least 24 hours. For example, the valve 10 can be controlled to maintain a certain valve state during at least 99% of a total operational life-time of the valve (i.e., most of 20 the time, the valve 10 holds a certain desired operative valve state, to hydraulically control an apparatus H that is coupled to the valve 10). Then, preferably, the bypass-device 20 is set to ensure that a hydraulic bypass-flow (‘leakage’ flow) flows through the valve 10 during such a long period, to thermally condition the valve. In this way, precipitation of certain oxidation 25 products (such as sludge and varnish) in the hydraulic system and its components can be prevented surprisingly well.

Although the illustrative embodiments of the present invention have been described in greater detail with reference to the accompanying drawings, it will be understood that the invention is not limited to those 30 embodiments. Various changes or modifications may be effected by one 15 skilled in the art without departing from the scope or the spirit of the invention as defined in the claims.

It is to be understood that in the present application, the term "comprising" does not exclude other elements or steps. Also, each of the 5 terms "a" and "an" does not exclude a plurality. Any reference sign(s) in the claims shall not be construed as limiting the scope of the claims.

For example, in the depicted example, the bypass device is mounted onto the valve housing, preferably between the valve and a fluid line connector plug 45. In an alternative configuration (not shown), the 10 bypass device can be spaced-apart from the respective valve.

Claims

A hydraulic system comprising: at least one hydraulic device (H), controllable by hydraulic fluid; at least one valve (10) configured to control the device (H) using the hydraulic fluid, the valve (10) having a housing (11) provided with at least a first fluid port (P, T ) and at least a second fluid port (A, B); and a valve controller (C) configured to control the valve (10); wherein the system is characterized by a fluid bypass device configured to allow a fluid bypass connection between at least a first port (P, T) and a second port (A, B).

2. The system of claim 1, wherein the valve housing (11) comprises a valve mechanism (13) that is adjustable between a neutral position to block fluid connections between the first port and second port, and at least one fluid transmission position to fluid connections between the first port and second port.

The system according to claim 1 or 2, wherein the valve comprises at least two second fluid ports (A, B) that are in fluid communication with the hydraulic device (H), wherein the valve comprises at least two first fluid ports (P, T) comprises those in fluid communication with a fluid supply (S) and a fluid discharge (D), wherein the fluid bypass device (20) is arranged to provide a fluid bypass connection in at least one of the fluid connections between the valve (20) on the one hand and the hydraulic device (H), source (S) and drain (D) on the other.

The system according to any one of the preceding claims, wherein the bypass device is configured such that a bypass fluid flow through the device (20) leads to a respective fluid flow through the valve housing 30 (11).

The system according to any of the preceding claims, wherein the fluid bypass device (20) has a housing (21) that is separate from the valve housing (11), wherein the fluid bypass device (20) is preferably configured to be releasably connected are at the valve housing (11), in particular in an operative position to provide the fluid communication between at least a first port (P, T) and a second port (A, B).

The system of claim 5, wherein the housing (21) of the fluid bypass device (20) and the valve housing (11) are configured to exchange heat with each other.

The system according to any of the preceding claims, wherein the fluid bypass device is configured to be thermally conditioned by a respective bypass fluid flowing through the fluid bypass device.

8. The system according to any of the preceding claims, wherein the bypass device (20) is controllable to control a bypass flow flowing through a respective fluid connection.

9. The system according to any of the preceding claims, wherein the bypass device (20) comprises one or more first fluid channels (31) connected to respective first fluid ports (P, T) of the valve (10), as well as a or more second fluid channels (32a, 23b) connected to respective second fluid ports (A, B) of the valve (10).

The system of claim 9, wherein the bypass device (20) comprises at least one bypass channel (33a, 33b) connecting a first and second fluid channel (31t, 32a, 23b), the bypass channel 25 (33a, 33b) is preferably provided with a control valve (25a, 25b) to control a flow rate through the channel (33a, 33b).

The system of claim 9 or 10, wherein the first and second channels (31, 32) of the bypass device (20) extend parallel to each other.

The system according to any of the preceding claims, wherein the bypass device is provided with first fluid ports (p1, t1, a1, b1) facing the valve housing (11), and respective second fluid ports (p2, t2, a2, b2) facing away from the valve housing (11).

A method for thermally conditioning a valve, wherein the valve is adapted to supply hydraulic fluid to a hydraulic device, wherein the valve (10) has a housing (11), the housing (11) being provided with first fluid ports (P, T) and second fluid ports (A, B), wherein a valve controller (C) controls the valve depending on one or more signals related to an operative condition of the hydraulic device, characterized by allowing a hypass heating between at least a first port (P, T) and a second port (A, B) to thermally condition the valve using a hydraulic bypass fluid flow.

The method of claim 13, wherein a temperature of the hydraulic bypass fluid is higher than 40 ° C.

15. The method of claim 14, wherein the valve is adjustable between a neutral position to block fluid connections between the first and second ports, and at least one fluid transfer position to allow fluid connections between the first ports and second ports, the bypass fluid flow causes the valve (10) to be in a fluid transfer position during a predetermined operating condition of the hydraulic device (H).

16. A method of thermally conditioning a servo valve, for example a method according to any of claims 14-15, wherein the servo valve is designed to supply hydraulic fluid to a hydraulic device, wherein the valve (10) has a housing (11) wherein the housing (11) is provided with first fluid ports (P, T) and second fluid ports (A, B), the valve housing (11) having a valve mechanism (13) that is adjustable between a neutral position about block fluid connections between the first ports and second ports, and at least one fluid transfer position to allow fluid connections between the first ports and second ports, a valve controller (C) controlling the valve mechanism (13) depending on one or more signals related to a working condition of the hydraulic device, characterized by applying heat to the valve when the valve mechanism is in the neutral position. 10