Claims:WE CLAIM: -

1. A hydraulic tripping system for steam turbine comprising a housing accommodating a plurality of solenoid operated 5 port 2 way spool valves (SV1, SV2 and SV3) arranged in series working in combination with a starting device (SD1) and hand trip valve (HTV1), wherein the housing is provided with three active inlet ports of each of the spool valves (SV1, SV2 and SV3).

2. The hydraulic tripping system for steam turbine as claimed in claim 1, wherein two of the inlet ports (SV1-3 & SV1-5) of the valve (SV1) are connected with upstream pressurized oil and the port (SV1-1) is connected to return oil tank.

3. The hydraulic tripping system for steam turbine as claimed in claim 1 or 2, wherein the two inlet ports (SV2-3 & SV2-5) of said valve (SV2) are connected with the outlet connections of the valve (SV1).

4. The hydraulic tripping system for steam turbine as claimed in any of the preceding claims, wherein the two inlet connections (SV3-3 & SV3-5) of the valve (SV3) are connected with the outlet connections of the valve (SV2)

5. The hydraulic tripping system for steam turbine as claimed in any of the preceding claims, wherein the ports (SV1-1, SV2-1 and SV3-1) for the three solenoid valves (SV1, SV2 and SV3) are connected to the common return oil tank.
6. The hydraulic tripping system for steam turbine as claimed in any of the preceding claims, wherein the solenoid valves (SV1, SV2 and SV3) in the energized state cause uninterrupted supply of the pressurized oil to the trip oil line.

7. The hydraulic tripping system for steam turbine as claimed in any of the preceding claims, wherein a starting device (SD1) is actuated by means of hand-lever on availability of control oil supply, in which the starting device (SD1) ensures supply of starting oil to stop valve piston.

8. The hydraulic tripping system for steam turbine as claimed in any of the preceding claims, wherein the stop valve comprises of a piston (ESV-PN), piston disc (ESV-PD), compression spring (ESV-CS) and a tester piston (ESV-TP) functioning such as herein described.

9. The hydraulic tripping system for steam turbine as claimed in any of the preceding claims, wherein the de-energization of any two of the three solenoid valves (SV1, SV2 and SV3) leads to the tripping of the turbine and isolation of the upstream control oil from the turbine trip oil circuit.

10. The hydraulic tripping system for steam turbine as claimed in any of the preceding claims, wherein the trip oil is returned to the tank through the drain ports of the stop valves (ESV1) and through ports (SV1-1, SV2-1, SV3-1) of the solenoids (SV1, SV2, SV3).
, Description:A hydraulic tripping system for steam turbine

FIELD OF INVENTION
[001] The invention relates to a hydraulic tripping system for steam turbine. The present invention discloses a hydraulic tripping system using a series arrangement of a 5-ports 2-positions type solenoid operated spool valves and hand operated starting device. This arrangement is used for opening of the steam turbine stop valve and realization of voted trip logics used in electro-hydraulic type steam turbine regulation system. This system is employed for opening of the turbine stop valve and reliable closure of the stop valve. Further, the present invention allows implementation of a variety of tripping logics like 2oo3, 2oo4 and 1oo2 by addition/removal of the solenoid valves and oil supply sources to them in series.

PRIOR ART OF THE INVENTION
[002] Now, reference may be made to the following prior arts.

[003] US patent 0152759/2017 attempted to implement 2oo3 tripping logic using a three solenoid operated 4-port 2-position type spool valve and hand operated 5-port 2-position spool valves arranged in a manner shown in the figure 2. The prior art concept also allows for online testing of the individual solenoid valves. The hydraulic scheme shown in the US patent 0152759 is applicable only for steam turbine regulation systems where the hydraulic control oil is separate from the turbine lubrication scheme.

[004] US patent 7409965 /2008 as shown in figure3 implemented 2oo3 tripping logic using a separate hydraulic block with three pilot operated 5-port 2-position type spool valve. Each pilot operated spool valve is provided by a pilot signal by separate solenoid valves. This hydraulic block and solenoid valve arrangement valves introduces many control elements reducing the total system reliability.

[005] The aforediscussed prior arts are associated with the following drawbacks:
- Sophisticated design with more number of components
- Less reliable owing to presence of more hydraulic components
- Expensive

[006] In view of the above, the present invention has been proposed in order to address the aforesaid disadvantages and serve the purpose efficiently.

OBJECTS OF THE INVENTION
[007] The object of the present invention is to provide a hydraulic tripping system for steam turbine which obviates shortcomings of the prior art(s).

[008] Another object of the present invention is to provide a hydraulic tripping system for steam turbine which ensures isolation of upstream control oil on turbine trip actuation for a combined lube and control oil system.

[009] Still another object of the present invention is to provide a hydraulic tripping system for steam turbine which enables the operator to carry out online testing for the healthiness of individual end trip hydraulic elements.

[010] Yet another object of the present invention is to provide a hydraulic tripping system for steam turbine which allows the evacuation of downstream pressurized oil to the tank through the return ports of the individual solenoid operated spool valves.

[011] Further object of the present invention is to provide a hydraulic tripping system for steam turbine which ensures easy replacement of trip solenoid from the trip scheme.

SUMMARY OF THE INVENTION
[012] Accordingly, there is provided a hydraulic tripping system for steam turbine comprising a housing accommodating a plurality of solenoid operated 5 port 2 way spool valves (SV1, SV2 and SV3) arranged in series working in combination with a starting device (SD1) and hand trip valve (HTV1), wherein the housing is provided with three active inlet ports of each of the spool valves (SV1, SV2 and SV3).

[013] Two of the inlet ports (SV1-3 & SV1-5) of the valve (SV1) are connected with upstream pressurized oil and the port (SV1-1) is connected to return oil tank.

[014] The two inlet ports (SV2-3 & SV2-5) of said valve (SV2) are connected with the outlet connections of the valve (SV1).

[015] The two inlet connections (SV3-3 & SV3-5) of the valve (SV3) are connected with the outlet connections of the valve (SV2).

[016] The ports (SV1-1, SV2-1 and SV3-1) for the three solenoid valves (SV1, SV2 and SV3) are connected to the common return oil tank.

[017] The solenoid valves (SV1, SV2 and SV3) in the energized state cause uninterrupted supply of the pressurized oil to the trip oil line.

[018] A starting device (SD1) is actuated by means of hand-lever on availability of control oil supply, in which the starting device (SD1) ensures supply of starting oil to stop valve piston.

[019] The stop valve comprises of a piston (ESV-PN), piston disc (ESV-PD), compression spring (ESV-CS) and a tester piston (ESV-TP) functioning such as herein described.

[020] The de-energization of any two of the three solenoid valves (SV1, SV2 and SV3) leads to the tripping of the turbine and isolation of the upstream control oil from the turbine trip oil circuit.

[021] The trip oil is returned to the tank through the drain ports of the stop valves (ESV1) and through ports (SV1-1, SV2-1, SV3-1) of the solenoids (SV1, SV2, SV3).

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
[022] Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings of the exemplary embodiments and wherein:-

Figure 1 Hydraulic sub-system for steam turbine trip logics in de-energized condition according to present invention.

Figure 2 Hydraulic Control Device for Emergency Stop Valve of a steam turbine arrangement according to US prior art (US 2017/0152759).
Figure 3 Trip block assembly in US prior art (US 7409965 /2008).
Figure 4.1 Trip solenoid valve assembly opening sequence in accordance with present invention.

Figure 4.2 Trip solenoid valve assembly opening sequence (Trip Solenoids Energized) of present invention.

Figure 4.3 Trip solenoid assembly for the invention (SD hand lever disengaged).

Figure 4.4 ESV in open condition in the present invention.

Figure 5 De-energization of the two solenoid valves according to present invention.

DETAIL DESCRIPTION OF THE PRESENT INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS OF PREFERRED EMBODIMENTS

[023] The present invention makes a disclosure regarding a technology pertaining to a hydraulic tripping system for steam turbine.

[024] Reference may be made to Fig. 1 illustrating a schematic representation of hydraulic trip block arrangement realized with the help of a solenoid actuated 5-port 2-position spool valves.

[025] The hydraulic trip scheme is shown in its tripped state in figure 4.1 with all the solenoid actuated 5-port 2-position spool valves (SV1, SV2, and SV3) in de-energized state. In this state, the upstream pressurized oil is isolated from the trip oil circuit. As indicated in the figure, upstream pressurized oil connection is provided to two inlet ports 1, 5 of valve SV1 with the port 3 of valve SV1 connected to tank return line. The control oil is provided with a hand trip valve HTV1 for manual tripping of the turbine by draining the downstream oil.

[026] The following arrangement has been devised so as to realize a 2oo3 hydraulic trip logic which implies that the oil downstream of the trip block is returned to the drain tank and oil upstream of the hydraulic trip block is isolated in case any two out of the three solenoid valves SV1, SV2 and SV3 are de-energized.

[027] The valve SV1 constitutes a Solenoid Actuated 5-port 2-position type directional valve which comprises of a valve spool placed in a housing, which is actuated by means of energization of the solenoid valve against a restoring spring. The housing is provided with three inlet ports with two of the inlet ports SV1-3 & SV1-5 of the valve (SVI) are connected with upstream pressurized oil and the port SV1-1 is connected to return oil tank. Valve SV2 is identical in construction with the valve SV1 with the two inlet ports SV2-3 & SV2-5 of said valve (SV2) are connected with the outlet connections of the valve SV1. Valve SV3 is identical in construction with the valve SV1 with the two inlet connections SV3-3& SV3-5 of the valve (SV3) are connected with the outlet connections of the valve SV2. The ports SV1-1, SV2-1 and port SV3-1 for the three solenoid valves SV1, SV2 and SV3 are connected to the common return oil tank. The upstream pressurized oil is isolated from the hydraulic block downstream when any one or two and even three solenoids are de-energized.

[028] The solenoid operated spool valves are arranged to achieve the following requirements:

1. Online testing of individual trip solenoid valves
2. 2oo3 logic for turbine tripping
3. Isolation of the upstream pressurized oil from the trip oil circuit in case of turbine trip.

[029] The individual solenoid valves SV1, SV2 and SV3 in the energized state cause uninterrupted supply of the pressurized oil to the trip oil line. On availability of the control oil supply, the starting device SD1 is actuated with the help of hand-lever. The starting device SD1 ensures the supply of starting oil to the stop valve piston. The stop valve comprises of a piston(ESV-PN), piston disc(ESV-PD) , compression spring(ESV-CS) and a tester piston(ESV-TP).The stop valve piston disc(ESV-PD) experiences the control oil pressure and moves in a direction to make oil tight seal with the piston(ESV-PN) by compressing the stop valve spring(ESV-CS). On measurement of full starting oil pressure by starting oil pressure indicator (starting oil pressure indicator), all the three solenoid valves (SV1, SV2, SV3) are energized to admit oil in order to stop valve trip oil line. Once the trip oil line is generated, the hand-lever is released and the spool of the starting device SD1 is brought to position such that the start-up oil is returned to drain via an orifice (OR1). The trip oil on account of energization of all the three solenoid valves (SV1, SV2, SV3) is generated which moves the piston disc in the opening direction thereby opening the stop valve. The starting oil is drained via the starting device orifice OR1 and the stop valve fully opens.

[030] The de-energization of any two of the three solenoid valves (SV1, SV2, and SV3) leads to the tripping of the turbine and isolation of the upstream control oil from the turbine trip oil circuit. The trip oil is returned to the tank through the drain ports of the stop valves ESV1 and through ports (SV1-1, SV2-1, SV3-1) of the solenoids.

[031] This allows for online testing of the individual solenoid valves to be carried out by de-energizing it without the actual closure of the stop valve (ESV) without disrupting the turbine operation. The de-energization of any one of said solenoids leads to reduction of the pressure recorded by the trip oil pressure gauge (Trip oil PG)/trip pressure indicator (PI).

[032] The arrangement therefore increases the system reliability significantly reducing false tripping of the turbine on account of malfunctioning of the solenoid valves.

[033] The hydraulic sub-system also allows for carrying out of healthiness checks with steam turbine in operation. When all the three said solenoid valves (SV1, SV2 and SV3) are energized mode, the pressure gauge PG reads the control oil pressure. Malfunctioning of any one of the three solenoid valves (SV1, SV2 and SV3) could lead to the drop in the pressure read by trip oil pressure gauge PG.

[034] As shown in figure 5 the de-energization of any of the two solenoids leads to the isolation of upstream control oil and drain of the trip oil to the tank.

[035] The present trip logic eliminates all other hydraulic components and uses only direct operated 5/2 solenoid valves as compared to the prior arts US 0152759 and US 7409965. This simplifies the total hydraulic circuit reducing the number of components thereby increasing the reliability of the system and reducing failures. The direct operated 5/2 solenoid valves are standard valves universally available with ease thereby eliminating the manufacturing of OEM specific proprietary components.

[036] The advantages of the present system over the prior arts US 0152759 and US 7409965 can be listed hereinunder:
a) Simplified design with less number of components.
b) Increasing reliability and achievement of required trip functions due to use of less hydraulic components.
c) Use of standard 5/2 valves widely and easily available.

[037] It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particulars claim containing such introduced claim recitation to inventions containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogues to “at least one of A, B and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that virtually any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B”.

[038] It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-