Compact turbine emergency trip throttle

Abstract

This invention discloses a compact emergency shut-off throttle for a steam turbine, comprising a housing, a slide valve, a spring, a bottom cover, and a hook assembly. The slide valve is installed inside the housing cavity, with a clearance fit between the slide valve and the housing, achieving a sliding seal through this clearance fit. The housing has a safety port and a reset port. The spring is positioned between the inner side of the slide valve and the bottom cover, and the hook assembly is connected to the stop position at the front end of the slide valve. When the steam turbine experiences mechanical overspeed, the hook assembly disengages from the stop position at the front end of the slide valve, causing the slide valve to move forward under the spring force. The oil pressure at the safety port quickly connects with the drain groove at the rear end of the slide valve, rapidly releasing the safety oil pressure and quickly closing the main valve. After the fault is cleared, the oil pressure at the reset port enters the oil chamber through the inlet groove at the front end of the slide valve, achieving automatic reset of the slide valve based on the reset oil pressure. This throttle structure is highly simplified, significantly reducing costs, with a reasonable oil circuit layout, sensitive and reliable protection action, and a wide oil pressure adaptability range, solving the problem of low-pressure automatic reset.

Description

Technical Field

[0001] This invention belongs to the technical field of turbine overspeed safety protection structure, specifically a turbine emergency shutdown throttle. Background Technology

[0002] The current turbine emergency shutdown throttle has the following structure: Figure 1 As shown, the traditional emergency trip throttle structure of a steam turbine consists of numerous components, including the casing, hook assembly, handle striker assembly, handle slide valve assembly, return spring, and sealing ring. The overall structure is complex with many parts and low integration. For example... Figure 1 As shown, the conventional emergency shutdown throttle is usually installed inside the turbine bearing housing, with a handle located outside the bearing housing.

[0003] During normal operation of the steam turbine, the spool valve assembly is locked in place by the hook-and-stop engagement structure to maintain stable safety oil pressure. When a mechanical overspeed fault occurs, the rotor bolt strikes the hook assembly, causing the hook-and-stop to disengage. The spool valve assembly moves under the force of the return spring, opening the safety oil and return oil passages, allowing for rapid pressure relief of the safety oil. The main steam valve actuator then closes rapidly under its own spring preload, achieving overspeed and rapid closure protection. After the fault is cleared, the spool valve can be reset by introducing reset oil or manually pulling the handle. Simultaneously, an emergency shutdown can be initiated by manually striking the strike bar.

[0004] However, existing traditional structures have many shortcomings in practical engineering applications:

[0005] First, the complex overall structure, numerous parts, high precision requirements, and cumbersome assembly process result in high overall processing, assembly, and maintenance costs.

[0006] Secondly, the traditional throttle drain path has a complicated design, which can easily lead to pressure relief delay and poor stability of protection actions.

[0007] Third, with the widespread use of self-contained main steam valves in steam turbines, the safety oil for steam turbines is generally taken directly from low-pressure lubricating oil sources, resulting in generally low oil supply pressure. Traditional structures have a fixed pressure-bearing area in the oil chamber and a small margin for reset thrust. Under low-pressure lubricating oil conditions, insufficient thrust can easily occur, leading to problems such as the slide valve failing to automatically reset. This results in poor equipment adaptability and makes it difficult to meet the operational requirements of existing units.

[0008] Among the existing related patent technologies, such as the hydraulic emergency shut-off throttle disclosed in patent document (CN207728973U), this patent adopts a three-layer nested structure of "shell (2) - valve sleeve (3) - spool valve (6)", and the interior is filled with a complex cross hole system (such as the first / second oil passage hole, the first / second valve sleeve oil passage hole, the safety oil passage hole, etc.). The exterior is also equipped with a guide flange (7), a top cover (8), a top rod (11), a protective cover (12), and a number of components such as upper and lower spring seats. The three-layer sleeve nesting fit has extremely high requirements for the coaxiality, cylindricity and surface roughness of the parts. If the machining accuracy is slightly off, it is very easy to produce the phenomenon of "hydraulic jamming" in the high pressure oil environment, which will cause the spool valve to jam; at the same time, the complex internal cross transverse holes (such as the oil passage hole that passes through the valve sleeve laterally) are difficult to process, are easy to produce burrs, and have high requirements for sealing and isolation between the hole systems, which can easily cause internal oil leakage. The numerous and nested components make the assembly process extremely complex, requiring repeated alignment and adjustment of spring preload and seals. In actual power plant operation, if the internal oil circuit is blocked or the spring is fatigued, the workload of maintenance and disassembly is enormous, directly leading to high overall manufacturing cost, assembly cost and maintenance cost throughout the entire life cycle of the equipment. According to the specification and claims 4 and 5, its oil drain path is: "Second oil chamber (16) -> Second valve sleeve oil passage (5) -> Oil drain passage (4) -> Safety oil drain port (1)". The slide valve must be moved to a specific position so that the second oil chamber is aligned with the transverse hole on the valve sleeve, and then discharged through the transverse hole of the housing. The core requirement of the emergency shut-off throttle is "millisecond-level" instantaneous pressure relief. This patent uses a multi-stage series of small transverse holes for the oil drain path, resulting in extremely high fluid resistance (flow resistance). During the displacement of the slide valve, there is a large "overlapping amount" at the orifice. The oil discharge needs to go through multiple throttling stages, which seriously weakens the explosive force of the oil discharge and causes the pressure relief of the safety oil circuit to be delayed, making it impossible to achieve rapid emergency braking. The small oil passages that run horizontally through (such as the oil passage 5 of the second valve sleeve) are easily blocked by tiny mechanical impurities or sludge in the lubricating oil system. Once the passage is blocked, it will directly lead to "failure to operate" or incomplete pressure relief during emergency shutdown, greatly reducing the stability and reliability of the protection action and posing a great safety hazard. The slide valve (6) is provided with "two annular bosses arranged vertically" on its outer periphery to form the first and second oil chambers. The effective pressure-bearing area is determined by the diameter difference of the bosses and is completely solidified after machining. Reset mainly relies on the elasticity of the oil valve spring (10) and the oil pressure difference. During the start-up and shutdown of the unit or under the condition of low system lubricating oil pressure, since the pressure-bearing area of ​​the upper and lower end faces of the slide valve is fixed and cannot be adjusted, the hydraulic thrust margin generated by the oil pressure difference is very small. At this point, the thrust is often insufficient to overcome the resistance of the throttle spring, the weight of the spool valve, and the mechanical friction caused by the multi-layer nesting, which can easily lead to fatal problems such as spool valve jamming and failure to automatically reset. For different models and capacities of steam turbine units, the rated oil pressure and flow characteristics of their safety oil systems vary considerably.The patent's "one-size-fits-all" fixed pressure area design lacks the ability to adaptively compensate for oil pressure fluctuations, making it difficult to be compatible with and meet the diverse operating requirements of existing units, resulting in extremely poor versatility and adaptability.

[0009] In summary, existing turbine emergency trip throttles suffer from structural redundancy, low reliability, high cost, poor high and low pressure compatibility, and difficulty in low-pressure reset. There is an urgent need for a compact turbine emergency trip throttle with a simplified structure, high reliability, wide compatibility, and the ability to achieve overspeed protection and automatic low-pressure reset. Summary of the Invention

[0010] The purpose of this invention is to propose a compact emergency shutdown throttle for steam turbines. Compared with the traditional emergency shutdown throttle structure, this throttle structure is highly simplified, significantly reduces costs, has a reasonable oil circuit layout, provides sensitive and reliable protection action, has a wide range of oil pressure adaptability, and can solve the problem of low-pressure automatic reset.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A compact emergency shutdown throttle for a steam turbine includes a housing, a slide valve, a spring, a bottom cover, and a hook assembly. The slide valve is installed in the inner cavity of the housing, and the slide valve and the housing are fitted with a clearance fit, which achieves sliding sealing. The housing is provided with a safety port and a reset port. The spring is located between the inner side of the slide valve and the bottom cover. The front stop of the slide valve is fitted with the hook assembly. When the steam turbine mechanically overspeeds, the hook assembly disengages from the front stop of the slide valve, and the slide valve moves forward under the action of the spring force. The oil pressure at the safety port quickly connects with the oil drain groove at the rear end of the slide valve, the safety oil is rapidly depressurized, and the main valve closes quickly. After the fault is cleared, the oil pressure at the reset port enters the oil chamber through the oil inlet groove at the front end of the slide valve, and the slide valve is automatically reset by the reset oil pressure.

[0012] Furthermore, the casing is fixedly installed to the internal support of the turbine bearing housing by bolts.

[0013] Furthermore, the top of the housing is provided with independent safety oil port and reset oil port, and the inside of the housing is machined with annular oil grooves corresponding to the safety oil port and reset oil port.

[0014] Furthermore, the front and rear ends of the slide valve are machined with integrated flow grooves of different depths. The front end is the oil inlet flow groove, and the rear end is the oil outlet flow groove, so that the functions of the oil circuit are clearly distinguished and do not interfere with each other.

[0015] Furthermore, one end of the spring abuts against the inner end face of the slide valve, while the other end is limited to the bottom cover, and the spring stiffness meets the impact resistance requirements of marine steam turbines.

[0016] Furthermore, the bottom cover is sealed and installed at the bottom of the housing. The bottom cover is equipped with a through-type extra-large oil return port for rapid return of pressure relief oil, ensuring that the oil discharge passage is unobstructed.

[0017] Furthermore, the hook assembly includes a hook, a tension spring, and a positioning pin. The hook is mounted on the front of the housing via a pin, and the lower end of the hook is connected to the housing via a tension spring.

[0018] Furthermore, during normal operation of the unit, the hook engages with the end stop of the slide valve to maintain the slide valve in a locked and balanced state, allowing the turbine to operate normally.

[0019] Furthermore, the shell is formed by integral high-strength forging.

[0020] Furthermore, the sealing sliding fit tolerance between the slide valve and the housing is H8 / e7.

[0021] Compared with the prior art, the present invention has the following significant advantages: First, the structure is highly streamlined, significantly reducing costs. This invention, tailored to the needs of steam turbine development, eliminates essential components of traditional structures such as the handle striker assembly, external operating handle, and multiple sets of sealing rings. This drastically reduces the number of parts, resulting in high overall integration and a compact structure. While still providing overspeed protection and automatic reset functions, it effectively reduces manufacturing and assembly difficulties, as well as subsequent maintenance costs, demonstrating excellent economic efficiency.

[0022] Secondly, the reduced width of the metal clearance mating surface simplifies the assembly of parts, avoids jamming of the metal sealing surface, and eliminates the need for rubber sealing rings, significantly improving the long-term stability and service life of the equipment.

[0023] Third, the oil circuit layout is simplified, and the protection action is sensitive and reliable. This invention features an integrated independent flow channel at both the front and rear ends of the slide valve. The front end is responsible for the reset oil inlet after activation, while the rear end is responsible for overspeed oil discharge. When the turbine mechanically overspeeds, the stop valve disengages, and the slide valve moves forward under spring force. The oil pressure at the safety port quickly connects with the oil discharge flow channel at the rear end of the slide valve, rapidly releasing the safety oil pressure, quickly closing the main valve, and providing a rapid overspeed protection response. After the fault is cleared, the reset oil pressure enters the oil chamber through the front inlet flow channel, relying on oil pressure to automatically reset the slide valve without manual intervention.

[0024] Fourth, it has wide oil pressure adaptability, solving the problem of low-pressure reset. This invention can flexibly match the pressure-bearing area of ​​the oil chamber according to the actual safe oil pressure of the unit: high-pressure oil can reduce the pressure-bearing area, reduce the overall structural size, and achieve miniaturized layout; low-pressure lubricating oil can increase the pressure-bearing area and improve the reset thrust, completely solving the industry pain point of difficult automatic reset under low-pressure oil source in traditional structures. It is compatible with various new and old steam turbines and has strong versatility. Attached Figure Description

[0025] Figure 1 A schematic diagram of the emergency shutdown throttle structure of a traditional steam turbine. Figure 2 This is an orthogonal full sectional view of the emergency shutdown throttle of the steam turbine in this invention; Figure 3 for Figure 2 Top view; Figure 4 This is a diagram illustrating the emergency shutdown throttle action of the steam turbine in this invention. Figure 5 This is a top-down view of the actual product of this invention; Figure 6 This is a side view of the actual product of the present invention. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0027] like Figures 2 to 6 As shown in the figure, the present invention provides a compact turbine emergency shutdown throttle, which is mainly composed of a housing 1, a slide valve 2, a spring 3, a bottom cover 4, and a hook assembly 5. The overall structure is compact and highly integrated. The overall cross-sectional structure is shown in the figure. Figure 2 As shown. While retaining the overspeed shut-off and automatic reset functions, the structure has been greatly simplified, reliability improved, and the hydraulic pressure compatibility range broadened.

[0028] The housing 1 is bolted to the internal support of the turbine bearing housing, making disassembly and assembly convenient and ensuring accurate positioning. Independent safety oil ports and reset oil ports are respectively provided on the top of the housing. Each oil port corresponds to an annular oil groove machined inside the housing, minimizing the precision machining range of the housing's internal cavity.

[0029] The slide valve 2 and the inner cavity of the housing 1 are fitted with a clearance fit, which achieves sliding sealing by means of metal clearance fit. The structure is durable and has no risk of aging failure. The slide valve is equipped with integrated flow grooves with different depths machined at the front and rear ends. The front end is the oil inlet flow groove and the rear end is the oil outlet flow groove. The functions of the oil circuit are clearly separated and do not interfere with each other.

[0030] Spring 3 is arranged between the inner side of slide valve 2 and bottom cover 4, with one end abutting against the inner end face of slide valve 2 and the other end limited to bottom cover 4. The spring 3 is designed with increased stiffness to meet the impact resistance requirements of marine steam turbines.

[0031] The bottom cover 4 is sealed and installed at the bottom of the housing 1. The bottom cover 4 is provided with a through-type extra-large oil return port for rapid return of pressure relief oil, ensuring that the oil discharge passage is unobstructed.

[0032] The hook assembly 5 consists of a hook, a tension spring, and a positioning pin. The hook assembly is installed at the front of the housing. During normal operation of the unit, the hook engages with the end stop of the slide valve to maintain the slide valve in a locked and balanced state, and the turbine operates normally.

[0033] The housing 1 is machined from a single high-strength forging. The slide valve 2 and the housing 1 achieve sealing sliding through a gap. The recommended tolerance is H8 / e7. The stiffness of the compression spring 3 is selected to meet the impact resistance requirements. The structure is simple and compact, the operation is reliable, the failure rate is low, the hydraulic pressure adaptability is wide, and the overall performance is superior to traditional structures, showing good prospects for promotion and application. When the turbine operates at overspeed, the stop valve disengages, and the slide valve moves forward under the action of the spring force. Figure 4 As shown, the safety oil port pressure is quickly connected to the drain groove at the rear end of the spool valve, the safety oil is rapidly depressurized, the main valve closes quickly, and the overspeed protection responds rapidly. After the fault is cleared, the reset oil pressure enters the oil chamber through the front inlet groove, and the spool valve is automatically reset by oil pressure without manual intervention.

[0034] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the concept and scope of the present invention. Therefore, all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A compact emergency shutdown throttle for a steam turbine, characterized in that: The system includes a housing, a slide valve, a spring, a bottom cover, and a hook assembly. The slide valve is installed inside the housing cavity, and the slide valve and the housing are fitted with a clearance fit, which is used to achieve sliding sealing. The housing is provided with a safety oil port and a reset oil port. The spring is located between the inner side of the slide valve and the bottom cover. The front stop of the slide valve is fitted with the hook assembly. When the turbine mechanical overspeeds, the hook assembly disengages from the front stop of the slide valve, and the slide valve moves forward under the action of the spring force. The oil pressure at the safety oil port is quickly connected to the oil drain groove at the rear end of the slide valve, the safety oil is quickly depressurized, and the main valve closes quickly. After the fault is cleared, the oil pressure at the reset oil port enters the oil chamber through the oil inlet groove at the front end of the slide valve, and the slide valve is automatically reset by the reset oil pressure.

2. The compact steam turbine emergency shutdown throttle according to claim 1, characterized in that: The casing is fixedly installed to the internal support of the turbine bearing housing by bolts.

3. The compact steam turbine emergency shutdown throttle according to claim 1, characterized in that: The top of the housing is equipped with independent safety oil port and reset oil port, and the inside of the housing is machined with annular oil grooves corresponding to the safety oil port and reset oil port.

4. The compact steam turbine emergency shutdown throttle according to claim 1, characterized in that: The front and rear ends of the slide valve are machined with integrated flow grooves of different depths. The front end is the oil inlet flow groove and the rear end is the oil outlet flow groove, which makes the oil circuit functions clearly distinguished and do not interfere with each other.

5. The compact steam turbine emergency shutdown throttle according to claim 1, characterized in that: One end of the spring rests against the inner end face of the slide valve, while the other end is limited to the bottom cover. The spring stiffness meets the impact resistance requirements of marine steam turbines.

6. The compact steam turbine emergency trip throttle structure according to claim 1, characterized in that: The bottom cover is sealed and installed at the bottom of the housing. The bottom cover is equipped with a through-type extra-large oil return port for rapid return of pressure relief oil, ensuring that the oil discharge passage is unobstructed.

7. The compact steam turbine emergency shutdown throttle according to claim 1, characterized in that: The hook assembly includes a hook, a tension spring, and a positioning pin. The hook is mounted on the front of the housing via a pin, and the lower end of the hook is connected to the housing via a tension spring.

8. The compact steam turbine emergency trip throttle according to claim 7, characterized in that: When the unit is running normally, the hook engages with the stop at the end of the slide valve to maintain the slide valve in a locked and balanced state, and the turbine runs normally.

9. The compact steam turbine emergency shutdown throttle according to claim 1, characterized in that: The shell is formed by integral high-strength forging.

10. The compact steam turbine emergency trip throttle according to claim 1, characterized in that: The sealing sliding fit tolerance between the slide valve and the housing is H8 / e7.

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