A low level protection device for steam turbine lubricating oil tank

Abstract

This invention discloses a low-level protection device for a turbine lubricating oil tank, comprising a vent pipe, an oil suction pipe, and an oil outlet pipe. The vent pipe and the oil suction pipe are connected by an intermediate pipe. The upper opening of the vent pipe is higher than the maximum shutdown level, and the lower opening of the oil suction pipe is lower than the low-low level. The oil outlet pipe connects to the intermediate pipe and the oil suction pipe at the junction via a horizontal pipe with a perforated plate, forming a low-suction oil path. The oil outlet pipe extends horizontally out of the tank side plate. A horizontal pipe is connected at the junction of the vent pipe and the intermediate pipe, and the other end of the horizontal pipe connects to the oil outlet pipe via a downcomer, forming a high-suction oil path. The horizontal pipe is parallel to the horizontal pipe with a perforated plate. The highest point of the inner wall of the horizontal pipe is flush with the low level. The lowest point of the perforation in the horizontal pipe with a perforated plate is flush with the low-low level. This invention has a simple structure and effectively avoids rapid leakage of lubricating oil from the oil suction interface of the lubricating oil tank side plate, thus protecting the lubricating oil tank from low levels.

Description

Technical Field

[0001] This invention relates to the field of turbine lubricating oil tank technology, and specifically to a low-level protection device for turbine lubricating oil tanks. Background Technology

[0002] During normal operation, steam turbines require lubricating oil to lubricate the turbine bearings and dissipate the heat generated by the rotor's rotational friction, preventing overheating. The turbine lubricating oil tank, a key component of the turbine lubrication system, is primarily responsible for storing lubricating oil, ensuring a stable supply to the turbine bearings. Therefore, the lubricating oil tank level is a crucial monitoring parameter for ensuring safe turbine operation. This level includes the maximum shutdown level (the level when the entire lubrication system is shut down), the low level (the lowest level during normal turbine operation), and the very low level (the level during turbine shutdown). In the event of a lubricating oil leak, insufficient lubricating oil supply can cause the main oil pump to cavitate, potentially leading to serious accidents such as turbine bearing failure and rotor dynamic / static friction. Therefore, maintaining a low lubricating oil level in the tank is critical for ensuring the safety of the turbine bearings.

[0003] With the advancement and development of steam turbine technology both domestically and internationally, lubrication systems are becoming increasingly complex, and the number of interfaces between the lubrication oil tank and external equipment is gradually increasing. Currently, the interfaces of auxiliary oil pumps and exhaust fans are generally located on the top plate of the lubrication oil tank. However, large external equipment such as oil purification devices and jacking pumps, due to limitations in size and weight, are usually located on the foundation of the lubrication oil chamber near the lubrication oil tank. The interfaces are connected by opening holes in the side plate of the lubrication oil tank and welding pipes. To facilitate oil suction, the oil suction ports of external equipment on the foundation of the lubrication oil chamber are usually located at the lower liquid level of the lubrication oil tank. At this point, if an accident such as an external equipment or pipeline failure occurs and oil leakage occurs, the presence of the oil suction pump or siphon effect can easily cause a rapid and large-scale leakage of lubrication oil from the tank through the interfaces, making it difficult to maintain the low liquid level in the tank and causing the liquid level to drop rapidly, thereby affecting the safety of the steam turbine bearings. Summary of the Invention

[0004] The purpose of this invention is to solve the above-mentioned technical problems and provide a low-level protection device for a turbine lubricating oil tank. This device has a simple structure and effectively avoids rapid leakage of lubricating oil from the oil suction interface on the side plate of the lubricating oil tank, thereby protecting the lubricating oil tank from low levels.

[0005] The technical solution for implementing this invention is as follows: it includes a vent pipe, an oil suction pipe, and an oil outlet pipe; the vent pipe and the oil suction pipe are connected by an intermediate pipe; the upper opening of the vent pipe is higher than the maximum shutdown liquid level, and the lower opening of the oil suction pipe is lower than the low-low liquid level; the oil outlet pipe is connected to the intermediate pipe and the oil suction pipe at the junction through a horizontal pipe with a perforated plate, forming a low-suction oil pipeline; the oil outlet pipe is horizontally led out of the side plate of the oil tank; a horizontal pipe is connected at the junction of the vent pipe and the intermediate pipe, and the other end of the horizontal pipe is connected to the oil outlet pipe through a downcomer, forming a high-suction oil pipeline; the horizontal pipe is parallel to the horizontal pipe with a perforated plate; the highest point of the inner wall of the horizontal pipe is flush with the low liquid level; the lowest point of the orifice diameter of the perforated plate in the horizontal pipe with a perforated plate is flush with the low-low liquid level.

[0006] The horizontal pipe consists of multiple parallel pipes, which are connected to the oil outlet pipes via multiple or the same downcomer pipe.

[0007] The protective device is vertically installed inside the lubricating oil tank via a bracket.

[0008] The upper opening of the vent pipe is positioned above the maximum shutdown liquid level to prevent air from entering the liquid surface when lubricating oil is drawn in through the vent pipe, thus avoiding the formation of vortices on the liquid surface.

[0009] The lowest oil suction point of the oil suction pipe is set at approximately 100mm from the bottom of the lubricating oil tank to ensure that oil is drawn from the bottom of the tank and to avoid drawing in oil sludge from the bottom of the tank.

[0010] The oil suction pipe opening is beveled to increase the oil suction port area and improve oil suction efficiency.

[0011] The perforated plate inside the horizontal tube with the perforated plate is a single-stage or multi-stage perforated plate.

[0012] The beneficial effects of this invention are:

[0013] 1. This invention can protect the oil tank from low liquid level and prevent a large amount of lubricating oil from leaking from external equipment and the oil suction interface on the side plate of the lubricating oil tank, thereby maintaining the low liquid level of the lubricating oil tank.

[0014] 2. This invention features two parallel oil suction protection pipelines, one high and one low. Utilizing the siphon effect, it employs a two-stage protection system for low oil levels in the turbine lubricating oil tank. When the oil level drops to the low level, the high-level protection of the first stage slows down the significant leakage of lubricating oil from the outlet pipe. When the oil level drops to the very low level, the low-level protection of the second stage promptly cuts off the oil suction from the external equipment, thus ensuring a very low oil level in the lubricating oil tank and preventing the turbine's main oil pump from drawing air, which could compromise turbine safety.

[0015] 3. When the oil level in the tank drops to a low level, this invention can, on the one hand, provide a minimum oil suction flow rate for the external equipment's oil suction pump, preventing vibration, overheating, and other malfunctions caused by the pump running dry due to a sudden drop in oil level, thus protecting the pump's safety. On the other hand, it can buy time to handle lubricating oil leaks, facilitating a quick restoration of the lubrication system and external equipment's operation.

[0016] 4. The two parallel oil suction lines of the present invention share the oil suction pipe, oil suction port tee, oil outlet tee and oil outlet pipe, thereby avoiding the multiple settings of redundant functional pipelines and simplifying the protection device.

[0017] 5. The vent pipe of this invention is positioned approximately 50mm above the maximum shutdown liquid level. Therefore, regardless of changes in the liquid level within the turbine lubricating oil tank, the small air-side space inside the protection device remains connected to the large air-side space of the external lubricating oil tank, ensuring that the liquid level inside the protection device and the external lubricating oil tank remain consistent. Simultaneously, it effectively prevents air from entering through the traditional oil suction port due to vortices generated on the liquid surface during oil suction, thus avoiding vibration of the external oil suction equipment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention.

[0019] Numbering in the diagram: 1—Ventilation pipe, 2—Upper support plate, 3—Upper tee, 4—Horizontal pipe, 5—Bend, 6—Downcomer pipe, 7—Oil outlet pipe, 8—Oil outlet tee, 9—Horizontal pipe with perforated plate, 10—Lower support plate, 11—Oil suction pipe, 12—Oil suction tee, 13—Intermediate pipe, 14—Oil tank top plate, 15—Oil tank bottom plate, 16—Oil tank side plate, 17—Lubricating oil tank, 18—Oil suction port of external connection equipment, 19—Oil tank suction port, 20—Maximum shutdown liquid level, 21—Low liquid level, 22—Very low liquid level. Detailed Implementation

[0020] Example 1

[0021] like Figure 1As shown, a low-level protection device for a turbine lubricating oil tank includes a vent pipe 1, an oil suction pipe 11, and an oil outlet pipe 7. The vent pipe 1 and the oil suction pipe 11 are connected by an intermediate pipe 13. The upper opening of the vent pipe 1 is higher than the maximum shutdown level 20, and the lower opening of the oil suction pipe 11 is lower than the low-low level 22. The oil outlet pipe 7 is connected to the intermediate pipe 13 and the oil suction pipe 11 by an oil suction tee 12 via a horizontal pipe 9 with a perforated plate, forming a low-suction oil pipeline. Oil pipe 7 extends horizontally out of oil tank side plate 16; at the junction of vent pipe 1 and intermediate pipe 13, a horizontal pipe 4 is connected via an upper tee 3. The horizontal pipe 4 is connected to a downcomer pipe 6 via a bend 5. The downcomer pipe 6 is connected to the oil outlet pipe 7 via an oil outlet tee 8, forming a high-suction oil pipeline; the horizontal pipe 4 is parallel to the horizontal pipe 9 with perforated plate; the highest point of the inner wall of the horizontal pipe 4 is flush with the low liquid level 21; the lowest point of the perforated plate in the horizontal pipe 9 with perforated plate is flush with the low liquid level 22. The protective device is supported by an upper support plate 2 and a lower support plate 10 and is vertically installed inside the lubricating oil tank 17 between the top plate 14 and the bottom plate 15 of the oil tank. The lowest oil suction point of the suction pipe 11 is set at approximately 100mm from the bottom of the lubricating oil tank to ensure oil is sucked from the bottom of the oil tank and to avoid sucking in oil sludge from the bottom of the oil tank. The suction pipe 11 has a beveled opening, thereby increasing the area of ​​the oil tank suction port 19 and improving the oil suction efficiency. The perforated plate inside the horizontal pipe 9 is a single-stage or multi-stage perforated plate. The external connection device for the oil tank draws oil through the external connection device suction port 18 connected to the oil outlet pipe 7.

[0022] Example 2

[0023] The difference from Embodiment 1 is that the horizontal pipe 4 consists of multiple parallel pipes, which are connected to the oil outlet pipe 7 via multiple downcomer pipes 6. The rest are the same.

[0024] Example 3

[0025] The difference from Embodiments 1 and 2 is that the perforated plate inside the horizontal tube 9 with the perforated plate is a multi-stage perforated plate. Everything else is the same.

[0026] The operating process and principle of this invention are as follows:

[0027] Taking Example 1 as an example, the present invention includes two parallel oil suction pipes with varying heights. The external connection device of the oil tank can draw oil from the oil suction pipe 11 through the high suction pipe formed by the horizontal pipe 4, and then draw it out through the oil suction port 18 of the external connection device of the oil outlet pipe 7 via the oil suction tee 12, intermediate pipe 13, upper tee 3, horizontal pipe 4, bend 5, downcomer 6, and oil outlet tee 8. Simultaneously, it also draws oil from the oil suction pipe 11 through the low suction pipe formed by the horizontal pipe 9 with a perforated plate, and then draws it out through the oil suction port 12, horizontal pipe 9 with a perforated plate, and oil outlet tee 8, and then draws it out through the oil outlet 18 of the external connection device of the oil outlet pipe 7. The two parallel oil suction pipes share the oil suction pipe 11, oil suction port tee 12, oil outlet tee 8, and oil outlet pipe 7, thereby avoiding multiple installations of redundant functional pipelines and simplifying the protection device. The entire protection device is fixed to the oil tank side plate 6 by welding through a bracket consisting of an upper support plate 2 and a lower support plate 10.

[0028] This invention includes a vertical venting pipe. The venting section, which changes with the oil tank level, mainly comprises a vent pipe 1, an upper tee 3, an intermediate pipe 13, and an oil suction tee 12. The vent pipe 1 is positioned approximately 50mm above the maximum shutdown oil level 20. Therefore, regardless of changes in the oil level within the turbine lubricating oil tank 17, the small air-side space inside the protection device remains connected to the large air-side space of the external lubricating oil tank, ensuring that the oil level inside the protection device and the external lubricating oil tank remain consistent. Simultaneously, it effectively prevents air from entering through the traditional oil suction port due to vortices generated on the oil surface during oil suction, thus avoiding vibration of the external equipment.

[0029] The main function of the high-suction oil pipeline of this invention is to provide the amount of lubricating oil needed for the normal operation of external connected equipment and to provide primary high-level protection against low liquid levels in the turbine lubricating oil tank. During normal operation of the turbine lubricating oil system, most of the lubricating oil required by the external connected equipment is provided by the high-suction oil pipeline, with a small portion provided by the low-suction oil pipeline. The lowest suction point of the suction pipe 11 is set approximately 100mm from the bottom of the lubricating oil tank 17. This ensures oil is drawn from the bottom of the lubricating oil tank 17 and avoids drawing in oil sludge from the bottom of the tank. Simultaneously, the suction pipe 11 has a beveled opening to increase the suction port area and improve suction efficiency. The highest point of the inner diameter of the horizontal pipe 4 in the high-suction oil pipeline is positioned flush with the low liquid level of the external oil tank, thus forming primary high-level protection against low liquid levels in the turbine lubricating oil tank 7. When an external connection device or pipeline malfunctions, causing an oil leak, lubricating oil will rapidly leak from the oil tank outlet. At this time, the lubricating oil level in tank 17 will gradually decrease. Since the internal level of the protection device and the external lubricating oil tank level remain consistent, when the tank level drops to the low level 21, the protection device's vent pipe, together with the high-suction oil pipe, will act as a siphon-breaking device, providing primary protection against low-level lubricating oil in tank 17. The flow rate of lubricating oil in the horizontal pipe 4 of the high-suction oil pipe will decrease as the lubricating oil level in the tank decreases, gradually slowing down the leakage of lubricating oil from the high-suction oil pipe. When the tank level drops to the lowest point of the horizontal pipe 4's inner diameter, the protection device will completely cut off the flow of lubricating oil from the high-suction oil pipe. After the protection device cuts off the flow of lubricating oil from the high-suction oil pipe, the lubricating oil supply at the equipment outlet will be provided solely by the low-suction oil pipe. The main function of the low-suction oil pipeline of the protection device is to provide the minimum operating lubricating oil volume for externally connected equipment and to provide secondary low-level protection for the low liquid level in the turbine lubricating oil tank 17.

[0030] In the low-suction oil pipeline of this invention, a throttling orifice plate is welded inside the horizontal pipe 9 with an orifice plate. Given the low lubricating oil suction pressure, a single-stage orifice plate is generally used. Figure 1 The protective device is illustrated by a single-stage orifice plate. The orifice diameter of the single-stage orifice plate is calculated using the following formula to ensure that the low-suction oil pipeline provides the minimum amount of lubricating oil required for the operation of externally connected equipment.

[0031]

[0032] In the formula:

[0033] d - orifice diameter of the throttling plate, in meters;

[0034] Q min -Minimum volumetric flow rate of lubricating oil required for the equipment, m³ 3 / h;

[0035] γ-Relative density under working conditions (compared to the density of water at 4°C);

[0036] △P - Differential pressure across the orifice plate, Pa;

[0037] C - Orifice plate flow coefficient (obtainable from the chart according to standard HG / T 20570.15-95);

[0038] Meanwhile, the lowest point of the orifice plate in the horizontal pipe 9 of the low-suction oil pipeline is set flush with the low-low level of the external oil tank, thus forming a secondary low-level protection for the turbine lubricating oil tank. When the lubricating oil tank level reaches the low-low level, the vent pipe of the protection device, together with the low-suction oil pipeline, will act as a siphon breaking device, playing a secondary low-level protection role for the lubricating oil tank, cutting off the flow of lubricating oil from the equipment outlet, thereby maintaining the minimum amount of lubricating oil required for turbine safety.

[0039] When the lubricating oil level in tank 17 drops to the low level 21, a low level alarm is typically triggered, notifying the operator to investigate the cause and resolve the issue. At this time, the primary protection device cuts off the lubricating oil supply from the high-suction oil line, slowing the rapid leakage of lubricating oil through the external equipment's outlet. Simultaneously, the protection device continues to supply the external equipment with a minimum flow rate of lubricating oil through the low-suction oil line. This setup protects the external equipment's suction pump, preventing sudden lubricating oil cutoff from causing cavitation, vibration, and affecting subsequent normal equipment operation. Furthermore, because the lubricating oil level in tank 17 drops to the very low level, only the minimum flow rate of lubricating oil required by the equipment is supplied through the low-suction oil line during this period, operators have more time to handle the incident without needing to shut down the external equipment and lubrication system. It also facilitates the rapid restoration of the lubrication system and external equipment's normal operation after the incident is resolved.

[0040] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A low-level protection device for a steam turbine lubricating oil tank, characterized in that: The protective device is vertically installed inside the lubricating oil tank via a bracket, and includes a vent pipe, an oil suction pipe, and an oil outlet pipe. The vent pipe and the oil suction pipe are connected by an intermediate pipe. The upper opening of the vent pipe is higher than the maximum shutdown liquid level, and the lower opening of the oil suction pipe is lower than the low-low liquid level. The oil outlet pipe is connected to the oil suction pipe at the junction of the intermediate pipe and the oil suction pipe through a horizontal pipe with a perforated plate, forming a low oil suction pipeline. The oil outlet pipe extends horizontally out of the side plate of the oil tank; A horizontal pipe is connected at the junction of the vent pipe and the intermediate pipe. The other end of the horizontal pipe is connected to the oil outlet pipe through the downcomer, forming a high oil suction pipeline. The horizontal tube is parallel to the horizontal tube with the perforated plate; The highest point of the inner wall of the horizontal pipe is flush with the low liquid level; The lowest point of the orifice in the horizontal pipe with the orifice plate is flush with the low liquid level. The low liquid level refers to the lowest liquid level during normal operation of the steam turbine. The term "low liquid level" refers to the liquid level at which the turbine is shut down.

2. The turbine lubricating oil tank low level protection device according to claim 1, characterized in that: The horizontal pipe consists of multiple parallel pipes, which are connected to the oil outlet pipes via multiple or the same downcomer pipe.

3. The turbine lubricating oil tank low level protection device according to claim 1, characterized in that: The upper opening of the vent pipe is positioned above the maximum shutdown liquid level to prevent air from entering the liquid surface when lubricating oil is drawn in through the vent pipe, thus avoiding the formation of vortices on the liquid surface.

4. The turbine lubricating oil tank low level protection device according to claim 1, characterized in that: The lowest oil suction point of the oil suction pipe is set at approximately 100mm from the bottom of the lubricating oil tank to ensure that oil is drawn from the bottom of the tank and to avoid drawing in oil sludge from the bottom of the tank.

5. The turbine lubricating oil tank low level protection device according to claim 1, characterized in that: The oil suction pipe opening is beveled to increase the oil suction port area and improve oil suction efficiency.

6. The turbine lubricating oil tank low level protection device according to claim 1, characterized in that: The perforated plate inside the horizontal tube with the perforated plate is a single-stage or multi-stage perforated plate.

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