Oil mixing prevention oil pump structure on floating production storage and offloading (FPSO) ship

Abstract

The invention relates to the technical field of ocean engineering equipment pump set sealing, in particular to an FPSO ship oil mixing prevention oil pump structure which comprises an oil pump shell, a bottom plate, an oil pump cover plate and a pump shaft arranged on the oil pump shell in a penetrating mode, the oil pump shell and the oil pump cover plate are matched to form a sealing installation cavity, and a main sealing plate and an auxiliary sealing plate are arranged in the sealing installation cavity. The main sealing plate and the auxiliary sealing plate are mechanical sealing components which are coaxially arranged along the pump shaft in a sleeved mode, and an isolation cavity is formed between the main sealing plate and the auxiliary sealing plate. The isolation cavity is communicated with a flow guide pipe through a flow drainage opening, the flow guide pipe is communicated with a flow drainage pipe, a throttling orifice plate and / or a reducing section pipe are / is arranged in the flow drainage pipe, the downstream of the flow drainage pipe is connected with a check valve, and the downstream of the check valve is connected with an anti-siphon pipe and leads to a collecting barrel and a recycling pipe, so that controllable discharge of leaked fluid in the isolation cavity is achieved, and backflow is restrained; the main sealing plate is an inner ring type mechanical sealing component close to the pump shaft, and the auxiliary sealing plate is an outer ring type mechanical sealing component coaxially arranged on the periphery of the main sealing plate in a sleeving mode.

Description

Technical Field

[0001] This invention relates to the field of sealing technology for pump sets in marine engineering equipment, specifically a structure for an anti-oil-crossing pump on an FPSO vessel. Background Technology

[0002] FPSO (Floating Production System) pump sets are typically used for the transport and circulation of crude oil, water-containing oil, chemical processing media, and related auxiliary media. Their operating environment is characterized by high salt spray, high humidity, large temperature variations, strong vibration and shock, and frequent hull rolling and tilting. The pump set's sealing areas are high-risk areas for leakage and contamination; once the seals fail or even a small leak occurs, the following problems can easily arise: 1. Significant issues of oil cross-contamination and leakage: Pump units often contain both process medium chambers and lubricating oil chambers. After seal failure, the process medium may enter the lubricating oil side along the pump shaft and seal gap, causing lubricating oil emulsification, decreased lubrication performance, and increased bearing heat and wear. Conversely, lubricating oil may also enter the process medium side, causing the process medium to be contaminated with oil, affecting subsequent separation, metering, or chemical treatment, and bringing environmental and safety risks. For FPSO platforms, the cost of handling media leaks and oil contamination is high, and maintenance windows are limited, making oil cross-contamination a clearly costly problem. 2. Hull rolling and pressure fluctuations make "backflow-injection-secondary oil leakage" more likely to occur. Under fixed land-based operating conditions, leaked liquid can usually be discharged through discharge or recovery pipelines. However, under FPSO operating conditions, continuous hull rolling causes changes in the liquid column height in the pipeline, and the pump unit's operating conditions may also experience pressure pulsations with load switching. When the discharge or recovery pipeline is connected to the sealed isolation chamber, if there is a lack of stable flow and anti-backflow measures, the following typical failure chain can easily occur: pressure fluctuations cause transient negative pressure or suction in the discharge branch, and the liquid in the isolation chamber is drawn back and splashed with gas; changes in hull attitude and changes in pipeline liquid level create siphon conditions, and the liquid at the recovery end flows back into the isolation chamber along the pipeline; the backflowing liquid accumulates in the isolation chamber and is pushed to the weak point of the seal when the pressure changes, and then flows into the lubricating oil side or the process side for secondary oil leakage. The above phenomenon often manifests as "repeated oil leakage or early seal failure despite the discharge and recovery system being set up," which is a typical challenge in offshore platform applications. Given the shortcomings of the existing technologies, developing a comprehensive technology that simultaneously meets the requirements of preventing oil spillage, preventing backflow, resisting corrosion, and facilitating maintenance under conditions of hull rolling and pressure fluctuation has become an urgent technical problem to be solved. Summary of the Invention

[0003] The purpose of this invention is to provide an anti-cross-oil pump structure for FPSO vessels to solve the problems mentioned in the background art.

[0004] The technical solution adopted by this application to solve its technical problem is: an anti-cross-oil pump structure on an FPSO ship, including a pump housing, a base plate, a pump cover plate and a pump shaft passing through the pump housing, characterized in that: the pump housing and the pump cover plate cooperate to form a sealed mounting cavity, and the sealed mounting cavity is provided with a sealing component: the sealing component is used to form a sealed space; The sealing assembly includes a main sealing plate and a secondary sealing plate disposed within the sealing mounting cavity. The main sealing plate and the secondary sealing plate are mechanical sealing components arranged in a ring-like manner along the pump shaft, and an isolation cavity is formed between them. The isolation chamber is connected to the guide pipe through the drain port. The guide pipe is connected to the drain pipe. The drain pipe is equipped with a throttling orifice plate and / or a reduced diameter section pipe. A check valve is connected downstream of the drain pipe. The check valve is connected through the mounting hole. Downstream of the check valve is an anti-siphon pipe that leads to the collection cylinder and the recovery pipe, so as to realize the controllable discharge of leaked fluid in the isolation chamber and suppress backflow.

[0005] Preferably, the main sealing plate is an inner ring mechanical seal component close to the pump shaft, the secondary sealing plate is an outer ring mechanical seal component coaxially sleeved on the outer periphery of the main sealing plate, and the isolation cavity is an annular cavity formed by the outer peripheral surface of the main sealing plate and the inner peripheral surface of the secondary sealing plate.

[0006] Preferably, the drain port is located in the lower region of the oil pump housing, and the guide pipe is connected to the drain port and guides the fluid in the isolation chamber into the drain pipe.

[0007] Preferably, the drain pipe is connected to the side of the oil pump housing via an extension pipe, and the extension pipe has an external thread on its outer circumference so that the drain pipe and the extension pipe form a detachable structure with a threaded connection.

[0008] Preferably, the orifice plate is disposed in the cavity of the drain pipe, and the orifice plate is provided with at least one flow hole; the orifice plate is positioned and installed in the drain pipe by mounting protrusions to limit the displacement of the orifice plate in the axial and circumferential directions.

[0009] Preferably, the reduced-diameter section pipe is disposed inside the drain pipe and forms a reduced-diameter flow channel transitioning from a large radial diameter to a small diameter, which is used to reduce the backflow and stabilize the discharge conditions of the isolation chamber when pressure fluctuates.

[0010] Preferably, the check valve has a flow port and is provided with a flip plate that cooperates with the flow port to open and close, and a reset torsion spring for driving the flip plate to reset, so as to form a one-way cut-off to the drain pipe in the return direction.

[0011] Preferably, the check valve is provided with an adjustment handle for adjusting the opening resistance and / or preload of the tilting plate; the check valve is provided with a thickened plate to improve the structural strength and vibration resistance reliability of the check valve.

[0012] Preferably, the anti-siphon pipe is an elevated circuit structure connected between the check valve and the collection cylinder to form a high-level section, thereby suppressing siphon backflow; the recovery pipe is provided with vent holes for pressure balance.

[0013] Preferably, the oil pump housing is connected to the oil pump cover plate by a reinforcing rod to improve the overall rigidity and vibration resistance of the sealed mounting cavity.

[0014] The beneficial effects of this application are: This application provides a structure for an anti-cross-flow oil pump on an FPSO vessel. 1. Both the main sealing plate and the auxiliary sealing plate are mechanical seal components, and are coaxially fitted along the pump shaft to form an inner ring and an outer ring structure; the main sealing plate is located on the side closer to the pump shaft, and the auxiliary sealing plate is coaxially fitted on the outer circumference of the main sealing plate; an isolation cavity is formed between the main sealing plate and the auxiliary sealing plate to receive the minor leakage of the main sealing plate or the auxiliary sealing plate during operation, so that the leaking fluid preferentially enters the isolation cavity rather than directly enters the external area, thereby reducing the risk of oil cross-contamination.

[0015] 2. The orifice plate and the reduced diameter section of the pipe suppress transient backflow and splashing under pressure fluctuations, while the check valve and anti-siphon pipe further block backflow and prevent secondary oil leakage in the isolation chamber.

[0016] 3. The check valve has a flow port and is equipped with a flap plate that opens and closes in conjunction with the flow port, as well as a return torsion spring for driving the flap plate to return to its original position. This allows the flap plate to open when the fluid in the drain pipe is flowing in the forward direction and to close under the action of the return torsion spring in the backflow direction, thus forming a one-way shut-off to prevent backflow. The check valve may be equipped with an adjustment handle to adjust the opening resistance and / or preload of the flap plate. A thickened plate may be installed at the check valve to improve structural strength and vibration resistance reliability. The check valve and the drain pipe may be connected as an integral unit or as a detachable unit.

[0017] 4. The check valve is connected to an anti-siphon pipe downstream. The anti-siphon pipe is a raised circuit structure, which makes the drainage circuit rise to a high point near the pump body and then descend to connect to the collection cylinder, thereby suppressing siphon backflow. The collection cylinder is used to collect the leaked fluid. The collection cylinder is connected to the recovery pipe to guide the leaked fluid to the recovery end. The recovery pipe is equipped with a vent for pressure balance, reducing the probability of backflow or suction caused by negative pressure at the recovery end.

[0018] In addition to the purposes, features, and advantages described above, this application has other purposes, features, and advantages. These will be further described in detail below with reference to figures. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the internal structure of the present invention; Figure 3 This is a first-view schematic diagram of the oil pump housing of the present invention; Figure 4 This is a second-view schematic diagram of the oil pump housing of the present invention; Figure 5 This is a partial cross-sectional view of the oil pump housing of the present invention; Figure 6 This is a partial cross-sectional view of the secondary sealing plate of the present invention; Figure 7 This is a partial cross-sectional view of the drain pipe of the present invention; Figure 8 This is a schematic diagram of the throttling orifice plate of the present invention; Figure 9 This is a partial schematic diagram of the check valve of the present invention; Figure 10 This is a schematic diagram of the liquid flow direction in the orifice plate of the present invention; Figure 11 This is a schematic diagram of the reduced diameter section of the pipe of the present invention.

[0020] Drawing number explanation: 1. Mounting frame; 2. Control panel; 3. Generator set; 4. Cooling fan; 5. Delivery pipe assembly; 6. Oil pump housing; 7. Base plate; 8. Oil pump cover plate; 9. Pump shaft; 10. Reinforcing rod; 11. Extension pipe; 12. External thread; 13. Drain pipe; 14. Protective shell; 15. Main sealing plate; 16. Secondary sealing plate; 17. Isolation chamber; 18. Drain port; 19. Guide pipe; 20. Reduced diameter section pipe; 21. Check valve; 22. Mounting hole; 23. Adjusting handle; 24. Anti-siphon pipe; 25. Collection cylinder; 26. Throttling orifice plate; 27. Flow hole; 28. Mounting protrusion; 29. ​​Recovery pipe; 30. Vent hole; 31. Flow port; 32. Flip plate; 33. Thickened plate; 34. Return torsion spring; 35. Sealed mounting chamber. Detailed Implementation

[0021] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.

[0023] Please refer to Figures 1 to 3 A structure for an anti-cross-oil pump on an FPSO ship, such as Figure 1 and Figure 2 As shown, the present invention includes a mounting frame 1, an operating platform 2, a generator set 3, a cooling fan 4, and a delivery pipe assembly 5; the mounting frame 1 provides a load-bearing and installation space for the pump set and its accessories; the operating platform 2 is used to realize start-up, shutdown, monitoring, and maintenance operations; the generator set 3 provides a power source for the oil pump or supplies power to related control systems; the cooling fan 4 is used to dissipate heat from the generator set 3 and the surrounding environment of the pump set, reducing the risk of seal failure due to temperature rise; the delivery pipe assembly 5 is used to connect the oil pump to external process pipelines or a recovery system; The oil pump housing 6 and the oil pump cover plate 8 cooperate to form a sealed mounting cavity 35. The sealed mounting cavity 35 is provided with a sealing assembly: the sealing assembly is used to form a sealed space; the sealing assembly includes a main sealing plate 15 and a secondary sealing plate 16 disposed in the sealed mounting cavity 35. The main sealing plate 15 and the secondary sealing plate 16 are mechanical sealing components arranged in a coaxial ring along the pump shaft 9, and an isolation cavity 17 is formed between them; the oil pump housing 6 is fixed on the base plate 7 and installed in the mounting frame 1. The base plate 7 is used to improve the overall structural stability and facilitate overall hoisting; the oil pump housing 6 and the oil pump cover plate 8 cooperate to form a sealed mounting cavity 35, which is the installation space for the sealing components and the drainage circuit; the pump shaft 9 passes through the oil pump housing 6 and is connected to the pump group transmission structure. The pump shaft 9 forms a rotary sealing interface during operation; To improve the overall rigidity and vibration resistance of the oil pump housing 6 and the oil pump cover plate 8, a reinforcing rod 10 can be provided between the oil pump housing 6 and the oil pump cover plate 8. Preferably, the reinforcing rod 10 is distributed along the connection area between the oil pump housing 6 and the oil pump cover plate 8 to improve the uniformity of circumferential force on the sealing installation cavity 35, reduce the deformation of the sealing cavity caused by hull vibration and impact load, thereby improving the alignment stability and end face fit reliability of the main sealing plate 15 and the secondary sealing plate 16.

[0024] Please refer to Figures 3 to 6 An anti-cross-flow oil pump structure for an FPSO vessel includes a main sealing plate 15 and a secondary sealing plate 16 within a sealed mounting cavity 35. Both the main sealing plate 15 and the secondary sealing plate 16 are mechanical seal components and are coaxially fitted along the pump shaft 9 to form an inner and outer ring structure. The main sealing plate 15 is located on the side closer to the pump shaft 9 and serves as the first barrier to the leakage path near the pump shaft 9. The secondary sealing plate 16 is coaxially fitted around the outer periphery of the main sealing plate 15 and serves as the second barrier to the leakage path on the outer periphery of the main sealing plate 15, thereby forming a "radial nested" sealing system with dual mechanical seals. An isolation chamber 17 is formed between the main sealing plate 15 and the secondary sealing plate 16. The isolation chamber 17 is an annular space, preferably a circumferentially continuous annular cavity, so that the leaked fluid can still be uniformly received in the isolation chamber 17 when the hull rolls or the installation attitude changes, and it is not easy to form local concentrated splashes or irregular backflow paths. The isolation chamber 17 is used to receive the small amount of leakage from the main sealing plate 15 or the secondary sealing plate 16 during the operation, so that the leaked fluid preferentially enters the isolation chamber 17 rather than directly enters the external area, thereby reducing the risk of oil cross-contamination and facilitating subsequent drainage and recovery. The isolation chamber 17 is provided with a drain port 18, which is connected to the guide pipe 19 to guide the leaked fluid in the isolation chamber 17 to the drain circuit. Preferably, the drain port 18 is located in a relatively low area of ​​the isolation chamber 17 so that the liquid in the isolation chamber 17 can naturally collect and be discharged under the action of gravity. At the same time, several drain ports 18 can be provided around the isolation chamber 17 to adapt to different installation directions or swaying postures. The guide pipe 19 can be configured as a flow channel integrally formed with the oil pump housing 6 or as an independent pipe structure, and is connected to the drain pipe 13. Using an integrally formed flow channel reduces exposed connection points and lowers the risk of corrosion and leakage. Using an independent pipe structure facilitates maintenance, replacement, and layout optimization, making it suitable for space-constrained or frequently maintained operating conditions. like Figure 7 As shown, the guide pipe 19 is connected to the drain pipe 13, and the drain pipe 13 is connected to the side of the oil pump housing 6 through the extension pipe 11; the extension pipe 11 is provided with an external thread 12 on its outer periphery, so that the drain pipe 13 and the extension pipe 11 can be connected by a threaded detachable connection, which improves the convenience of maintenance; preferably, a sealing structure (such as a sealing gasket or sealing ring) is provided at the connection of the external thread 12 to avoid leakage caused by vibration loosening or corrosion at the threaded connection; A protective shell 14 may be provided on the outside of the drain pipe 13 to isolate corrosive media in the marine environment and protect the drain pipe 13 and related connecting parts; preferably, the protective shell 14 covers the key connection area and valve area of ​​the drain pipe 13 to reduce direct erosion by salt spray and reduce structural damage caused by external impact; the protective shell 14 may be made of corrosion-resistant materials or have a surface anti-corrosion treatment structure.

[0025] like Figure 8 and Figure 10 As shown, a throttling orifice plate 26 is provided in the cavity of the drain pipe 13, and at least one flow hole 27 is provided on the throttling orifice plate 26; the throttling orifice plate 26 is positioned and installed in the drain pipe 13 by mounting protrusion 28 to limit the axial and / or circumferential displacement of the throttling orifice plate 26, so as to avoid displacement under pressure pulsation or pipeline vibration, which would cause changes in throttling characteristics. The orifice plate 26 is used to limit transient flow when the differential pressure fluctuates, reduce the risk of backflow and splashing, and improve the stability of the drainage condition. Its working mechanism is as follows: when the external recovery end pressure drops for a short time or the liquid level in the pipeline changes and causes a suction tendency, the flow hole 27 forms a local resistance to the fluid, reducing the speed at which the liquid in the isolation chamber 17 is temporarily drawn away, and reducing gas-liquid entrainment and splashing. When the external pressure rises for a short time or a backflow tendency occurs, the orifice plate 26 can also reduce the backflow flow, providing more stable operating conditions for the closure of the check valve 21. Preferably, the flow orifice 27 can be a single-hole or multi-hole structure. The multi-hole structure can reduce the risk of blockage and improve the uniformity of flow distribution. The throttling orifice plate 26 can be designed as a detachable and replaceable structure so as to adjust the throttling characteristics according to different operating conditions.

[0026] like Figure 11 As shown, a reduced-diameter section pipe 20 can also be installed inside the discharge pipe 13. The reduced-diameter section pipe 20 forms a reduced-diameter flow channel transitioning from a large radial diameter to a small diameter, which is used to further reduce the backflow and stabilize the discharge state of the isolation chamber 17 under the conditions of hull rolling and pressure fluctuation. The working mechanism of the reduced-diameter section pipe 20 is to generate friction resistance and local pressure loss through the reduced-diameter flow channel, thereby "damping" the transient flow. The orifice plate 26 and the reduced-diameter section pipe 20 can be installed separately or in combination. When installed in combination, the orifice plate 26 provides a clear orifice throttling characteristic, and the reduced-diameter section pipe 20 provides additional friction loss and flow stabilization effects. Together, they improve the ability to resist pressure fluctuations, so that the isolation chamber 17 can still maintain a controllable discharge state under complex conditions.

[0027] like Figure 9As shown, a check valve 21 is connected downstream of the drain pipe 13. The check valve 21 is connected through a mounting hole 22. The check valve 21 has a flow port 31 and is equipped with a tilting plate 32 that cooperates with the flow port 31 to open and close, and a return torsion spring 34 for driving the tilting plate 32 to return to its original position. During operation, when the fluid in the drain pipe 13 flows in the forward direction into the check valve 21, the tilting plate 32 opens under the action of the fluid. When a backflow trend occurs, the tilting plate 32 quickly returns to its original position and closes under the action of the return torsion spring 34, thereby forming a one-way cutoff to prevent backflow. The check valve 21 can be equipped with an adjusting handle 23 to adjust the opening resistance and / or preload of the tilting plate 32, so that the opening sensitivity of the check valve 21 can be adjusted according to different working conditions, taking into account the discharge direction. Smooth flow and backflow prevention reliability; a thickened plate 33 can be installed at the check valve 21 to improve structural strength and vibration resistance reliability, especially suitable for long-term vibration environment of FPSO; the check valve 21 and the drain pipe 13 can be connected as an integral part or as a detachable connection, preferably a detachable connection for easy maintenance and replacement; the check valve 21 is connected downstream of the anti-siphon pipe 24; the anti-siphon pipe 24 is a raised circuit structure, so that the drain circuit rises to a high point near the pump body and then descends to connect to the collection cylinder 25, thereby suppressing siphon backflow; the anti-siphon pipe 24 forms a liquid column height difference through geometric elevation, so even if the liquid level at the recovery end changes or the external pipeline has a siphon tendency, it is difficult for the liquid at the recovery end to backflow into the isolation chamber 17 without sufficient pressure difference; The collection cylinder 25 is used to collect the leaked fluid in a centralized manner. The collection cylinder 25 is connected to the recovery pipe 29 to guide the leaked fluid to the recovery end. The recovery pipe 29 is provided with a vent 30 for pressure balance to reduce the probability of backflow or backflow caused by negative pressure at the recovery end. Preferably, the vent 30 is located at the upper part of the recovery pipe 29 near the collection cylinder 25 to reduce the possibility of liquid clogging the vent 30.

[0028] Working process: When the pump unit is running, the main sealing plate 15 and the auxiliary sealing plate 16 form a seal around the pump shaft 9. When a small leak occurs in the main sealing plate 15 or the auxiliary sealing plate 16, the leaking fluid preferentially enters the isolation chamber 17 and then enters the guide pipe 19 through the drain port 18, and subsequently enters the drain pipe 13. Under pressure fluctuations or ship swaying conditions, the throttling orifice plate 26 and / or the reduced diameter section pipe 20 limit and stabilize the flow in the drain channel, suppressing transient backflow and splashing. The check valve 21 automatically closes in the backflow direction to block backflow. The anti-siphon pipe 24 reduces the possibility of siphon backflow by raising the circuit. The leaking fluid finally enters the collection cylinder 25 and is recovered through the recovery pipe 29, thereby achieving controllable discharge of leakage from the isolation chamber 17 and avoiding secondary oil cross-contamination.

[0029] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary. Under the framework of this invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

[0030] This invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A structure for an anti-cross-flow oil pump on an FPSO vessel, comprising a mounting frame (1), an operating platform (2), a generator set (3), a cooling fan (4), and a delivery pipe assembly (5), and also including an oil pump housing (6), a base plate (7), an oil pump cover plate (8), and a pump shaft (9) passing through the oil pump housing (6), characterized in that: The oil pump housing (6) and the oil pump cover plate (8) cooperate to form a sealed mounting cavity (35), and the sealed mounting cavity (35) is provided with a sealing assembly: the sealing assembly is used to form a sealed space; The sealing assembly includes a main sealing plate (15) and a secondary sealing plate (16) disposed in the sealing mounting cavity (35). The main sealing plate (15) and the secondary sealing plate (16) are mechanical seal components coaxially arranged in a ring shape along the pump shaft (9), forming an isolation cavity (17) between them. A protective shell (14) is provided on the pump shaft (9). The main sealing plate (15) is an inner ring mechanical seal component close to the pump shaft (9), and the secondary sealing plate (16) is an outer ring mechanical seal component coaxially sleeved on the outer periphery of the main sealing plate (15). The isolation cavity (17) is an annular cavity formed by the outer peripheral surface of the main sealing plate (15) and the inner peripheral surface of the secondary sealing plate (16). The isolation chamber (17) is connected to the guide pipe (19) through the drain port (18). The guide pipe (19) is connected to the drain pipe (13). The drain pipe (13) is provided with a throttling orifice plate (26) and / or a reduced diameter section pipe (20). The downstream of the drain pipe (13) is connected to a check valve (21). The check valve (21) is connected through the mounting hole (22). The downstream of the check valve (21) is connected to an anti-siphon pipe (24) and leads to the collection cylinder (25) and the recovery pipe (29) to achieve controlled discharge of leaked fluid in the isolation chamber (17) and suppress backflow.

2. The anti-cross-oil pump structure for an FPSO ship according to claim 1, characterized in that, The drain port (18) is located in the lower region of the oil pump housing (6), and the guide pipe (19) is connected to the drain port (18) and guides the fluid in the isolation chamber (17) into the drain pipe (13).

3. The structure of an anti-cross-oil pump on an FPSO ship according to claim 1, characterized in that, The drain pipe (13) is connected to the side of the oil pump housing (6) through the extension pipe (11). The extension pipe (11) is provided with an external thread (12) on its outer periphery so that the drain pipe (13) and the extension pipe (11) form a detachable structure with a threaded connection.

4. The anti-cross-oil pump structure for an FPSO ship according to claim 3, characterized in that, The orifice plate (26) is located in the cavity of the drain pipe (13), and the orifice plate (26) is provided with at least one flow hole (27); the orifice plate (26) is positioned and installed in the drain pipe (13) by mounting protrusions (28) to limit the displacement of the orifice plate (26) in the axial and circumferential directions.

5. The anti-cross-oil pump structure for an FPSO ship according to claim 1, characterized in that, The reduced diameter section pipe (20) is installed inside the drain pipe (13) and forms a reduced diameter flow channel with a large radial diameter transition, which is used to reduce the backflow and stabilize the discharge conditions of the isolation chamber (17) when the pressure fluctuates.

6. The anti-cross-oil pump structure for an FPSO ship according to claim 1, characterized in that, The check valve (21) has a flow port (31) and is provided with a flip plate (32) that cooperates with the flow port (31) to open and close, and a reset torsion spring (34) for driving the flip plate (32) to reset, so as to form a one-way cut-off to the drain pipe (13) in the return direction.

7. The anti-cross-oil pump structure for an FPSO ship according to claim 1, characterized in that, The check valve (21) is provided with an adjustment handle (23) for adjusting the opening resistance and / or pre-tightening force of the flip plate (32); the check valve (21) is provided with a thickened plate (33) to improve the structural strength and vibration resistance reliability of the check valve (21).

8. The anti-cross-oil pump structure for an FPSO vessel according to claim 7, characterized in that, The anti-siphon pipe (24) is a raised circuit structure and is connected between the check valve (21) and the collection cylinder (25) to form a high section to suppress siphon backflow; the recovery pipe (29) is provided with a vent hole (30) for pressure balance.

9. The anti-cross-oil pump structure for an FPSO ship according to claim 8, characterized in that, The oil pump housing (6) is connected to the oil pump cover plate (8) by a reinforcing rod (10) to improve the overall rigidity and vibration resistance of the sealed mounting cavity (35).

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