Quick gas replacement device and system for cleaning storage tank

Abstract

The invention discloses a gas rapid replacement device and system for cleaning a storage tank, the device can be applied before and / or in the cleaning process of the storage tank, and the device at least comprises a manhole sealing bin which is defined by an upper bin body and a lower bin body; the upper bin body and the lower bin body are detachably connected in a sealed mode, and a matching opening matched with a manhole flange neck is formed in one end of the installed manhole sealing bin. The flange fixer is of an ejector rod and fixed disc structure; the fixing disc is arranged in a manhole sealing bin and matched with a manhole flange plate in structure and size, and the manhole flange plate can be selectively clamped and released through telescopic fixing claws. The ejector rod extends out of the manhole sealing bin and provides operation power for the fixing claw. The storage tank manhole serves as a gas channel for gas replacement, so that gas replacement and robot access share the channel, gas replacement can be achieved before and in the storage tank cleaning process, and harm caused by gas escape can be effectively prevented through arrangement of the manhole sealing bin and the flange plate fixator.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and in particular to a rapid gas replacement device and system for cleaning storage tanks. Background Technology

[0002] Gas replacement in petrochemical storage tanks generally falls into two categories: one is replacement of tanks that have been in production for many years and require maintenance; the other is replacement of newly built tanks or tanks that have passed maintenance and are ready to be put into production. The replacement principle is the same in both cases: first, a carrier (such as nitrogen) is used to replace the original medium, and then the target medium is used to replace the carrier. The carrier is used to complete the exchange of the two media, preventing them from mixing directly and exploding upon contact with fire.

[0003] General nitrogen purging method: Open the vent valve of the storage tank to release the remaining liquid in the tank. When the pressure drops to about 5000 Pa, close the vent valve. Maintain the pressure inside the tank at 3000-5000 Pa. Purge the pipeline connecting the storage tank to the purging gas pipeline and introduce nitrogen gas. Control the nitrogen flow rate to maintain the pressure inside the tank at 3000-5000 Pa. Measure and record the combustible gas and oxygen content at the outlet at regular intervals. Adjust the purging gas flow rate and time in real time based on these two indicators. The purging is considered successful when the content of combustible gas is below the lower limit of the explosion limit and the oxygen content is less than 1%.

[0004] Chinese patent application CN109269845A discloses an online sampling and monitoring system and method for mixed gas in an internal floating roof storage tank. The system includes a sampling pipe assembly, an air pump, a gas detection and analysis device, and a control unit. The storage tank includes a tank body and an elliptical top end cap. The sampling pipe assembly includes a main pipe and several branch pipes. One end of the main pipe extends outside the storage tank, and the other end extends vertically to both sides, branching into several sets of branch pipes at equal intervals. A solenoid valve is installed at the lower end of the main pipe, and miniature pneumatic pumps are installed at both ends of the branch pipes. The end of the main pipe extending outside the storage tank is connected to the air inlet of the air pump, and the air outlet of the air pump is connected to the gas detection and analysis device. Although this type of solution can displace the gas inside the tank, it requires a dedicated gas outlet, has low displacement efficiency, and lacks effective gas escape prevention measures.

[0005] When storage tanks require cleaning, especially using robotic cleaning, existing gas replacement methods often suffer from narrow gas replacement channels, resulting in low efficiency. Furthermore, these channels are not shared with the robot's access channels (manholes), increasing the risk of gas leaks. Additionally, the use of manholes can allow flammable hydrocarbons and toxic hydrogen sulfide to escape and diffuse into the air, posing hazards to the environment and personnel. Moreover, explosion-proof considerations are crucial for storage tank gas replacement. Explosive atmospheres are categorized into three zones—Zone 0, Zone 1, and Zone 2—based on the frequency and duration of gas occurrence. Zone 0 indicates a continuous or prolonged presence of explosive gas; Zone 1 indicates a potential for explosive gas atmospheres during normal operation; and Zone 2 indicates an unlikely, or only occasional, short-lived explosive gas atmosphere during normal operation. In oil and gas environments, equipment must meet the corresponding explosion-proof rating, and equipment with different explosion-proof ratings can only be used in specific environments. Equipment with Zone 0 explosion-proof certification can be used in any area. Equipment with Zone 1 explosion-proof certification can be used in both Zone 1 and Zone 2 environments. Equipment with Zone 2 explosion-proof certification can only be used in Zone 2 environments. Storage tanks typically contain large amounts of flammable gases, constituting a Zone 0 explosive gas environment. For existing robots with only Zone 1 explosion-proof certification, cleaning the tank requires changing the environment inside to Zone 1. This can be achieved by replacing the gas inside the tank.

[0006] Therefore, there is an urgent need for a rapid gas replacement device and system for tank cleaning that can not only rapidly replace gas through the manhole of the tank, but also achieve gas replacement before and during tank cleaning, and effectively prevent the hazards caused by gas leakage.

[0007] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0008] The purpose of this invention is to provide a rapid gas replacement device and system for tank cleaning. The gas replacement is carried out through the manhole of the tank as a gas channel, so that the gas replacement and robot entry and exit share the same channel. Gas replacement can be achieved not only before and during tank cleaning, but also through the setting of manhole sealing chamber and flange fixation device to effectively prevent the hazards caused by gas leakage.

[0009] To achieve the above objectives, according to a first aspect of the present invention, the present invention provides a rapid gas replacement device for tank cleaning, applied before and / or during tank cleaning, comprising at least: a manhole sealing chamber, which is formed by an upper chamber and a lower chamber; the upper chamber and the lower chamber are detachably and sealingly connected, and one end of the installed manhole sealing chamber is provided with a mating port adapted to the neck of a manhole flange; a flange retainer, which is a push rod and a fixing plate structure; the fixing plate is disposed in the manhole sealing chamber and adapted to the structure and size of the manhole flange, and can selectively clamp and release the manhole flange by means of a retractable fixing claw; the push rod extends out of the manhole sealing chamber and provides operating power for the fixing claw.

[0010] Furthermore, in the above technical solution, a gear may be provided in the center of the fixed disk on the side facing the top rod. The gear is fixedly connected to one end of the top rod and can rotate relative to the disk body of the fixed disk.

[0011] Furthermore, in the above technical solution, the fixed disk can have three channels evenly spaced along the circumference to accommodate three retractable fixed claws; the fixed claws can be a single-sided rack and pinion structure that meshes with a gear.

[0012] Furthermore, in the above technical solution, the outer end of the fixing claw may be provided with a V-shaped groove that matches the thickness of the manhole flange, for clamping and fixing the manhole flange.

[0013] Furthermore, in the above technical solution, a bearing seal can be provided at the part of the push rod that passes through the manhole sealing chamber; a rotating disk can be provided at the outer end of the push rod for operating the rotation of the push rod.

[0014] Furthermore, in the above technical solution, the upper and lower compartments can be sealed and connected by bosses and bolts.

[0015] Furthermore, in the above technical solution, the top of the upper compartment may be equipped with an air inlet, a pressure measuring port, and a gas analysis port. The bottom of the lower compartment may be equipped with an oil sludge discharge port.

[0016] According to a second aspect of the present invention, the present invention provides a rapid gas replacement system for tank cleaning, employing any of the foregoing rapid gas replacement devices. The system comprises two devices, each disposed at a different manhole location opposite to the tank. One device is used to draw the gas to be replaced from the tank, and the other is used to introduce replacement gas into the tank. The replacement gas is preferably an inert gas such as nitrogen.

[0017] Furthermore, in the above technical solution, the gas rapid replacement device for tank cleaning may include a first device and a second device (both of which are the aforementioned sealed chamber structures); the gas port of the first device is connected to the gas adsorption unit through a variable frequency exhaust fan, and a first gas flow regulating valve is provided on the connecting pipeline between the gas port and the variable frequency exhaust fan, which is an electromagnetic flow regulating valve; the oil sludge discharge port of the first device is connected to the sludge collection and treatment unit through a hydraulic diaphragm pump.

[0018] Furthermore, in the above technical solution, the gas inlet of the second device is connected to a nitrogen source via a frequency converter blower; a second gas flow regulating valve is provided on the connecting pipeline between the frequency converter blower and the second device, which is an electromagnetic flow regulating valve; the internal pressure of the storage tank and the start and stop of the gas replacement process are controlled by adjusting the frequency converter power of the exhaust fan and the blower, as well as by cooperating with the first gas flow regulating valve and the second gas flow regulating valve.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) The gas replacement method of this invention is designed for tank cleaning in the petrochemical industry, and is particularly suitable for robotic cleaning. It can replace the gas environment inside the tank with the gas environment required for robotic operation. The inventors found that the existing gas replacement method (i.e., constructing a replacement channel through the tank's vent) has low replacement efficiency. Since the gas replacement channel is not shared with the robot's entry and exit channel (i.e., entering and exiting through the tank's manhole), multiple channels will significantly increase the risk of gas leakage. However, robotic cleaning of the tank requires opening the manhole. Therefore, this invention creatively constructs a technical solution for gas replacement using the manhole, thereby meeting the special application scenario of tank cleaning and reducing the increased risk of leakage caused by multiple channels.

[0021] 2) This invention, through the detachable sealing structure design of the manhole sealing chamber (i.e., the semi-enclosed structure design of the upper and lower chambers) and the structure design of the flange fixing plate + top rod, can remove the flange fixing bolts before the upper and lower chambers are closed and still maintain the sealing of the manhole. After closing, the flange can be removed and the manhole can be opened in the sealed chamber environment for gas replacement. Since the manhole has a larger diameter than the vent, it creates better conditions for rapid gas replacement.

[0022] 3) In this invention, when the cleaning robot is placed in the sealed chamber in advance, gas replacement can be performed before cleaning. When the gas environment in which the robot is located meets the requirements, the robot is started and enters the manhole of the storage tank for cleaning. During the cleaning process, gas replacement can be dynamically performed by monitoring the gas environment in real time, so that gas replacement can be performed before and during the cleaning of the storage tank. This is more targeted and maximizes the explosion-proof safety, and prevents gas from escaping after the manhole is opened.

[0023] 4) By setting up the manhole flange fixer, the V-shaped groove of the fixing claw can clamp the flange and the flange when the fixing plate abuts against the flange. At this time, when the upper and lower chambers of the sealing chamber are not closed and not sealed, all the fixing bolts of the flange can be removed. Under this condition, the fixing and sealing of the flange can still be guaranteed.

[0024] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, and to make the above and other objects, technical features and advantages of the present invention easier to understand, one or more preferred embodiments are listed below and described in detail with reference to the accompanying drawings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the rapid gas replacement device for tank cleaning according to the present invention.

[0026] Figure 2 This is a schematic diagram of the flange fixator in the device of the present invention.

[0027] Figure 3 This is a connection diagram of the rapid gas replacement system for tank cleaning according to the present invention.

[0028] Explanation of key figure labels:

[0029] 1A-First device, 1B-Second device, 11-Upper chamber of sealing chamber, 111-Bolt hole, 12-Lower chamber of sealing chamber, 121-Support leg, 13-Fixing plate, 130-Gear, 131-Fixing claw, 132-V-groove, 14-Top rod, 141-Rotating plate, 15-Manhole flange mating port, 16-Gas port, 17-Pressure measuring port, 18-Gas analysis port, 19-Oil and sludge discharge port;

[0030] 2-Exhaust fan, 21-First gas flow regulating valve, 3-Gas adsorption unit, 4-Hydraulic diaphragm pump, 41-Liquid flow regulating valve, 5-Sludge collection and treatment unit, 6-Pressure gauge, 7-Gas analyzer, 8-Blower, 81-Second gas flow regulating valve, 9-Nitrogen source;

[0031] 100 - Storage tank. Detailed Implementation

[0032] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0033] Unless otherwise expressly stated, throughout the specification and claims, the term "comprising" or its variations such as "including" or "comprises" shall be understood to include the stated elements or components without excluding other elements or other components.

[0034] In this document, for ease of description, spatial relative terms such as “below,” “under,” “down,” “above,” “above,” “upper,” etc., are used to describe the relationship of one element or feature to another element or feature in the accompanying drawings. It should be understood that spatial relative terms are intended to encompass different orientations of an object in use or operation, in addition to those depicted in the figures. For example, if an object in the figure is flipped, an element described as “below” or “under” another element or feature would be oriented “above” that element or feature. Thus, the exemplary term “below” can encompass both the downward and upward orientations. An object may also have other orientations (rotated 90 degrees or other orientations), and the spatial relative terms used herein should be interpreted accordingly.

[0035] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0036] This invention relates to a gas replacement solution designed for tank cleaning in the petrochemical industry, particularly suitable for robotic cleaning. Considering that tanks typically contain large amounts of flammable gases, constituting a Zone 0 explosive environment, and given that existing robots only have Zone 1 explosion-proof certification, cleaning the tank requires transforming the environment inside to Zone 1. Therefore, this transformation can be achieved by replacing the gas inside the tank. The inventors discovered that existing gas replacement methods (i.e., constructing replacement channels through tank vents) result in narrow and inefficient gas replacement channels. Furthermore, since these channels are not shared with the robot's access channels (i.e., through the tank manhole), multiple channels significantly increase the risk of gas leakage. Since robotic cleaning of tanks necessitates opening the manhole, this invention creatively constructs a gas replacement solution using the manhole, thus meeting the specific application scenario of tank cleaning and reducing the increased leakage risk associated with multiple channels. Meanwhile, the use of manholes may cause flammable hydrocarbon gases and toxic hydrogen sulfide gases to escape from the manholes and diffuse into the air, which is harmful to the environment and operators. Therefore, this invention has designed a sealed chamber scheme for the manholes of storage tanks, which can not only use the manholes to perform gas replacement before the storage tank is cleaned, but also maintain dynamic gas replacement during the cleaning process.

[0037] Example 1

[0038] like Figure 1 , 2 As shown, this embodiment provides a rapid gas replacement device for tank cleaning, particularly suitable for use before and / or during tank cleaning. The device includes at least a manhole sealing chamber (i.e.,...). Figure 3 The first device 1A and the second device 1B are described. The manhole sealing chamber is formed by an upper chamber 11 and a lower chamber 12. The upper chamber 11 and the lower chamber 12 are detachably sealed together, preferably using a boss and bolt structure for sealing and connection. (Refer to...) Figure 1 The installation includes bolt holes 111. One end of the installed manhole sealing chamber has a mating port 15 that matches the neck of the manhole flange. The flange retainer is a combination of a push rod 14 and a fixing plate 13. The fixing plate 13 is located within the manhole sealing chamber and is adapted to the structure and size of the manhole flange. The manhole flange can be selectively clamped and released via retractable fixing claws 131. The push rod 14 extends from the other end of the manhole sealing chamber and provides operating power to the fixing claws 131 (i.e., power for clamping and releasing the fixing claws).

[0039] This embodiment utilizes a detachable sealing structure design for the manhole sealing chamber (i.e., a semi-enclosed structure design of the upper and lower chambers) and a structure design of a fixing plate + top rod for the flange retainer. This allows the flange fixing bolts to be removed before the upper and lower chambers are closed while maintaining the manhole's seal. After closure, the flange can be removed, allowing the manhole to be opened in the sealed chamber environment for gas replacement. Since the manhole has a larger diameter than the vent, it creates better conditions for rapid gas replacement. When the cleaning robot (not shown in the figure) is placed in the sealed chamber beforehand, gas replacement can be performed before cleaning. Once the gas environment in which the robot is located meets the requirements, the robot is started and enters the tank manhole for cleaning. During the cleaning process, gas replacement can be dynamically performed by monitoring the gas environment in real time, thereby achieving gas replacement before and during tank cleaning and preventing gas leakage that may occur after the manhole is opened.

[0040] Further as Figure 1 , 2 As shown, a gear 130 (i.e., gear teeth facing the push rod) is provided in the center of the fixed disk 13 on the side facing the push rod 14. The gear 130 can be fixedly connected to one end of the push rod 14 and can rotate relative to the disk body of the fixed disk 13. With this arrangement, the rotation of the push rod 14 can drive the gear 130 to rotate, and the gear 130 can rotate relative to the center of the fixed disk 13 through rolling friction. Further as... Figure 2As shown, the fixed plate 13 has three evenly spaced holes along its circumference to accommodate three retractable fixing claws 131. Each fixing claw 131 has a single-sided rack-and-pinion structure that meshes with a gear 130. Specifically, this single-sided rack-and-pinion structure faces the teeth of the gear 130. The rotation of the gear 130 and the meshing of the gear with the rack drive the three fixing claws to extend and retract together. The outer end of the fixing claw 131 has a V-shaped groove 132 adapted to the thickness of the manhole flange for clamping and fixing the manhole flange. With this arrangement, when the fixed plate 13 abuts against the flange (not shown in the figure), the V-shaped groove 132 clamps the flange and the flange opening. At this time, in the non-sealed state where the upper and lower chambers of the sealing chamber are not closed, the fixing bolts of the flange can be removed because the abutting action of the fixed plate 13 achieves both fixing and sealing of the flange.

[0041] Furthermore, the push rod 14 has translational and rotational functions, and a bearing seal can be provided at the penetration point of the manhole sealing chamber to serve as a dynamic seal. A rotating disk 141 can be provided at the outer end of the push rod 14 for operating the rotation of the push rod. The rotation of the push rod can be operated manually or by mechanical transmission.

[0042] Further as Figure 1 As shown, the top of the upper chamber 11 of the manhole sealing chamber is equipped with an air inlet 16, a pressure measuring port 17, and a gas analysis port 18. (Reference) Figure 3 When the manhole sealing chamber is used as the first device 1A, the vent 16 is the exhaust port, which is also the outlet for the gas being replaced in the storage tank; when the manhole sealing chamber is used as the second device 1B, the vent 16 is the inlet port, which is also the inlet for the replacement gas (nitrogen). Since oily wastewater will flow out when the liquid level in the storage tank is higher than the manhole after the manhole is opened, an oil sludge discharge port 19 can be provided at the bottom of the lower chamber 12.

[0043] Example 2

[0044] like Figure 3 As shown, this embodiment provides a rapid gas replacement system for tank cleaning, which utilizes the rapid gas replacement device of Embodiment 1 described above. In this system, there are two devices from Embodiment 1: a first device 1A and a second device 1B, respectively located at two opposite manholes on either side of the tank 100. One device is used to draw the gas to be replaced from the tank 100, and the other is used to fill the tank with replacement gas, i.e., an inert gas such as nitrogen. Further, preferably but not limitingly, the gas port 16 of the first device 1A (as an outlet, see reference...) Figure 1The first device 1A is connected to the gas adsorption unit 3 via an exhaust fan 2. The gas adsorption unit 3 adsorbs the escaping gas to meet emission requirements. The explosion-proof exhaust fan 2 has a frequency conversion function and can adjust its power through PLC signal feedback, thereby changing the speed of gas replacement. The oil sludge discharge port 19 of the first device 1A is connected to the sludge collection and treatment unit 5 via a hydraulic diaphragm pump 4. The oil sludge discharge port 19 and the support legs 121 of the sealed chamber are located at the bottom of the lower chamber 12. The oil sludge discharge port 19 is connected to the pipeline for conveying sludge. The pipeline is equipped with a liquid flow regulating valve (preferably an explosion-proof electromagnetic flow regulating valve) to regulate the speed of sludge discharge. The air port 16 of the second device 1B (as an air inlet) is connected to the nitrogen source 9 via a blower 8. A second flow regulating valve 81 is provided on the connecting pipeline between the blower 8 and the second device 1B. In this embodiment, the speed of oil sludge discharge is regulated by the pressure inside the sealed chamber. Together with the first gas flow regulating valve 21, the exhaust fan 2 (preferably a variable frequency exhaust fan) and the blower 8 (preferably a variable frequency blower), the internal pressure is stabilized. The pipeline for transporting oil sludge is connected to the explosion-proof hydraulic diaphragm pump 4, which is used to pump oil sludge and other materials to the sludge collection and treatment unit.

[0045] Further as Figure 1 , 3 As shown, pressure gauge 6 is used to measure the gas pressure inside storage tank 100 and the sealed chamber. The inlet and outlet gas volumes can be adjusted according to operational requirements to ensure that the pressure inside the tank is slightly positive, thus preventing negative pressure from causing safety accidents. Explosion-proof gas analyzer 7 is used to monitor the gas composition inside storage tank 100 in real time. When the gas composition inside the tank meets the requirements, subsequent robotic tank cleaning operations are performed.

[0046] The following details the usage of the system in this embodiment:

[0047] 1) First, place the lower chamber 12 of the sealed chamber of the first device 1A and the second device 1B below the manhole of the storage tank, so that the neck of the manhole is located on the manhole mating hole 15 of the sealed chamber (the second device is only a nitrogen supply device, and the following description will only focus on the sealed chamber of the first device).

[0048] 2) Place the manhole flange holder inside the sealed chamber, and use the push rod 14 to push the fixing plate 13 to fix the manhole flange. Rotate the push rod 14 to make the fixing claws 131 gather and grip the flange (that is, clamp the flange to the plate opening).

[0049] 3) Remove all manhole flange bolts. At this time, the flange is fixed by the flange retainer, the flange is still in a sealed state and will not fall off, and the contents of the storage tank 100 will not leak or overflow.

[0050] 4) Place the unstarted cleaning robot into the appropriate position in the lower chamber 12 of the sealed compartment;

[0051] 5) Close the upper chamber 11 and lower chamber 12 of the sealed chamber and seal them with bolts;

[0052] 6) Rotate the top rod 14 in the opposite direction to release and open the fixing claw 131. Pull the top rod 14 in the opposite direction of the storage tank. At this time, the flange is no longer fixed. Under the restriction of the V-groove 132, the flange retainer is released from the manhole, and the material in the storage tank enters the sealed chamber through the manhole.

[0053] 7) First, open the air port (i.e., air inlet) of the second device 1B, open the second gas flow regulating valve 81, turn on the blower 8 to pump nitrogen, and at the same time open the oil sludge discharge port and the air port (i.e., exhaust port) of the first device 1A, the liquid flow regulating valve 41, and the hydraulic diaphragm pump 4 to pump the medium outward. When no medium flows out, close the oil sludge discharge port 19 and the liquid flow regulating valve 41.

[0054] 8) Monitor pressure and flow rate changes at all times, and adjust the speed and time of gas inlet and outlet according to the pressure and flow rate to ensure a slight positive pressure inside the storage tank. At the same time, observe the gas component analyzer 7. After the standard is reached, stop the gas supply and exhaust to complete the rapid gas replacement.

[0055] 9) Activate the cleaning robot in the sealed chamber, allow it to enter the storage tank, and clean the storage tank in a qualified gas environment. During the cleaning process, the gas composition is measured in real time to dynamically replace the gas, ensuring that the robot is always in a qualified gas environment (i.e., the gas environment of Zone 1) during the cleaning process.

[0056] The foregoing description of specific exemplary embodiments of the present invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. Any simple modifications, equivalent changes, and alterations made to the foregoing exemplary embodiments should fall within the scope of protection of the present invention.

Claims

1. A rapid gas replacement device for tank cleaning, characterized in that, Applications before and / or during tank cleaning include: The manhole sealing chamber is formed by an upper chamber and a lower chamber; the upper chamber and the lower chamber are detachably sealed, and one end of the installed manhole sealing chamber is provided with a mating port that is compatible with the neck of the manhole flange. The flange retainer is a push rod and a fixed plate structure; the fixed plate is disposed in the manhole sealing chamber and is adapted to the structure and size of the manhole flange, and can selectively clamp and release the manhole flange by means of retractable fixed claws; the push rod extends out of the manhole sealing chamber and provides running power to the fixed claws.

2. The rapid gas replacement device for tank cleaning according to claim 1, characterized in that, A gear is provided in the center of the fixed plate on the side facing the top rod. The gear is fixedly connected to one end of the top rod and can rotate relative to the plate body of the fixed plate.

3. The rapid gas replacement device for tank cleaning according to claim 2, characterized in that, The fixed disk has three channels evenly spaced around its circumference for accommodating the three retractable fixed claws; the fixed claws are single-sided rack and pinion structures that mesh with the gears.

4. The rapid gas replacement device for tank cleaning according to claim 3, characterized in that, The outer end of the fixing claw is provided with a V-shaped groove that matches the thickness of the manhole flange, for clamping and fixing the manhole flange.

5. The rapid gas replacement device for tank cleaning according to claim 1, characterized in that, The push rod is equipped with a bearing seal at the penetration point of the manhole sealing chamber; a rotating disk is provided at the outer end of the push rod for operating the rotation of the push rod.

6. The rapid gas replacement device for tank cleaning according to claim 1, characterized in that, The upper and lower compartments are sealed and connected by a boss and bolt structure.

7. The rapid gas replacement device for tank cleaning according to claim 1, characterized in that, The top of the upper chamber is equipped with an air inlet, a pressure measurement port, and a gas analysis port.

8. The rapid gas replacement device for tank cleaning according to claim 1, characterized in that, The bottom of the lower compartment is equipped with an oil and sludge discharge port.

9. A system, characterized in that, The gas rapid replacement device for tank cleaning as described in any one of claims 1 to 8 is used, wherein there are two such devices, which are respectively installed at two manholes opposite to the tank, one for absorbing the gas to be replaced in the tank and the other for filling the tank with replacement gas.

10. The system according to claim 9, characterized in that, The replacement gas is nitrogen.

11. The system according to claim 10, characterized in that, The gas rapid replacement device for tank cleaning includes a first device and a second device; the gas port of the first device is connected to the gas adsorption unit through a variable frequency exhaust fan, and a first gas flow regulating valve is provided on the connecting pipeline between the gas port and the variable frequency exhaust fan, which is an electromagnetic flow regulating valve; the oil sludge discharge port of the first device is connected to the sludge collection and treatment unit through a hydraulic diaphragm pump.

12. The system according to claim 11, characterized in that, The gas inlet of the second device is connected to a nitrogen source via a frequency converter blower; a second gas flow regulating valve, which is an electromagnetic flow regulating valve, is installed on the connecting pipeline between the frequency converter blower and the second device; the internal pressure of the storage tank and the start and stop of the gas replacement process are controlled by adjusting the frequency converter power of the exhaust fan and the blower, as well as by cooperating with the first gas flow regulating valve and the second gas flow regulating valve.

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