Differential pressure liquid level meter suitable for PTA (pure terephthalic acid) slurry tank

Abstract

The utility model relates to the technical field of PTA (pure terephthalic acid) production equipment, in particular to a differential pressure liquid level meter suitable for a PTA slurry tank, which comprises a tank body, a pressure tapping device, a measuring device, a flushing device and an emergency dredging device, the pressure tapping device comprises two pressure tapping valves, two buffer tanks and two straight rod type two-valve groups; the measuring device comprises a pressure sensor master meter, a pressure sensor slave meter and a communication cable. The continuous flushing device comprises a flushing water one-way valve, a steady-flow metal rotor flow meter and a flushing water main valve; the emergency dredging device comprises an emergency dredging cut-off valve, an emergency dredging check valve, a dredging steam cut-off valve and a dredging condensate cut-off valve. The differential pressure liquid level meter suitable for the PTA slurry tank is not influenced by the height range of pressure tapping of the tank body, can well resist the influence of measured value distortion caused by wall attachment of the tank body and blockage of a pressure tapping opening, and is high in environmental interference resistance, low in consumption, safe and convenient to maintain and stable in performance.

Description

Technical Field

[0001] The utility model relates to the technical field of PTA production equipment, in particular to a differential pressure level meter suitable for a PTA slurry tank. Background Art

[0002] In the PTA production device, the PTA slurry tank often needs to use a level gauge for level measurement. There are two main types of level gauges. One is a radiometric level gauge, which is expensive and inconvenient to maintain. When the tank wall is formed or there is a foam layer on the liquid surface, the level measurement value will be distorted; the other is a differential pressure level gauge. There are two types of traditional differential pressure level gauges. One is a pressure pipe structure. The isolation liquid in the pressure pipe of this differential pressure level gauge has many instabilities, and the pressure-taking components are easily blocked, which can easily affect the measurement value; the other is a double-flange differential pressure level gauge. This level gauge consists of a differential pressure transmitter, a capillary tube and a flange with a sealing diaphragm. It is usually used with a flushing device. The flushing water consumption is large. Improper control of the flushing water volume can easily cause inaccurate measurement values ​​and even damage to the sealing diaphragm. In addition, it is difficult to select a model for high-temperature and high-pressure slurry tanks. Once the slurry is blocked, it is difficult to clear it; in addition, if the tank level changes in a large range, a longer capillary tube is required, and the capillary tube length has a direct impact on the measurement accuracy. Therefore, it is necessary to design a differential pressure level gauge suitable for PTA slurry tanks. Utility Model Content

[0003] In order to solve the above technical deficiencies, the utility model provides a differential pressure level gauge suitable for a PTA slurry tank, particularly a differential pressure level gauge suitable for a refined crystallizer. The differential pressure level gauge is not affected by the pressure taking height range of the tank body, can better resist the influence of measurement distortion caused by tank wall formation and pressure taking port blockage, has strong environmental interference resistance, low consumption, safe and convenient maintenance, and stable performance.

[0004] The utility model discloses a differential pressure level gauge suitable for a PTA slurry tank, comprising a tank body, a pressure taking device, a measuring device, a flushing device and an emergency dredging device;

[0005] The tank body is a mounting carrier for the above four devices;

[0006] The pressure taking device comprises two pressure taking valves, two buffer tanks and two straight-rod two-valve groups. The two pressure taking valves are installed on the cylinder side of the tank body and are distributed up and down. The upper ports of the two buffer tanks are respectively connected to the two pressure taking valves through pipelines and flanges, and the two straight-rod two-valve groups are respectively connected to the bottom interface of the buffer tank through thick-walled pipes.

[0007] The measuring device comprises a pressure sensor main meter, a pressure sensor slave meter and a communication cable, wherein the pressure sensor main meter is connected to a lower straight-rod two-valve group, the pressure sensor slave meter is connected to an upper straight-rod two-valve group, and the pressure sensor slave meter is connected and communicated with the pressure sensor main meter through the communication cable;

[0008] The flushing device includes a flushing water one-way valve, a steady-flow metal rotor flowmeter and a flushing water main valve; the flushing water one-way valve is connected to the bottom interface of the buffer tank through a joint, the flushing water one-way valve is connected in parallel with the corresponding straight-rod two-valve group, the outlet of the steady-flow metal rotor flowmeter is connected to the flushing water one-way valve, the outlet of the flushing water main valve is divided into two paths, which are connected to the inlet of the steady-flow metal rotor flowmeter respectively, and the flushing water main valve is connected to the flushing water system;

[0009] The emergency dredging device includes an emergency dredging cut-off valve, an emergency dredging check valve, a dredging steam cut-off valve and a dredging condensate cut-off valve; the two emergency dredging cut-off valves are respectively connected to the two pressure-taking valves, forming a parallel relationship with the buffer tank; the outlet of the emergency dredging check valve is divided into two paths, which are respectively connected to the two emergency dredging cut-off valves; after the outlet pipeline of the dredging steam cut-off valve merges into the outlet pipeline of the dredging condensate cut-off valve, it is connected to the inlet of the emergency dredging check valve; the inlet of the dredging steam cut-off valve is connected to the saturated steam system, and the inlet of the dredging steam cut-off valve is connected to the steam condensate system.

[0010] The pressure-taking valve and the tank body, as well as the buffer tank and the pressure-taking valve are connected at the shortest distance. The pressure-taking valve is a ball valve structure, and the size is 3 inches or 4 inches. The pipe section between the buffer tank and the pressure-taking valve is a 1.5-inch pipe or a 2-inch pipe, which is connected to the buffer tank through a 1 / 2-inch pipe transition. The inner diameter of the buffer tank is 80mm, and the height difference between the upper port and the bottom interface is 120mm. The center line of the straight-rod two-valve group interface is at a 90° angle to the center line of the bottom interface of the buffer tank, and the distance between the center line of the straight-rod two-valve group interface and the end face of the bottom interface of the buffer tank should be less than 200mm.

[0011] The pressure sensor slave meter and the pressure sensor main meter are selected according to the maximum working pressure of the tank body, and the two are compatible with each other in communication. The pressure sensor main meter is responsible for detecting the pressure signal on the high-pressure side of the tank body, and the pressure sensor slave meter is responsible for detecting the pressure signal on the low-pressure side of the tank body. The pressure signal detected by the pressure sensor slave meter is transmitted to the pressure sensor main meter through the communication cable. The pressure sensor main meter compares and calculates the pressure signal detected by itself with the pressure signal detected by the pressure sensor slave meter, and finally outputs the differential pressure signal from the pressure sensor main meter to the control system. The control system converts the pressure difference into a liquid level signal based on the relationship between the pressure difference value and the liquid level height.

[0012] The flushing water one-way valve is installed in a vertical direction and maintains the shortest distance from the bottom interface of the buffer tank while meeting the installation conditions of the straight-rod two-valve group; the steady-flow metal rotor flowmeter controls the flow rate within 30 ml / min, and the control flow rates of the two steady-flow metal rotor flowmeters must be consistent.

[0013] The emergency unblocking cut-off valve, the emergency unblocking check valve, the unblocking steam cut-off valve, and the unblocking condensate cut-off valve are all adapted to the size of the pipe section between the buffer tank and the pressure taking valve, and have good closing performance; the inlets of the two emergency unblocking cut-off valves are both installed upwards.

[0014] The utility model is suitable for a differential pressure level gauge for a PTA slurry tank, which uses the working principle that when the liquid level in the tank changes, the static pressure generated by the liquid column also changes. Compared with the related art, the PTA slurry tank differential pressure level gauge provided by the utility model has the following beneficial effects:

[0015] During the actual liquid level measurement process of the tank body, the flushing water in the continuous flushing device is 3 to 5 bar higher than the pressure in the tank body. The flushing water flows through the pipeline, which has a long-term cleaning effect on the pipeline to improve the measurement accuracy of the differential pressure level gauge. Since the flushing water volume is controlled at a reasonable value, blockage will not occur in the pipeline, and since the flushing water flow and pressure values ​​on both sides of the differential pressure are the same, the differential pressure value will not be affected when the pipelines are installed at a short distance. Even if the flushing water is abnormal and carries bubbles, the buffer tank will eliminate interference factors such as bubbles and the differential pressure value will not be affected because the pipeline is equipped with the buffer tank. After long-term operation, the slurry in the tank body may coke, and severe coking will block the pipeline of the pressure-taking device. When the pipeline diameter is less than 10mm , the differential pressure value will increase significantly, and the flow rate of the steady-flow metal rotor flowmeter will decrease; at this time, the emergency dredging device is activated to ensure that the liquid level meter quickly resumes normal measurement. The working principle of the emergency dredging device is: when the pipeline is blocked, the emergency dredging cut-off valve and the dredging steam cut-off valve corresponding to the blocked pipeline are opened, and the pipeline is flushed with saturated steam. The steam pressure is 10 to 30 bar higher than the pressure in the tank body; when the steam ends, in order to avoid vacuum in the pipeline, the coke block in the tank body is sucked back into the pipeline. While closing the dredging steam cut-off valve, the dredging condensate cut-off valve is opened for secondary cleaning. The dredging condensate is equal to the dredging steam pressure; when the dredging is completed, the emergency dredging device is disabled, that is, the emergency dredging cut-off valve is closed. The device is efficient, convenient and safe.

[0016] The utility model provides a differential pressure level gauge suitable for a PTA slurry tank, particularly a differential pressure level gauge suitable for a refined crystallizer, which is not affected by the pressure taking height range of the tank body, can better resist the influence of measurement distortion caused by tank wall formation and pressure taking port blockage, has strong environmental interference resistance, low consumption, safe and convenient maintenance, and stable performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the utility model. DETAILED DESCRIPTION

[0018] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined purpose of the utility model, the specific implementation method, structure, characteristics and effects of the present invention are described in detail below in combination with the accompanying drawings and preferred embodiments.

[0019] Embodiment 1:

[0020] like Figure 1 As shown, the utility model discloses a differential pressure level gauge suitable for a PTA slurry tank, comprising a tank body 1, a pressure taking device, a measuring device, a flushing device and an emergency unblocking device;

[0021] The tank body 1 is a mounting carrier for the above four devices;

[0022] The pressure taking device comprises two pressure taking valves 2, two buffer tanks 3 and two straight-rod two-valve groups 4. The two pressure taking valves 2 are installed on the cylinder side of the tank body 1 and are distributed according to the upper and lower limits of the liquid level of the tank body 1. The upper ports of the two buffer tanks 3 are connected to the two pressure taking valves 2 through pipes and flanges, respectively. The two straight-rod two-valve groups 4 are connected to the bottom interfaces of the buffer tanks 3 through thick-walled pipes, respectively. The pressure rating of all components should be equal to or higher than the pressure rating of the tank body 1.

[0023] The measuring device includes a pressure sensor main meter 5, a pressure sensor slave meter 6 and a communication cable 7. The pressure sensor main meter 5 is connected to the straight-rod two-valve group 4 at the lower end, and the pressure sensor slave meter 6 is connected to the straight-rod two-valve group 4 at the upper end. The pressure sensor slave meter 6 is connected and communicated with the pressure sensor main meter 5 through the communication cable 7.

[0024] The continuous flushing device comprises a flushing water check valve 8, a steady-flow metal rotor flowmeter 9, and a flushing water main valve 10; the flushing water check valve 8 is respectively connected to the bottom interface of the buffer tank 3 through a joint, and is connected in parallel with the straight-rod two-valve group 4, the outlet of the steady-flow metal rotor flowmeter 9 is respectively connected to the flushing water check valve 8, the outlet of the flushing water main valve 10 is divided into two paths, respectively connected to the inlet of the steady-flow metal rotor flowmeter 9, and the flushing water main valve 10 is connected to the flushing water system; the flushing water system is used to provide high-pressure flushing water;

[0025] The emergency dredging device includes an emergency dredging cut-off valve 11, an emergency dredging check valve 12, a dredging steam cut-off valve 13, and a dredging condensate cut-off valve 14; the two emergency dredging cut-off valves 11 are respectively connected to the two pressure-taking valves 2, and form a parallel relationship with the buffer tank 3; the outlet of the emergency dredging check valve 12 is divided into two paths, which are respectively connected to the two emergency dredging cut-off valves 11; the outlet pipeline of the dredging steam cut-off valve 13 merges into the outlet pipeline of the dredging condensate cut-off valve 14, and is connected to the inlet of the emergency dredging check valve 12; the inlet of the dredging steam cut-off valve 13 is connected to the saturated steam system, and the inlet of the dredging steam cut-off valve 13 is connected to the steam condensate system; the Baohe steam system is used to provide high-pressure steam, and the steam condensate system is used to provide high-pressure condensate.

[0026] During the specific implementation process, the following data is only an example of a better solution and is not intended to limit the technical solution.

[0027] In the specific implementation process, Figure 1 As shown, in order to reduce the probability of pipeline blockage or material accumulation, and at the same time to reduce the flow resistance of the flushing process, the pressure-taking valve 2 and the tank body 1, and the buffer tank 3 and the pressure-taking valve 2 are connected at the shortest distance. The pressure-taking valve 2 is a ball valve structure, and the size is 3 inches or 4 inches. The pipe section between the buffer tank 3 and the pressure-taking valve 2 should be a 1.5-inch pipe or a 2-inch pipe, and is connected to the buffer tank 3 through a 1 / 2-inch pipe transition. In order to reduce the impact of flushing pressure fluctuations and meet the working temperature requirements of the pressure sensor main table 5 and the pressure sensor slave table 6, the inner diameter of the buffer tank 3 is 80mm, and the height difference between the upper port and the bottom interface is 120mm; the center line of the interface of the straight-rod two-valve group 4 is at a 90° angle to the center line of the bottom interface of the buffer tank 3, and the distance between the center line of the interface of the straight-rod two-valve group 4 and the end face of the bottom interface of the buffer tank 3 should be less than 200mm.

[0028] In the specific implementation process, in order to ensure the accuracy of the liquid level meter, the pressure sensor slave table 6 and the pressure sensor main table 5 are selected according to the maximum working pressure of the tank body 1, and the communications of the two are compatible with each other. The pressure sensor main table 5 is responsible for detecting the pressure signal on the high-pressure side of the tank body 1, and the pressure sensor slave table 6 is responsible for detecting the pressure signal on the low-pressure side of the tank body 1. The pressure signal detected by the pressure sensor slave table 6 is transmitted to the pressure sensor main table 5 through the communication cable 7. The pressure sensor main table 5 compares and calculates the pressure signal detected by itself with the pressure signal detected by the pressure sensor slave table 6, and finally outputs the differential pressure signal from the pressure sensor main table 5 to the control system. The control system converts it into a liquid level signal based on the relationship between the pressure difference value and the liquid level height.

[0029] In the specific implementation process, in order to reduce the flow resistance and prevent a small amount of slurry from entering the pipeline, the flushing water check valve 8 is installed in the vertical direction, and the shortest distance is maintained with the bottom interface of the buffer tank 3 under the installation conditions of the straight-rod two-valve group 4; the steady-flow metal rotor flowmeter 9 controls the flow rate within 30ml / min to prevent water hammer from occurring in the pipeline due to excessive flushing water volume. At the same time, the control flow rates of the two steady-flow metal rotor flowmeters 9 must be consistent to ensure the best flushing effect, and at the same time ensure that the pressure sensor slave table 6 and the pressure sensor main table 5 are subjected to the same pressure to prevent affecting the measurement accuracy;

[0030] During the specific implementation process, in order to reduce the interference of flushing on the entire liquid level meter system, the emergency unblocking cut-off valve 11, the emergency unblocking check valve 12, the unblocking steam cut-off valve 13, and the unblocking condensate cut-off valve 14 are all adapted to the size of the pipe section between the buffer tank 3 and the pressure taking valve 2, and have better closing performance; at the same time, the inlets of the two emergency unblocking cut-off valves 11 are installed upward to prevent the slurry from gathering at the flushing port under extreme conditions, forming a blockage and making the emergency unblocking system ineffective.

[0031] During the actual liquid level measurement process of the tank body 1, the flushing water in the continuous flushing device is 3 to 5 bar higher than the pressure in the tank body 1. The specific pressure value can be selected within this range, such as 3.5 bar, 4 bar, 4.6 bar, etc. The flushing water flows through the pipeline, which has a long-term cleaning effect on the pipeline to improve the measurement accuracy of the differential pressure level gauge; since the flushing water volume is controlled at a reasonable value, blockage will not occur in the pipeline, and since the flushing water flow and pressure values ​​on both sides of the differential pressure are the same, the differential pressure value will not be affected when the pipelines are installed at a short distance; even if the flushing water is abnormal and carries bubbles, the buffer tank 3 is provided in the pipeline, and the buffer tank 3 will eliminate interference factors such as bubbles, and the differential pressure value will not be affected; after long-term operation, the slurry in the tank body 1 may produce coking, and severe coking will block the pipeline of the pressure taking device. When the pipeline diameter is less than 10 mm, the differential pressure value will increase significantly. Increases, the flow rate of the steady-flow metal rotor flowmeter 9 becomes smaller; at this time, the emergency unblocking device is activated to ensure that the liquid level meter quickly resumes normal measurement. The working principle of the emergency unblocking device is: when the pipeline is blocked, the emergency unblocking shut-off valve 11 and the unblocking steam shut-off valve 13 corresponding to the blocked pipeline are opened, and the pipeline is flushed with saturated steam. The steam pressure is 10 to 30 bar higher than the pressure in the tank body 1, and can be specifically selected within the above range, such as 15 bar, 20 bar, 21 bar, 25 bar, etc.; when the steam ends, in order to avoid vacuum in the pipeline, the coke block material in the tank body 1 is sucked back into the pipeline. While closing the unblocking steam shut-off valve 13, the unblocking condensate shut-off valve 14 is opened for secondary cleaning. The unblocking condensate pressure is equal to that of the unblocking steam pressure; when unblocking is completed, the emergency unblocking device is deactivated, and the emergency unblocking device plays an efficient and safe unblocking role.

[0032] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0033] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be an interactive relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0034] In the present application, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0035] The above description is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simplified modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A differential pressure level gauge suitable for a PTA slurry tank, characterized by: Including tank body, pressure taking device, measuring device, flushing device and emergency dredging device; The tank body is a mounting carrier for the above four devices; The pressure taking device comprises two pressure taking valves, two buffer tanks and two straight-rod two-valve groups. The two pressure taking valves are installed on the cylinder side of the tank body and are distributed up and down. The upper ports of the two buffer tanks are respectively connected to the two pressure taking valves through pipelines and flanges, and the two straight-rod two-valve groups are respectively connected to the bottom interface of the buffer tank through thick-walled pipes. The measuring device comprises a pressure sensor main meter, a pressure sensor slave meter and a communication cable, wherein the pressure sensor main meter is connected to a lower straight-rod two-valve group, the pressure sensor slave meter is connected to an upper straight-rod two-valve group, and the pressure sensor slave meter is connected and communicated with the pressure sensor main meter through the communication cable; The flushing device includes a flushing water one-way valve, a steady-flow metal rotor flowmeter and a flushing water main valve; the flushing water one-way valve is connected to the bottom interface of the buffer tank through a joint, the flushing water one-way valve is connected in parallel with the corresponding straight-rod two-valve group, the outlet of the steady-flow metal rotor flowmeter is connected to the flushing water one-way valve, the outlet of the flushing water main valve is divided into two paths, which are connected to the inlet of the steady-flow metal rotor flowmeter respectively, and the flushing water main valve is connected to the flushing water system; The emergency dredging device includes an emergency dredging cut-off valve, an emergency dredging check valve, a dredging steam cut-off valve and a dredging condensate cut-off valve; The two emergency dredging cut-off valves are respectively connected with the two pressure-taking valves, forming a parallel relationship with the buffer tank; the outlet of the emergency dredging check valve is divided into two paths, respectively connected with the two emergency dredging cut-off valves; after the outlet pipeline of the dredging steam cut-off valve merges into the outlet pipeline of the dredging condensate cut-off valve, it is connected with the inlet of the emergency dredging check valve; the inlet of the dredging steam cut-off valve is connected to the saturated steam system, and the inlet of the dredging steam cut-off valve is connected to the steam condensate system.

2. The differential pressure level meter for a PTA slurry tank according to claim 1 is characterized in that: The pressure-taking valve and the tank body, as well as the buffer tank and the pressure-taking valve are connected at the shortest distance. The pressure-taking valve is a ball valve structure, and the size is 3 inches or 4 inches. The pipe section between the buffer tank and the pressure-taking valve is a 1.5-inch pipe or a 2-inch pipe, which is connected to the buffer tank through a 1 / 2-inch pipe transition. The inner diameter of the buffer tank is 80mm, and the height difference between the upper port and the bottom interface is 120mm. The center line of the straight-rod two-valve group interface is at a 90° angle to the center line of the bottom interface of the buffer tank, and the distance between the center line of the straight-rod two-valve group interface and the end face of the bottom interface of the buffer tank should be less than 200mm.

3. The differential pressure level meter for a PTA slurry tank according to claim 1 is characterized in that: The pressure sensor slave meter and the pressure sensor main meter are selected according to the maximum working pressure of the tank body, and the two are compatible with each other in communication. The pressure sensor main meter is responsible for detecting the pressure signal on the high-pressure side of the tank body, and the pressure sensor slave meter is responsible for detecting the pressure signal on the low-pressure side of the tank body. The pressure signal detected by the pressure sensor slave meter is transmitted to the pressure sensor main meter through the communication cable. The pressure sensor main meter compares and calculates the pressure signal detected by itself with the pressure signal detected by the pressure sensor slave meter, and finally outputs the differential pressure signal from the pressure sensor main meter to the control system. The control system converts the pressure difference into a liquid level signal based on the relationship between the pressure difference value and the liquid level height.

4. The differential pressure level meter for a PTA slurry tank according to claim 1 is characterized in that: The flushing water one-way valve is installed in a vertical direction and maintains the shortest distance from the bottom interface of the buffer tank while meeting the installation conditions of the straight-rod two-valve group; the steady-flow metal rotor flowmeter controls the flow rate within 30 ml / min, and the control flow rates of the two steady-flow metal rotor flowmeters must be consistent.

5. The differential pressure level meter for a PTA slurry tank according to claim 1 is characterized in that: The emergency unblocking cut-off valve, the emergency unblocking check valve, the unblocking steam cut-off valve, and the unblocking condensate cut-off valve are all adapted to the size of the pipe section between the buffer tank and the pressure taking valve, and have closing performance; the inlets of the two emergency unblocking cut-off valves are both installed upwards.

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