Design method for bridge main cable fire-fighting water curtain protection system

Abstract

Disclosed is a design method for a bridge main cable fire-fighting water curtain protection system, comprising the following steps: S1: a fire detector and spraying branch pipes are arranged along a bridge main cable, a plurality of water curtain nozzle groups for extinguishing fire of a bridge are arranged on the spraying branch pipes, the water curtain nozzle groups are connected to a water supply system, and the water supply system and the fire detector are electrically connected to a control system; S2: the arrangement distance and the spraying protection area of the water curtain nozzle groups are determined, water curtain spraying appearance curves under a set design pressure and flow rate are drawn on a vertical and horizontal coordinate grid diagram and on the basis of a provided water curtain nozzle spraying profile diagram, and it is ensured that the water curtain spraying appearance curves of two adjacent water curtain nozzles have an intersection point; and S3, each spraying branch pipe is connected to a corresponding water supply branch, each water supply branch is provided with a pressure reducing valve for controlling the water pressure of the corresponding spraying branch pipe, and the pressure reducing valve on each water supply branch needs to independently set an outlet pressure.

Description

A design method for fire protection system of bridge main cable water curtain Technical Field

[0001] The invention belongs to the technical field of bridge fire protection, and relates to a design method of a fire protection water curtain system for a bridge main cable. Background Art

[0002] Currently, most long-span bridges in my country are suspension bridges, where cables, especially main cables, are the key load-bearing structures. In recent years, fires on cable-type bridges caused by vehicles catching fire have occurred frequently. When a fire occurs on the bridge deck (particularly a fuel tanker fire), fire damage is very likely to occur, including burning of the PE sheath, continuous temperature rise of the steel wire, loss of the anti-corrosion coating, and degradation of the steel wire performance. Furthermore, main cables are not replaceable and are difficult to repair after fire damage. This poses a serious safety hazard to bridges and can even cause the entire bridge to collapse, resulting in casualties and major safety incidents with adverse social impacts.

[0003] At present, the main fire prevention measures adopted for bridge main cables are passive fire prevention measures such as coating with fire-retardant paint or fire-retardant materials. These measures have the following problems: short fire resistance time (generally about 1 hour), deterioration of fire resistance due to aging by wind and sun, and the need for re-maintenance at regular intervals. Especially in the event of a large oil tanker fire accident, the fire lasts for more than one hour, far exceeding the fire resistance capacity of the fire prevention measures, making it impossible to provide long-term protection for the bridge main cables. Summary of the Invention

[0004] In view of this, in order to improve the fire resistance of the bridge main cable and overcome the shortcomings of the existing technology, the present invention provides a design method for a bridge main cable fire water curtain protection system, which can actively and long-term protect the bridge main cable and has high insulation efficiency.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A design method for a bridge main cable fire water curtain protection system includes the following steps:

[0007] S1: Fire detectors and sprinkler branches are arranged along the main cables of the bridge. The sprinkler branches are equipped with several water curtain nozzle groups for bridge fire extinguishing. The water curtain nozzle groups are connected to the water supply system. The water supply system and fire detectors are electrically connected to the control system respectively. The fire detectors transmit the detection signals to the control system, and the control system controls the water supply system to supply water to the sprinkler branches;

[0008] S2: Determine the spacing between the water curtain nozzle groups and the spray protection area. On the vertical and horizontal coordinate grid diagram, draw the water curtain spray profile curve under the set design pressure and flow rate based on the provided water curtain nozzle spray profile diagram, and ensure that the water curtain spray profile curves of two adjacent water curtain nozzles have an intersection point;

[0009] S3: Each sprinkler branch is connected to a corresponding water supply branch. A pressure reducing valve is installed on the water supply branch to control the water pressure of the sprinkler branch. The outlet pressure of each pressure reducing valve on the water supply branch needs to be set separately. The outlet pressure is calculated according to the following formula:

[0010]

[0011] Where: P—the outlet setting pressure of the pressure reducing valve (MPa);

[0012] —Cumulative value of pipeline head loss along the pipeline and in local areas (MPa);

[0013] P0—working pressure of the water curtain nozzle group at the most unfavorable point (MPa);

[0014] Z—Elevation difference between the water supply branch and the pressure reducing valve (MPa).

[0015] Furthermore, in step S2, the straight-line distance d between the intersection points of the water curtain spraying profile curves of two adjacent water curtain nozzle groups is measured, which is the arrangement spacing of the water curtain nozzle groups. A circle is drawn with the center of the water curtain nozzle group as the center and the distance from the intersection point to the center of the circle as the radius r. The circle formed at this time is the water curtain spraying protection area of ​​the water curtain nozzle group. The water curtain spraying protection circle radius r of the water curtain nozzle group should meet the following requirements:

[0016]

[0017] Where: D is the distance between the water curtain nozzle group and the axis of the bridge main cable; R is the radius of the bridge main cable.

[0018] Furthermore, the length of the sprinkler branch pipe should ensure that the height difference between the highest point water curtain nozzle group and the lowest point water curtain nozzle group does not exceed 20 meters.

[0019] Furthermore, the water supply system includes a fire water source, the outlet of the lower end of the fire water source is connected to one end of the main water supply pipeline, the other end of the main water supply pipeline is connected to the water inlet of the partition control valve group, the other end of the partition control valve group is connected to each water supply branch pipe, a fire water pump is provided on the main water supply pipeline, the control system is electrically connected to the fire water pump, the fire detector transmits the detected fire signal to the control system, the control system controls the start of the fire water pump, and at the same time starts the partition control valve group to provide water to the sprinkler branch pipe for water curtain spraying.

[0020] Furthermore, a one-way valve, a water pump coupler and a pressure reducing valve are installed on the water supply branch pipe. The water pump coupler is arranged on the water supply branch pipe between the one-way valve and the pressure reducing valve. The one-way valve is close to the partition control valve group, and the water pump coupler can be connected to the water source of the fire truck.

[0021] Furthermore, the water pump coupler is arranged on the roadside of the bridge deck.

[0022] Furthermore, the water curtain nozzle group includes a nozzle base, on which a number of water curtain nozzles are fixed. The water curtain nozzles are connected to the spray branch pipes, and the nozzle base is fixed on the spray branch pipes. The water curtain nozzles are arranged in a circular shape on the nozzle base and are evenly arranged. The nozzles of the water curtain nozzles face outward, and the water curtains sprayed from the nozzles of the water curtain nozzles forming a circle form a 360-degree circular water curtain.

[0023] Furthermore, the water curtain nozzles are selected with an angle of 120°, so the number of nozzles n=360° / 120°=3.

[0024] Furthermore, the water inlet axis of the water curtain nozzle group is arranged at an angle of 45° to the horizontal line, and the water curtain spraying direction is at an angle of 90° to the water inlet axis of the water curtain nozzle group.

[0025] The beneficial effects of the present invention are:

[0026] Compared to existing passive fire protection measures, this system relies on fire detectors to provide fire alarms and proactively activates a continuous water curtain to protect the bridge's main cables. This water curtain effectively blocks the flame's high temperature and thermal radiation, preventing damage to the bridge's main cables. The protection lasts for a long time. When the fire water source is exhausted, fire trucks can continue to provide water curtain protection through water pump connectors, significantly improving the safety and protection of the bridge's main cables. The system also offers the advantages of simple design, high reliability, and ease of maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0028] FIG1 is a schematic structural diagram of an embodiment of the present invention;

[0029] FIG2 is a diagram showing the distribution structure of water supply branches and water curtain nozzle groups on a bridge according to an embodiment of the present invention;

[0030] FIG3 is a schematic structural diagram of a water curtain nozzle group according to an embodiment of the present invention;

[0031] FIG4 is a bottom view of the water curtain nozzle assembly according to an embodiment of the present invention;

[0032] FIG5 is a schematic diagram of the arrangement spacing and spray protection area of ​​the water curtain nozzle group according to an embodiment of the present invention;

[0033] FIG6 is a schematic diagram of the relative positions of the water curtain nozzle group and the main cable of the bridge according to an embodiment of the present invention.

[0034] Description of reference numerals:

[0035] 1. Fire water source; 2. Fire water pump; 3. On-off valve; 4. Filter; 5. Main water supply pipeline; 6. Zone control valve group; 7. Water supply branch pipe; 8. One-way valve; 9. Water pump coupler; 10. Pressure reducing valve; 11. Sprinkler branch pipe; 12. Water curtain nozzle group; 13. Control system; 14. Fire detector; 15. Bridge main cable; 121. Nozzle base; 122. Water curtain nozzle. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0037] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention 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 limiting the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0038] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0039] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0040] As shown in the figure, a fire water curtain protection system for bridge main cables includes a fire water source 1 for providing water for the water curtain protection. Fire water source 1 can be a fire water pool or a fire water tank, determined based on the actual water consumption of the fire water curtain protection system. The outlet at the lower end of fire water source 1 is connected to a main water supply pipeline 5. One end of main water supply pipeline 5 is connected to the outlet of fire water source 1, and the other end of main water supply pipeline 5 is connected to the water inlet of a zone control valve group 6.

[0041] The main water supply pipeline 5, running from the fire water source 1 to the zoned control valve assembly 6, is equipped with a fire pump 2, an on / off valve 3, and a filter 4. A control system 13 is electrically connected to the fire pump 2 and controls its on / off. The control system 13 also works in conjunction with a fire detector 14, which transmits detected signals to the control system 13, which then turns the fire pump 2 on and off. The fire pump 2 is capable of meeting the water supply needs of the entire fire water curtain system and is preferably a centrifugal pump.

[0042] The other end of the zoning control valve group 6 is connected to each water supply branch pipe 7. The zoning control valve group 6 has a corresponding number of solenoid valves integrated therein according to the number of water supply branch pipes 7. Each solenoid valve is connected to one water supply branch pipe 7. The switching of the solenoid valves in the zoning control valve group 6 is controlled by the control system 13. When receiving the switching signal from the control system 13, the corresponding solenoid valve is actuated to control the opening and closing of the water supply branch pipe 7.

[0043] A one-way valve 8, a water pump adapter 9, and a pressure reducing valve 10 are installed on the water supply branch pipe 7. The water pump adapter 9 is installed on the water supply branch pipe 7 between the one-way valve 8 and the pressure reducing valve 10. The outlet of the water supply branch pipe 7 is connected to the middle position of the sprinkler branch pipe 11. The one-way valve 8 is installed at the front end of the water pump adapter 9. The one-way valve 8 prevents water from flowing back into the fire pump and back into the fire water source 1 when the fire truck uses the water pump adapter 9 to supply water to the pipeline.

[0044] The water inlet of the spray branch pipe 11 is connected to the water supply branch pipe 7. A plurality of water curtain nozzle groups 12 are installed and arranged on the side wall of the spray branch pipe 11 along its length direction. When working, the water curtain nozzle group 12 can form a circular water curtain to block the high temperature and heat radiation of the flame and protect the main cable 15 of the bridge from damage.

[0045] The water pump connector 9 is arranged on the roadside of the bridge deck, so that after the fire water source 1 is used up, a fire truck can be used to supply water to the water supply branch, thereby increasing the spraying time of the fire water curtain system.

[0046] The pressure reducing valve 10 is used to control the working pressure of the water curtain nozzle 122 of this branch. Due to the large height difference along the main cable 15 of the bridge, in order to ensure the rated working pressure of the water curtain nozzle group 12 on this branch, the required water inlet pressure is different. The water inlet pressure of each branch is adjusted by the corresponding pressure reducing valve 10 separately.

[0047] The control system 13 is simultaneously connected to the fire water pump 2, the partition control valve group 6 and multiple fire detectors 14. When a fire occurs, the fire detector 14 detects the fire and sends a fire signal to the control system 13. The control system 13 controls the fire water pump 2 to start under automatic control or manual control, and simultaneously starts the solenoid valve of the branch corresponding to the fire detector 14 in the partition control valve group 6, thereby providing water to the sprinkler branch 11 for water curtain spraying.

[0048] The fire detector 14 is used to detect fire and send an alarm signal to the control system 13. The fire detector 14 preferably adopts a linear temperature-sensing cable or a temperature-sensing optical fiber. The fire detector 14 and the sprinkler branch pipe 11 are arranged along the main cable 15 of the bridge. The arrangement length of the fire detector 14 is consistent with the length of the sprinkler branch pipe 11.

[0049] The water curtain nozzle assembly 12 includes a nozzle base 121, to which are fixed a plurality of water curtain nozzles 122. The water curtain nozzles 122 are connected to the spray branch pipe 11. The nozzle base 121 is fixed to the spray branch pipe 11. The water curtain nozzles 122 are arranged uniformly in a circle around the nozzle base 121. The nozzles of the water curtain nozzles 122 face outward, and the water inlet direction of the water curtain nozzles 122 is perpendicular to the water outlet direction. The nozzles of the water curtain nozzles 122 arranged in a circle form a 360-degree circular water curtain. The water curtain nozzles 122 preferably have an angle of spread a of 120 degrees, and the number of nozzles n = 360 degrees / 120 degrees = 3.

[0050] The water curtain nozzle group 12 is arranged obliquely below the bridge main cable 15 facing the bridge side. The water inlet axis of the water curtain nozzle group 12 is arranged at a 45° angle to the horizontal line, and the water curtain spraying direction is at a 90° angle to the water inlet axis of the water curtain nozzle group 12.

[0051] As shown in Figures 5 and 6, a design method for a bridge main cable fire water curtain protection system includes the following steps:

[0052] S1: Determine the spacing and spraying protection area of ​​the water curtain nozzle group 12.

[0053] On the vertical and horizontal coordinate grid, based on the spray profile diagram of the water curtain nozzle 122 provided by the manufacturer, draw the water curtain spray profile curve for the set design pressure and flow rate. Ensure that the water curtain spray profile curves of two adjacent water curtain nozzles 122 intersect. Measure the straight-line distance d between the two adjacent intersection points to determine the spacing of the water curtain nozzle group 12. Draw a circle with the center of the water curtain nozzle group 12 as the center and the distance from the intersection point to the center as the radius r. The circle formed is the water curtain spray protection area of ​​the water curtain nozzle group 12.

[0054] The water curtain spray protection circle radius r of the water curtain nozzle group 12 should meet the following requirements:

[0055]

[0056] Wherein: D is the vertical distance between the center of the water curtain nozzle group 12 and the axis of the bridge main cable 15; R is the radius of the bridge main cable 15.

[0057] S2: Length of spray branch pipe 11,

[0058] The length of the spray branch pipe 11 should meet the requirement that the height difference between the highest point water curtain nozzle group 12 and the lowest point water curtain nozzle group 12 does not exceed 20 meters.

[0059] S3: Determine the pressure value set at the outlet of the pressure reducing valve 10,

[0060] The outlet pressure of each pressure reducing valve 10 installed on each water supply branch needs to be set separately. The outlet pressure is calculated according to the following formula:

[0061]

[0062] Where: P—the outlet setting pressure of the pressure reducing valve 10 (MPa);

[0063] —Cumulative value of pipeline head loss along the pipeline and in local areas (MPa);

[0064] P0—the working pressure of the water curtain nozzle group 12 at the most unfavorable point (MPa);

[0065] Z—elevation difference between the water supply branch 7 and the pressure reducing valve 10 (MPa).

[0066] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A design method for a bridge main cable fire water curtain protection system, characterized in that: The following steps are involved: S1: Fire detectors (14) and sprinkler branches (11) are arranged along the main cable (15) of the bridge. A plurality of water curtain nozzle groups (12) for extinguishing bridge fires are arranged on the sprinkler branches (11). The water curtain nozzle groups (12) are connected to a water supply system. The water supply system and the fire detectors (14) are respectively electrically connected to a control system (13). The fire detectors (14) transmit detected signals to the control system (13). The control system (13) controls the water supply system to supply water to the sprinkler branches (11). S2: Determine the arrangement spacing and spray protection area of ​​the water curtain nozzle group (12), and draw a water curtain spray profile curve under a set design pressure and flow rate on the vertical and horizontal coordinate grid diagram according to the provided water curtain nozzle (122) spray profile diagram, to ensure that the water curtain spray profile curves of two adjacent water curtain nozzles (122) have an intersection point; S3: Each spray branch pipe (11) is connected to a corresponding water supply branch, and a pressure reducing valve (10) for controlling the water pressure of the spray branch pipe (11) is provided on the water supply branch. The pressure reducing valve (10) on each water supply branch needs to set an outlet pressure individually, and the outlet pressure is calculated according to the following formula: Where: P—the outlet setting pressure of the pressure reducing valve (10) (MPa), —The cumulative value of the water head loss along the pipeline and locally (MPa); P0—The working pressure of the water curtain nozzle group (12) at the most unfavorable point (MPa); Z—The elevation difference between the water supply branch and the pressure reducing valve (10) (MPa).

2. The design method of the bridge main cable fire water curtain protection system according to claim 1 is characterized by: In step S2, the straight-line distance d between the intersection points of the water curtain spraying profile curves of two adjacent water curtain nozzle groups (12) is measured, which is the arrangement spacing of the water curtain nozzle groups (12). A circle is drawn with the center of the water curtain nozzle group (12) as the center and the distance from the intersection point to the center of the circle as the radius r. The circle formed at this time is the water curtain spraying protection area of ​​the water curtain nozzle group (12). The water curtain spraying protection circle radius r of the water curtain nozzle group (12) should satisfy: Wherein: D is the distance between the water curtain nozzle group (12) and the axis of the bridge main cable (15); R is the radius of the bridge main cable (15).

3. The design method of the bridge main cable fire water curtain protection system according to claim 1 is characterized by: The length of the spray branch pipe (11) should ensure that the height difference between the highest point water curtain nozzle group (12) and the lowest point water curtain nozzle group (12) does not exceed 20 meters.

4. The design method of the bridge main cable fire water curtain protection system according to claim 1 is characterized by: The water supply system comprises a fire water source (1), a water outlet at the lower end of the fire water source (1) is connected to one end of a main water supply pipeline (5), the other end of the main water supply pipeline (5) is connected to a water inlet of a partition control valve group (6), the other end of the partition control valve group (6) is connected to each water supply branch pipe (7), a fire water pump (2) is arranged on the main water supply pipeline (5), a control system (13) is electrically connected to the fire water pump (2), a fire detector (14) transmits a detected fire signal to the control system (13), the control system (13) controls the fire water pump (2) to start, and simultaneously starts the partition control valve group (6) to provide water source to the sprinkler branch pipe (11) for water curtain spraying.

5. The design method of the bridge main cable fire water curtain protection system according to claim 4 is characterized by: A one-way valve (8), a water pump adapter (9) and a pressure reducing valve (10) are also installed on the water supply branch pipe (7). The water pump adapter (9) is arranged on the water supply branch pipe (7) between the one-way valve (8) and the pressure reducing valve (10). The one-way valve (8) is close to the partition control valve group (6). The water pump adapter (9) can be connected to the water source of the fire truck.

6. The design method of the bridge main cable fire water curtain protection system according to claim 5 is characterized by: The water pump coupling (9) is arranged on the roadside of the bridge deck.

7. The design method of the bridge main cable fire water curtain protection system according to claim 1 is characterized by: The water curtain nozzle group (12) comprises a nozzle base (121), a plurality of water curtain nozzles (122) are fixed on the nozzle base (121), the water curtain nozzles (122) are connected to the spray branch pipe (11), the nozzle base (121) is fixed on the spray branch pipe (11), the water curtain nozzles (122) are arranged in a circular shape on the nozzle base (121) and are evenly arranged, the nozzles of the water curtain nozzles (122) face outward, and the water curtains sprayed by the nozzles of the water curtain nozzles (122) arranged in a circle form a 360-degree circular water curtain.

8. The design method of the bridge main cable fire water curtain protection system according to claim 7 is characterized by: The water curtain nozzle (122) uses a water curtain nozzle (122) with an extension angle of 120°, so the number of nozzles n=360° / 120°=3.

9. The design method of the bridge main cable fire water curtain protection system according to claim 1 is characterized by: The water inlet axis of the water curtain nozzle group (12) is arranged at an angle of 45° to the horizontal line, and the water curtain spraying direction is at an angle of 90° to the water inlet axis of the water curtain nozzle group (12).

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