Installation Construction Method of FRP Chimney for Granulation Tower in Blast Furnace Slag System

Abstract

The present invention relates to a construction method for installing a fiberglass chimney in a granulation tower of a blast furnace slag system. Before installation, the chimney needs to be designed and segmented. The vertical section is installed on a steel support, and the steel support is fixed on the top platform of the blast furnace. Operating platforms are arranged on the vertical section corresponding to each layer of the top platform of the blast furnace. The operating platform expands 1000 mm outward from the center hole of the pipe hoop, and the operating platform is supported by a steel frame and paved with diamond plate; each vertical section is respectively combined into multiple hoisting units; hoisting and plug-in installation are carried out successively from bottom to top; before installing the inclined section, an inclined bridge is installed first. One end of the inclined bridge is fixed to the granulation tower, and the other end is fixed to the steel support; the A1A2 section is combined into a hoisting unit and connected to the steel structure chimney of the granulation tower; A3A4 is combined into a hoisting unit, A3 is plugged and bonded with A2; A4 is plugged and bonded with A5. An operating platform is erected based on the original stainless steel hoop, which can provide an operating platform for the connection between fiberglass pipes and the connection between the hoop and the blast furnace frame.

Description

Technical Field

[0001] The present invention belongs to the technical field of blast furnace construction, and specifically relates to an installation construction method for a fiberglass chimney of a granulation tower in a blast furnace slag water system. Background Art

[0002] When boiler tail gas and industrial furnace tail gas are discharged, they are all discharged into the atmosphere through a chimney. The size and height of the chimney are determined by the components and exhaust volume of the tail gas discharge. The Ministry of Environmental Protection of the country has strict emission standards for waste gas emissions. There are many hazardous substances in the tail gas discharge, so the height of the chimney is correspondingly increased.

[0003] The volume of newly built blast furnace projects is mostly large furnaces of about 1000 m³, and the height is close to 100 m. The granulation tower chimney of the blast furnace slag water system is also required to be close to the height of the blast furnace frame. The chimney needs to consider requirements such as environmental protection performance and process steam corrosion. In recent years, fiberglass chimneys have been mostly used. The fiberglass chimney has an integral structure without corrosion weak points, excellent corrosion resistance, high cost performance, low maintenance cost for a long time, high temperature resistance performance, and low overall life cost. The product has strong designability and can be customized according to different customer needs.

[0004] In the prior art, construction platforms need to be built for ultra-high buildings. To protect the stability of the chimney, a reinforcement frame is generally configured. For example, the fiberglass chimney project of Teng Shida (Hebei) Engineering Co., Ltd. is a product. A steel frame with basically the same height is configured outside the fiberglass chimney for protection, and the cost of the facilities is extremely high. Summary of the Invention

[0005] The present invention aims to solve the above technical problems and provides an installation construction method for a fiberglass chimney of a granulation tower in a blast furnace slag water system that is convenient for installation and has a low cost.

[0006] To solve the above problems, the specific technical solution provided by the present invention is as follows:

[0007] An installation construction method for a fiberglass chimney of a granulation tower in a blast furnace slag water system. The fiberglass chimney is composed of an inclined section and a straight section, with a diameter of Φ2200 and a elevation of 45 m to 96 m. It is divided into eight segments from A1 to A8. The weights of each segment are as follows: the weight of A1 is about 1.5 t, the weight of A2 is about 0.67 t, the weight of A3 is about 2.05 t, the weight of A4 is about 2.05 t, the weight of A5 is about 2.9 t, the weight of A6 is about 2.2 t, the weight of A7 is about 2 t, and the weight of A8 is about 2.2 t. Among them, the segments from A5 to A8 are the vertical sections of the chimney, and the vertical sections are installed above the blast furnace top. Pipe clamps are installed at the corresponding heights of the vertical sections and the blast furnace platforms, and the pipe clamps are connected to the blast furnace platforms through connecting rods. The segments from A1 to A4 are the inclined sections of the chimney. One end of the inclined section is connected to the steel structure chimney of the granulation tower, and the other end is connected to the A5 segment.

[0008] The specific construction steps are as follows:

[0009] Step 1: Weld the steel supports of the fiberglass chimney on the ground. Use a 150t truck crane to hoist the steel supports onto the top platform frame of the blast furnace and install and fix them.

[0010] Step 2: Complete the installation of the steel structure chimney of the granulation tower and the installation of the base of the diagonal bridge reinforcement ring.

[0011] Step 3: Weld the diagonal bridge structure on the ground. Calculate the lifting points according to the plan. Use a 150t truck crane to hoist the diagonal bridge. The crane directly hoists the diagonal bridge slowly to the in-place position and places the diagonal bridge between the granulation tower and the blast furnace.

[0012] Step 4: Use a 500t truck crane to install sections A5 to A8.

[0013] Step 5: Use a 150t truck crane to install sections A1 to A4.

[0014] Among them, the specific operation of Step 4 is as follows: 1) Take section A5 as a hoisting unit, combine sections A6 and A7 as a hoisting unit, and section A8 as a hoisting unit; 2) When assembling sections A6 - A7 on the ground, pre-fix the embedded plates at the connection ends of the two sections. After the two sections are inserted into each other, the embedded plates of the two sections are connected by channel steel, and both ends of the channel steel are fixed to the embedded plates with high-strength bolts; 3) Vertically set each hoisting unit of the vertical section on the ground, install pipe clamps at the design positions, and then set up an operation platform with the pipe clamps as the central holes, and set safety fences around the platform; 4) Hoist section A5 alone onto the steel supports completed in Step 1 and fix it; 5) Hoist the A6 - A7 hoisting unit onto section A5 so that section A6 is inserted into section A5; 6) Weld the temporary straight ladder between the operation platforms of section A7 and section A8, then connect the straight ladder to the operation platform of section A8, and hoist the whole onto section A7, and section A8 is inserted into section A7.

[0015] The specific operation of Step 5 is as follows: 1) Combine section A1 and section A2 as a hoisting unit, and combine section A3 and section A4 as a hoisting unit. The combination method is the same as that of sections A6 and A7; 2) Hoist the A1 - A2 hoisting unit as a whole, and connect section A1 to the steel structure chimney of the granulation tower; 3) Hoist the A3 - A4 hoisting unit as a whole, insert section A3 into section A2, and set fiberglass cloth at the insertion end for bonding and reinforcement. Insert section A4 into section A5 and also bond and reinforce it.

[0016] For the present invention adopting the above technical structure, compared with the prior art, its beneficial effects are as follows:

[0017] 1. The upper part of the granulation tower adopts a fiberglass chimney, which can play a role in corrosion resistance. At the same time, the high emission of water slag steam can reduce the impact on the steel structure and equipment of the blast furnace body.

[0018] 2. An operation platform is erected on the original stainless steel hoop, which can provide an operation platform for the connection between fiberglass pipes and the connection between the hoop and the blast furnace frame, and can provide an operation surface for unhooking during hoisting operations.

[0019] 3. This platform can be set as a permanent platform, which can reduce the safety risks brought by demolishing the technical measures platform and can facilitate future maintenance at the same time.

[0020] 4. Due to the high hoisting height, large hoisting machinery must be used. Therefore, by adopting this construction method, aerial operations can be minimized, safety risks can be reduced, the construction period can be shortened, the use of large machinery can be reduced, and the construction cost can be lowered. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the overall structure diagram of the present invention;

[0022] Figure 2 is the schematic diagram of the segment insertion structure of the present invention;

[0023] Figure 3 is the schematic diagram of the connection structure at the lower end of the inclined bridge of the present invention;

[0024] Figure 4 is the schematic diagram of the connection structure of two segments combined into a hoisting unit of the present invention;

[0025] Figure 5 is the schematic diagram of the structure of the operation platform on the fiberglass chimney of the present invention from a top-down perspective;

[0026] Figure 6 is the schematic diagram of the elevation structure of the operation platform of the present invention;

[0027] Figure 7 is the schematic diagram of the hoisting of the fiberglass chimney of the present invention.

[0028] In the figure: 1. Granulation tower; 2. Inclined bridge; 3. Inclined section; 4. Vertical section; 5. Pipe hoop; 6. Operation platform; 7. Steel support; 8. Top platform of the blast furnace; 9. Steel plate embedded part; 10. Reinforcing channel steel; 9. Checkered plate; 10. Rail; 11. Cross beam; 12. Triangular support; 13. Straight ladder. DETAILED DESCRIPTION OF THE INVENTION

[0029] The following further describes the present invention in conjunction with embodiments, and the purpose is only to better understand the content of the present invention. Therefore, the examples given do not limit the protection scope of the present invention.

[0030] The construction of the fiberglass chimney of the granulation tower in the blast furnace slag system of the present invention includes two parts: the butt joint construction of the fiberglass chimney structure and the installation construction of the inclined bridge and the steel structure base.

[0031] The following is a detailed description of the workpieces involved in the construction of the present invention:

[0032] Refer to Figure 1 , a fiberglass chimney is installed above the granulation tower of the blast furnace, which is a combination of an inclined section 3 and a vertical section 4. The diameter of the fiberglass chimney is Φ2200, and the elevation is from 45m to 96m, with a total of 8 sections A1 to A8. The distance from the blast furnace frame is 1.5 meters to 7.1 meters (the length of the inclined section). In the implementation of the present invention, the weight distribution of each section is as follows: the weight of A1 is about 1.5t, the weight of A2 is about 0.67t, the weight of A3 is about 2.05t, the weight of A4 is about 2.05t, the weight of A5 is about 2.9t, the weight of A6 is about 2.2t, the weight of A7 is about 2t, and the weight of A8 is about 2.2t.

[0033] The sections from A5 to A8 are the vertical section 4 of the fiberglass chimney. A steel support 7 is provided at the bottom of this part of the fiberglass chimney. The steel support 7 of the fiberglass chimney is arranged on the top platform 8 of the blast furnace, and the height of the steel support 7 is slightly higher than the chimney opening of the granulation tower 1. The sections from A1 to A4 connect the chimney opening of the granulation tower and the vertical section 4 of the fiberglass chimney. This part is the inclined section 3 of the fiberglass chimney. A skew bridge 2 is provided on the lower side of the inclined section 3 of the fiberglass chimney. The self-weight of the skew bridge 2 is 8t, and the skew bridge 2 is a bridge-shaped truss assembled from angle steel and section steel.

[0034] Each section of the fiberglass chimney is connected by socket connection and bonding. The material is high-strength FRP fiberglass, and it also includes pipelines, pipeline connections, hoop, flanges, and bolt connection fasteners, etc. The whole has acid resistance, alkali resistance, and high temperature resistance of 120°C. For the straight section length, the manufacturer considers the system compensation for the high and low temperature difference. The exhaust pipeline is required to be used for more than 10 years. The fiberglass chimney has a large height. Originally, in order to stabilize the chimney, a pipe hoop 5 (i.e., a hoop) was installed on the chimney, and the pipe hoop was connected to each layer of the platform on the blast furnace with a connecting rod. Generally, two angle steels are used as the connecting rods.

[0035] The following is a detailed description of the construction method of the present invention in combination with specific working conditions and specific embodiments:

[0036] A construction method for installing a fiberglass chimney in a blast furnace slag water system is as follows:

[0037] I. First, use a 150t truck crane to complete the installation of the steel structure of the steel support 7 of the fiberglass chimney above the top platform frame of the blast furnace.

[0038] II. Complete the installation of the steel structure chimney of the granulation tower 1 and the installation of the base of the reinforcement ring of the skew bridge 2. The reinforcement ring of the skew bridge 2 is a structure installed on the steel support 7. These two steps are both preparatory work for the installation of the skew bridge 2. Refer to Figure 3 .

[0039] III. Since the BF downcomer has been installed, the crane's standing position is relatively narrow and can only be located between the BF tapping yard and Granulation Tower 1, and the hoisting is carried out close to Granulation Tower 1 of the BF. For the specific hoisting standing position, see Figure 6 . Calculate the lifting points according to the plan. The center line position of the 150t truck crane is 15000mm away from the north side of the tapping yard. The 150t truck crane hoists the inclined bridge 2. The crane directly hoists the inclined bridge 2 and slowly reaches the installation position, and places the inclined bridge 2 between Granulation Tower 1 and Steel Support 7. Specifically, during the hoisting process, adjust the angle of the hoisted inclined bridge 2. Preferably, the inclined bridge 2 is close to and slightly larger than the designed angle.

[0040] IV. Use a 500t truck crane to hoist the FRP chimney sections A5 - A8.

[0041] V. Use a 150t truck crane to hoist the FRP chimney sections A1 - A4.

[0042] Regarding the fourth and fifth steps, for the installation construction of each section, the specific operations are as follows:

[0043] 1. Generally, Section A1 and Section A2 of the FRP chimney are an integral whole; the connections between Section A2 and Section A3, and between Section A4 and Section A5 are bonded with fiberglass cloth, and the connections of other sections are socket joints (see Figure 2 ). Determine that A1A2 is one hoisting unit, A3A4 is one hoisting unit, A5 is one hoisting unit, A6A7 is one hoisting unit, and A8 is one hoisting unit, totaling 5 hoisting units. Among them, A1A2 is an integral whole by itself and can be hoisted independently; the connection between A3A4 and A6A7 is a socket connection and needs to be connected as an integral whole. After communicating with the equipment manufacturer, the connection plan is determined: see Figure 4 , set steel plate embedded parts 9 at the interface of the FRP chimney, and bond them around the interface of the chimney shell with fiberglass cloth. Our unit uses high-strength bolts and reinforcing channel steel 10 for connection on site. For the specific assembly method, see Figure 7 . The assembly site of the FRP chimney is required to be flat, clean, firm and durable. At the same time, considering the economic performance of the construction plan and the safety of aerial operations, the number of aerial hoisting components should be minimized as much as possible.

[0044] 2. Specific hoisting method

[0045] 2.1 Technical measures preparation before hoisting

[0046] Before the installation construction of the FRP chimney, the corresponding steel structure framework needs to be installed first to ensure the stability of the FRP chimney installation. Since the FRP is far from the BF framework, for socket connection construction, hoisting hook removal, and the connection of the hoop to the steel framework of the BF top platform 8, personnel need to operate at close range. In the present invention, at the position of the hoop connected to the upper platform of the BF, an operating platform 6 based on the hoop (hereinafter referred to as the pipe hoop) is provided. Specifically, seeFigure 5 , Figure 6 , a platform surface with a diameter of 1000 mm is extended outward from the center hole of the pipe coupling 5 and paved with diamond plate 11-1. Its bottom is supported by a steel frame. The bottom frame of the diamond plate 11-1 is fixedly connected by a number of triangular supports 11-4 and steel crossbeams 11-3. The vertical part of the triangular support 11-4 is in contact with the surface of the FRP chimney, and the horizontal part is in contact with the bottom surface of the diamond plate 11-1. The steel crossbeam 11-3 connects each triangular support 11-4. Railings 11-3 are provided at the periphery of the operating platform 6. The operating platform 6 can be circular or square. The bottom frame of the operating platform 6 uses 10# channel steel as the platform steel crossbeam 11-3, and angle steel L60*6 is used to make the triangular support 11-4.

[0047] See Figure 1 , in the embodiment of the present invention, a total of five operating platforms 6 are provided on the FRP chimney. Among them, the two top operating platforms 6 are relatively far from the blast furnace frame (referring to the steel structures of the blast furnace top platform and the platforms above), reaching about 7 meters. Two angle steels L100*8 are set up between the two platforms at 75 meters and 88 meters as the support 12 for the temporary straight ladder, and this straight ladder 12 can be removed or not removed after installation.

[0048] Assembly of each layer of operating platform 6 on the FRP chimney: The FRP steel pipe is first erected vertically on the ground, and the operating platform 6 and the pipe coupling 5 are installed in advance at the corresponding positions of the FRP chimney. A straight ladder is provided between the two top operating platforms 6. This temporary straight ladder 12 is connected and fixed to the A8 section in advance and hoisted integrally with the A8 section; the connecting rod of the pipe coupling 5 is hoisted in advance to the corresponding platform at the upper part of the blast furnace.

[0049] The A1-A2 hoisting unit is hoisted integrally by a 150-ton truck crane; the A3-A4 hoisting unit is assembled together on the ground and hoisted to the installation position by a 150-ton truck crane; the A5 section is hoisted separately by a 500-ton truck crane; the A6-A7 hoisting unit is assembled together on the ground and hoisted by a 500-ton truck crane; the A8 section is hoisted separately by a 500-ton truck crane; after hoisting, since it is necessary to paste and install between the A2 section and the A3 section, and between the A4 section and the A5 section, temporary supports are erected at the top of the granulation tower and the base of the FRP chimney on both sides for personnel to operate. The additional technical measures materials required for the new operation are as follows:

[0050] Serial Number Name Specification Quantity Remarks 1 Channel Steel 10# 200 Main Structure of Technical Measure Platform 2 Angle Steel L60*6 150 Support of Technical Measure Platform 3 Round Steel Φ12 200 Horizontal Bar of Ladder 4 Round Tube 50*4 160 Guard Rail 5 Round Tube 26.5*3.5 160 Guard Rail 6 Flat Steel 100*4 70 Guard Rail 7 Patterned Plate 6 65 Patterned Plate of Platform 8 Angle Steel 100*8 26 Vertical Bar of Ladder

[0051] 2.2 Structural Hoisting Performance Selection

[0052] Due to the narrow site on-site, the slewing radius of the crane is very small. After calculation and actual full-scale lofting, the lifting height is about 100 meters. A 500t truck crane is adopted, with a working condition of a 78m main boom, a 30m auxiliary boom, and a 20m slewing radius. The rated lifting capacity is 94t, far exceeding the heaviest lifting unit of the fiberglass steel structure, which is 4.2t, meeting the lifting requirements. The installation of Sections A1 to A4 is carried out by a 150t truck crane, with a working condition of a 58m main boom, an elevation angle of 85°, and a 10m slewing radius. The rated lifting capacity is 13.5t > the heaviest lifting unit of 8t, meeting the lifting requirements.

[0053] 2.3 Calculation of the selection of lifting steel ropes

[0054] The steel structure inclined bridge of this project is the heaviest lifting unit, about 8t. The designed angle between the body structure and the horizontal ground is 25°. The distribution of each component of the inclined bridge structure is symmetrically arranged. Therefore, the center of gravity of the inclined bridge assembly unit is in the vertical plane of the center line of the inclined bridge. Through force calculation, the center of gravity position of the inclined bridge body in the height and width directions is basically at the center position.

[0055] For the two lifting points below the inclined bridge body, one 15m long and Ф22mm diameter steel rope is selected and used after being folded in half. For the upper lifting point, one 10m long and Ф22mm diameter steel rope is selected and used after being folded in half. The lifting points are set on the lower chord lifting lugs of the inclined bridge truss (the lifting lugs are set at about 3.5m above and below the center).

[0056] 2.4 Lifting of fiberglass steel structure

[0057] Lifting of the inclined bridge body: At the position of the inclined bridge body as shown in the figure, according to the calculation results, 4 lifting lugs are welded for lifting. After the lifting is completed, the lifting lugs are directly used as a part of the structure without further treatment. The lifting ropes are 2 fiber core steel ropes, of the 6*37+1 type, with a nominal tensile strength of 1770MPa, a diameter of φ22mm, lengths of 15m and 10m respectively, and a maximum allowable lifting capacity of 3.9t. 4 10t shackles are selected, and the total weight of the hook head, lifting rope, and shackle is 2t, meeting the lifting requirements.

[0058] Since the self-weight of the fiberglass steel chimney is relatively light, the manufacturer-designed embedded lifting lugs are adopted. The lifting is carried out by using 2 φ22mm and 8m steel ropes folded in half for lifting, and four lifting points are symmetrically set above the original round opening. The lifting schematic diagram is shown in Figure 7 .

[0059] The beneficial effects of the present invention:

[0060] 1) The use of a fiberglass chimney in the upper part of the granulation tower can play a role in corrosion resistance. At the same time, the high emission of water slag steam can reduce the impact on the steel structure and equipment of the blast furnace body. 2) In the present invention, an operation platform is erected on the original stainless steel hoop, which can provide an operation platform for the connection between fiberglass pipes and for the connection between the hoop and the blast furnace frame, and can provide an operation surface for unhooking during hoisting operations. 3) The operation platform of the present invention can be used as a permanent platform, reducing the safety risks brought by demolition technical measures, and can also provide convenience for future maintenance. 4) Due to the high hoisting height, large hoisting machinery must be used. Therefore, by adopting this construction method, aerial operations can be minimized, safety risks can be reduced, the construction period can be shortened, the use of large machinery can be reduced, and the construction cost can be lowered.

[0061] The above are only the preferred and feasible embodiments of the present invention, and do not limit the scope of rights of the present invention. Any equivalent changes made by using the content of the specification and drawings of the present invention are included within the scope of rights of the present invention.

Claims

1. A construction method for installing a fiberglass chimney in a granulation tower of a blast furnace water slag system. The fiberglass chimney consists of an inclined section and a straight section, with a diameter of Φ2200mm and a height from 45m to 96m. It is divided into eight segments from A1 to A8, and the weights of each segment are as follows: the weight of A1 is 1.5t, the weight of A2 is 0.67t, the weight of A3 is 2.05t, the weight of A4 is 2.05t, the weight of A5 is 2.9t, the weight of A6 is 2.2t, the weight of A7 is 2t, and the weight of A8 is 2.2t. Among them, the segments from A5 to A8 are the vertical sections of the chimney, and the vertical sections are installed above the blast furnace top. Pipe clamps are installed at the corresponding heights of each layer of the blast furnace platform for the vertical sections, and the pipe clamps are connected to the blast furnace platform through connecting rods. The segments from A1 to A4 are the inclined sections of the chimney. One end of the inclined section is connected to the steel structure chimney of the granulation tower, and the other end is connected to the A5 segment. The specific construction steps are as follows. Step 1: Weld the steel supports of the fiberglass chimney on the ground, and use a 150t truck crane to hoist the steel supports onto the blast furnace top platform frame for installation and fixation. Step 2: Complete the installation of the steel structure chimney of the granulation tower and the installation of the base of the inclined bridge reinforcement ring. Step 3: Weld the inclined bridge structure on the ground, calculate the lifting points according to the plan, and use a 150t truck crane to hoist the inclined bridge. The crane directly hoists the inclined bridge slowly to the in-place position and places the inclined bridge between the granulation tower and the blast furnace. Step 4: Use a 500t truck crane to install the segments from A5 to A8. Step 5: Use a 150t truck crane to install the segments from A1 to A4. It is characterized in that: The specific operation of Step 4 is as follows: 1) Take the A5 segment as a hoisting unit, combine the A6 segment and the A7 segment as a hoisting unit, and the A8 segment as a hoisting unit. 2) When assembling the A6 - A7 hoisting unit on the ground, pre - fix the embedded plates at the connecting ends of the two segments. After the segments are inserted into each other, the embedded plates of the two segments are connected by channel steel, and both ends of the channel steel are fixed to the embedded plates with high - strength bolts. 3) Vertically position each hoisting unit on the ground, install pipe clamps at the designed positions, and then set up an operating platform with the pipe clamps as the central holes, and install safety railings around the platform. 4) Hoist the A5 segment alone onto the steel support completed in Step 1 and fix it. 5) Hoist the A6 - A7 hoisting unit above the A5 segment so that the A6 segment is inserted into the A5 segment. 6) Weld the temporary straight climbing ladder between the operating platforms of the A7 segment and the A8 segment. 7) Then connect the welded straight climbing ladder to the operating platform of the A8 segment; hoist the combination of the A8 segment and the straight climbing ladder as a whole above the A7 segment, and insert the A8 segment into the A7 segment. The specific operation of Step 5 is as follows: 1) Combine the A1 segment and the A2 segment as a hoisting unit, and combine the A3 segment and the A4 segment as a hoisting unit. The combination method is the same as that of the A6 segment and the A7 segment. 2) Hoist the A1 - A2 hoisting unit as a whole, and connect the A1 segment to the steel structure chimney of the granulation tower. 3) Hoist the A3 - A4 hoisting unit as a whole, insert the A3 segment into the A2 segment, and set up fiberglass cloth at the inserted end for bonding and reinforcement. Insert the A4 segment into the A5 segment and also bond and reinforce it.

2. The installation construction method of the FRP chimney of the granulation tower in the blast furnace slag system according to claim 1, characterized in that: When the inclined bridge is hoisted in Step 2, the angle of the inclined bridge is greater than or equal to its installation angle.

3. The installation construction method of the FRP chimney of the granulation tower in the blast furnace slag system according to claim 1 is characterized in that: The surface of the operation platform is paved with diamond plate, and the width of the platform extends 1000 mm outward based on the pipe clamp; the bottom frame of the diamond plate is fixedly connected by a number of triangular supports and steel crossbeams. The vertical part of the triangular support is in contact with the surface of the fiberglass chimney, and the horizontal part is in contact with the bottom surface of the diamond plate. The steel crossbeams connect the triangular supports.

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