Modular detachable large PPH vertical storage tank structure

Abstract

The utility model relates to a modularization detachable large -scale PPH vertical storage tank structure, including tank bottom, tank body and tank top, at least two between tank bottom, tank body, tank top are detachably fixed connection through annular connecting mechanism, the connecting mechanism includes a pair of each other butt joint's composite flange, the composite flane includes a metal framework and a PPH cladding, the PPH cladding is through hot melt mode cladding in the metal framework outside, and the PPH cladding with the PPH material body of tank bottom, tank body or tank top is through hot melt and forms integral structure, a pair of composite flanges are connected through fastener, the utility model provides a modularization detachable large -scale PPH vertical storage tank structure, and the storage tank passes through an innovative composite flange connecting mechanism, realizes the reliable connection of tank body each component, and the contradiction between large -scale equipment transportation, installation and long -term corrosion resistance requirement is preferably solved.

Description

Technical Field

[0001] This utility model relates to the field of chemical equipment technology, specifically to a modular, detachable large PPH vertical storage tank structure. Background Technology

[0002] Polypropylene (PPH) storage tanks are widely used for liquid storage and treatment in industries such as chemical, environmental protection, and metallurgy due to their excellent corrosion resistance. With the expansion of production scale, the demand for large and even ultra-large PPH vertical storage tanks is increasing. However, the overall manufacturing, transportation, and installation of large PPH storage tanks face many challenges, such as exceeding transportation size limits, road load-bearing restrictions, and difficulties in on-site installation.

[0003] Currently, to address the aforementioned issues, some technical solutions attempt to adopt a segmented structure, connecting each tank segment via flanges. However, traditional plastic flanges suffer from insufficient rigidity, limited pressure-bearing capacity, and susceptibility to deformation leading to sealing failure. Furthermore, the significant difference in thermal expansion coefficients between metal flanges and the PPH tank body makes the connection interface prone to gaps under fluctuating temperature conditions, allowing corrosive media to penetrate. This not only corrodes the metal flange itself but may also create crevice corrosion at the interface, becoming a weak point for leakage and structural failure, ultimately affecting the overall lifespan of the equipment and the purity of the stored medium.

[0004] Therefore, there is an urgent need for a solution that can meet the requirements of detachable transportation and installation of large storage tanks, while ensuring that the connection has high strength, high sealing performance and full corrosion resistance comparable to the main body. Utility Model Content

[0005] In view of this, the present invention provides a modular and detachable large PPH vertical storage tank structure. The storage tank achieves reliable connection of various components of the tank body through an innovative composite flange connection mechanism, which effectively solves the contradiction between the transportation and installation of large equipment and the long-term corrosion resistance requirements.

[0006] The objective of this utility model is achieved through the following technical solution: A modular, detachable large PPH vertical storage tank structure includes a tank bottom, a tank body, and a tank top. At least two of the tank bottom, tank body, and tank top are detachably and fixedly connected by an annular connecting mechanism. The connecting mechanism includes a pair of mating composite flanges. Each composite flange includes a metal frame and a PPH coating layer. The PPH coating layer is applied to the outside of the metal frame by heat fusion, and the PPH coating layer is integrally formed with the PPH material body of the tank bottom, tank body, or tank top by heat fusion. The pair of composite flanges are connected by fasteners.

[0007] By employing a detachable ring-shaped connection mechanism to connect the main components of the storage tank, modular design and installation of large storage tanks are achieved. This detachable connection method significantly reduces the difficulty of manufacturing, transporting, and on-site construction of large equipment, allowing the storage tank to be disassembled into multiple parts for transportation. This effectively solves the problem of exceeding size limits during overall transportation and greatly expands the application scenarios of large storage tanks. The core of the connection mechanism is a pair of composite flanges, which innovatively adopt a composite structure of a metal skeleton and a PPH coating layer. The metal skeleton provides the necessary mechanical strength and structural rigidity for the connection, ensuring that the flange interface maintains shape stability and connection reliability under the action of fastener pre-tightening force and internal medium pressure, overcoming the shortcomings of insufficient pressure bearing capacity and rigidity of pure plastic flanges. At the same time, the PPH coating layer perfectly covers the metal skeleton through hot-melt and forms a seamless integrated structure with the tank body through hot-melt. This design fundamentally ensures the material continuity and consistency of the connection area, completely eliminating the leakage channels that may exist between the metal material and the plastic tank body due to physical connection. This integrated hot-melt connection method ensures that the entire connection area possesses the same excellent corrosion resistance and sealing integrity as the tank body, enabling it to withstand the erosion of highly corrosive chemical media for extended periods. Furthermore, this solution provides a novel, safe, and reliable connection technology for the design and manufacture of large plastic pressure vessels, combining the high strength of metal structural components with the comprehensive corrosion resistance of plastic materials.

[0008] Preferably, the composite flange has an annular sealing groove on its mating end face.

[0009] It provides precise positioning and accommodating space for installing resilient seals. The sealing groove confines the sealing ring in a preset position, preventing it from shifting, twisting, or being squeezed out during assembly. This ensures that the sealing element is uniformly compressed after flange mating, forming a uniform and reliable static sealing barrier. This sealing barrier, as the primary line of defense, combined with the sealing properties of the flange material itself, enhances the overall sealing safety level of the flange connection interface, effectively preventing media leakage from the flange mating surface.

[0010] Preferably, a sealing element is provided in the sealing groove.

[0011] This constitutes a complete secondary sealing system. When a pair of composite flanges are tightened by fasteners, the seal undergoes elastic deformation within the sealing groove, tightly filling the microscopic unevenness between the flange end faces and actively compensating for minor displacements caused by machining errors or thermal expansion and contraction. This design significantly enhances the sealing capability of the interface against internal media pressure, especially for gaseous media or volatile liquids, effectively blocking leakage paths. Combined with the inherent excellent sealing properties of the PPH material, it forms multiple sealing safeguards, further improving the sealing reliability and safety of the connection during long-term use.

[0012] Preferably, it also includes a PPH material sealing cover, which is disposed on the outside of the fastener.

[0013] A sealing cover made of PPH material was added to completely cover the fasteners. This design completely isolates the metal fasteners exposed to the environment from the external corrosive environment, creating a relatively stable microenvironment. The PPH material is the same as the tank material and has good chemical stability, ensuring that the sealing cover itself will not introduce new corrosion points.

[0014] Preferably, the sealing cover and the outer walls of the composite flanges on both sides form a sealed anti-corrosion cavity. The two ends of the sealing cover are respectively connected to the PPH coating layer of the composite flanges on both sides by hot-melt welding to form a sealed connection, thus forming a sealed anti-corrosion cavity together with the outer walls of the flanges.

[0015] The sealing cover and the outer walls of the two composite flanges further define a sealed cavity. This structure successfully encapsulates all metal fasteners within a sealed space made of corrosion-resistant PPH material. This cavity effectively prevents contact between external humid air, chemical splashes, or corrosive atmospheres and the metal parts, fundamentally avoiding electrochemical or chemical corrosion of the metal fasteners. Since the integrity of the fasteners is crucial for maintaining the preload of the flange connection, this design indirectly ensures the long-term mechanical stability and sealing durability of the flange connection interface by protecting the fasteners from corrosion, thus extending the service life of the entire connection structure.

[0016] Preferably, the cross-sectional shape of the metal skeleton is "L".

[0017] The metal skeleton is designed with an "L"-shaped cross-section. This specific geometry provides a larger surface area and a better spatial structure, facilitating its bonding with the PPH overlay via hot-melt. The long and short sides of the "L" shape are embedded into the PPH material from different directions, creating mechanical interlocking and constraint on the overlay in multiple directions. This structure significantly enhances the bonding strength and load transfer efficiency between the metal skeleton and the PPH plastic, making them more firmly integrated and reducing the risk of delamination or relative displacement under complex stresses.

[0018] Preferably, the metal skeleton includes a horizontal portion and a vertical portion, wherein the horizontal portion is embedded within the end face of the PPH coating layer.

[0019] The horizontal portion of the metal skeleton is clearly embedded within the end face of the PPH cladding. This embedded structure allows the metal skeleton to directly bear and disperse the axial compressive stress and bolt preload transmitted from the flange mating face, effectively transferring these stresses to a larger area through its rigid skeleton. This design enhances the flange end face's resistance to compression and deformation, ensuring that the flange face remains flat when the bolts are tightened. This guarantees uniform compression of the seal, facilitating a reliable end face seal and improving the flange face's resistance to internal medium pressure.

[0020] Preferably, the vertical portion of the metal skeleton is embedded within the outer peripheral surface of the PPH coating layer.

[0021] The vertical portion of the metal skeleton is clearly embedded within the outer circumferential surface of the PPH cladding. This design allows the metal skeleton to effectively withstand and resist radial forces, bending moments, and potential shear stresses acting on the flange. It enhances the overall bending and torsional stiffness of the flange, preventing excessive deformation under asymmetric loads or external pipeline forces, and maintaining the alignment and stability of the flange connection. The combined embedding of the horizontal and vertical portions achieves all-around reinforcement from the end face to the outer circumference, resulting in more balanced and reliable mechanical properties of the composite flange.

[0022] Preferably, the composite flange has a reinforcing boss on its PPH coating layer, the reinforcing boss being located at the mounting hole of the fastener and protruding outward.

[0023] A reinforcing boss protrudes outwards from the PPH cladding around the fastener mounting holes. This boss structure increases the material thickness and section modulus in the area around the bolt holes, significantly enhancing the mechanical strength in this localized region. This better disperses and withstands the high concentrated compressive stress generated during bolt and nut tightening, preventing creep or plastic deformation of the PPH material under bolt preload, thus maintaining a stable bolt preload and preventing loosening due to stress relaxation. The boss design also improves the compressive and impact resistance of the mounting hole area, increasing the structure's durability.

[0024] Preferably, the fastener is a double-ended stud, and the two ends of the double-ended stud are equipped with nuts, which are in contact with the PPH coating layer of the composite flange.

[0025] Double-ended studs with nuts are selected as fasteners. The double-ended studs allow for tightening from both sides, facilitating installation and alignment in confined spaces. The nuts directly contact the PPH coating of the composite flange; their flat bottom provides uniform contact pressure, helping to reduce pressure on the PPH material surface and lowering the risk of localized compressive creep. This connection method contributes to a more uniform bolt load distribution, helps maintain the sealing pressure of the flange connection, and its structure also facilitates the inspection and replacement of individual bolts during maintenance.

[0026] The advantages of this utility model compared to the prior art are: This utility model discloses a modular, detachable large PPH vertical storage tank structure. Through an innovative detachable ring connection mechanism, the tank is divided into modules such as the tank bottom, tank top, and tank body, which can be composed of multiple sections. This modular design allows each component to be manufactured and transported independently, effectively overcoming the physical limitations of transporting large equipment as a whole, significantly reducing logistics complexity and costs, and providing greater flexibility and convenience for on-site installation.

[0027] The core of this solution lies in its unique composite flange structure. This flange innovatively combines a metal skeleton with a PPH cladding layer. The internal metal skeleton provides the necessary mechanical strength and structural rigidity for the entire connection area, effectively withstanding bolt preload, internal medium pressure, and external loads, ensuring a stable and reliable connection interface and addressing concerns about insufficient strength and rigidity inherent in pure plastic flanges. The external PPH cladding layer perfectly covers the metal skeleton through a hot-melt process, and more importantly, it forms a seamless integrated structure with the PPH material of the tank body through hot-melt bonding. This manufacturing process fundamentally ensures that the connection area and the tank body have continuous and consistent material properties, completely avoiding the interface leakage risk that may occur when connecting dissimilar materials, and giving the entire connection area the same high corrosion resistance as the tank body, achieving a unity of structural strength and comprehensive corrosion resistance.

[0028] Furthermore, the use of sealing grooves on the mating faces of the composite flanges, in conjunction with sealing components, helps to further improve the sealing reliability of the interface and enhances the protection against media leakage. The removable PPH material sealing cover design isolates the metal fasteners from the external environment, forming a protective cavity that helps slow down the corrosion rate of the fasteners. This is beneficial for maintaining the integrity of the bolted connections during long-term use, thus supporting the long-term stable operation of the entire tank connection system.

[0029] In summary, this solution provides a relatively effective and reliable systematic solution to address a series of issues related to structural strength, sealing durability, and all-material corrosion resistance in large PPH vertical storage tanks with detachable connections. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a structural diagram of a modular, detachable large PPH vertical storage tank structure according to an embodiment of the present invention.

[0032] Figure 2 This is a partial cross-sectional schematic diagram of a modular, detachable large PPH vertical storage tank structure according to an embodiment of the present invention.

[0033] Labeling explanation: 1 Tank bottom, 2 Tank top, 3 Tank body, 4 Connecting mechanism, 5 Composite flange, 6 Metal frame, 7 PPH coating layer, 8 Fastener, 9 Sealing groove, 10 Seal, 11 Sealing cover, 12 Reinforcing boss. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0036] It should be noted that similar reference numerals and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. In the description of the embodiments of this application, it should be understood that the terms "upper," "lower," "left," "right," "vertical," "horizontal," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures, or the orientation or positional relationship commonly used when the product of this application is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0038] The technical solutions in this application will now be described with reference to the accompanying drawings.

[0039] This embodiment provides a modular, detachable large PPH vertical storage tank structure, including a tank bottom 1, a tank body 3, and a tank top 2. At least two of the tank bottom 1, tank body 3, and tank top 2 are detachably fixedly connected by an annular connecting mechanism 4. The connecting mechanism 4 includes a pair of mating composite flanges 5. Each composite flange 5 includes a metal frame 6 and a PPH coating layer 7. The PPH coating layer 7 is wrapped around the metal frame 6 by hot-melt, and the PPH coating layer 7 is integrated with the PPH material body of the tank bottom 1, tank body 3, or tank top 2 by hot-melt. The pair of composite flanges 5 are connected by fasteners 8.

[0040] By employing a detachable ring-shaped connection mechanism 4 to connect the main components of the storage tank, modular design and installation of large storage tanks are achieved. This detachable connection method significantly reduces the difficulty of manufacturing, transporting, and on-site construction of large equipment, allowing the storage tank to be disassembled into multiple parts for transportation. This effectively solves the problem of exceeding size limits during overall transportation and greatly expands the application scenarios of large storage tanks. The core of the connection mechanism 4 is a pair of composite flanges 5, which innovatively adopt a composite structure of a metal skeleton 6 and a PPH coating layer 7. The metal skeleton 6 provides the necessary mechanical strength and structural rigidity for the connection, ensuring that the flange interface can maintain shape stability and connection reliability under the pre-tightening force of the fasteners 8 and the pressure of the internal medium, overcoming the shortcomings of insufficient pressure bearing capacity and rigidity of pure plastic flanges. At the same time, the PPH coating layer 7 perfectly covers the metal skeleton 6 through hot-melt and forms a seamless integrated structure with the tank body 3 through hot-melt. This design fundamentally ensures the material continuity and consistency of the connection area and completely eliminates the leakage channels that may exist between the metal material and the plastic tank body due to physical connection. This integrated hot-melt connection method ensures that the entire connection area possesses the same excellent corrosion resistance and sealing integrity as the tank body, enabling it to withstand the erosion of highly corrosive chemical media for extended periods. Furthermore, this solution provides a novel, safe, and reliable connection technology for the design and manufacture of large plastic pressure vessels, combining the high strength of metal structural components with the comprehensive corrosion resistance of plastic materials.

[0041] In this embodiment, an annular sealing groove 9 is provided on the mating end face of the composite flange 5.

[0042] The sealing groove 9 provides precise positioning and accommodating space for the installation of the resilient seal 10. It confines the sealing ring in a preset position, preventing displacement, twisting, or extrusion during assembly. This ensures the sealing element is uniformly compressed after flange mating, forming a uniform and reliable static sealing barrier. This sealing barrier, as the primary sealing defense, combined with the material sealing properties of the flange itself, enhances the overall sealing safety level of the flange connection interface, effectively preventing media leakage from the flange mating surface.

[0043] In this embodiment, a sealing element 10 is provided inside the sealing groove 9.

[0044] This constitutes a complete secondary sealing system. When the pair of composite flanges 5 are tightened by fasteners 8, the seal 10 undergoes elastic deformation within the sealing groove 9, tightly filling the microscopic uneven gaps between the flange end faces and actively compensating for minor displacements caused by machining errors or thermal expansion and contraction. This design significantly enhances the sealing capability of the interface against internal media pressure, especially for gaseous media or volatile liquids, effectively blocking leakage paths. Combined with the inherent excellent sealing properties of the PPH material, it forms multiple sealing guarantees, further improving the sealing reliability and safety of the connection during long-term use.

[0045] In this embodiment, a PPH material sealing cover 11 is also included, which covers the outside of the fastener 8.

[0046] A sealing cover 11 made of PPH material was added, which completely covers the fastener 8. This design completely isolates the metal fastener 8 exposed to the environment from the external corrosive environment, creating a relatively stable microenvironment. The PPH material is the same as the tank material and has good chemical stability, ensuring that the sealing cover 11 itself will not introduce new corrosion points.

[0047] In this embodiment, the sealing cover 11 and the outer walls of the composite flanges 5 on both sides form a sealed anti-corrosion cavity. The two ends of the sealing cover 11 are sealed to the outer walls of the composite flanges 5 by hot-melt welding of PPH material, thereby forming a sealed anti-corrosion cavity.

[0048] The sealing cover 11 and the outer walls of the two composite flanges 5 together form a sealed cavity. This structure successfully encapsulates all metal fasteners 8 within a sealed space made of corrosion-resistant PPH material. This cavity effectively prevents contact between external humid air, chemical splashes, or corrosive atmospheres and the metal parts, fundamentally avoiding electrochemical or chemical corrosion of the metal fasteners 8. Since the integrity of the fasteners 8 is crucial for maintaining the preload of the flange connection, this design indirectly ensures the long-term mechanical stability and sealing durability of the flange connection interface by protecting the fasteners 8 from corrosion, thus extending the service life of the entire connection structure.

[0049] In this embodiment, the cross-sectional shape of the metal skeleton 6 is "L".

[0050] The cross-section of the metal skeleton 6 is designed in an "L" shape. This specific geometry provides a larger surface area and a better spatial structure, which is beneficial for its bonding with the PPH coating layer 7 via hot-melt bonding. The long and short sides of the "L" shape are embedded into the PPH material from different directions, thereby forming mechanical interlocking and constraint on the coating layer in multiple directions. This structure significantly enhances the bonding strength and load transfer efficiency between the metal skeleton 6 and the PPH plastic, making them more firmly bonded as a whole and reducing the risk of delamination or relative displacement under complex stress.

[0051] In this embodiment, the metal skeleton 6 includes a horizontal portion and a vertical portion, with the horizontal portion embedded in the end face of the PPH covering layer 7.

[0052] The horizontal portion of the metal skeleton 6 is clearly embedded within the end face of the PPH covering layer 7. This embedded structure allows the metal skeleton 6 to directly bear and disperse the axial compressive stress and bolt preload transmitted from the flange mating face, effectively transferring these stresses to a larger area through its rigid skeleton. This design enhances the flange end face's resistance to compression and deformation, ensuring that the flange face remains flat when the bolts are tightened. This guarantees that the seal 10 is uniformly compressed, facilitating the formation of a reliable end face seal and improving the flange face's resistance to internal medium pressure.

[0053] In this embodiment, the vertical portion of the metal skeleton 6 is embedded in the outer peripheral surface of the PPH covering layer 7.

[0054] The vertical portion of the metal skeleton 6 is embedded within the outer circumferential surface of the PPH cladding layer 7. This design enables the metal skeleton 6 to effectively withstand and resist radial forces, bending moments, and potential shear stresses acting on the flange. It enhances the overall bending and torsional stiffness of the flange, preventing excessive deformation under asymmetric loads or external pipeline forces, and maintaining the alignment and stability of the flange connection. The combined embedding of the horizontal and vertical portions achieves all-around reinforcement from the end face to the outer circumferential surface, making the mechanical properties of the composite flange 5 more balanced and reliable.

[0055] In this embodiment, the PPH coating layer 7 of the composite flange 5 is provided with a reinforcing boss 12, which is located at the mounting hole of the fastener 8 and protrudes outward.

[0056] A reinforcing boss 12 protrudes outward on the PPH coating layer 7 surrounding the mounting holes of fasteners 8. This boss structure increases the material thickness and section modulus in the area around the bolt holes, significantly enhancing the mechanical strength in this localized region. This better disperses and withstands the high concentrated compressive stress generated during bolt and nut tightening, preventing creep or plastic deformation of the PPH material under bolt preload, thus maintaining a stable bolt preload and preventing loosening of the connection due to stress relaxation. The boss design improves the compressive and impact resistance of the mounting hole area, increasing the durability of the structure.

[0057] In this embodiment, the fastener 8 is a double-ended stud with nuts at both ends, and the nuts are in contact with the PPH coating layer 7 of the composite flange 5.

[0058] Double-ended studs with nuts are selected as fasteners 8. The double-ended studs allow tightening from both sides, facilitating installation and alignment in confined spaces. The nuts directly contact the PPH coating 7 of the composite flange 5; their flat bottom surface provides uniform contact pressure, helping to reduce pressure on the PPH material surface and lowering the risk of localized compressive creep. This connection method helps achieve a more uniform bolt load distribution, which is beneficial for maintaining the sealing pressure of the flange connection. Its structure also facilitates the inspection and replacement of individual bolts during maintenance.

[0059] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A modular, detachable large-scale PPH vertical storage tank structure, comprising a tank bottom, a tank body, and a tank top, wherein at least two of the tank bottom, tank body, and tank top are detachably fixedly connected by an annular connecting mechanism; the connecting mechanism includes a pair of mating composite flanges, each composite flange comprising a metal frame and a PPH coating layer, the PPH coating layer being heat-fused onto the outside of the metal frame, and the PPH coating layer being integrally formed with the PPH material body of the tank bottom, tank body, or tank top by heat fusion; the pair of composite flanges are connected by fasteners; characterized in that... The composite flange has an annular sealing groove on its mating end face, and a sealing element is installed in the sealing groove; it also includes a PPH material sealing cover, which is placed on the outside of the fastener; the two ends of the sealing cover are respectively connected to the PPH coating layer of the composite flange on both sides by hot melt welding to form a sealed connection, thereby forming a closed anti-corrosion cavity together with the outer wall of the flange; the cross-sectional shape of the metal skeleton is "L".

2. The modular, detachable large PPH vertical storage tank structure according to claim 1, characterized in that, The metal skeleton includes a horizontal portion and a vertical portion, with the horizontal portion embedded within the end face of the PPH coating layer.

3. The modular, detachable large PPH vertical storage tank structure according to claim 2, characterized in that, The vertical portion of the metal skeleton is embedded in the outer peripheral surface of the PPH coating.

4. The modular, detachable large PPH vertical storage tank structure according to claim 1, characterized in that, The composite flange has a reinforcing boss on its PPH coating layer. The reinforcing boss is located at the mounting hole of the fastener and protrudes outward.

5. The modular, detachable large PPH vertical storage tank structure according to claim 1, characterized in that, The fastener is a double-ended stud, with nuts at both ends of the double-ended stud, and the nuts are in contact with the PPH coating layer of the composite flange.

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