A protective process for high-strength marine fasteners

Abstract

This invention relates to the field of marine fastener protection technology, and particularly to a protection process for high-strength marine fasteners. The protection process for high-strength marine fasteners includes: S100, pre-treating the connecting assembly; S200, bonding the gasket and bolt head together with polysulfide sealant, applying a sealant film to the smooth shank of the bolt, and sealing the gaps between the bolt head and the gasket, as well as between the sealant film and the bolt shank; S300, installing the bolts through the connecting assembly, sealing the gaps between the bolt assembly components and the threaded portion with polysulfide sealant, and applying a pre-tightening force to the connecting assembly; S400, allowing the polysulfide-sealed connecting assembly and bolt assembly to stand for a preset time until the polysulfide sealant solidifies. The advantage of this high-strength marine fastener protection process is that it prevents the bolts from corroding when immersed in seawater.

Description

Technical Field

[0001] This invention relates to the field of marine fastener protection technology, and in particular to a protection process for high-strength marine fasteners. Background Technology

[0002] High-strength marine fasteners that have been in service for a long time often experience fracture failure due to corrosion and hydrogen-induced damage, seriously threatening operational safety. Although the connection pairs of high-strength marine fasteners are sealed with rubber seals, after long-term use in the marine environment, as the rubber seals age, seawater or marine atmosphere can still slowly seep into the connection pairs through the gaps between the fasteners and the rubber seals. This leads to galvanic corrosion and crevice corrosion at the fastener mating points, and pitting or uniform corrosion occurs within the gaps. At the same time, under the influence of corrosive media and potential, hydrogen gradually penetrates into the fastener matrix, which may cause hydrogen-induced damage.

[0003] Currently, the protection of high-strength marine fasteners mainly focuses on the substrate and surface treatment technology. For example, Chinese invention patent CN115747660A discloses a high-strength weather-resistant bolt and its manufacturing process, involving hardware accessory manufacturing technology. It aims to solve the problem that existing coating methods cannot fundamentally address bolt failures such as corrosion cracking and hydrogen-induced delayed fracture under environmental conditions. The key technical points are: it includes a bolt body, which is made of medium-carbon alloy steel composite microalloying elements in an integrated structure. The microalloying elements, by mass fraction, include: V 0.01-0.05wt%; Ti 0.01-0.04wt%; B 0.01-0.07wt%; Nb 0.35-0.75wt%; Mo 0.2-0.95wt%; Cu The total content of V, Ti, and B is 0.2-0.35 wt%; the total content of Nb, Mo, and Cu is 0.03-0.12 wt%, and the total content of Nb, Mo, and Cu is 1.2-2.00 wt%. This patented technical solution improves the corrosion resistance of bolts by selecting appropriate materials. However, during long-term use, bolts immersed in seawater will still gradually corrode, especially between the bolt and connecting parts, and between various components in the fastening assembly, where seawater can easily accumulate and cause further corrosion. Summary of the Invention

[0004] In view of this, the present invention aims to provide a protective process for high-strength marine fasteners. It adopts measures such as bonding the gaps between the components of the bolt assembly, between the bolt assembly and the connecting components, and between the threads of the bolt and nut with polysulfide sealant, and applying a protective film to the peripheral sidewalls of the bolt head and nut. This solves the problem that bolts will still be gradually corroded when immersed in seawater, especially between the bolt and the connecting parts, and between the components of the fastening assembly, where seawater is easily trapped and corroded.

[0005] To address the above problems, this invention provides a protective process for high-strength marine fasteners, comprising:

[0006] S100. Preprocess the connection pair;

[0007] S200: The gasket and bolt head are bonded together with polysulfide sealant, and a sealant film is pasted on the smooth part of the bolt shank to seal the gaps between the bolt head and the gasket, as well as between the sealant film and the bolt shank.

[0008] S300. Install each bolt assembly by passing the bolts through the connecting assembly, seal the gaps between the bolt assemblies and the threaded portion with polysulfide sealant, and apply preload to the connecting assembly.

[0009] S400. Allow the joints and bolts coated with polysulfide sealant to stand for a preset time until the polysulfide sealant solidifies.

[0010] Furthermore, in step S100, the method for preprocessing the connection pair includes:

[0011] Clean the surfaces of the connecting parts and perform protective operations on the sidewalls of the bolt heads and nuts.

[0012] Furthermore, a method for protecting the sidewalls of bolt heads and nuts involves applying adhesive film to the sidewalls.

[0013] Furthermore, in step S200, the gasket that is adhesively bonded to the bolt cap is a circular gasket.

[0014] Furthermore, step S300 includes:

[0015] S310. Pass the bolt through the connecting assembly and seal the gap between the circular gasket and the connecting assembly with polysulfide sealant.

[0016] S320. Install square washers and spring washers sequentially on the threaded portion of the bolts of the connecting components, and seal the gap between the connecting components, square washers and spring washers with polysulfide sealant.

[0017] S330. Apply polysulfide sealant to the threaded portion protruding outside the spring washer;

[0018] S340. Install the nut and seal the gap between the spring washer and the nut with polysulfide sealant.

[0019] S350, tighten the nut to apply preload to the connection.

[0020] Furthermore, step S300 also includes:

[0021] S360. The gaps between the threaded portions of nuts and bolts are filled with polysulfide sealant.

[0022] Furthermore, in step S400, the preset time for settling is 3-4 hours.

[0023] Furthermore, in step S400, the polysulfide sealant is left to stand for 3-5 days after curing.

[0024] Furthermore, the protective process also includes:

[0025] S500, The bolt mounting holes of the connecting pair are filled with a protective material, the protective material including at least one of cement and epoxy resin.

[0026] Furthermore, the protective process also includes:

[0027] S600: After a water pressure test, under preset pressure and preset holding time conditions, and after a preset number of pressure cycles, the polysulfide sealant was visually inspected and found to be undamaged, the overall sealing performance of the joint was good, and no internal water ingress was observed.

[0028] Compared with existing technologies, the protective process for high-strength marine fasteners described in this invention has the following advantages:

[0029] The advantages of this technical solution are that it uses polysulfide sealant to bond the gaps between the components of the bolt assembly, between the bolt assembly and the connecting components, and between the threads of the bolt and nut. It also uses a protective film to protect the peripheral sidewalls of the bolt head and nut. These measures prevent the bolts from being corroded by being immersed in seawater. Furthermore, seawater can easily remain between the bolts and the connecting components, and between the components in the fastening assembly, making it less susceptible to corrosion. Attached Figure Description

[0030] Figure 1 This is a schematic diagram showing the state of the fastener of the present invention after a protective process has been applied during installation.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1-Polysulfide sealant, 2-Bolt, 3-Round gasket, 4-Square gasket, 5-Spring gasket, 6-Nut, 7-Connecting assembly, 8-Sealant film. Detailed Implementation

[0033] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0034] In this invention, the terms "first," "second," "upper," and "lower," etc., are used for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first," "second," "upper," or "lower" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. Where the technical solutions of the embodiments can be combined, they are all within the scope of protection claimed by this invention.

[0035] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0036] like Figure 1 As shown, a protective process for high-strength marine fasteners includes:

[0037] S100. Pre-treatment of the connection pair. The pre-treatment method includes: cleaning the surface of the connection pair, and protecting the sidewalls of the bolt head and nut by applying adhesive film to prevent polysulfide sealant from being applied to the sidewalls of the bolt head and nut when applying adhesive, which would affect the tightening of the bolt and nut. The adhesive film can be made of adhesive tape, adhesive paper, etc.

[0038] S200: The gasket and bolt head are bonded together with polysulfide sealant. The gasket is preferably a round gasket. A sealant film is pasted on the smooth part of the bolt to seal the gap between the bolt head and the gasket, as well as between the sealant film and the bolt shank.

[0039] S300, Install the bolt assemblies by passing bolts through the connecting assembly, seal the gaps between the bolt assemblies and the threaded portions with polysulfide sealant, and apply preload to the connecting assembly, including:

[0040] S310. Pass the bolt through the connecting assembly and seal the gap between the circular gasket and the connecting assembly with polysulfide sealant.

[0041] S320. Install square washers and spring washers sequentially on the threaded portion of the bolts of the connecting components, and seal the gap between the connecting components, square washers and spring washers with polysulfide sealant.

[0042] S330. Apply polysulfide sealant to the threaded portion protruding outside the spring washer;

[0043] S340. Install the nut and seal the gap between the spring washer and the nut with polysulfide sealant.

[0044] S350, tighten the nut to apply preload to the connection.

[0045] S360. The gap between the threaded parts of the nuts and bolts is filled with polysulfide sealant.

[0046] S400. Allow the joints and bolts coated with polysulfide sealant to stand for a preset time, preferably 3-4 hours, until the polysulfide sealant solidifies. After solidification, allow the polysulfide sealant to stand for 3-5 days. After 3 days, the hardness of the polysulfide sealant reaches 80-90% of the standard state; after 5 days, the polysulfide sealant reaches the target state.

[0047] S500. The bolt mounting holes of the connecting pair are filled with protective material, which includes at least one of cement and epoxy resin. The filling of the protective material further protects the connecting pair.

[0048] S600: After a water pressure test, under preset pressure and preset holding time conditions, and after a preset number of pressure cycles, the polysulfide sealant was visually inspected and found to be undamaged, the overall sealing performance of the joint was good, and no internal water ingress was observed.

[0049] After sealing and protecting the connection pairs and bolt pairs, the effect is tested by a hydrostatic test. The process requirements must be met to ensure that the bolts will not be corroded in seawater for a long time.

[0050] Through the above-mentioned protective processes, such as using polysulfide sealant to bond the gaps between the components of the bolt assembly, between the bolt assembly and the connecting components, and between the threads of the bolt and nut, and applying a protective film to the peripheral sidewalls of the bolt head and nut, the bolts are prevented from being corroded by being immersed in seawater. Seawater can easily remain between the bolts and the connecting components, and between the components in the fastening assembly, making them less susceptible to corrosion.

[0051] The above process is illustrated below with specific embodiments.

[0052] Wipe the surfaces of the joints to remove stains and grease with an organic solvent. Apply adhesive tape to the six sidewalls of the hexagonal bolts. Use M56 bolts.

[0053] Apply polysulfide sealant to the surface of the bolt head near the bolt shank, and then attach the circular washer to the bolt head. Apply sealant to the smooth portion of the bolt shank, and seal the gap between the bolt head and the circular washer with polysulfide sealant. Seal the gap between the sealant film and the bolt shank with polysulfide sealant.

[0054] Insert the bolt through the connecting assembly and seal the gap between the bolt and the component with polysulfide sealant. Apply polysulfide sealant to both sides of the square washer and place the square washer over the threaded portion of the bolt, ensuring it is flush against the surface of the connecting assembly. Place the spring washer over the threaded portion, ensuring it is flush against the square washer. Apply polysulfide sealant to the side of the spring washer away from the square washer. Screw the nut into the threaded portion of the bolt until it contacts the spring washer. Seal the gaps between the components with polysulfide sealant. Continue tightening the nut to apply a preload to the connection pair, which is 70% of the yield strength (0.7Rp0.2). Fill any gaps between the threads of the nut and bolt with polysulfide sealant.

[0055] The joints and bolts coated with polysulfide sealant are left to stand for a preset time, preferably 3.5 hours, until the polysulfide sealant solidifies. After solidification, the polysulfide sealant is left to stand for 5 days to reach the target state.

[0056] A water pressure test was conducted on the connection pair using a pump and valve test bench, with a pressure cycle of 0–4.5 MPa and a pressure holding time of 5 minutes. A total of 10 pressure cycles were completed.

[0057] After the hydrostatic test, the appearance of the bolted connection showed no significant changes, the polysulfide sealant showed no cracks or defects, the overall sealing performance of the connection remained good, and no water ingress was observed in the internal gaps. The high-strength marine fastener protection process and materials exhibit excellent sealing performance, effectively meeting the requirements for high-strength marine fasteners used in special critical components for extended periods where mid-service replacement is inconvenient.

[0058] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A protective process for high-strength marine fasteners, characterized in that, include: S100. Pre-treat the connection pair, clean the surface of the connection pair, and perform protective operations on the sidewalls of the bolt heads and nuts; S200: The gasket and bolt head are bonded together with polysulfide sealant. The gasket is a round gasket. The sealant film is pasted on the smooth part of the bolt to seal the gap between the bolt head and the gasket, as well as between the sealant film and the bolt shank. S300. Install each bolt assembly by passing the bolts through the connecting assembly, seal the gaps between the bolt assemblies and the threaded portion with polysulfide sealant, and apply preload to the connecting assembly. Step S300 includes: S310. Pass the bolt through the connecting assembly and seal the gap between the circular gasket and the connecting assembly with polysulfide sealant. S320. Install square washers and spring washers sequentially on the threaded portion of the bolts of the connecting components, and seal the gap between the connecting components, square washers and spring washers with polysulfide sealant. S330. Apply polysulfide sealant to the threaded portion protruding outside the spring washer; S340. Install the nut and seal the gap between the spring washer and the nut with polysulfide sealant. S350, tighten the nut to apply preload to the connection pair; S360. The gap between the threaded parts of the nuts and bolts is filled with polysulfide sealant. S400. Allow the joints and bolts coated with polysulfide sealant to stand for a preset time until the polysulfide sealant solidifies.

2. The protective process for high-strength marine fasteners according to claim 1, characterized in that, The method for protecting the sidewalls of bolt heads and nuts involves applying adhesive film to the sidewalls.

3. The protective process for high-strength marine fasteners according to claim 1, characterized in that, In step S200, the gasket that is glued to the bolt cap is a circular gasket.

4. The protective process for high-strength marine fasteners according to claim 1, characterized in that, In step S400, the preset time for settling is 3-4 hours.

5. The protective process for high-strength marine fasteners according to claim 4, characterized in that, In step S400, the polysulfide sealant is left to stand for 3-5 days after it solidifies.

6. The protective process for high-strength marine fasteners according to claim 1, characterized in that, The protective process also includes: S600: After a water pressure test, under preset pressure and preset holding time conditions, and after a preset number of pressure cycles, the polysulfide sealant was visually inspected and found to be undamaged, the overall sealing performance of the joint was good, and no internal water ingress was observed.

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