How to Manufacture a Good Metal Wound Gasket?
Posted Aug 12, 2025

How to Manufacture a Good Metal Wound Gasket?

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In modern industry, metal wound gaskets are essential sealing components widely used in petrochemical, power, and mechanical manufacturing sectors. The precision of their manufacturing process directly affects their sealing performance and service life. This article will provide a detailed interpretation of the manufacturing process of metal wound gaskets, helping readers gain a comprehensive understanding of this complex and intricate production process.

Manufacturing Process of Metal Wound Gaskets

The manufacturing process of metal wound gaskets mainly includes four basic steps: slitting, forming, winding, and spot welding. For reinforced ring-type wound gaskets, two additional processes, ring making and assembly, are required. Each step is interlinked, and the quality of each stage directly impacts the final product's performance.

1. Slitting

Slitting is the first and foundational step in the manufacturing process. The raw metal strip is usually placed on a belt shaft support. Through the guiding device on the slitting machine, the steel strip is guided into the upper and lower sets of cutting knives on the machine. The design of the cutting knives is crucial; they must ensure pure shearing of the metal strip and a smooth exit of the strip. The cut metal strip should be flat, burr-free, without sharp edges, tears, or twists, and then wound onto a steel strip reel for later use.

Manual winding is not only time-consuming but also unsafe, and the quality of the steel strip is hard to guarantee. Therefore, modern manufacturing processes typically employ automatic winding devices, which adjust the tension of the steel strip to ensure it remains flat during winding. Quality control at this stage is vital for the subsequent forming and winding processes.

2. Forming

Forming involves processing the cut metal flat strip into a shape suitable for winding. The metal flat strip is fed through a guide wheel into a pair of forming wheels. The structure of the forming wheels is designed based on the optimal structural parameters of the steel strip to ensure that the formed strip is flat, symmetrical, and free from twists, meeting the required width. By adjusting the excitation voltage provided to the electromagnetic clutch at the shaft end by a dedicated DC voltage regulator, the formed steel strip can be automatically wound onto the winding sheet.

The quality of the forming process directly affects the mechanical properties of the wound gasket. Therefore, the design and adjustment of the forming wheels must be precise to ensure the forming effect of the steel strip meets the standard requirements.

3. Winding

Winding is the core step in manufacturing wound gaskets. The body of the wound gasket is made by spirally winding the formed metal and non-metal strips on a dedicated winding machine. The winding process must be carried out on a fixture, but standards and specifications vary, and the size of the fixture must be adjusted accordingly. During winding, it is essential to ensure that the gear system composed of the formed metal strip reel, filler strip reel (long strip), guide wheel, and add-strip wheel, along with the cutting and pressing wheels, are all on the same center plane. The steel strip requires tension and clamping force, two key process parameters that significantly impact the gasket's mechanical properties.

The initial and final winding of the gasket body should have 2-4 turns of metal strip filling the non-metal strip (commonly referred to as "empty turns"). For gaskets with a nominal diameter greater than 1500mm, the number of empty turns can be appropriately increased. For gaskets with an outer reinforcement ring, after spot welding the end of the body, continue winding the metal strip for 2-4 turns to facilitate gap adjustment and positioning during the outer ring assembly. These 2-4 turns of metal strip are not counted in the gasket's outer diameter.

4. Spot Welding

Spot welding is an important step to ensure the structural stability of the wound gasket. Spot welding of the wound gasket should be performed using a specially designed high-frequency pulse spot welding machine, which is required to be stable in performance, safe and reliable, fast in welding speed, and of good welding quality. Uniform spot size, even spacing, no burnt spots, no burn-through of the steel strip, and good welding strength are the basic requirements for spot welding.

5. Ring Making and Assembly (for Reinforced Ring-Type Wound Gaskets)

For reinforced ring-type wound gaskets, two additional processes, ring making and assembly, are required. The inner and outer reinforcement rings can be made by punching and cutting a whole plate, with the cutting diameter determined by the press tonnage. For larger diameter reinforcement rings, methods such as butt welding and ring welding can be used to assemble the rings before inserting them, or the plate can be cut into strips and bent and welded on a dedicated ring bending machine. The ring plane should be flat, with a flatness tolerance of less than 1%. The chamfer on the outer circle of the inner ring and the ring groove on the inner diameter of the outer ring should be concentric with their respective inner and outer circles and symmetrical with the two ends. The angles of the chamfer and ring groove should match the forming angle of the steel strip.

The assembly of the reinforcement ring mainly refers to the assembly of the outer ring with the gasket body. The domestic process involves manual ring installation, where the gasket body is squeezed towards the ring groove side and rotated unidirectionally along the ring groove, allowing the empty ring to gradually spiral into the groove until the gap between the ring grooves is filled, without rotating the body. Then, the excess steel strip is cut off, and the end of the steel strip is pressed into the ring groove. After assembly, the gasket body should be able to float appropriately within the ring groove, and the sealing surface should not be scratched by the steel strip to avoid affecting surface quality.

Selection of Raw Materials for Metal Wound Gaskets

Raw materials are the foundation for ensuring the quality of gaskets. Matching metal strips of different materials with non-metal strips can produce wound gaskets suitable for various usage conditions. The gasket material is generally specified by the user, or the user can provide usage conditions (including medium, temperature, pressure, etc.), and the manufacturer can assist in the selection.

1. Metal Strip Material

The metal strip material is usually a cold-rolled stainless steel strip with a thickness of 0.15-0.25mm and a width of 80-100mm. The hardness is tested according to GB4340, with Hv≤200 (preferably 160-180). The surface should be smooth and flat, free from cracks, scratches, rust spots, and other defects. Currently, the materials on the market are divided into imported, domestic, and recycled domestic types, with significant price differences. When purchasing, it is necessary to request a warranty certificate from the manufacturer, and re-inspection should be carried out if necessary.

2. Non-Metal Filler Strip Material

Common non-metal filler strip materials include special asbestos, flexible graphite, and polytetrafluoroethylene (PTFE), with a thickness of 0.3-0.8mm. Their chemical composition and physical and mechanical properties should comply with the relevant standards or specifications. Special asbestos has a small amount of low-molecular polymer added during the manufacturing process to fill internal pores, resulting in higher strength than ordinary asbestos paper, a greasy feel, and strong resistance to penetration. Flexible graphite requires high purity with a carbon content of 99.9%. Under special operating conditions, the content of sulfur and chloride ions should be strictly limited. PTFE is generally made from raw materials, and the best quality is produced using imported raw materials.

3. Reinforcement Ring Material

Reinforcement rings are usually made from cold-rolled plates. The material of the inner reinforcement ring is the same as that of the metal strip. The outer reinforcement ring is made of Q235 steel and treated for rust prevention, or the material can be specified by the user.

Control of Process Parameters in Gasket Manufacturing

The main process parameters in manufacturing wound gaskets are the tension and clamping force of the steel strip during winding, which directly affect the density and uniformity of the gasket winding. Currently, advanced winding equipment can continuously adjust the tension and pressure of the steel strip during operation. Especially for large-diameter, wide-sealing-face gaskets, to prevent collapse during the manufacturing process, these two parameters must also be able to attenuate uniformly. It has been found in production that by adjusting the tension and clamping force of the steel strip, gaskets suitable for different pressure and temperature ratings (which must match the material) can be manufactured. The empirical control range is between 200-450N for clamping force and 10-30N for tension.

Size and Appearance of Metal Wound Gaskets

The size of the wound gasket (including thickness and diameter) should be strictly controlled within the tolerance range specified by the standard. For flat and raised face flanges, the thickness of the gasket does not affect installation; however, for tongue-and-groove and male-and-female face flanges, if the thickness exceeds the groove depth, the flange cannot be positioned. The thickness of the gasket is controlled by the width of the pressing wheel groove during winding, which is related to the design of the pressing wheel structure. Measuring the diameter of the gasket with a displacement sensor can ensure that each gasket has the same diameter tolerance and can control the number of empty turns of the steel strip, ensuring the same sealing performance for gaskets of the same specification. Using feedback signals to measure displacement can also control when to add material, cut the tape, and spot weld, thus automating the gasket winding process.

During the manufacturing process of wound gaskets, there should be no exposed metal strips on the surface. The non-metal filler strips should have uniform protrusions, clear textures, even and aesthetically pleasing spot weld spacing, and be firmly attached. After the ring is installed, the surface should be free from scratches, the sealing face should be symmetrical with the reinforcement ring face, the inner reinforcement ring should be securely fixed to the gasket body without looseness, and the outer reinforcement ring should be able to float appropriately.

Inspection of Metal Wound Gaskets

Inspection is divided into factory inspection and type inspection. Factory inspection mainly checks the size and appearance quality to ensure that the product meets basic usage requirements. Type inspection is more stringent, including not only size and appearance quality but also compression and rebound performance, stress relaxation performance, nitrogen sealing performance, etc. Therefore, manufacturing enterprises should regularly send products to quality supervision departments for inspection. If problems are found, the causes should be analyzed promptly, and the corresponding parameters and processes should be changed to improve product quality.

Conclusion

The manufacturing process of metal wound gaskets is a complex and meticulous process involving quality control at multiple stages. From the selection of raw materials to the inspection of the final product, each step is crucial. By adopting advanced manufacturing processes and strict quality control measures, high-quality metal wound gaskets can be produced to meet the high demands of modern industry. It is hoped that the introduction in this article will help readers better understand the manufacturing process of metal wound gaskets and provide a useful reference for practitioners in related industries.

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Isaac
Isaac