New technology and equipment for the production of

New technology and equipment for spiral wound gasket production

as a combined metal and non-metal gasket, spiral wound gasket is widely used in equipment and pipelines in petroleum, chemical, electric power, machinery, pharmaceutical and other departments with its excellent performance. Its quality directly affects the safe operation of production devices and the life and safety of operators. According to the preliminary investigation, the domestic static seal manufacturers have poor equipment and backward technology. The production of spiral wound gaskets is at a low level, and the quality is very unstable. There are no unified regulations on the structural parameters of spiral wound gaskets, including the flat belt width of metal belt and non-metal belt, the forming angle of steel belt, the width of formed belt and its straight edge length. Based on their own experience, each manufacturer determines that the spiral wound gaskets produced are not the bare metal belt, or the non-metal belt is extruded too much, which directly affects the gasket and feeds it back to the computer control system through the data collection card; The hydraulic system is the appearance and quality of the power system piece of the tensile testing machine. In addition, in the current winding process, the tension and compression force of the steel belt cannot be continuously adjusted and quantitatively controlled. The non-metallic filler belt is added manually, and the size is measured manually. The production efficiency is low, the product quality is unstable, and human factors are great, which affect the mechanical performance and sealing performance of the gasket. With the development of industrial devices towards large-scale and high parameters, the demand for high-quality spiral wound gaskets is increasing day by day. Therefore, the research on advanced production technology and equipment is of great significance to improve the quality of spiral wound gaskets. Research on new technology 1 Structural parameters of spiral wound gasket

spiral wound gasket is formed by spiral winding of metal and non-metal forming belt. The width of metal and non-metal flat belt before forming is determined on the basis of analyzing foreign famous seal companies such as valqua company in Japan, pillar company and flextalic company in the United States and integrating the experience data of domestic manufacturers. The width of the metal flat belt of the 4.5mm thick series of spiral wound gaskets is generally 5.1, 5.3 and 5.5mm, and the non-metal flat belt has different widths according to different materials. The author only selected the flexible graphite strip which is widely used as the filler for research, and its width is 5.8 ~ 6.0mm

the metal flat belt is pressed and formed by a pair of specially designed forming wheels. In order to ensure that the thickness of the gasket after winding is 4.5+0.4mm, the steel belt is not exposed, and the surface filler texture is clear, then the width of the formed steel belt is B, the width of the flat steel belt is B ', the thickness is t, and the forming angle is 2 α And the width of the formed straight edge B (as shown in Figure 1), through the derivation of the geometric relationship, the structural parameters can be obtained, as shown in Table 1. Table 1 structural parameters of spiral wound gasket flat steel strip width B '(mm) 5.15.35.5 forming belt width b (mm) 4.1 forming belt height h (mm) 1.5 forming angle 2 α (°) 99.384.268.3 straight edge width b (mm) 0.240.701.04 Figure 1 steel strip structure diagram 2 Production process parameters of spiral wound gasket

in addition to the structural parameters of spiral wound gasket, the process parameters in the production process have a great impact on the performance of gasket. The process parameters mainly refer to the pressing force when winding the gasket and the tension force required by the steel strip. They can be adjusted respectively by adjusting the gas pressure P in the cylinder and the exciting voltage U applied to the electromagnetic clutch. Suppose the pressing force on the pressing wheel is FC, then fc= π d2p/4 (1), where D - cylinder piston diameter

according to literature [1], the torque T of electromagnetic clutch is t=k μ In rmu2 (2), K -- constant related to the structure of electromagnetic clutch

μ—— Dynamic friction coefficient between friction plates

rm - average diameter of friction surface

for the selected electromagnetic clutch, its K μ、 RM is unchanged. If the diameter of the formed steel strip disc is d ', the tangential tension FP of the steel strip is fp=2k μ Rmu2/d ′ (3) changing the excitation voltage u can adjust the tension on the steel strip

3. Optimization of structure and process parameters

the structure and process parameters of spiral wound gaskets directly affect the performance of gaskets. For the formed steel strips with three different structural parameters listed in Table 1, corresponding to different process parameters, the author takes the gasket wound by the self-developed new winding machine as the test sample, and carries out the mechanical properties (compression rate, rebound rate) and sealing performance tests on the multi-function fully automatic gasket comprehensive performance testing machine [2]. The samples are DN80 and pn5.0 inner and outer ring flexible graphite spiral wound gaskets. The test conditions are: the pre tightening specific pressure is 70mp. After years of experience accumulation and continuous breakthroughs in technical research and development a, the test medium is 99.9% nitrogen, the medium pressure is 5.5mpa, room temperature, and the loading and unloading speed is 0.5mpa/s. Three factor three level orthogonal test is adopted, that is, the test is arranged according to L9 (34) to find the most relevant standard: BBT 0024 (2) 004 the match between the best structural parameters and process parameters

the structure and process parameters of the gasket used for the test are

α—— Forming belt half angle, α 1=49.6°， α 2=42.1°， α 3=34.2°；

fp -- winding tension, fp1=11.8n, fp2=14.7n, fp3=17.6n

fc -- winding pressing force, fc1=251.3n, fc2=314.2n, fc3=377.0n

nine groups of gasket performance tests with different combinations of structure and process parameters were carried out [3], and the leakage rate data were listed in Table 2 after variance analysis. It can be seen that the angle of formed steel strip 2 α And the winding pressing force FC has a significant impact on the sealing performance of the gasket. According to the technical indicators in gb4622.3-93 "technical conditions for spiral wound gaskets", the compression rate of flexible graphite spiral wound gaskets is 18% - 30%, and the rebound rate is ≥ 17% 9 Controller: touch screen PLC control, leakage rate ≤ 1.0 × (recommended by petrochemical industry). The goal of optimization is to minimize the leakage rate and maximize the rebound rate on the premise of meeting the requirements of the national standard. Under test α 2fp2fc3 combination [3] meets the requirement of minimum leakage rate, but the rebound rate is not up to standard. Therefore, with the FP level unchanged, change the two levels that have a significant impact on performance α And FC, and then conduct the gasket performance test. The results are shown in Table 3. Table 2 leakage rate data [3] analysis of variance variance

source deviation flat

square and s degree of freedom

f mean square

s/ff ratio significance

βα 8.0224.01 24.830.01