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The applicable temperature range of flanges and pressure resistance capacity affect and restrict each other, the specific relationship is as follows:
Influence of temperature on pressure resistance capacity
High temperature situation
As the temperature rises, the crystal structure of flange materials will change, and the strength and hardness of the materials will usually decrease, leading to a reduction in their pressure resistance capacity. For example, the yield strength of carbon steel decreases significantly above 300°C, making the flange more susceptible to deformation under the same pressure.
High temperatures may also cause the performance of sealing materials in the flange connection area to deteriorate. For example, rubber gaskets will deteriorate and harden at high temperatures and lose their elasticity, resulting in poorer sealing performance, thus limiting the flange's ability to withstand pressure at high temperatures.
Low Temperature Situation
When the temperature decreases, the material becomes brittle and the toughness and impact resistance decreases, which means that the flanges are more prone to brittle fracture when they are subjected to pressure at low temperatures. For example, ordinary carbon steel may become cold embrittled at low temperatures, reducing its ability to withstand pressure significantly.
Low temperatures may also lead to inconsistent shrinkage between the flange's connecting parts, creating additional stresses that affect the flange's overall pressure resistance.
Impact of Pressure Resistance on Applicable Temperature Range
High Pressure Situation
When flanges are subjected to higher pressures, the stresses within the material increase. In a high temperature environment, the synergistic effect of this stress and high temperature accelerates the creep and fatigue damage of the material, so that the flange may fail at lower temperatures, thus narrowing its high temperature range of application.
Under high pressure, the deformation of the flange will also increase, which puts higher requirements on the sealing performance. In a low temperature environment, the elasticity of the sealing material deteriorates, and high pressure is more likely to lead to sealing failure, which in turn limits the flange's applicable temperature range at low temperatures.
Low pressure situation
For flanges subjected to lower pressure, the material is subjected to less stress, and to some extent the adaptability to temperature will be enhanced. At high temperatures, the reduction of material strength has relatively little effect on its pressure resistance, so it can be used at relatively high temperatures; at low temperatures, the smaller stress also reduces the risk of brittle fracture of the material, so that the flanges can maintain a certain pressure resistance at lower temperatures, thus expanding their applicable temperature range.
In practical application, when selecting flanges, it is necessary to comprehensively consider the temperature range and pressure resistance requirements, and meet the requirements of the applicable temperature range and pressure resistance of the flanges under different working conditions by reasonably selecting materials and optimizing the manufacturing process.