Flange with neck collar

In the \"Technical Specifications for Flange Joint Installation,\" flanges with neck collars are only permitted for Class 150 and PN16, likely due to considerations of safety and suitability outlined in those specifications. Under high-pressure conditions, the connection of the loop flanges may not be secure enough; the use of metal gaskets can result in poor sealing at the flange connections or increased risk of damage due to the high hardness and low plasticity of the metal. Non-metallic flat gaskets are better able to adapt to various irregular surfaces, and possess good flexibility and sealing performance. The specified constraints are usually derived from extensive experimental and practical experience, in order to ensure the safety and reliability of the engineering. Although necked slip-on flanges may be used in practical applications at higher pressures, their safety may need to be ensured through other methods or standards. .