法兰是管道中起连接作用的重要部分，种类多，标准繁杂。由于其主要起连接作用，因此，法兰的主要特性就是连接方式及密封形式，主导影响参数是管道压力（介质不同影响材质选定）：一般地讲，低压系统（PN<2.5MPA）采用平焊或板式法兰，普通突面(RF)密封,中压系统(2.5-64MPA)采用对焊法兰，RF或凹凸面(FM/M)密封，高压系统(10.0MPA以上)，通常采用对焊法兰，梯型槽(RJ)密封。在低压不锈钢系统中，有时为节约成本及检修方便，还采用松套法兰或活套环法兰。

The flange is an important part of pipeline connection role, variety, standard multifarious. Due to its main connection role, therefore, the main features of the flange is connecting method and seal form, the dominant influence parameter is the line pressure (media different influence material selected) : generally speaking, the low pressure system (PN < 2.5 MPA) the use of flat or plate flange, common face seal (RF), medium voltage system (2.5-64 MPA) using butt welding flange, RF or concave and convex surface (FM/M), high pressure system (more than 10.0 MPA), usually USES the butt welding flange, ladder type slot (RJ) seal. Stainless steel in the system at low pressure, sometimes to save costs and maintenance is convenient, also adopts loose flange or loop ring flange.