VSSJA / AF-type flange loose set of expansion joints Loose flange expansion joints: loose expansion joint installed in the pipe, tighten the nut elastic seals, gland nut under the action of the mutual inclination, pressed in the outer tube from sealing and connecting role. The tube when the temperature changes in the middle of the free expansion joints, the local base goes down, the tube can be skewed, and to ensure no leakage sealing, which played the purpose of automatic compensation.