BUTTERFLY VALVE

摘要

Butterfly valve assembly for installation in a pipe line between flanges. Assembly includes rigid tubular valve body and resilient valve seat insert to make tight seal with flanges when installed and to make tight seal with valve disc in service. Seat insert has certain dimensions undersize relative to valve body so that insert must be stretched when fitted to body and is further stretched when flanges are tightened during installation. Stretching assures secure fit between insert and body before installation and leak proof seal after installation. Seat insert and valve body have cooperating radial ledges asymmetrically located to prevent relative movement when valve disc is closed. Insert has annular flange sealing portions each with an inturned bead which enters an annular groove formed in the valve body. Flange sealing portions are so shaped that when valve is installed between flanges of a pipe line the beads are forced into but do not fill the grooves thus reducing tendency toward squeezing excess resilient material into, and consequent loosening of, the portion of the insert in which the disc must seat.