韩国三级电影播放_成年黄色电影_美国做爰xxxⅹ性视频_日本一区二区在线_bbbbbbbbb免费毛片视频_91欧美_91成人app_国产91免费视频_国产精品成人免费视频_欧美一级二级三级_亚洲制服丝袜在线播放_日本韩国欧美一区_非洲一级片_亚洲国产精品久久久久_日本va欧美va国产激情

Check valve is generally composed of valve body, plastic or ceramic seat and ruby ball. Under the action of pressure, the gem ball leaves the valve seat, and the flow phase flows through the check valve; on the contrary, under the action of reverse force, the gem ball returns to the valve seat, and the flow phase no longer flows through the check valve.