久操亚洲-久操小视频-久操网址-久操网站-久操视屏-久操视频在线免费观看

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.