porn indin,the nude girls,teen sexy massage
A lift plug valve has many kinds of structures. According to the sealing surface material, it can be divided into the soft sealing plug valve and the hard sealing plug valve. The basic principle is that when the valve is opened, the plug will rise with rotation at 90 degrees until the valve is fully opened, which can reduce the friction with the sealing surface of the valve body. When the valve is closed, rotate the plug at 90 degrees to the close position and then drop down the plug to contact with the sealing surface of the valve body to achieve sealing.