Brake stem is more and more widely used in various industrial systems because of its pressure resistance, temperature resistance (high and low temperature resistance), corrosion resistance (various materials), two-way sealing function, wear resistance and long service life. Opening and closing of the system plays an important role in the stability and control of the system. Valve stem fracture usually occurs at the root of the upper and lower threads, the cross-sectional area is small, and stress concentration and over-standard phenomena are easy to occur. Especially when the working conditions deviate greatly from the design parameters. For example, in a power plant, the bonnet pretightening nut is loose, the bonnet moves upward, and the stem nut is stuck. Obviously, this is due to the accident caused by the overadjustment of the Denso stroke and the excessive protection torque.

The manufacturer of the hard sealing closed rod tells you that there is another case because the gate has not been separated from the seat and the stem breaks at the root of the upper or lower thread. It is generally believed that the reason is that the door is stuck, but in fact it is only a partial or secondary reason. An important reason is that after the valve body cavity is closed, that is, after the valve is closed, the pressure increases abnormally, and the fluid pressure in the cavity sealed between upstream and downstream of the sealing surface is much higher than the upstream pressure.