Why is the straight stroke valve stem finer?
To solve this problem, a good way is to turn the valve stem with a tour, or rotary type control valve, the valve stem stroke than the straight stem diameter of 2 ~ 3 times, and the long life of the graphite packing, valve stem stiffness, filling long life, but a small friction torque, small hysteresis.
To this end, the stem design is very small, packing and friction coefficient commonly used PTFE stuffing, in order to reduce back difference, but the problem is to send the stem thin, easy bending, filling life is short.
It involves a simple mechanical principle: large sliding friction, small rolling friction. Straight stroke valve stem movement up and down, and packing a little bit tight, it will be very tight stem, resulting in greater errors.
