Upper Threaded Stem and Lower Threaded Stem

Because of the different positions of stem thread, stem of globe valve can be divided into upper threaded stem and lower threaded stem.

 

Transmission thread is located on the upper part of the stem, outside the cover and stuffing box. Without contacting the media, it is not subject be corroded and easy to lubricate. Upper threaded stem is difficultly skewed, which can guarantee the well contact between seat and disc, good for sealing. What’s more, unrestricted stuffing box depth can avoid the external leakage. Upper threaded stem is suitable for globe valve with large caliber, high temperature and pressure, or corrosive media.

 

Transmission thread is located on the lower part of the stem in the body cavity. Contacting with the media, it is easy to be corroded and can not be lubricated. For larger viscosity media or media with suspended solids, they will be easily condensed into liquid and cause thread jams. With short stem length advantage, lower threaded stem can reduce the opening height, which typically used for globe valve with small caliber and non-corrosive, clean medium.