Page 108 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

PIPING

2.58 CHAPTER TWO

Stem Construction. There are also five basic types of stem construction, shown in
Fig. 2.26.
Rising Stem /Outside Screw and Rising Stem /Outside Screw and Yoke. These two types
of stem construction keep stem threads outside the valve and are recommended where high
temperatures, corrosives, and solids in the line might damage stem threads inside the valve.
When the hand wheel (nonrising) is turned, the stem rises as the yoke bushing engages the
stem threads. The external threads enable easy lubrication; however, care must be taken to
protect the exposed stem threads from damage.
Rising Stem /Inside Screw. Rising stem /inside screw is the most common stem design
in bronze gate valves. Because the hand wheel and stem both rise, adequate clearance must
be provided for operation. The stem and hand wheel positions indicate the position of the

FIGURE 2.26 Basic stem construction. (a) Rising stem, outside screw; (b) rising stem, inside screw;
(c) nonrising stem, inside screw; (d) rising stem, outside screw and yoke; (e) sliding stem.

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