Habonim Catalog Interactive 2021 V04 070621 - Flipbook - Page 29
The valve trim - and the valve stem seal design in particular - determine the quality of a valve.
The stem seal must perform two tasks: keep the media within the boundaries of the pressure
vessel, and allow uninterrupted leak-free continuous open/closed quarter-turn rotation.
Unlike the valve body’s static seal, the stem seal is subject to dynamic operation of the valve,
as well as to side loads resulting from actuator misalignment or from the operator forcing
the handle incorrectly. The valve trim typically comprises two Belleville springs assembled
Face-to-Face, which preload the stem seal. This self- adjusting mechanism compensates
for wear and pressure/temperature differentials - ensuring a leak-tight seal and extended
service life. Habonim’s trim design for heavy-duty service, such as high cycle applications, uses
four or even six sets of Belleville springs so as to maintain preload over a longer operational
cycle life. The Belleville springs are compressed by the stem nut, which is locked to prevent
unintentional release during cycles.
Habonim’s stem seal design, consisting of a live-loaded thrust bearing and anti-abrasion ring
combined with a stem seal, significantly increases valve cycle life over conventional ball
valves and extends the time between adjustments.