Effects of a Surface Engineered Metallic Coating on Elastomeric Valve Stem Seal Leakage Page: 62
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150 in-lbs using a calibrated breakaway torque wrench. The manufacturer's
recommended torque range for cap screws on this size valve is 120 to 180 in-lbs (Grove
Valve 1980). For test sequences that involved lubrication, the upper stem seal O-ring
was then lubricated by liberally applying grease manually to the surface of the O-ring.
The upper stem seal to be tested was installed by sliding it along the stem and seating it in
the gland plate. The bearing housing was then installed and the bearing housing cap
screws were torqued to 150 in-lbs using the breakaway torque wrench. The valve was
then position to the half open position.
The valve was pressurized using the pressure regulator and the high precision
pressure gage was used to monitor pressure during pressurization and testing. After the
pressure was raised to 500 + 25 psi, pressure was allowed to stabilize for 20 minutes
(Leefe and Davies 1995) prior to cycling so that the O-ring would be seated by pressure
into the gland plate.
The technique used for leak measurement followed EPA guidelines (United States
Environmental Protection Agency 1995; United States Environmental Protection Agency
1999). Prior to any measurement, each detector was zeroed at least one meter away from
the test valve. The tip of the each detector was placed directly at the valve stem/bearing
housing interface. When leakage was found, the tip of a detector remained at the location
of the leak until a maximum reading was obtained and for a duration of at least twice the
response time. The GOW MAC 21-250 was used to slowly sweep the circumference of
the interface to locate a leak. The Ion Science 3000IS was then used to quantify the leak.
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Taylor, John Abner. Effects of a Surface Engineered Metallic Coating on Elastomeric Valve Stem Seal Leakage, thesis, December 2000; Denton, Texas. (digital.library.unt.edu/ark:/67531/metadc2690/m1/70/: accessed May 22, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .