MKS HPS LPV1-25-AC Series, Руководство по эксплуатации и обслуживанию

Страница: 21 / 52

13
HPS HPS
HPS HPS
HPS
®
Square Body LoPro Square Body LoPro
Square Body LoPro Square Body LoPro
Square Body LoPro
Seri es Seri es Seri es Seri es Serie s
5.2 Operation & Performance
5.2.1 Cycle Rate and Life
5.2.1.1 Pneumatic Actuation
The opening and closing times are the limiting factors of the
maximum cycle rate. If the valve is cycled faster than the sum of the
opening and closing time, it will fail to open or close completely,
possibly resulting in failure. Although opening and closing times are
dependent upon the pneumatic pressure, flow available and other
parameters, the following values represent the time for the poppet to
move full stroke at median recommended pneumatic pressure, with
unrestricted flow, and at room temperature.
Opening Closing
NW25 0.12 sec 0.18 sec
NW40 0.27 sec 0.53 sec
NW50 0.45 sec 1.13 sec
Under normal conditions, Pneumatic Square Body LoPro valves will greatly
exceed
1 million cycles before failure.
5.2.1.2 Manual Actuation
The opening and closing times are the limiting factors of the maximum cycle
rate. Opening and closing times are dependent upon the operator and will
vary dependent upon the application. Under normal conditions, Manual
Square Body LoPro valves will greatly exceed 100,000 cycles before failure.
5.2.2 System Pressure Limits
Square Body LoPro Series valves are designed to function from UHV to
greater than 2 Atm pressure (depending on size). Due to the elastomer seal
on the bonnet, the lower pressure limit is determined by the vacuum
system’s tolerance for the gas load due to permeation through and leakage
around that seal. All vacuum seals and welds in Square Body LoPro Series
valves are He mass spectrometer tested with the maximum allowable leak
rate being 1 x 10
-9 std Atm cc/ sec. Although the Square Body LoPro valves
may be a factor in the base pressure of a system, there is, in fact, no low
system pressure limiting the valves’ function.
High pressure, however, can cause failure in the pneumatic version. With
the valve open, the opening force exerted on the nosepiece by excessive
internal pressures will exceed the spring’s closing force and the valve will
fail to close completely. A similar pressure applied to the bottom port of a
closed valve could force the valve to open or “blow by.” These pressures
are as follows: