Granville-Phillips Mini-Convectron 275 Series, Инструкция по установке, эксплуатации и обслуживанию, Страница: 35 / 52

Installation, Configuration
Mini-Convectron
®
Module with DeviceNet
®
Digital Interface 27
Example 1 – Maximum Safe Indicated Pressure
Assume a certain system will withstand an internal pressure of 1000 Torr or
19.3 psia. For safety, you wish to limit the maximum internal pressure to 760
Torr during backfilling. Assume you wish to measure the pressure of Argon
(Ar).
On Figure 4-3, locate 760 Torr on the left hand scale, travel to the right to
the intersection with the Argon curve, and then down to an indicated
pressure of 24 Torr (N
2
equivalent). Thus, in this hypothetical situation, the
maximum safe indicated pressure for Argon is 24 Torr.
For the sake of safety, it is prudent to place a warning label on the instrument
face which under the assumed conditions would read “DO NOT EXCEED 24
TORR FOR ARGON”.
Example 2 – Indicated To True Pressure Conversion
Assume you wish to determine the true pressure of Argon in a system when
the Mini-Convectron is indicating 10 Torr. On Figure 4-3, read up from 10
Torr (N
2
equivalent) indicated pressure to the Argon curve and then
horizontally to the left to a true pressure of 250 Torr. Thus 250 Torr Argon
pressure produces an indication of 10 Torr (N
2
equivalent).
Example 3 – True To Indicated Pressure Conversion
Assume you wish to set a process control trip point at a true pressure of 20
Torr of C02. On Figure 4-3, locate 20 Torr on the true pressure scale, travel
horizontally to the right to the C02 curve and then down to an indicated
pressure of 6 Torr (N
2
equivalent). Thus the correct process control setting
for 20 Torr of C0
2
is 6 Torr (N
2
equivalent).
Example 4 – True To Indicated Pressure Conversion
Assume you wish to obtain a helium pressure of 100 Torr in the system. On
Figure 4-3, locate 100 Torr on the left hand scale, travel horizontally to the
right to attempt to intersect the He curve. Because the intersection is off
scale, it is apparent that this true pressure measurement requirement for
helium exceeds the capability of the instrument.
For gases other than those listed, the user must provide accurate conversion
data for safe operation. The Mini-Convectron Gauge is not intended for use
above 1000 Torr true pressure.