17
Pressurization and Startup
NOTE
A standard nitrogen cylinder (9 inch diameter by 55 inches tall)
contains about 200 cubic feet (2.6 m
3
) of gas. Shively Labs Mod-
els 1235 and 2577 compressor-dehydrators will provide about 12
cubic feet (0.34 m
3
) per hour; the Model 1234 about 78 cu ft (2.2
m
3
) per hour.
e. Connect a source of dry gas (cylinder nitrogen or air from a compres-
sor-dehydrator) to the system as shown in
Figure 7
.
f. Raise the gas pressure to 12 or 13 psig (83 - 90 kPa).
g. If the relief valve has opened, the nitrogen cylinder will slowly drain
or the compressor-dehydrator will not shut down.
Remember
It is critical to blow dry gas
through
the system, rather than
merely maintain a pressure; the gas volume accomplishes the
purge.
Step 3. Leaving the
System Pressurized
After completion of the purge, reduce the supply pressure to about 5 to
7 psig, allowing the pressure relief valve to close and seal the system.
After the pressure has stabilized, keep careful note of cylinder pres-
sure or compressor-dehydrator running time, to be sure that no large
leaks have been overlooked. This is especially important immediately
after installation or any subsequent opening and reassembly.
Before Beginning
Intial
Characterization:
Although initial characterization is at your discretion, we strongly rec-
ommend it as the best way to identify both initial problems and possi-
ble future system damage.
Table 3. Volume of Coax per 1000 Feet of Length
Coax Size
Volume
1/2"
2 cu. ft. (0.06 m
3
)
5/8"
3 cu. ft. (0.08 m
3
)
7/8"
4 cu. ft. (0.11 m
3
)
1-5/8"
13 cu ft. (0.37 m
3
)
