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Note: To determine the total C value for a specific unit,
add the appropriate C values for the evaporator,
standard condenser, and economizer. If the unit
is equipped with any options (e.g., heat recovery,
free cooling, or an auxiliary condenser), add the
applicable C value(s) for those options to the
total as well.
Note: The table and figure in
Reference," p. 44
are applicable only for non-
manifolded vent-line runs connected to a 15 psig
(103.4 kPaG) rupture disk relief device. The pipe
length provided by the table is in "equivalent feet."
The vent-line length in equivalent feet is the sum of
the linear pipe length plus the equivalent length of
the fittings (e.g., elbows).
Vent Line Installation
Important: Before constructing the rupture disk vent line,
consult local codes for applicable guidelines
and constraints.
All CenTraVac™ centrifugal chillers are equipped with
rupture disks. If refrigerant pressure within the evaporator
exceeds 15 psig (103.4 kPaG), the rupture disk breaks and
shell pressure is relieved as refrigerant escapes from the
chiller.
A cross-section of the rupture disk assembly appears inthe
following figure (rupture disk location and cross section),
along with an illustration indicating the location of the
rupture disk on the suction elbow.
Important: If a RuptureGuard™ is to be installed, remove
and discard the factory-installed rupture disk;
for more information, refer to RuptureGuard
Pressure Relief System OptionInstallation,
Operation, and Maintenance (CTV-SVX06*-
EN).
Several general recommendations for rupture disk vent line
installation are outlined as follows.
Note: If the rupture disk was removed for service or vent-
line piping installation, the rupture disk must be
reinstalled (as shown in the following figure [rupture
disk location and cross section]). Refer to the
following procedure and contact CenTraVac™
Chiller Technical Service when reinstalling the
rupture disk.
•
Verify that the vacuum support side of the rupture disk
is positioned as shown in the cross-section view that
appears in the following figure (rupture disk location
and cross section).
–
Install the two bottom hex head screws though the
pipe flanges.
–
Install the rupture disk with a gasket on each side
between the pipe flanges. Orient the disk with the
reference arrow or vacuum support bar facing the
chiller side as shown in the following figure (rupture
disk location and cross section).
–
Install the two top hex head screws.
CVHE-SVX005C-EN
"Vent Line Sizing
–
Center the disk and gaskets to the flange bore.
–
Hand-tighten all screws, assuring equal pressure.
–
Use a torque wrench set to 240 in·lb (27.1 N·m)
with a 9/16-in. socket.
–
Tighten screws in a star pattern, one half turn each,
to maintain even pressure on the disk.
–
Final torque on all screws should be 240 in·lb
(27.1 N·m).
•
When attaching the vent line to the chiller, do NOT
apply threading torque to the outside pipe of the rupture
disk assembly.
NOTICE
Rupture Disk Damage!
Failure to follow instruction could result in damage to
the rupture disk assembly.
Do not apply threading torque to the outside pipe.
•
Provide support as needed for the vent line. Do NOT
use the rupture disk assembly to support the vent-line
piping.
•
Use a flexible connection between the vent line and the
rupture disk assembly to avoid placing stress on the
rupture disk. (Stress can alter rupture pressure and
cause the disk to break prematurely.) The flexible
connector used to isolate the rupture disk from
excessive vent line vibration must be compatible with
the refrigerant in use. Use a flexible, steel connector
(such as the stainless-steel type MFP, style HNE,
flexible pump connector from Vibration Mounting and
Control, Inc.), or equivalent. Refer to the following
figure (arrangement for rupture disk relief piping) for a
recommended relief piping arrangement.
•
An individual vent line is normally installed for each
relief device. It is permissible to manifold the rupture
disks of several machines into a common vent line
provided that the appropriate ASHRAE Standards and
local code requirements for manifolded relief devices
are followed.
Note: The following figure (arrangement for rupture disk
relief piping) does NOT apply for manifolded
vent lines.
WARNING
Pressure-Relief Device Discharge
Hazard!
An improper vent-line termination could result in
death or serious injury or equipment damage.
When a pressure-relief device operates, it could
discharge a large amount of fluid and/or vapor. Units
MUST be equipped with a vent-line termination that
discharges outdoors in an area that will not spray
refrigerant on anyone.
Vent Piping
41
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