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SECTION 3 – HANDLING, STORAGE, INSTALLATION AND REASSEMBLY
RUPTURE DISK AND RELIEF PIPING
NOTE: The ANSI/ASHRAE 15-2001
safety standard code was recently re-
vised to include absorption chiller relief
devices. Please read and follow these
instructions closely to ensure the chiller
installation is compliant to the revised
code.
For YHAU units, this device is a metallic, one time
use, rupture disk burst rated at 7.0 PSIG, +/- 2.0 PSI
(48.2 kPa, +/- 13.8 kPa).The size of the rupture disc
will depend on the chiller capacity.
The rupture disk will protect the chiller's integrity
should there ever be a tube rupture or in the very un-
likely event that the unit's refrigerant vapor pressure
gets too high. Unlike vapor compression cooling ma-
chines that relieve refrigerant vapor, if the rupture disk
bursts, absorption machines could expel a vapor and a
liquid.
The metallic disk is mounted at the factory between
two special flanges. The flanges have a knife-edge that
perforates a special flange on the disk to create an air-
tight seal.
CAUTION: Liquid coming out of the
rupture disk could be in excess of 200°F
(93.3°C)!
NOTE: Do not loosen the bolts around the
flange or remove the disk from the holder.
If the disk is removed for any reason, it
must be replaced with a new one!
The outer flange of the disk holder has a plastic pipe
stub supplied by the factory for shipping purposes. The
PLASTIC stub must be removed! Refer to Figure 8 on
page 30.
Rupture Disk Discharge Piping Material
ANSI/ASHRAE 15-2001 calls for the relief piping
material to be compatible with the refrigerant in the
system. The refrigerant is de-ionized water that could
exceed 200°F (93.3°C) in some cases. Johnson Con-
trols recommends using schedule 40 steel pipe for the
rupture disk discharge line material.
30
Rupture Disk Discharge Piping Construction
For the piping material, Johnson Controls recommends
carbon steel. The relief piping must be fabricated and
constructed in accordance with piping best practices.
Follow any local codes (if applicable) governing the
rupture disk discharge relief piping. Due to the high
temperatures of an absorption unit during operation,
and the expansion and contraction associated with this,
the rupture disk vent piping must have a flexible con-
nection between the rupture disk outlet and the relief
piping. The installing contractor must supply the flex-
ible connection and the relief piping.
Piping supports must be spaced according to the pipe
material, size and temperature.
NOTE: At no time should there be any
weight or moment arm forces imposed on
the flanges of the rupture disk!
Rupture Disk Discharge Piping Sizing
The sizing of the rupture disk discharge piping must
not be less than the rupture disk diameter. Where two
or more relief devices are connected to a common line
or header the effect of back-pressure that will be de-
veloped when more than one relief device operates
shall be considered. The sizing of the discharge line
for above condition must be based on the sum of each
rupture disk outlet area in addition to the pressure drop
allowance through the outlet piping.
FORM 155.31-ICOM2.EN.UL
ISSUE DATE: 12/21/2018
LD27778
JOHNSON CONTROLS
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