15
Appendix “B”
Excerpt from Guideline BSR/ASHRAE 15-1992R
9.7.5
The minimum required discharge capacity of the pressure-relief device or
fusible plug for each pressure vessel shall be determined by the following:
C =
f
DL
WHERE:
C =
minimum required discharge
capacity of the relief device in
POUNDS OF AIR PER MINUTE (KG/S),
*
(
emphasis and asterisk added
)
D =
outside diameter of vessel
in feet (m),
L =
length of vessel
in feet (m),
f
=
factor dependent upon
type of refrigerant.
Note:
When combustible materials are used within 20 feet (6.1 m) of a pressure
vessel, multiply the value of
f
by 2.5.
REFRIGERANT
VALUE OF
f
When used on the lowside of a limited-
charge cascade system:
R-170, R-744, R-1150
1.0 (0.082)
R-13, R-13B1, R-503
2.0 (0.163)
R-14
2.5 (0.203)
Other applications:
R-717
0.5 (0.041)
R-11, R-40, R-113, R-123, R-142b,
R-152a, R-290, R-600, R-600a,
R-611, R-764
1.0 (0.082)
R-12, R-22, R-114, R-134a,
R-C318, R-500, R-1270
1.6 (0.163)
R-115, R-502
2.5 (0.203)
When one pressure-relief device or fusible plug is used to protect more than one
pressure vessel, the required capacity shall be the sum of the capacities required for
each pressure vessel.
*
Note: To convert from
pounds of air per minute
to
SCFM
, multiply by
13.3
.