46
CVHE-SVX005B-EN
L =
0.214d
5
(
P
2
0
– P
2
2
)
–
d * ln(P
0
/ P
2
)
fC
2
R
6f
ASHRAE Standard 15
For CenTraVac
™
chillers using a rupture disk relief:
•
L
= equivalent length of discharge piping, ft (m)
•
C
r
= rated capacity as stamped on the relief device
in lb/min (kg/s), or SCFM multiplied by 0.0764 lb/
min (convert multiplier in lb/min to kg/s for SI)
C
r
= C
C value from the preceding table (convert C
C
in lb/min to kg/s for SI)
•
f
= Moody friction factor in fully turbulent flow
•
d
= inside diameter of pipe or tube, in. (mm)
•
ln = natural logarithm
•
P
2
= absolute pressure at outlet of discharge piping,
psi (kPa)
•
P
0
= allowed back pressure (absolute) at the outlet
of pressure relief device, psi (kPa)
P
0
= (0.50
P
) + atmospheric pressure
N
No
otte
e:: For rupture disks on CenTraVac
™
chillers, P
is 15 lb (6.8 kg). Atmospheric pressure is at
the elevation of the installation above sea
level; a default value is the atmospheric
pressure at sea level, 14.7 psi (101.34 kPa).