Page 482 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

448 Applied Process Design for Chemical and Petrochemical Plants

VARIABLE OR CONSTANT BACK PRESSURE SIZING FACTOR
Kv
10% OVERPRESSURE
BalanSeal Valves Only-Vapors & Gases

ii!
:,
� "' ; 1.00
.,
:,o.
� .90
><t-
�a .BO
<DJ:
Ei
J � .70
�- ��::��'e:;�URE= 100 PSIG
BACK PRESSURE= ZERO TO 80 PSIG
UC , % GAUGE B.P. = fb%-x 100 = 60% MAX.
� .50 :;::: FOLLOW DOTTED LINE. Kv - O. 88 (FROM CURVE)
a: ::: �PACITY WITH B.P. - 0.88 X RATED CAPACITY WITHOUT B. P.
II
l .40
I I I I I
0 10 20 30 40 50 60 70 80 90 100
Figure 7-27 A. Variable or constant backpressure sizing factor, Kv, at 10% overpressure, BalanSeal® valves only: vapors and gases. By per-
mission, Teledyne Farris Engineering Co.

VARIABLE OR CONSTANT BACK PRESSURE SIZING FACTOR
Kv
210/oOVERPRESSURE
BalanSeal Valves Only-Vapors & Gases

.90
.80
"
.70 ,mmfiSET PRESSU E= :1
l:l BACK PRESSURE= ZERO TO 7. PSIG
H- 0 /a GAUGE B. P. =
.60 � X 100 = 70 % MAX.
FOLLOW DOTTED i1NE. Kv =0,87 (F'ROM CURVE)
CAPACITY WITH B. P. = 0.87 X RATED CAPACITY WITHOUT B. P.
.60
..
l .40
I I I I I
0 10 20 30 40 50 60 70 80 90 100
Figure 7-278. Variable or constant backpressure sizing factor, Kv, at 21 % overpressure, BalanSeal® valves only: vapors and gases. By per-
mission, Teledyne Farris Engineering Co.

A = required orifice area, sq in. Typical Values for Cubical Expansion Coefficient*
P 1 = set pressure of valve, psig
Liquid Value
3-34.9 degree API gravity 0.0004
35-50.9 degree API gravity 0.0005
51-63.9 degree API gravity 0.0006
Ref [33a] in Appendix C cautions that if the vapor 64-78.9 degree API gravity 0.0007
pressure of the fluid at the temperature is greater than 79-88.9 degree API gravity 0.0008
the relief set/ design pressure that the valve must be 89---93.9 degree API gravity 0.00085
capable of handling the rate of vapor generation. 94-100 degree APJ gravity and lighter 0.0009
Other situations should be examined as the thermal Water 0.0001
relief by itself may be insufficient for total relief. *By permission API, Ref [33a]