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d) (valid for P15/A pilot) the breakage of the diaphragm (4) does not damage the
valve operation because the leakage, if any, feeds the chamber (D) that balancing
itself with the ( C) allows the spring (16) to raise the plug-pilot (8) by means of the
rod (15) thus allowing the emptying of the chamber (B).
e) ( valid for P 16/A and P 17/A pilot ) the breakage of the diaphragm (4) does not
damage the valve operation because any leakage through the ''piston effect'' on the
spring support causes the opening of the valve-pilot ( 8 ) and the consequent
opening of the valve plug ( 6 ).
The adjustment of the setting value is made by means of the ring nut (12) inside the
pilot and by using different springs according to the predetermined setting value.
The spring (11) allows the extra stroke of the spring-diaphragm unit without loading
the plug-pilot (8) on its seal seat
1.4 VALVE SIZING
The PVS 782 valve is sized by means of the formula reported on the RACCOLTA E
chapter E. 1. D. that is
q = ( 0,9 x K ) x (394,9 x C ) x P
where:
q = max. flow rate to be discharged in Kg/h
A = min. passage way in cm
K = flow coefficient ( 0,56 )
P
= setting pressure plus 10% (abs. bar)
1
T
= temperature of the fluid at the valve inlet in ° K
1
M = molecular mass of the fluid in Kg/Kmol
Z
= compressibility factor of the fluid at the discharge conditions ( = 1 if not known)
1
C = Coefficient of expansion
M
x A x
1
Z
xT
1
1
2
( see table 1 )
2
=
C
k
(
+
k
8
| sales@mvandc.com | Phone: 877.566.3837 | Fax: 925.407.2903
(
)
+
k
1
(
)
−
k
1
)
1
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