ISO/DIS 21922:2018(E)
Table 3 — Test requirements for seat tightness
Seat tightness class Type test
a
A
b
B
C 0,1 % of K
VS
D 0,25 % of K
VS
E 0,5 % of K
VS
F 1 % of K
VS
G
c
a
pressure range. For manual valves, see Table 4
b
c
b) Valves leading to the atmosphere during service shall be seat tightness class A or B.
As alternate methods for valves with independent double seating (such as double disc or split wedge
performed.
7.6.2 Seat tightness: type test
The leakage rate LK
VS
The manufacturer shall measure the leakage covering the whole differential pressure range for which
the valve is designed using gas (for instance air or nitrogen). The leakage rate L
limits given in Table 3
For seat tightness class G the leakage rate L
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