2
EN2R--9023 9705R0--NE
GENERAL
Application (continued)
The A4021A can be used for both single and combination
valves with or without pilot valve.
For valves with large nominal sizes, valve proving is possible
by use of auxiliary valves (pre--configuration only, see page 4).
For mounting the A4021 on a typical combination valve as the
VQ400 Series or on a large valve like the VE5000 Series
there is a mounting bracket available (order separately)
According the European standard EN676 a valve proving
system can be used under certain conditions, as an
alternative for pre--purging the combustion chamber. EN676
prescribes a valve proving system for capacity rating over
1,200 kW, see Table 1.
Table 1. Application valve proving systems according EN676
Heat--Input
With Pre--Purge
Without Pre--Purge
p
[kW]
Main Gas
Start Gas
Main Gas
Start Gas
[kW]
≤
10%
≥
10%
≤
10%
≥
10%
≤
70
2 x B
B*)
2 x B
2 x A or
2 x B +VPS
A**)
2 x A
> 70,
≤
1200
2 x A
2 x A
2 x A
2 x A + VPS
2 x A
2 x A
> 1200
2 x A + VPS
2 x A
2 x A
2 x A + VPS
2 x A
2 x A
NOTE:
A:
Automatic shut--off valve approved on EN161, class A
B:
Automatic shut--off valve approved on EN161, class B
Valve Proving System required
Valve Proving System as alternative for pre--purge of the combustion chamber
*)
For third family gases: two class B valves are required
**)
For third family gases: two class A valves are required
Fig. 1. VQ400 combination valve with A4021 valve proving System.