KST – KROMSCHRÖDER SYSTEM TECHNOLOGY
5.2.5.3.5.1 Flame failure on start-up
In the event that flame failure occurs during the safety time, the burner shall go to lock-out (see 3.48).
However, re-cycling is acceptable providing equipment safety is not compromised. The number of re-cycles shall not exceed 2.1) The control of the re-cycle(s) shall be designed in accordance with the requirements for a protective system according to 5.7.2 and 5.7.3. If there is no flame signal at the end of these re-cycles, the failing burner shall go to lock-out (see 3.48). The conditions of and the time period between recycle and the number of re-cycles shall be specified in the instruction handbook.
For pulse firing burners, flame failure of a single burner shall cause safety shut-down instead of lock-out. Three consecutive flame failures shall cause lock-out. The total number of burners subject to this provision shall be limited to comply with 5.2.5.3.1 (see 3.48). The number of burners shall be specified in the instruction handbook.
5.2.5.3.5.2 Flame failure during operation
In the event of flame failure during operation the burner shall go to lock-out (see 3.48).2)
However, in certain cases, safety shut-down is acceptable providing equipment safety is not compromised. Not more than one re-cycle shall be permitted, the conditions for which shall be specified in the instruction handbook. If there is not a flame signal at the end of this re-cycle, the failing burner shall go to lock-out (see 3.48).
The IThE shall be designed such that a recycle of a single burner system requires a complete recycle including pre-purge.
The following chapters are printed with the permission of the DIN Deutsches Institut für Normung e.V. (German Institute for Standardization). For the implementation of the DIN Standard, the version with the most recent issue date is deemed authoritative. This is available from Beuth Verlag GmbH, Burggrafenstrasse 6, 10787 Berlin, Germany.
Our note on this Standard:
1) The predecessor Standard allowed more than two re-cycles (restarts) at this point. Allowance must be made for this when selecting automatic burner control units.
2) The total closing time is stated at 3 s in subclause 5.2.5.3.4.3. An extinction safety time (safety time during operation) of up to 2 s is possible for the automatic burner control unit on the basis of a closing time of the automatic shut-off valve of 1 s. However, we recommend a safety time of 1 s (in accordance with EN 298) be complied with.
