Prepurging - Siemens LMV50 Series Manual

Prepurge time after
safety shutdown
Prepurge times 1 and
3
Start without prepurging
66/327
Building Technologies

4.2.3.6 Prepurging

The prepurge position is approached in phase Traveling to prepurging (24).
The prepurge time is determined via the following parameters:
Parameter PrepurgeTmeGas
PrepurgeTmeOil
These 2 parameters determine the minimum prepurge time, provided the following
parameters do not become effective.
This means that the prepurge time is allocated to phases 30 through 34:
In phase 30, the time defined in PrepurgePt1... is observed, followed by phase 32 or
valve proving. Then, the time of PrepurgeTmeGas possibly remaining, or
PrepurgeTmeOil in phase 34, is observed, but always PrepurgePt3... as a minimum.
These parameters determine the prepurge time after the following events:
• Alterable lockout position
• Off time >24 hours (standby)
• Power failure (Power-on)
• Shutdown due to interruption of gas supply (safety shutdown)
Parameter PrepurgeSafeGas
PrepurgeSafeOil
If these times are used, they are equally assigned to phases 30 and 34.
These are minimum times that are always observed in phases 30 (prepurge time 1) and
34 (prepurge time 3)!
These parameters determine the minimum times for prepurging part 1 and part 3.
Parameter PrepurgePt1Gas
PrepurgePt1Oil
PrepurgePt3Gas
PrepurgePt3Oil
Example:
If the sum of prepurge time part 1 and part 3 exceeds PrepurgeTmeXX or
PrepurgeSafeXX, this longer prepurge time applies!
When using valve proving and 2 class «A» fuel valves, prepurging will not be required
(as per EN 676).
Skipping prepurging can be activated through parameterization.
In spite of an activated parameter, prepurging is performed under the following
conditions:
• Alterable lockout position
• Off time >24 h (standby)
• Power failure (Power-on)
• Shutdown due to interruption of gas supply (safety shutdown)
• Direct start
Parameter SkipPrepurgeGas (deactivated / activated)
SkipPrepurgeOil (deactivated / activated)
Caution!
Deactivating valve proving does not automatically deactivate skipping
prepurging. Hence, the person making the settings must ensure that
SkipPrepurgeGas is activated only if permitted for the relevant type of plant.
Basic Documentation LMV5...
4 Burner control
CC1P7550en
22.05.2018