Operation
Z33081_00_001 53
Figure7.20:EndofBatchDeliveryProcess
7.6 GeneratorShutdown
TheBPHG90canbeleftinReadymodewithoutdetrimentaleffectstotheinstrument.If,
however,itisenvisagedthatnoparahydrogenisrequiredforaprolongedperiodoftime,it
isrecommendedthatthesystembeswitchedoff.Itisnotrecommended,however,thatthe
BPHG 90 is switched off by means of the main power switch when the conversion
chamber is cold. This could lead to pressure build up in the conversion chamber and (a
small amount of) H
2
gas being released through the pressure safety valves in the
instrument.
Thepreferredprocedureforswitchingthesystemoffisbyfirstwarmingitupasdescribed
inthefollowingsection.
7.6.1 WarmUp
Upon terminating either of the two delivery modes, the BPHG 90 returns to the Ready
screen. When the user presses the Exit button on this screen the system will return to
StandbyfromwhichaforcedwarmupcanbeinitiatedbytappingtheWarmUpbutton.
The Warm Up procedure allows the user to warm the system up quickly to a preset
temperatureinordertoclearasuspectedconversionchamberblockage,orinpreparation
forasystemshutdown.
A forced warmup takes typically less than 20 minutes. When the Warmup button is
pressed, the system asks for a user confirmation (Warm up dialogue and information
screen [} 53]) and then proceeds to heat the conversion chamber under continuous
pumpingontheworkingvolume.