3 replies to this topic

[AZIZ_MN]

Hello everyone,
for furnace startup sequence steps are
1. preventilation
2. tightness test of fuel gas ON-OFF valves
3. release fuel gas
4. lightup burners
my question is
1. for force draft and for induced draft furnace fan or blower is provided for preventilation but for natural draft furnace how to do preventilation as there is no fan or blower for that
2. after prolonged shut down while starting up furnace why funace box is pressurising after preventilation and due to that burner lightingup is difficult due to +ve draft
3. logically tightness test of fuelgas on-off valve should be first and then preventilation step should come but normally squences like stated above why?.
thanks and best regards
azzu

[hasriabdan]

Hello everyone,
for furnace startup sequence steps are
1. preventilation
2. tightness test of fuel gas ON-OFF valves
3. release fuel gas
4. lightup burners
my question is
1. for force draft and for induced draft furnace fan or blower is provided for preventilation but for natural draft furnace how to do preventilation as there is no fan or blower for that
2. after prolonged shut down while starting up furnace why funace box is pressurising after preventilation and due to that burner lightingup is difficult due to +ve draft
3. logically tightness test of fuelgas on-off valve should be first and then preventilation step should come but normally squences like stated above why?.
thanks and best regards
azzu

[Beergson]

1. for force draft and for induced draft furnace fan or blower is provided for preventilation but for natural draft furnace how to do preventilation as there is no fan or blower for that

For natural draft for ventilation confirmation engineering practice is to equipp stack damper in high (open) limit switch and burner air damper (register) in high limit switch - to have confirmation that air path through heater is open. Acc to API (560 or 535) min. ventilation time is 15 min or 5 heaters volumes. Moving force for natural draft heater in ventilation is stack height - draft.

[AZIZ_MN]

1. for force draft and for induced draft furnace fan or blower is provided for preventilation but for natural draft furnace how to do preventilation as there is no fan or blower for that

For natural draft for ventilation confirmation engineering practice is to equipp stack damper in high (open) limit switch and burner air damper (register) in high limit switch - to have confirmation that air path through heater is open. Acc to API (560 or 535) min. ventilation time is 15 min or 5 heaters volumes. Moving force for natural draft heater in ventilation is stack height - draft.

Thanks very much Beergson for answering i tried to surch my ans. on net there i found lengthy informations i want to know how it works practically and can you pl tell me where i can get more information about startup sequence of various type of furnace
thanks and best regards
azzu.