Q & A > Question Details
We are using born heaters for CRU unit where all heaters inlet lines are covered with ceramic fiber Jacket as air seal purpose but few outlets pipeline from radiation section are not covered. Currently bluish flame is observed coming out from gap/clearance between the outlet pipe and and heater shell casing pipe during night time. What could be the reason for that (from 3rd Heater which has no convection section but has common stack with 1st & 2nd heaters) ?
Another day in the same heater, red hot spot at the inlet of pilot line (pressurized ) was observed and became normal just after the pilot air line had been isolated/closed. But at the pilot inlet found little flame coming out from pilot fuel gas line and disappeared when pilot fuel was isolated. Although pilot should remain close just after the main burner lighted but in our case we keep the pilot in on position all the time. What could be the reason of this red hot spot?
We have VFD operated blower , some time blower noise becomes very high and try to reduce the noise by adjusting the VFD speed . So, what could be the reason for high sound ?
21/05/2018 A: Ralph Ragsdale, Ragsdale Refining Courses, ralph.ragsdale@att.net
I agree. Temporary loss of adequate draft. Automatic damper controls may be malfunctioning. You may be simply overfiring the heater.
21/05/2018 A: Ashutosh Garg, Furnace Improvements Inc, agarg@heatflux.com
Please check your heater arch pressure. It appears to be running positive.
21/05/2018 A: Peter Marsh, XBP Refining Consultants Ltd, peter.marsh@xbprefining.co.uk
Have you checked the draft in your heater? You should be targeting approx. 2.5 mm WG at the top of the radiant section. If you have a positive pressure in the firebox and the VFD is operating near to its max capacity then the back-pressure in the firebox may cause a reduction in flow from the VFD blower and the resulting oxygen deficiency may lead to "afterburn" of unburned fuel as the fuel-rich flue gas leaks through holes and tube penetrations in the heater casing. You should be targeting approx. 2 vol% oxygen at the top of the radiant section. If draft and excess oxygen are too low, reduce firing rate immediately (throughput or furnace outlet temperature) to restore safe conditions. Are you seeing hot spots on the heater casing or scorched paint around peepholes? Please note that a positive firebox pressure is a very hazardous situation; operators should not approach the furnace if it is operating in a fuel-rich atmosphere and should wear eye protection and face shield when using the peepholes after the furnace is restored to 2 vol% excess oxygen target if there is still a positive firebox pressure.