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We have 2 combustion air blowers for meeting the total air demand in our FCC unit. Main air blower(MAB) is a fixed speed one while auxiliary man air blower(AMAB) contains VFD. Whenever AMAB is started, oil vapours start escaping from its antisurge vent line creating a vapour cloud. Recently the vent line silencer also caught fire because of this. What could be the reason? Is it normal for lube oil to escape from the blower antisurge vent line? There is also a small 3 inch balancing line connecting the blower casing and the blower vent line downstream of its antisurge control valve, is it a good practice to have this line?
 
Answers
01/08/2012 A: Vijay Srinivasan, H P C L, svijay24@rediffmail.com
The blower is centrifugal; make:BHEL, model:MCL1004. It takes suction from atmosphere and discharges into the air header common for MAB & AMAB with antisurge control facility. The suction and antisurge controllers are from M/s CCC.The suction control is based on load sharing between the 2 blowers when they are running in parallel and antisurge controller operates independently to maintain a safe margin away from surge point.
23/05/2012 A: Bruce Carr, Suncor Inc, matukaze1@hotmail.com
Can you post more information of the layout, also post more information as to the type of blower (make, model.....)