Retrotec USACE - Manual (Page 192)

D62 ENERGY & PROCESS ASSESSMENT PROTOCOL
lowest viscosity being number 6. The most commonly used fuel oil is number
2, which pours the most easily and is the fuel oil of choice for all but large
central energy system boilers. Number 2 fuel oil, commonly stored above
ground outdoors (Figures D107 and D108), can be atomized in all but very
cold temperatures. Fuel oil grades number 4 and higher need preheating
before burning, with the following recommended temperatures:
No. 4 57 °C (135 °F)
No. 5 85 °C (185 °F)
No. 6 99 °C (210 °F)
This is a good application for a heat recovery system.
D.4.1.32 No Automatic Stack Damper (Waste)
Figure D109. Stack damper in breeching
branch before main breeching run to stack.
A stack damper is used to isolate boilers that are off or in standby mode
(Figure D109). Closing these dampers when a boiler goes offl ine prevents
the loss of the retained heat in the boiler after fi ring. Without a closed stack
damper, air would continue to fl ow through the boiler and up the stack,
taking heat from the system. Also, cold air could enter the boiler from the
stack, posing a freezing problem during very cold weather. If automatic stack
dampers are present on multiple boiler systems, their application should be
investigated.