This has happened over the years as not much attention is paid to the design and operation of stack dampers. Most of the stacks are sized for summer ambient temperature and 115% heater load. The damper loss considered in design is 1.5 velocity heads although fully open damper consumes only 0.5 velocity heads. Stack heights are also controlled by the pollution considerations. Stack diameters are dictated by structural considerations.
As a result of all the over sizing, the damper ends up consuming lot more pressure drop during the actual operation. The stack damper could be operating at 40-50% open at full loads. The heater gain draft in the night due to lower ambient temperatures and it could mean another 0.1 inch WC of draft or more. This means that the stack damper should be controlling draft accurately during the day and night cycle. However most of the dampers are kept fully open all the time. This type of operation causes considerable loss of energy and inefficiency. We have developed a new type of damper operation for controlling draft in the fired heaters. Our patent pending damper design has multiple pneumatic operators for controlling the damper. Typically two operators will cover most of the range but in some very large dampers, we may recommend installing 3 operators. By installing multiple operators, we are able to change the control characteristics of the damper itself and damper can work smoothly from 50 % to 115% load without any issues. We are going to talk about the draft control in firing heaters using the new patent pending control system. It is possible to save substantial amount of energy by improving the controls. We can take care of tramp air by operating the heater at correct draft. We have developed a Safe and Reliable Damper Control System which can be used by itself or can be integrated with draft control system.
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