Understanding the structure is the first step in maintaining a regulating damper. Our unit is built as follows.
- The damper has a double-layer blade structure, and a stainless steel sealing strip is fitted around the perimeter of every blade. When the damper closes, sealing air is injected between the two blade layers so that the medium on either side is effectively isolated.
- Opening and closing are carried out by an electric (or pneumatic) actuator through a linkage. The linkage uses ball joints, which guarantees rotation without lost travel.
- An open/close interlock device and external limit switches are fitted, which makes operation reliable and effectively prevents mis-operation.
What to maintain
- Sealing strip. Check the stainless strip at every outage. A strip that has been eroded by dust will not seal no matter how tight the blade closes, and replacing it is a workshop job, not a plant job.
- Ball joints. These are the parts most often neglected. A dry ball joint develops backlash, the blade then lags the actuator, and the control loop starts hunting. Grease them on the same interval as the rest of the duct dampers.
- Sealing air. Confirm the sealing air pressure is above the flue gas pressure at the gate. A seal that is present but unpressurised is worse than no seal, because it traps moisture between the blade layers.
- Limit switches. Verify the open and closed positions after any work on the linkage. The interlock is only as good as the switch setting.