The advantage of speed for damper drive applications

Paul Boughton

For combustion air and flue gas applications, some critical services are very dependent on rapid speed to ensure equipment life, operator safety and peak plant performance. Rand Underwood reports.

At the Florida Power & Light 3-Unit Manatee Station, a 2,735MW generating plant in Parrish, Florida, Rotork Type K damper drives have provided a solution to a critical application demanding quick damper operation.

In the case of balanced-draft power generation boilers, low pressure conditions inside the combustion chamber can lead to some very serious equipment failures.

Boiler pressure transients can cause combustion issues that lead to irregular heating in the steam tubes. In extreme conditions, excess negative boiler pressure can collapse boiler walls and buck stays, leading to additional catastrophic failures such as ruined boiler tubes and refractory or even wholesale structural damage.

The nature of these events often equate to long term unit shutdown, lost kilowatt production, and expensive emergency site construction repairs.

Power generation boilers need a somewhat consistent internal operating pressure environment for efficient and manageable combustion.

The ID Fans on a combustion boiler play a critical role in maintaining that reliable boiler pressure.

The ID Fan Inlet Damper Controls that regulate fan induced pressure and airflow need to be vigilant 'soldiers at the ready' to help keep these pressure fluctuations in check.

The ID Fan Damper Inlet Drives required for Florida Power & Light Manatee Station Units1 & 2 require full 90 degree drive and damper movement at full torque load in three seconds or less to safeguard the operation of the boilers.

The existing drives were in excess of 30 years old. In addition, they were not HART compatible with the plant's new DCS system and the manual overrides were unreliable on the aging damper drives.

Type K offered a drop-in-place retrofit drive matching the existing damper drive footprint that featured smart positioner technology and integrated air volume boosters to obtain the rotation speed required. Type K also completed factory acceptance testing on the drives and obtained the test cycle times as recorded by the smart positioner.

The results of the testing were video recorded and documented for Florida Power & Light to review prior to shipment.

The on-site performance testing for damper drive speed was conducted at the power plant early on a Sunday morning at about 2:00AM. This was a full load/installed equipment proof-test scheduled typically toward the end of a planned outage. This acceptance test is critical to build confidence in the plant unit trip and boiler shutdown process.

The Type K Drives performed as quickly and as smoothly as factory testing had indicated.

At full boiler pressure and damper load, the drives rapidly failed to the fully closed position as required.

Passing this test is primary to outage completion and full sign-off for boiler readiness to generate electricity.

For more information at www.engineerlive.com/ipe

Rand Underwood is General Manger of K-TORK International Inc, part of the Rotork Group, Bath, England, UK. www.rotork.com

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