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INTRODUCTION

Flue gas isolation and control equipment has progressed from simple fan control to critical process and man safe isolation applications.  With the increased importance of reliable damper equipment, the specifying Engineer is faced with no industry standards to evaluate equipment.  Failures of dampers have caused plant shutdowns, and many plants have invested hundreds of man-hours in their dampers to get them to work properly.   Buying heavy-duty dampers does not necessarily end problems as undersized actuators, binding, and seal failures are common on all types of dampers.  Many of the FGD dampers installed during the 70's have been replaced at great expenses. 

Failures of dampers can have a serious effect on station safety, on unit capacity or unit availability, and on plant environment.  In spite of clear evidence of this, dampers were until recently a neglected area of design.  Because dampers appeared to be part of sheet-metal ducting or breeching, their selection, construction details, and installation were often left to the contractor who was bidding on gas and air ducting.  These firms with structural and civil background had not developed the mechanical background necessary for dampers. 

Contracts for the ducting were frequently not let until late in the project at a time when effects of inflation, errors, and initial over optimism were forcing economics on the project.  In addition, low price dampers seemed to work and fail at about the same rates as misapplied high price ones.  Apparently few Engineers knew or cared about the basics or the intricacies of damper design and installation. 

Several operating factors in recent years have developed an even more serious situation for damper, however.  First, unit size increases, calling for larger dampers.  Second, the need to improve the poor availability record of large generating units indicated more on-line inspection and work on failed parallel equipment.  Third, the trend to coal, and to poorer grades of coal, meant more ash and corrosives in gas streams.  Fourth, flue-gas desulphurization required the addition of chemical plants to boilers, and required ducting and dampers that would resist corrosion, erosion, and heavy, sticky deposits. 

Under pressure of widespread damper failures, engineering and operating staffs have been forced to take more interest in damper technology.  A damper, consisting of light plate and sheet metal, will not in the foreseeable future be a true "machine" with rigid, machined elements and close tolerances.  Instead, analytic skill and application of lessons from field failures will be what will make the comparatively lightweight and flimsy damper a cost-effective and reliable component. 

An industry overview of dampers and specific examples of areas to evaluate will be provided in these pages.

Damper Don © 2009

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