Tall Slender Structures Such As Stacks Are Subject To Wind Induced Vibrations Due To Vortex Shedding. In Most Cases The Tuned Mass Damper Is The Most Efficient And Cost-Effective Way To Prevent Excessive Dynamic Stack Movement. The TMD System Is Customizable To Match A Broad Range Of Stack Configurations And Frequencies. Warren Environment First Pioneered The Use Of The Tuned Mass Damper In North America In The 1980s And No Company Has More Experience Utilizing The TMD In Stack Design. The Warren Tuned Mass Damper Does Not Require Adjustment And Is Maintenance Free.
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Many types of devices have been developed throughout the years to prevent harmful stack vibrations. These include helical strakes (spoilers), absorption pads, impact damping, hanging chains, wind shrouds and the Tuned Mass Damper. As a practical matter, helical spoilers and the Tuned Mass Damper are the primary tools for the prevention of excessive cross-wind vibrations. For additional information of all prevention devices refer to ASME Steel Stack Standard STS-1.
The Tuned Mass Damper is a passive damping approach to the vortex shedding problem in steel stacks. The intent of the damper is to control the Stack’s response to the wind induced movement as vortices are formed around the Stack. The Tuned Mass Damper will exert an appropriate counteractive force on the Stack structure when it is excited from its vertical plumb position.
The damper consists simply of a cylindrical skirt (weighted mass) two feet larger than the Stack’s outer diameter. The skirt is hung from stainless steel pendulum near the top of the stack. Between this skirt and the stack shell are stainless steel coiled springs. These springs are constructed such that they have a pre-determined spring constant and damping coefficient. The natural frequency of the swinging skirt mass coupled with the springs are tuned closely to the Stack’s natural frequency.
The specific dynamic properties of these elements are determined by mass weight, pendulum length, spring coil (cable diameter, number of strands per coil, coil diameter and number of springs). The damper system is designed to exceed the life of the stack by the use of stainless steel material and heavy duty construction.
The Tuned Mass Damper lends itself to retrofit of problem stacks because the increase in stack moment at the foundation is no greater than without the installed damper. The increased damping allows for stack designs with a height-to-diameter ratio in excess of 30:1. Since the 1980s over fifteen hundred TMDs have been successfully installed by Warren on new and existing Stacks throughout the world.
APPLICATIONS:
New Installations with the Stack Designed Specifically Around the Tuned Mass Damper
Retrofit Existing Installations Where Aerodynamic Instability is Present
Increasing Stack Heights
Existing Stacks Threatened by the Subsequent Erection of a New Adjacent Structure