Effective Compression
Unlike static perimeter joint protection, effective compression of a
dynamic perimeter joint protection decreases when the perimeter
joint opens from the nominal joint width. To understand changes in
effective compression, consider the following equations. UL uses
the following equation below to calculate the uncompressed width
of the insulation to be used in the perimeter joint protection installed
at a nominal joint width.
For example, consider a nominal joint width of 2.00 inches requiring
the insulation of a perimeter joint protection installed at 25%
compression. The T uncomp of the insulation would be 2.67 inches.
The maximum joint width for the dynamic perimeter joint protection
is 2.25 inches. Maximum joint width is the widest joint opening the
fire-resistance rated perimeter joint protection can expand to during
the movement of the perimeter joint and maintain its ASTM E2307
fire-resistance rating.
The following equation is used to determine the decrease in
insulation compression of a dynamic perimeter joint protection,
when the nominal joint width expands to the maximum joint width.
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