Direct Tension Control-Washer Control
The least expensive and simplest tension control systems use direct tension indicating (DTI) washers.
Several different types of DTI washers are available. The most common type of washer involves the use of
“bumps” on one side of the washer. These “bumps” are flattened plastically as the fastener is tightened. A
feeler gage is used to measure the gap developed by bumps. When the fastener has developed the appropriate tension, the feeler gage will no longer fit in the gap. Some of the newer types employ the use
of silicone embedded under the “bumps”. The silicone squirts out once the “bumps” are compressed to indicate proper tension. The DTI washer has been used in the structural bolting industry for years and is now starting to carry over into other fields as well.
