Head Terminology refers to the terms used by the Industry to describe the different attributes that make up the heads of the tank. The tank heads are also sometimes called domed or dished ends.
The thickness tells us how thick the head will be after forming. All thickness dimensions are considered nominal unless otherwise specified. All heads will have a thin out after forming. In cases where a minimum thickness is required this should be clearly indicated in your inquiry or order.
DISH RADIUS (DR):
Also known as crown radius. It is the major radius of the formed head, usually measured from the inside of the head.
KNUCKLE RADIUS (ICR):
Also known as inside corner radius. It is the formed radius of the head which transitions the dish portion of the head to the straight flange.
STRAIGHT FLANGE (SF):
The straight flange refers to the straight potion of the head measured from the tangent line to the edge of the head. The industry standard is 1 ½” for ASME F&D’s and 2.0” for Ellipticals but most head manufactures can change this to suit your needs.
The tangent line describes the point on the head where the knuckle radius meets the straight flange.
OVER-ALL HEIGHT (OAH):
This is the total height of the head and is measured by adding inside depth of dish, straight flange height, and the thickness together.
Now that you know the different industry terms and their meanings, this will give you tremendous help the next time you design a tank or inquire about having a custom tank fabricated.