Select the type of diameter from the list.
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ID - Inside diameter
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OD - Outside diameter
Torispherical heads should always be specified on the inside diameter basis. Even though the head catalogs refer to these as OD heads, inspection of the catalog nomenclature reveals that the dimensions listed are inside dimensions. Because of this, the inside dimensions from the catalog can be entered directly when the ID basis is specified.
Normally, for a torispherical head the inside crown radius is equal to the vessel outside diameter.
For flat heads, this value is ignored. Always enter the outside diameter of the flat head.