Prior to 1986 most manufacturers that made clamps, to fit clamp hub connections that utilized  API  ring gaskets as seal rings, made them from cast steel. Cast steel has a greater likelihood of discontinuities that can cause failure in these products. Today, most clamp manufacturers making clamps to fit API Spec 16A hubs utilize forged steel. When possible, users of older cast steel clamps should inspect them to reasonably assure their continued safe use. See photograph below for an example of a cast steel swing bolt clamp.

#13 Swing Bolt Clamp
Fits Current 13-5/8″ 5M and Older, Non API 11″ 10M Hubs

WOODCO USA suggests the following as a minimum inspection routine. Perform a Brinell hardness test on each clamp half to assure the material has tensile strength at least equal with that required by API Spec 16A for the hubs the clamp connects. Further inspection requires a through cleaning by blasting or brushing, removing all dirt, rust, paint, and scale. Next perform a visual inspection for obvious corrosion damage, cracks, etc. and if the clamp appears OK 1 perform a 100% magnetic particle inspection using acceptance criteria as shown in API Spec 16A. Evaluate bolting to the same criteria as used for flange bolting, and replace if questionable 1.  Replace any missing or damaged 1 washers. These inspections may reasonably assure safety 1 when using older clamps. Before making any assembly of pressure control equipment using cast steel clamps, conduct a pressure test on the clamp before use.

For a table of Clamp Test Pressures and Applied Loads Click Here.

1Words in bold italic indicate they have subjective meaning and persons using this information must use experience to improve the reliability of their judgement when the meaning of these words can have impact on performance.

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