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Subject: Equipment Marking.


For years I have observed manufacturer's marks on pressure control equipment made up of letters formed by small closely spaced dots; more recently, I find the marks in conventional letters. Has something changed?


The following paragraph appears in API Spec 6A 19th Edition:

8.1.2 Marking method
Marking using low-stress (dot, vibration or rounded V) stamps is acceptable. Conventional sharp V-stamping is acceptable in low-stress areas, such as the outside diameter of flanges. Sharp V-stamping is not permitted in high-stress areas unless subsequently stress-relieved at 590 C (1,100 F) minimum. The method of marking on nameplates is optional.

Offshore equipment users have asked manufacturers to use rounded V low-stress line stencil letter stamps to mark equipment that will have thick paint coatings. These line stencil letters prove easier to read after application of paint than dot stencil letters.

The following information appears in the catalog of a leading manufacturer of hand stamp stencils:

These round face characters (.005 to .025 radius) were developed to combat the fact that sharp or pointed impressions may cause fractures in parts subjected to extreme conditions. Stress-Less Stamps - available in full character or dot style.

WOODCO USA has adopted the low-stress full character line type stencils as our standard method for product marking. WOODCO USA places almost all product identification marking on the outside diameter of flanges where almost no operating stress occurs. We still  currently (2006) use low-stress dot stamps in very high stress areas, like the neck area immediately behind flanges, to make the marks necessary to identify areas inspected by radiographic examination. We do, however, read the words in API Spec 6A 19th Edition as allowing low-stress rounded V stamps for marks on equipment in all locations.

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