To:
Subject: Equipment marking.
Question:
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?
Answer:
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:
STRESS-LESS STAMPS
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.
