15
To:
Subject:
Equipment pressure rating
Question:
Why, in the Oil Field Industry
literature and specifications today, do I find the abbreviation 10M,
instead of 10K, for 10,000 psi? I believe it has something to do with
referencing the working pressure rather than the pressure rating. I went
to your Web Site Glossary and found the following definition; it didn’t
help me with my question.
| Pressure, Maximum
Service: |
Also, Working Pressure;
the maximum pressure
which assembled equipment should experience in use. API specifies
Maximum Service Pressure for connected equipment; the pressure rating
included in the connector description, e.g. 13-5/8" 10,000 psi
Maximum Service Pressure.
|
|
If you can shed any light on my question, please
do.
Answer:
In response to your question we
have changed our definition for Pressure, Maximum Service, to read as
follows.
| Pressure, Maximum
Service: |
Also, Working Pressure; the
maximum pressure that specific units of equipment should experience in
use. API specifies the manufacturer clearly mark the Maximum Service
Pressure on each unit of equipment; the equipment pressure rating
limited by the lowest pressure connector on the equipment, or the
manufacturers design.
|
|
In short, Working Pressure and
Pressure Rating mean the same thing.
Manufacturers apply much of the
marking on pressure control equipment by striking hand stamps, with a
hammer, to apply individual numbers and letters. The Roman numeral for
one thousand (1,000), M, provides a simple symbol to use and save the
space used by 3 zeros and 3 letters when hand stamping parts, e.g. 10M,
rather than 10,000 psi. This same term of abbreviation has become
commonplace now in the literature.
As for pressure rating, all
pressures used in descriptions or identification of connections,
valves, etc. are field rated working
pressures. An individual connector identified as 13-5/8" 10M has a rated
working pressure of 10,000 psi as a connector, but if another connector
on the same piece of equipment has a rated working pressure of 5,000
psi, e.g. 11” 5M, the unit of equipment will have marking indicating the
working pressure as 5M. Equipment so marked may be used to control any
pressure up to 5,000 psi. "Working pressure" and “Maximum Service
Pressure Rating" being the same thing in reference to this equipment.
On the other hand there is a "Test
Pressure," this term should never be used to name or identify equipment.
The Test Pressure, used only for a proof pressure test applied to new or
repaired equipment, demonstrates the equipment can later be used safely
at the nominal rated working pressure. For example, 10M equipment has a
Test Pressure of 15,000 psi. Manufacturers apply this test pressure to
the connections and body of equipment, in a method specified by API, but
never to any internal closure mechanisms.
A field "Pressure Test" should
never exceed the rated working pressure of the equipment. In the case of
10M equipment, any field pressure test should not exceed 10,000 psi. The
body and closure mechanisms in this case would experience the same
testing pressure. Field pressure tests demonstrate operational
functionality only.
As for “K.” K also represents
1000. You will see K used
most often in scientific work, or in mechanical testing, but it has
appeared more lately as an alternative to the symbol M.
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