Shell MESC SPE 77/312 vs ISO 15848-1 Class B for Low Fugitive Emission 1

[bogiedreamer]

Shell MESC SPE 77/312 vs ISO 15848-1 Class B

Are these specs comparable? Which is more stringent?

Thanks,

 

[BigInch]

post um and we'll have a look!

**********************
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[vpl]

the information in the following thread is a bit old, but may be of interest to you. thread408-64093

Patricia Lougheed

Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of the Eng-Tips Forums.

 

[NGiLuzzu]

bogiedreamer,
Shell MESC SPE 77/312 specification until 2005 covered both type test qualification and production acceptance tests of valves with regards to fugitive emissions.
Since June 2007 edition, it deals with production tests only, standing as a set of amendments and/or supplements to ISO 15848-2 standard (while the type testing requiremens have been moved into the new Shell MESC SPE 77/300 specification, formerly known as T-2.973.873, which also includes thermal and mechanical cycling, seat leakage and Quality System aspects: see thread408-220025 and thread408-210086 within this Forum).

In both cases, SPE 77/312 calls for a "sniffer method" helium test (a local, semi-quantitative technique), with the results expressed in terms of a volumetric leak rate (Pa*m³/s or equivalent units): the maximum allowable values are given per mm of valve stem diameter (or per mm of gasket circumference, in case of body to bonnet joints).


On the other hand, ISO 15848-1 standard deals with valves' classification, qualification and type tests only (as production testing is covered by the above mentioned Part 2); for type testing, only total (or global) measurement techniques are accepted, like "vacuum method" or "flush method" described in Annex A (the second one may use also methane as test medium).


To answer the original question: even if, in the particular case of emission measurement from the stem packing using helium gas as test medium, the maximum allowable leak rates of Tightness Class B have the same numeric value for both Shell and ISO, the above mentioned differences make the two tests hardly comparable.



For more information, please also see:

- thread408-48808;

- thread408-100721;

- thread408-93211;

- thread408-115884;

- thread408-159429;

- thread408-191910;

within this Forum...



Hope this helps, 'NGL