valve packing selection guide

[SWMechanical]

Does any know if there is any guide for valve packing selection based on service and temperature?

Thanks,

 

[SJones]

The only one that I know of is Shell MESC specification: SPE 85/200

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[gerhardl]

The guides I know of are all based on either elastomer suppliers of products (sealings in general, O-rings) wich will be able to guide you regarding temperature, chemical resistence and pressure for known mechanical products (eg. o-rings etc)

or:

from larger suppliers of a wide range of for instance BFL centric valves. Bray, Tyco Controls and many others.

I think this would be the way to go.

As a curiosium: the German solenoid valve company Herion, now owned by Norgren, published in 1985 (In German only!) a very good handbook on different, common chemicals, chemical properties and crossrelated to different materials for body and sealings, again crossrelated to a limitid range of common temperatures and pressures, all materiales ranged as plus or minus.

Although limitid, and issued primarily for solenoid valves, this is still in my posession in a reachable shelf from my office chair.

I also would be grateful if somebody could point to something like this available today.

 

[SWMechanical]

Thanks.

Steve, how can I find a copy of Shell MESC specification: SPE 85/200?

 

[JLSeagull]

Remember that an O-ring failure at low temperature caused the Challenger shuttle explosion in 1986. Elastomer applications such as valve packing selection are more complex than most people recognize. One material may be suitable for a rotary valve and not for a sliding stem valve. Many grades of Viton exist. Few (if any) are compatible with amines. Few of the Teflon products are suitable for valve packing much above 400 degree F but may still be well suited for a seal component. Some materials absorb CO2 and decompress explosively when depressured. Some materials may work well in certain shapes and not other shapes. Some applications may require products with thermosetting properties instead of elastomers. Sometimes ceramics or glass may be best although not likely for valve packing. Some seal materials hold up to rough surfaces – most don’t.

Define the needs such as selecting an elastomer for the packing or seal to maximize the equipment reliability and minimize the risk of failure within a reasonable price. Don’t always select Kalrez. Some products are best used where nothing else works.

In addition to the base elastomer material there are different curing systems, additives, fillers, uniformity specifications, densities, hardness, etc. Checkout ASTM publications for product specifications, etc.

Search the manufacturers’ web sites such as DuPont Dow Elastomers, Green-Tweed, for technical product downloads for chemical compatibility and other properties. Obtain data on Nitrile (HSN/HNBR), Ryton, PEEK, Aflas, Perfluorocarbons (Kalrez/Chemraz),

Search the web for technical advisories regarding seal failures.

As mentioned, good charts are available on the web from sites such as Air Products, Flow Serve, … Publish your report here and I will download it.

 

[NGiLuzzu]

SWMechanical,
for Shell specifications you should refer to Shell Global Solutions International:

http://www.shell.com/home/content/global_solutions/

As far as I remember MESC SPE 85/200 was a mere listing of many types and brands of packings (probably built upon some kind of survey in the warehouses of the manyShell plants all over the world...?)... but may be in the meantime they updated the document.


Generally Valve Manufacturers define, with their own trusted Suppliers, a "standard" stem packing (usually in graphite) capable of covering the wider possible range of service conditions; for other "special" applications, the best packing design and material (usually elastomeric: PTFE, Viton, Kalrez, Kel-F, etc...) is selected case by case, also using the dedicated chemical compatibility guides pubblished by the material Suppliers.

See, for example:
-

http://www.dupontelastomers.com/Tech_Info/chemical.asp

-

http://www.dupontelastomers.com/kag/

-

http://www.coleparmer.com/techinfo/chemcomp.asp

Hope this helps, 'NGL

 

[SJones]

The Shell specification identifies specific packing materials per valve type and fluid service and then goes on to name specific packing suppliers. I can't vouch for its usefulness but it's a start. A request to Shell Global Solutions can be tried but they may be awkward!

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[JimCasey]

ALso remember that different valves have different architecture that affects the packing. Example: Some eccentric rotary plug control valves have standard extended bonnets, and the standard yarn-style packing serves to 750 degrees (F) process temperature. If you just look up the rated temperature of the packing, it's probably only rated to 450 (F) . Best to go with a manufacturer's rating of the packing he supplies than the ratings written in the packing catalog.