PTFE Packing for Fugitive Emission control 3

[tsenthil]

Can we use PTFE Gland packing in Fugitive Emission Control design (Globe Valves). I heard PTFE will fail during thermal cycle tests as prescribed in ISO 15848?

Also is double packing arrangement is a must for FE design?

 

[gerhardl]

Not having checked all relevant standards and tests, I believe there is more a question of if a certain constructed valve with a certain given sealing material and sealing construction will withstand a certain specific test and perform to a certain test-grade or not.

It is in my opinion not possible to answer your question on a general basis.

The only way to prove something like this will have to be either using a valve that has undergone an actual certified test, or is guaranteed by producer to be valid within certain parameters, if this is accepted, or to actually perform a test.

 

[JLSeagull]

If specifying the valve manufactured by others you can call out the fugitive emission requirement. If you are the manufacturer you need to test the various packing arrangements.

 

[mrctchlr]

Use certified gland packings

for example, tested in Stuttgart (VDI/VDE2440 / EN15848);
40 bar, 200°C, 1000 cycles - Burgermann 9650 T1

Even beter is gland packing set Burgermann 9650 T2 or T3

(9650 T3, 40 bar, 400°C, 1000 cycles)

Maybe you can use this info!

 

[NGiLuzzu]

mticheler,
maybe you wrote "Burgermann" instead of "Burgmann" (

http://www.burgmann.com/)...

is that possible?
;-)
In any case, which kind of materials are included in the "9650" packing set that passed the tests up to +400°C?
I argue it can't be PTFE only...

Thanks and Regards,
'NGL

 

[bcd]

To give a direct answer to your questions, and dispell the myths;

1. Yes you can use PTFE for FE valves and it is done everyday. One weakness of this material is the amount it wants to expand with temperature. If the temperature range is small, it will pass ISO-15848 testing. If you spring load the seal (live-loading)it can pass a higher thermal cycle.

2. Double packing is not a requirement for FE valves. Double packing is used when you want a port that connects between the packing sets to either monitor for leakage past the lower seal, return any leakage by the lower seal to a safe part of the system, or if you want to pressurize between the packing to prevent possible leakage out of the lower seal.

Pick the packing material that gives the best sealing performance over the temperature range with the longest cycle life. Be careful trusting certificates. Look at the product they were tested in. Were the packing bore and surface finishes the same as the product they will be used in? Was the stroke speed the same as the product they will be used in? Is 1,000 cycles the life of the product or what it will do in a day?

bcd

 

[mrctchlr]

anegri,

The packing set was something i remebered from a seminar in 2005. It is BURGMANN for sure.

I looked it up.

T= 400°C, 40 bar, 1000cycles, 9650 T2
Set containing:
2 endrings made of graphite thread
2 rings made of pressed graphite
1 middle ring made of fiberglass with a special impregnate.

PTFE max 180° - 200°C

 

[NGiLuzzu]

mticheler,
THANKS for the reply!

Bye, 'NGL

 

[RAISAMEX]

A PTFE packing will never support 400°C, but Graphite Packing will get there easily, and if you try a pretreated graphite with corrosion inhibitors you can get even hotter.
About thermal cycling don't worry for the gasket flexible graphite will support it big time.

To minimize emission the number one choice is flexible graphite packings.

there are plenty on the market.

Carlos Chapa
Application Engineer
RAISAMEX - hightech sealing products

http://raisamex.net

 

[belowzero]

ISO 15848 certification is one thing but as the reason for FE is to exclude noxious and harmfull chemicals the use of Graphite has to be questioned where medias exist that readily leach and errode graphite. Phosphoric acid comes to mind as an example.
PTFE packing is the only suitable material in this type of use and the design temperature of the chemical resistant materials is usually a large part of the medias process design.
In this case the Standard is taken as a marker but the various temperatures which would compromise the materials are taken out, although the ISO standard cannot be used to certify this material the manufacturer can show that the same testing has been applied in principle, cycles, leak rates etc.
Calling up ISO 15848 as a standard without understanding the plant and medias involved is not practical.
B