Use of Viton (FKM/FPM) with hot water or steam service
Lambda
know to be restistant to 'difficult' chemical media.
However, in many chemical resistance lists the use of Viton is not
recommended for hot water applications or steam service.
What is the specific danger of hot water ? Of steam to Viton ? Does it
restart the curing process ? Does it attack the cross linked polymers ?
What is the fysical result ? Does it increase hardness ? Does the viton
become more brittle ?
Thanks for your help !
Attila the Bum
acidic, and attacks the polymer.
Atty (Viton seals are compromised
by camel dung and fail
in short order :-)
Attila the Bum
Uncle Al
At the very least, Viton is eaten by amines. Steam is typically dosed
with morpholine to lessen line and vessel corrosion.
Stick a sample in a Soxlet extractor and suspend a sample in the
boiler vapor space, wrap with cheesecloth or whatever for thermal
insulation, and cook it up for a month (check that condenser water!).
If the Viton stays happy its degradation in use is due to steam
additives.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf
Attila the Bum
Uncle Al wrote:
> Lambda wrote:
> >
> > Viton is often used as elastomeric seat in butterfly valves. Viton is
> > know to be restistant to 'difficult' chemical media.
> >
> > However, in many chemical resistance lists the use of Viton is not
> > recommended for hot water applications or steam service.
> >
> > What is the specific danger of hot water ? Of steam to Viton ? Does it
> > restart the curing process ? Does it attack the cross linked polymers ?
> >
> > What is the fysical result ? Does it increase hardness ? Does the viton
> > become more brittle ?
>
> At the very least, Viton is eaten by amines. Steam is typically dosed
> with morpholine to lessen line and vessel corrosion.
OK.
In threads discussing ultrapure
water, you usually say that the
stuff is corrosive, very much
so.
In this thread you say steam
is dosed "to lessen line
and vessel corrosion."
I said:
> I'd guess, that steam is
> acidic, and attacks the polymer.
The data-books show that as T
increases, the ion product for
water _increases_.
---------------------------------------
Ionization Constants (molal scale)
pKw pKm
Temp. H20 D20
0 14.94
10 14.53 15.53
20 14.16 15.14
30 13.84 14.78
40 13.54 14.47
50 13.28 14.18
60 13.03
70 12.81
80 12.61
90 12.43
100 12.26
150 11.64
200 11.29
250 11.19
300 11.41 (Not a typo; at 275
the value is 11.25)
Molal pKw values from _Lange's Handbook_,
15th edition, page 8.6.
Molal pKm values from _CRC Handbook of
Tables for Applied Engineering Science_,
2nd edition, page 369.
---------------------------------------
What is going on here?
Higher concentrations of ions
attacking lines and vessels
with a thermal advantage would
be my guess.
But how does an additive
blunt the effect of the ions?
Small amounts of an added
compound wouldn't quench
steam's ionic activity all
that much. Is it protecting
the metal?
As an undergrad, work-study
lab assistant, I would clean
glassware (not for anything
critical) by allowing it to
soak in water for a day or
two, having learnt that H2O
did have some amount of ion
activity and thinking that
with time, even at room temp.,
the water would attack the
crud on the glass (maybe I
used a touch of soap -- I
had just finished a Jr. Col.
program that had heavy doses
of environmental issues along
with the water and wastewater
courses).
Atty (Swim with protection!)
muha
O-ring seals. Juts the last night, I had these rings disintegrating and
partialy dissolving in 2 of my reactions (a real bummer): one reaction
was with concentrated ammonia in methanol and the other was
concentrated methylamine in ethanol, both at 60-100C.
Uncle Al
>
> Uncle Al wrote:
> > Lambda wrote:
> > >
> > > Viton is often used as elastomeric seat in butterfly valves. Viton is
> > > know to be restistant to 'difficult' chemical media.
> > >
> > > However, in many chemical resistance lists the use of Viton is not
> > > recommended for hot water applications or steam service.
> > >
> > > What is the specific danger of hot water ? Of steam to Viton ? Does it
> > > restart the curing process ? Does it attack the cross linked polymers ?
> > >
> > > What is the fysical result ? Does it increase hardness ? Does the viton
> > > become more brittle ?
> >
> > At the very least, Viton is eaten by amines. Steam is typically dosed
> > with morpholine to lessen line and vessel corrosion.
>
> OK.
>
> In threads discussing ultrapure
> water, you usually say that the
> stuff is corrosive, very much
> so.
Ultrapure water eats everything short of (fluoro)plastic plumbing.
> In this thread you say steam
> is dosed "to lessen line
> and vessel corrosion."
Typically with traces of morpholine. Boilers are dosed with hydrazine
to deposit an adherent protective lawyer of magnetite on iron/steel.
The world is not built of 316SS. Everything is built just good enough
(or building inspectors get bigger short term payoffs).
> I said:
>
> > I'd guess, that steam is
> > acidic, and attacks the polymer.
Viton is not harmed by weak aqueous acid or base.
> The data-books show that as T
> increases, the ion product for
> water _increases_.
[snip]
> What is going on here?
Chemistry. Physical reality is what it is observed to be. If your
internal model of reality does not jibe with observation, you are
wrong.
> Higher concentrations of ions
> attacking lines and vessels
> with a thermal advantage would
> be my guess.
>
> But how does an additive
> blunt the effect of the ions?
Look it up. Amines as rust preventatives are ancient. Oleoyl
sarcosinate is the prime protectant additive for iron in oxide scale
pickling.
[snip]
> Atty (Swim with protection!)
Candiru catfish.
Attila the Bum
Uncle Al wrote:
> Attila the Bum wrote:
[snip ...]
> > In this thread you say steam
> > is dosed "to lessen line
> > and vessel corrosion."
>
> Typically with traces of morpholine. Boilers are dosed with hydrazine
> to deposit an adherent protective lawyer of magnetite on iron/steel.
> The world is not built of 316SS. Everything is built just good enough
> (or building inspectors get bigger short term payoffs).
>
> > I said:
> >
> > > I'd guess, that steam is
> > > acidic, and attacks the polymer.
>
> Viton is not harmed by weak aqueous acid or base.
Over what time-frame?
Boil water in a beaker long
enough and you'll eventually
etch the glass. How about
leaving a greased-stoppered
volumetric flask filled with
water to the mark, will it
get etched in time?
> > The data-books show that as T
> > increases, the ion product for
> > water _increases_.
> [snip]
>
> > What is going on here?
>
> Chemistry. Physical reality is what it is observed to be. If your
> internal model of reality does not jibe with observation, you are
> wrong.
>
> > Higher concentrations of ions
> > attacking lines and vessels
> > with a thermal advantage would
> > be my guess.
> >
> > But how does an additive
> > blunt the effect of the ions?
>
> Look it up. Amines as rust preventatives are ancient. Oleoyl
> sarcosinate is the prime protectant additive for iron in oxide scale
> pickling.
>
> [snip]
Your snarling depends upon your belief
that the OP uses steam that's been
treated. That was never stated in the
post (perhaps intentionally).
> > Atty (Swim with protection!)
>
> Candiru catfish.
Don't piss in the pool!
GOOGLE: candiru catfish site:.gov 4 hits
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=4601556&dopt=Abstract
GOOGLE: candiru catfish ~712 hits
http://www.angelfire.com/mo2/animals1/catfish/candiru.html
Atty (Believable? Certainly as a
social science lesson :-)