This topic has come up several times over the years. At temperatures around -20
C, carbon steel loses its toughness very quickly. Carbon steel, any form of
carbon steel, in fact, is not approved for use with cryogenic gases. I have
witnessed the results of explosions that occurred when carbon steel was used in
very cold service (less than -40 C). The explosions were a result of a pressure
vessel or fitting failure.
Such problems do not exist for copper, aluminum, or 300 series stainless steels. Unless your pressures are quite high, you might consider schedule 10 304 SS over schedule 40 CS, and your installed cost is comparable.
... Bruce D. Bullough ...
Sebesta Blomberg & Associates, Inc.
2381 Rosegate
Roseville, MN 55113 USA
+ 651-634-7344
www.sebesta.com
-----Original Message-----
From: <a href="/group/PipingDesign/post?postID=50MQRxvJ2mb7uUsTetYZOHqVYuLFcTvXggE6fFk8PMSIE1Llq8_DHOwTm648xjkHLKKXtfS6ZIbib9-OK7U">Pankaj.Mandal@fluor.com</a> [mailto:<a href="/group/PipingDesign/post?postID=50MQRxvJ2mb7uUsTetYZOHqVYuLFcTvXggE6fFk8PMSIE1Llq8_DHOwTm648xjkHLKKXtfS6ZIbib9-OK7U">Pankaj.Mandal@fluor.com</a>]
Sent: Thursday, September 16, 2004 10:50 PM
To: <a href="/group/PipingDesign/post?postID=ZrGcog64j-UWip7uDoYoB89_RDkRDNtYa3kI_ra-IWvPP-Nf4IrdOLhXD3CVQj9XTGxXWTQFlqk5Ert1C5b1DLxp">PipingDesign@yahoogroups.com</a>
Subject: [PipingDesign] Piping material for oxygen service (cold).
[bcc][faked-from]
Dear all,
Continuing on oxygen services, has anyone had any experience in handling oxygen (cold) in LTCS (low temperature carbon steel) pipes without internal lining. In my opinion this is risky since oxygen would burn the carbon phase in carbon steel granules resulting in loss of strength of the pipe as well as chances of corrosion in grain boundaries. I remember Monel being used in such cases.
Ambient temperature is expected to be -10°C while oxygen is supposed to be carried at 20°C in the pipeline.
Expert opinion solicited.
Regards,
Pankaj Mandal.
From: Ponnu C [mailto:c_ponnu@yahoo.com] Sent: Wednesday, September 15, 2004 1:46 PM To: <a href="/group/PipingDesign/post?postID=ZrGcog64j-UWip7uDoYoB89_RDkRDNtYa3kI_ra-IWvPP-Nf4IrdOLhXD3CVQj9XTGxXWTQFlqk5Ert1C5b1DLxp">PipingDesign@yahoogroups.com</a> Subject: Re: [PipingDesign] Spiral Wound Gaskets - Acidic Oxygen Service
Dear Steve,
I learn from the company site that Gylon is modified PTFE.
Spiral wound gaskets would be definitely more reliable with variations in pressures and the temperatures which maybe there.
Gylon, the manufacturer claims has all the properties required,but I could not get details.
History could be the only support for not changing.Difficult decision. I would vote for Spiral wound.
Regards
C. Ponnu
Steve McKenzie <mechproj@xtra.co.nz> wrote: Gents+1
an autoclave that I have "inherited" has oxygen injection lines which
oxidise sulphide ore slurry; releasing heat and forming acid. The
object is to shatter quartz encapsulation of gold particles in the
slurry by thermal shock and chemical attack thereby improving
downstream cyanide leach recovery ($$$). It works. Temperatures are
around 250C and pressures around 31 bar.
I think the internal (hot)oxy injection lines are Ferallium (havent
had time to find out) and (cold) external lines are stainless;
probably 316.But much of the wet area pipework is titanium, for
corrosion resistance. Titanium + oxygen is normally a no-no as Ti can
burn in oxygen. Ferallium doesnt burn but is becoming difficult to
source.
Flanges on the autoclave are Ti spiral wound. This is OK because the
oxy concentrations are fairly low and can be adjusted by partial
pressure regulation.
The external 36 bar(cold)oxy lines are flanged (typically 50NB) with
fawn (I think) Gylon gaskets which appear to have held up well (4
years).
However it has been suggested replacing with spiral wound gaskets and
I cant see the point. Presumably the flange faces would need to be
ground, and I expect a spiral wound gasket would not be as forgiving
as Gylon when it comes to alignment and torquing.
The question is: what advantage would there be in changing from Gylon to spiral wound, given successful operating experience with the former?
Personally I can only see disadvantages, but feel I may be missing something.
Your conjecture/experience would be appreciated.
Cheers
Steve
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