PVDF Hot conc sulfuric acid
PVDF Hot conc sulfuric acid
(OP)
Hi,
I am trying to source information on the suitability of PVDF (piping) with hot (up to 100C) 90-98.5 sulphuric acid. Information I have found so far gives the full range of "suitable" to "not suitable". I know that the temperature itself is OK, but am looking for clarity on the sulphuric acid side at these temperatures. Some literature suggests it can go brittle with time. Practicle experience appreciated.
Thanks
I am trying to source information on the suitability of PVDF (piping) with hot (up to 100C) 90-98.5 sulphuric acid. Information I have found so far gives the full range of "suitable" to "not suitable". I know that the temperature itself is OK, but am looking for clarity on the sulphuric acid side at these temperatures. Some literature suggests it can go brittle with time. Practicle experience appreciated.
Thanks





RE: PVDF Hot conc sulfuric acid
RE: PVDF Hot conc sulfuric acid
As to "experience", it depends on what you're doing with it. Is this tubing, pipe, a tank, an exchanger, or something else? Is the 100 C temperature and conc acid exposure continuous or intermittent? And does anyone get injured or killed if the PVDF does embrittle over time?
PFA would be a better choice from an absolute compatibility standpoint. Or you could use the PVDF as a lining material, using something else (steel, FRP etc.) so that you don't worry so much about the embrittlement. But the correct solution depends on answers to the questions listed above.
RE: PVDF Hot conc sulfuric acid
pvdf is not suitable in an operating environment
RE: PVDF Hot conc sulfuric acid
Can you ellaborate on your statement?
aspearin1
RE: PVDF Hot conc sulfuric acid
To elaborate, the equipment is an instrument tee (sound velocity/acid conc). Exposure to acid is constant, conc constant to +/- 1%, operating temp in range 50 to 80C. Instrument is installed in a 1" branch off a process tank circulation line, pressure up to 4 barg, so potentially significant consequences on failure. The fitting supplied as a package with the instrument a few years ago.
We have previously seen possible "embrittlement" ie failure at one location (we have a number of these on site), however failure at a weld was put down to mechanical stress due to piping allingment or vibration at the time.
What reference are you using?
Thanks
RE: PVDF Hot conc sulfuric acid
See “Handling Sulfuric Acid” at http://www.resistoflex.com/sulfuric.htm
Their chemical resistance table shows a maximum temperature of 65oC for PVDF in 98% sulfuric acid. PTFE is recommended.
RE: PVDF Hot conc sulfuric acid
At high temperatures, PVDF pipe would need more support (unless it's lined pipe). Don't have any comment on the embrittlement issue - never observed it in my system, which never ran over 35 C. Try kicking it around with the Lurgi or Monsanto Enviro-Chem people - they have the most experience with hot sulfuric acid.
RE: PVDF Hot conc sulfuric acid
I personally would not use unreinforced PVDF for the application you're describing. With pressures potentially to 4 barg, and a hazardous fluid like conc sulphuric acid, PVDF at 50-80 C is not safe. The application would require extensive mechanical safeguarding at minimum, with total secondary containment being recommended. I would recommend a complete tear-out and replacement with either PTFE or PFA-lined pipe, or PVDF-lined pipe.
RE: PVDF Hot conc sulfuric acid
http://www.piping.georgfischer.com/index.cfm?424D3C4A152F4697ABE3201FA7EC26D1
Regards
Mogens
RE: PVDF Hot conc sulfuric acid
Thanks for all the help. We have trialed modified tee (PVDF wiht steel support). Early indications seem encouraging. We will be upgrading the other strength meters following a longer successful trial.
Regards
RE: PVDF Hot conc sulfuric acid