×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Vinyl Chloride to Ammonia

Vinyl Chloride to Ammonia

Vinyl Chloride to Ammonia

(OP)
Does anyone have a good technical reference or insight on changing a vessel's commodity? I have a old rail car that stored vinyl chloride that I want to use to contain ammonia, and wanted to know if there are any concerns in doing so.  

Thanks!

RE: Vinyl Chloride to Ammonia

Anhydrous ammonia is no particular problem in carbon steel; pipeline, tankcars, etc. Except, be sure the anhydrous ammonia contains a trace of water; I think 0.1 % gives a safety factor. Pure anhydrous can stress corrosion crack higher strength "carbon" steels like T 1.  I believe many years ago, process units were adjusted to leave a trace of water in the anhydrous.  

RE: Vinyl Chloride to Ammonia

(OP)
Thanks Blacksmith 37 for the response!! Is there any problem switching the tank from vinyl chloride to the ammonia?  Was thinking more along the lines of residual chloride in the tank and then being introduced ammonia....any thoughts?

Have not been able to find good technical references regarding common commodities meeting each other when tank substances are changed.  Is there a standard cleaning method used before changing out commodity?

RE: Vinyl Chloride to Ammonia

Switching between ammonia and LPG was not a problem ; no experience with vinyl chloride.
T1 is  ASTM A514, 517 type material.  

RE: Vinyl Chloride to Ammonia

Was the railcar given PostWeld Heat Treatment?  PWHT is a requirement for liquid Ammonia service [due to stress-corrosion cracking].  And, due to an OSHA clause, it is also a legal requirement in USA.

RE: Vinyl Chloride to Ammonia

(OP)
Duwe6, thanks for the response!  Do you know the OSHA clause that requires it?  I assume ASME would have required it because Ammonia could be classified as a lethal service, hence requiring PWHT?

RE: Vinyl Chloride to Ammonia

1910.111(b)(2)(iii)(a)
"Containers shall be stress relieved after fabrication in accordance with the Code."

Poorly written clause.  Their intent is that all welds receive PWHT 'for process', including small nozzles.  This differs from the ASME VIII requirement of PWHT based on thickness and/or materials of construction.  

Go to OSHA.gov and read the whole of 1910.111, including the Intrepretation letters.  Among other 'perversions' of the B31.3 Code, OSHA does not allow threads on Sch40 pipe [welds only -- prudent], but refuses to allow backwelding of threads on anything thinner than Sch80 [not a B31.3 requirement, just a ridiculously stringent requirement thought up by OSHA burocrats].  Thus all installed threaded Sch40 is required by law to be removed.  You need to be well-informed about the OSHA requirements before you start your project.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources