This type of work is regulated by the ASME BPE Code (Bio-Processing Equipment).
Here are a couple of links to get you started:

http://www.highpurity.com/files/Seminars/BPE%20Seminar%2010-7-02%20DWS.doc

http://service.obcorp.com/Acrobat_Files/CardinalBPE/bioPUREBA-20.pdf

http://www.normas.com/ASME/pages/PVHO.html

If you are trying to set up a Quality System/ Procedures for these products, I recommend obtaining the consultant services of Purity Systems Inc.
They are the best in the buisness, in my opinion.
If you would like to see a typical BPE compliant Receiving Inspection and a Welding Procedure, e-mail your fax # and I'll send a copy.
Tim