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From: Eugene Ngai <eugene_ngai**At_Symbol_Here**COMCAST.NET>
Subject: Re: [DCHAS-L] PNNL Hydrogen Fire Event Video
Date: Jan 29, 2019 15:37 UTC
Reply-To:
ACS Division of Chemical Health and Safety
In-Reply-To: Re: [DCHAS-L] PNNL Hydrogen Fire Event Video
What Ken is referring to are RFO (Restrictive Flow Orifices), these were designed in the 1980's to be installed in the cylinder valve outlet. Initially a 0.010" was used to prevent silane from being released without immediate ignition. It continues to be used today for cylinders of silane. To comply with the Fire Code requirements for worst case releases, many users use a 0.006" RFO for highly toxic gases such as arsine or phosphine to reduce the size of the abatement system. There are many other sizes available. Ken's boss David Rainer wrote an excellent AIHA article on the origin and use of RFO's. If you want a copy please e-mail me
In addition lecture bottles (LB) have lecture bottle valves and CGA connections 160 or 170). These cannot have RFO's inserted. Lecture bottles that have standard cylinder valves and PRDs are called 7X cylinders. These can have RFO's inserted
Eugene Ngai
Chemically Speaking LLC
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On Behalf Of Richard Palluzi
Sent: Tuesday, January 29, 2019 10:16 AM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: Re: [DCHAS-L] PNNL Hydrogen Fire Event Video
You need to be very careful as the flow limiting orifice supplied in most commercial cylinders, while limiting vs. a fully open valve, still allows an awful large flow which is more than usually required for research purposes. Installing a custom sized flow limiting restrictive orifice (available from Swagelok among others) is usually more prudent.
Richard Palluzi
PE, CSP
Pilot plant and laboratory consulting, safety, design,reviews, and training
Richard P Palluzi LLC
72 Summit Drive
Basking Ridge, NJ 07920
rpalluzi**At_Symbol_Here**verizon.net
908-285-3782
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On Behalf Of Ken Kretchman
Sent: Tuesday, January 29, 2019 8:31 AM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: Re: [DCHAS-L] PNNL Hydrogen Fire Event Video
Depending on flow rates required..obtaining flammable and/or toxic gas cylinders with flow limiting orifices is also a good practice.
Ken
Ken Kretchman, CIH, CSP Director, Environmental Health and Safety
NC State University / Box 8007 / 2620 Wolf Village Way / Raleigh North Carolina 27695-8007
Email: Ken_Kretchman**At_Symbol_Here**ncsu.edu / Phone: (919).515.6860 / Fax: (919).515.6307
On Mon, Jan 28, 2019 at 10:10 PM jeskiekb**At_Symbol_Here**comcast.net <jeskiekb**At_Symbol_Here**comcast.net> wrote: