DCHAS-L Archives, Feb 06 2014 - Re: [DCHAS-L] Hydrostatic Test Date

Hi David,

Questions like this open the forum for good discussions.

I feel strongly that safety professionals, such as the folks on this list, must set the standards for the organization they represent and protect - but at the same time that does not mean that I believe one should set the standards low and easy, the bar for safety should be set high, and based on regulatory standards and industry guidance. So when I made this statement, I was actually backing another member's assertion that his organization chooses to not keep cylinders which are past the retest date.

As a member of CGA, I was looking for the industry guidance you were citing and I could not find it. Could you please let me know which CGA publication you are citing that says that cylinders should not be used past the retest date? It is absolutely correct that CGA does set standards for Hydrostatic testing (CGA C-1) and Ultrasonic Emissions testing (CGA C-20), two publications with which I am reasonably familiar, but neither make the assertion that a cylinder cannot be used past its retest date. Nor did I find any other publications that so assert in a (admittedly brief) literature search. I would be interested to see what documentation you have.

I have indeed routinely seen cylinders that were in use safely for decades past their retest date. That is entirely true, if not the norm. I expect that you have also seen this. And, as I said, I have seen cylinders in use for over a hundred years without any defect. That also is true, but not the norm.

Cylinders do not catastrophically fail because of being past the retest date, per se. As with the examples I gave in a prior email, cylinders fail because of other issues - having water introduced into the cylinder by user engineering failures, damage due to abuse or misuse by users, or in some specific cases because the user has let the cylinder sit unmonitored with a corrosive product in it for too long. Cylinders are designed to hold pressurized gas safely. The retest requirement is a routine safety precaution, for cylinders transported in commerce; it does not mean that the cylinder has "gone bad".

The above being said, I would like to reiterate some statements, and if necessary I can back it with facts and statistics:

1) Do not confuse a retest date with a product expiration date. The retest date is a date after which any cylinder transported in commerce should not be subjected to the stress of the filling process without DOT mandated safety test (Hydrotest or UE).

2) Cylinders should not be discarded simply because the retest date is past. There are additional factors which should be taken into account *regardless of the retest date* to determine if a cylinder should be immediately taken out of service and returned to the filler for safety reasons. (NOTE: If you want to bring back cylinders that are past the retest date out of concern for safety, I will not complain. Doing so also makes more money for the compressed gas manufacturer, which is good for our business as well.)

Aside from my disagreement over what words we are using, I believe we are both trying to promote an underlying safety focus. I completely agree with your assessment that an external visual examination by an untrained individual does not give any indication of the fitness of the cylinder. Even a trained individual can only tell so much by that examination, which is why cylinders are retested every 5 or 10 years.

BE SAFE. Make your own determination of the time frame which your organization will retain specific products past the retest date - or even the delivery date - based on the type of product. Nitrogen will not pose the same concerns or dangers as Boron Trifluoride, for example. If you determine that you will not accept cylinders on site past the retest date, please reiterate that to your supplier and get it on your contract.

Last but not least, If you have questions, reach out to your compressed gas supplier's safety team. This is what we do, and we are professionals trained to know about our products and containers. At Airgas, most of the safety Directors are directly involved in emergency management and response as well, which only expands our knowledge and experience.

Thanks for listening,

Todd Perkins BSc, MBA

Safety Director

Airgas USA,LLC

Mid America Region

Personal email: p3wt3r**At_Symbol_Here**charter.net

Personal phone: 314.803.2318

From: "dhaugen88**At_Symbol_Here**COMCAST.NET" <dhaugen88**At_Symbol_Here**COMCAST.NET>
To: DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU
Sent: Thursday, February 6, 2014 11:02 AM
Subject: Re: [DCHAS-L] Hydrostatic Test Date

Hello readers,

Having been retired for 2-3 years my attention to the DCHAS list serve is waning.

However, I have a strong sense of obligation to respectfully question the validity of two of Todd Perkin's statements: "everyone must set the standards for his/her organization" and "cylinders are routinely in use for many years past their retest date without any safety concerns."

At the major R&D organization from which retired, we routinely removed from service all compressed gas cylinders for which the date stamp for the most recent hydrostatic testing indicated a "past due" hydrostatic testing in accordance with CGA standards. The ONLY, RARE exception was for exceedingly high cost custom-mixed calibration gases for which the researcher's quality assurance required an EXACTLY identical calibration mixture for a multi-year period.

The Compressed Gas Association publishes industry standards for periodic hydrostatic testing (http://www.cganet.com/ ). The institution with which I was affiliated certainly had the "intent" -- if not an explicitly established "requirement" -- to conform with the most recent CGA standards, WITHOUT waiting for DOT or OSHA regulations to be revised to incorporate the most recent CGA standards by reference.

When (in approximately 2007-2008) I conducted an inventory of hundreds of compressed gas cylinders at the R&D institution, I observed that the first post-manufacture test date stamp ranged widely, a small fraction of cylinders having been in service for 30-40 years, and a smaller fraction bearing test date stamps in the 1920's and 1930's. During this inventory I observed some cylinders for which external corrosion was readily apparent, and some cylinders containing highly corrosive gases (e.g. anhydrous hydrogen chloride). A simple visual observation of the outer surface of a cylinder may not reveal thermal stress, over-pressurization, or mechanical stress that may have occurred elsewhere during the cylinder's multiple decades of post-manufacture service.

As I recall, the institution's procurement agreement/contract with the primary compressed gas cylinder vendor PROHIBITED delivery of cylinders for which the hydrostatic test requirement was past due..

YES, the cylinders manufactured 30-40+ years ago obviously remained "safe" for containment of compressed gas at their rated pressure maximum. However, anyone who has seen video recordings of a ruptured cylinder "rocketing" through a distant cinder-block wall establishes an understanding of the importance of periodic VERIFICATION via hydrostatic testing in accordance with the CGA schedules.

David Haugen

Retired in Illinois

From: "Todd Perkins" <p3wt3r**At_Symbol_Here**CHARTER.NET>
To: DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU
Sent: Wednesday, February 5, 2014 10:56:44 PM
Subject: Re: [DCHAS-L] Hydrostatic Test Date

Hi Jim,

Normal use shouldn't be of any concern. Filling, on the other hand, is, because of the stress that it places on the cylinder during the fill process. Normal use doesn't place that kind of stress on the cylinder, and cylinders are routinely in use for many years past their retest date without any safety concerns.

Obviously everyone here must set the standards for his/her own organization, and you can set those standards as high as you feel appropriate, but please don't confuse product expiration with packaging (cylinder) retest, because its not a true equivalency.

-------------------------------------------------

A couple other notes for anyone interested:

The DOT stamp on a cylinder is a packaging specification. For example, DOT 3AL 2015 is specific to aluminum cylinders with a working pressure of 2015psig, while a DOT 4BA 260 is a low working pressure (260psig), thin walled cylinder used for propylene and other compressed liquids with low vapor pressures, and a DOT 4L 200 is a cryogenic liquid cylinder with both an outer shell and an inner container, and a service pressure of 200 psig. A lot can be learned from these packaging specifications - see 49CFR178 for more info.

A cylinder that is removed from transportation in commerce to become part of a stationary cylinder bank (aka ground tubes, et al.) is not *required* to be retested because it does not fall under DOT's jurisdiction, regardless of how many times it is filled. Similarly a cylinder that was filled in test can be perfectly safe in circulation (normal use) a long long time before returning for a retest and refill.

Cylinders that have been sitting for multiple years at a customer location, which contain highly oxidizing "acid gases" (HBr, HCl, HF, and others) should be handled with extreme care as over time the cations can attack the iron, leaving Hydrogen. The original gases are usually a compressed liquid with a moderately low vapor pressure, but the hydrogen gas created can eventually over-pressurize the cylinder causing the safety or the cylinder to fail.

A similar danger is posed by cylinders of HCl, HBr, HF, Cl2, and others, if water is introduced back into the cylinder. Two different things can happen:

1) the heat of reaction can cause an over pressurization - and/or

2) the steel inside can be etched, leaving the cylinder wall thinned and weakened. This will also happen with Carbon Dioxide, as it forms Carbonic Acid which can etch the steel over time to the point of catastrophic failure. This is unfortunately common with beverage grade CO2 cylinders.

A typical hydrotest pressurizes a cylinder to 5/3 its normal working pressure, while a UE test looks at the thickness and microcrystalline structure of the steel to find any weak spots or invisible damage that could cause the cylinder to fail. Both have their advantages, but UE will fail cylinders that can pass a hydrotest, for reasons a hydrotest cannot detect.

When in doubt, talk to a professional in the compressed gas industry. Airgas has Safety Directors all across the US, as well as a nationwide network of highly trained Airgas Emergency Response Organization (AERO) team members to assist customers experiencing compressed gas cylinder incidents.

Todd Perkins BSc, MBA

Safety Director

Airgas USA,LLC

Mid America Region

Personal email: p3wt3r**At_Symbol_Here**charter.net

Personal phone: 314.803.2318

From: "JAKSAFETY**At_Symbol_Here**AOL.COM" <JAKSAFETY**At_Symbol_Here**AOL.COM>
To: DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU
Sent: Wednesday, February 5, 2014 2:30 PM
Subject: Re: [DCHAS-L] Hydrostatic Test Date

I would be prudent to not use a compressed gas cylinder after its hydrostatic test date has expired.

Jim Kaufman

Laboratory Safety Institute

In a message dated 2/5/2014 12:00:35 A.M. Eastern Standard Time, LISTSERV**At_Symbol_Here**listserv.med.cornell.edu writes:

Date: Wed, 5 Feb 2014 01:54:50 +0000
From: Benjamin G Owens <bowens**At_Symbol_Here**UNR.EDU>
Subject: Gas Cylinder Hydrostatic Testing

All,

I understand that compressed gas cylinders must have a current hydrostatic test to be filled. I have read a vendor site that indicates that a cylinder may be transported after the hydrostatic test expiration date if it was filled prior to the expiration date. If cylinders that have exceeded the hydrostatic test date are considered safe to transport are they considered safe to continue using? In other words, if a compressed gas cylinder is not empty but has exceeded the hydrostatic test expiration date is it required by regulation or prudent practice to be returned for testing or can it continue to be used?

Thanks,
Ben

----------------------------------------------------
Ben Owens
Assistant Director, Laboratory Safety
University of Nevada, Reno
EH&S Dept., MS 328
Reno, NV 89557
775-327-5196 (office)
775-843-2113 (cell)

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