Liquid Cylinder Reliefs- Getting it Right

You have a relief on a liquid cylinder that is opening like it is supposed to, but won't reseat properly so you decide to replace it. How are you going to determine what relief to replace it with?

a) Look at the relief that is in the vessel and replace it with one just like it?

b) Look up in the owner's manual and see what it says to do?

c) Look at a reference sheet provided by a reputable provider that translates the 4L-DOT ratings and helps specify the "proper" relief, burst disk and presure gauge for your unit.

"A" is an uncomfortably common response. "B" or "C" are the way to go.

Unfortunately- Information on the maximum pressure settings for reliefs and burst disks or pressure ranges is not obvious or plainly stated on cryogenic liquid cylinder data plates. It requires some knowledge of DOT 4L parlance to know that a 4L-292 liquid cylinder will typically have a 350 psi relief and 0-600 psi pressure gauge. The necessity of looking up information is a problem since most users and many distributors don't have handbooks or reference charts readily available at hand. The risk is that an relief and/or burst disk will be installed that is at too high a pressure for the 4L rating of a vessel. This creates a hazard resulting in a possible explosion of the vessel.

If you need help on determining the right relief, burst disk or pressure gauge for your unit drop me a note. I'll be happy to help.

Implosions Are Also A Mess......

There have been several posts in Cryogenic News regarding cryogenic tanks rupturing as a result of over-pressuring. This is important due to the real danger posed by tanks and cylinders that are improperly modified or otherwise malfunctioning.

Implosion is also a very real concern and Wil Ferch (Owner/Principal at Nordstern Associates LLC) has graciously allowed me to reprint his recent article "Don't Let This Happen to You!!" below without endorsement.

Interestingly enough, as I was reading Wil's article I remembered that Dan Ariely (of Predictably Irrational fame) is also a director with The Center for Advanced Hindsight which you can visit at http://web.mit.edu/ariely/www/MIT/thecenter.shtml.

Ideally, employing the lessons shared by Wil and others can help you avoid status as a case study for Dan's group so here it is:

"Don't Let This Happen to You !!!

The industrial gas industry, (producers of liquid oxygen, nitrogen and argon...amongst other products of air), require large site-erected tanks to be built in order to store these liquids for later use. These tanks can range in size up to 2 million gallons or more, and cost millions of dollars. The stored product, like liquid oxygen, exists at about minus 300 degrees Fahrenheit.

In the process of bringing such a newly constructed tank into service, it must first be carefully "cooled-down" such that it can accept incoming cold liquid later. Here is a photo of a typical tank on a representative plant site---> http://gazettextra.com/photos/2008/oct/02/10382/

Nordstern Associates LLC - CASE STUDY # 7

A major global producer of industrial gases, recently "cooled-down" such a tank as part of their commissioning process, utilizing their own qualified personnel and historical procedures. This time, however, things went horribly wrong, and their 450,000 gallon tank went from being a multi-million dollar asset... to nearly scrap metal value, in a fraction of a second ! In the process of cooling down the tank, it vacuum collapsed ! To illustrate the violence, sudden-ness and uncontrolled nature of the collapse, here is a YouTube film clip showing a similar ( this time, on purpose ! ) tank collapse of a railway tanker.---> http://www.liveleak.com/view?i=72e_1208694365&p=1

Also, when such a flat-bottom tank vacuum collapses, it may implode the top and side walls, and also start to "lift" the center of the flat floor. See here of what such damage looks like in yet another example ( once the web page is opened...move down to title, " Plastic bag vs. Storage tank" for photos and text.)----> http://www.driedger.ca/dp-1/Dirty%20Pictures%201.html

After the damaged tank was repaired, Wil Ferch of Nordstern Associates LLC was enlisted to provide both a revised cool-down procedure, and on-site supervision of the new attempt to cool-down the tank. Result?--> a perfect cool-down with no damage ! Wil Ferch, principal at Nordstern Associates had over 20 years of experience cooling down these types of tanks with a 100% recorded success rate throughout his career !

So....don't let this happen to you !

The industrial gas business has lost much in the way of retained skill sets and nuance-driven knowledge with long-term staff changes. Enlist people who have the training and knowledge to do this correctly. Call upon Nordstern Associates, LLC.

Contact--> Wil Ferch, principal at Nordstern Associates, LLC and let us discuss this.... or other support needs. ( ferch.wil@gmail.com .... business tel : +1 716 983 4089, alt tel: +1 716 662 7173). "

Predictably Irrational & Cryogenics

One of my favorite writers is Dan Ariely of "Predictably Irrational" (both book and blog) fame. In his most recent blog at http://www.predictablyirrational.com/ ("Are We More Rational Than Our Fellow Animals?" Dan uncovers some of the advantages we humans enjoy through possession of a neocortex. According to Dan, this is "the most recently evolved part of the brain and the center of higher mental functions" and "it’s thanks to our neocortex that we are able to plan for the future." The gist of his article is that our ability to think at a higher level and plan does not always add up to brilliantly rational actions benefitting our own best interest.

Witness the 4L-DOT cryogenic liquid cylinder shown above with both the safety relief and burst disk plugged.


What is the rational solution for a relief that continues to vent and make irritating noise? Someone apparently figured removing the relief and replacing it with a plug would do the job.


And then what do you do when the pressure builds so high that it blows the burst disk and pressure is lost? One solution is apparently to remove the blown burst disk safety and replace it with a plug.


OK- so maybe the planning capacity of the neocortex wasn't fully developed in this case....... as witnessed by the ultimate result of an overpressurized (exploded) liquid cylinder. The most fortunate part of all of this is the fact it happened at 3:00 a.m. which is about the only time where someone would not be in the lab to get hurt.


A more in depth article on this incident can be found at http://ucih.ucdavis.edu/docs/chemistry_301a.pdf. It is great reading for anyone open to learning from the mistakes of others.

Lifetime Learning

"......but tho' an old man, I am but a young gardener." - Thomas Jefferson to Charles Willson Peale, August 20, 1811

Jefferson's information request sent to one of his time's most noted gardeners speaks volumes. The fact is that, for all the things Jefferson did, it is quite fair to say his real lifetime hobby was learning.

As a model of "the more I learn, the more I realize I don't know" he personified one of the greatest joys there is by constantly pursuing new endeavours from architecture and design to philosophy, education, gardening and more.

Why do I mention this?

This is going to be another of those great weeks where I get to "learn as I teach" with at least three days at client sites delving into operations and working together towards continuous improvement. Not to mention a weekend of gardening, energy conservation, farmer's markets and Saturday morning cooking class........ (a special thanks to Monica Pope at T'Apia in Houston).

And herein also rests the beauty of the cryogenics and gases industry where there is so much to learn and so many really neat people to learn it with......

Low-Loss Liquid Fill- What Price Success?

Companies delivering liquid nitrogen, oxygen, and argon are fortunate these days to have some choices:

a) Pumped Systems- many of which have low transfer loss features

b) Pressure Driven Systems- some with MC-338 options allowing them to travel under pressure without venting between stops.

c) Pressure Driven Systems with Gas Use Capabilities- allowing them to be used not only for liquid delivery, but also for gas use for welding, purging, cutting, etc.

Which is best?

Of course- again we hit the millenium answer- It depends.

And it really does depend on what you are doing with the vessel- How much liquid you are delivering, what other uses (if any) you might have for the tank, and your budget.

The question crystallized after a client visit where it turns out they'd have been able to purchase two GOrilla 500s and a GOrilla 1500 (all tricked out with trailers) for what they paid for one low loss pumping truck. This is an irrelevant comparison where you need the pumping truck. Where you don't, it could be interesting to further explore where you get the most from your investment dollars.

Using High Pressure Gas Cylinders to Push Liquid Cylinder Output- Not Advised

Several conversations have occurred recently where people mentioned their use of high pressure gas cylinders to boost cryogenic liquid cylinder output. Specifically, they are hooking a high pressure liquid cylinder to the vent of a liquid cylinder to push liquid out of the cylinder faster or to maintain a higher pressure for gas withdrawal.

Is there a risk and, if so, what?

As with almost anything..... maybe. The concern here would be that gas coming out of the high pressure liquid cylinder will increase the pressure in the liquid cylinder faster than the relief and rupture disk can relieve it. The net result of this is that the vessel could eventually reach burst pressure and blow.

As for me- I'd be interested in exploring how the equipment might be used to function as designed and still get the job done.....

Cryogenic & High Pressure Nitrogen Gas Options for Laser Feed

A client called yesterday regarding problems he was having with a nitrogen feed for a laser system. The system has been in service for a few years and working fine until recently. Something had changed. The change turned out to be different material being cut which changed the feed gas flow and pressure requirements. The best solution turned out to be temporarilly supplying the laser system with high pressure gas 16-packs since the user's need is short-term and requires a relatively low total volume of nitrogen.

The link below is to an article I ran across while doing more research. It helps define some of the issues and options related to nitrogen feed options for laser cutting.

http://www.thefabricator.com/LaserCutting/LaserCutting_Article.cfm?ID=1741

E-mails with links to other helpful information on this subject are welcomed.

Tried a GOrilla; Bought Fifteen More

Hope's Hope asked if there is more to this article than the published 6-Word Novel. More expertly written 6-Word Novels such as Hemmingway's "For sale: baby shoes, never worn" obviously do a better job of telling their story.


"Tried a GOrilla; Bought 15 more" is also true which hurts the "novel" classification.


This is the story of a gas distributor who tried something new and used it as a great tool to exploit a niche. The point here is that experimentation and innovation is alive and well in the gases industry. And- we are in one of those great times when people can do things that allow them to write their own success stories by using "the liberating force of adversity" to their advantage.


Also- candidly- it is a lot of fun to help others succeed and then celebrate their accomplishments.

A Six Word Cryogenic Success Story

Tried a GOrilla; Bought 15 more.

Liquid Only Liquid Cylinders- Cruddy or The Good Stuff?

A gas distributor took me on a tour of their facility and showed me where they keep their good liquid cylinders and where they keep those needing repair. On a side of their yard was a third group of about two dozen liquid cylinders that I pointed out and was told they were scraps. When asked if they were inner leakers or otherwise beyond repair the client said essentially "Oh, no. They are just those cruddy old liquid-only vessels. No one uses them anymore."

Another distributor took over the business at a very large mixed use facility with a number of labs using nitrogen liquid. Scattered about the labs was a large number of liquid-only style liquid cylinders. The client was told that instead of liquid-only vessels they would be getting "the good stuff" all through their plant...... meaning VGLs.

Both cases share a pretty common perception and contributed to a belief among some users that vendors are somehow denying them top quality when they provide Liquid-Only liquid cylinders for applications where the only need is for nitrogen in a liquid form.

A counterpoint to this perception is the fact that liquid-only style 4L-DOT liquid cylinders will contain nitrogen in a liquid state longer than a same sized liquid cylinder with Gas Use capabilities.

Why?

Absent the gas use function, Liquid-Only liquid cylinders do not have Gas Use Vaporization Coils, Pressure Building Coils, Regulators and other heat syncs that transmit energy (heat) into the liquid and cause it to boil off more quickly.

The funny thing is that the myth of Liquid-Only vessels being "cruddy" is so pervasive that a large percentage of people are unaware you can even still buy Liquid-Only containers. And even those that do know you can are reluctant to get them due to backlash they often get from users who feel they are somehow being short-shrifted.

Paradigm shift?