4L DOT Cryogenic Liquid Cylinders - Age Coding

Client X has a few dozen liquid cylinders that they are considering repairing and want to be sure that they aren’t too old to be worth the trouble. So- Their very good question:

“Is there any way to tell from the data plate what year a DOT 4L- class vessel was manufactured?”

I’ll give you what I got from some quick targeted research and will appreciate any information you might have to share with the rest of us:

TAYLOR-WHARTON- The last letter in the serial number identifies the year of manufacture.
A=1985 to H=1992
J=1993 to N=1997
P=1998 to X=2005
BB=2005 to FF=2009

UCAR- Purchased by Taylor-Wharton in 1985 so anything UCAR is 1985 or before

CHART/MVE- Beginning in 1995 the Year of Manufacture was inserted right in the middle of the serial number. So this is the most obvious… 97, 99, 02, etc. If the unit is before 1995 then the only way to know is to call the number and ask.

CSI- Purchased by Chart in 1995 (?). No defined date code system.

CYLTEC- No date code imbedded in the serial number, but virtually all are 2005 or newer.

Cryogenic Fill Hose Safety Reliefs- An absolute necessity

Why are safety reliefs installed on all cryogenic liquid oxygen, nitrogen, argon or carbon dioxide fill hoses?

In fact- safeties are not only to be installed on all fill hoses. They are also installed on any cryogenic line that is sealed on both sides. This is because cryogenic liquid trapped in a line will vaporize and expand exponentially creating tremendous pressure in hoses, piping or tubing. This expanding liquid nitrogen, oxygen, argon, or CO2 can easily build enough pressure to cause the line or hose to explode with great force.

This is a danger that is easily overlooked and one that is not obvious to someone without prior knowledge or training. And- it is something that can be missed by even the most experienced personnel who are hooking up a new line out of necessity or otherwise in a hurry.

Whether you are filling medical oxygen bases, transfilling liquid from one DOT4L vessel to another or otherwise filling from a bulk source it is essential to have a relief for expanding vapor. So- never forget to be sure the hose you are using to fill has a properly rated safety relief installed somewhere between the valves or other connectinos that could trap liquid.

MedTrade Day 3

Clare Ulik of Cryovations sent these photos from Day 2 that tell the tale..... lots of folk with great attitudes.

Of course.... as always... Day 3 didn't have nearly the number of people, but moods were still great. And- the reduced activity allows for some more in depth discussions so all was good.

In the world of medical liquid oxygen delivery there are obviously still opportunities for operational improvements and optimizing gains from improved efficiency. And then there is also the situation presented by those with smaller client bases. For those with 5-25 or so patients with no real expectation of growth the option of subcontracting liquid delivery can often make a lot of sense.

How is it that an Airgas Puritan Medical or a Lifegas or others can turn a profit where a smaller company can't? Consolidation.

Trying to be profitable delivering to two or three patients in a given area can be almost impossible. Add them to a route that already has 10-15 patients and all the sudden they offer a great return as all the real cost of getting into the territory has been covered and everything extra is where the real return is made. It might seem obvious, but is still not universal knowledge.

MedTrade Day 2

Don't talk with your hands. I've heard it many, many times and still haven't learned.

Oh, and what a great day today at MedTrade. The good news/ bad news is that we'll be back next year. It was great to see a goodly number of client friends and new friends that we would not have seen otherwise. Also encouraging was the presale of booth space for next year's show.

And then there was the neat little information tidbit related to the BPR Medical FireSafe TM device for respiratory oxygen cannulas. This link http://www.lifegas.com/files/firesafeV2.htm will get you to a little video showing how it works.

MedTrade Day One 2009

Color me surprised and pleasantly so.

I was told that attendance at this year's MedTrade is down significantly and would have plenty of reason to believe this is true. Nonetheless, activity today was by no means the worst I've experienced at a trade show and the quality of discussions was was superior.

The ability to really converse with people and have in-depth visits about the needs and challenges of their business is one of the collateral benefits of this year's downturn. And- people have an interest in considering options that would reduce their costs of operations. One new introduction today was eTankPro (Roger MacClellan) and he seems to be one of those businesses keyed in on really helping clients reduce costs through improved efficiencies.

And a goodly number of people that might previously have brushed past or just quickly introduced and grabbed a card had a chance to consider how maybe 3 trucks with 290 gallon vessels delivery medical liquid oxygen could be a world more productive than 5 with 119s. This was especially true for one fellow who goes 30 miles everyday to fill a 119 and then only has enough liquid to fill 8-10 patient bases. This was a real case in point for what a difference a 290 gallon UltraSeries vessel could make. Just cutting trips to the bulk fill by 50% is huge without even taking into account the ability to make 5-15 more stops per week with the larger volume of liquid and time he'd have available.

Cryogenic Bulk Tanks- Vacuum & Leaks (d)

The principle differences between Bulk Tank and 4L-Liquid Cylinder vacuum investigations?

A) Size and B) More parts and Penetrations

Bulk Tank size matters a great deal when it comes to the ability to conduct and effective vacuum investigation. A liquid cylinder can typically be thoroughly investigated in less than an hour. A perlite bulk tank can take weeks just to get a vacuum good enough on it to perform an effective investigation. Investigating in place will also frequently require the use of a manlift or other device to get all the way up and around the vessel seams, lift plate, etc. Add just a little breeze and it can be well nigh impossible to get a accurate investigation completed due to helium dispersal. The only answer is tenting or bagging section of the vessel which further increases the time required.

Add to Size issues related to additional parts- especially the probe tube. Probe tubes frequently leak through causing vacuums to go bad just by trying to read them. This has been true in many cases even with new probe tubes. There have also been a number of leaks in the probe tube isolation valve handles that are sometimes only present with the valve open. Then there is the vacuum lift plate used on many bulk tanks. This plate is o-ring and lube sealed by the vacuum pulled on the tank. And unlike 4L- Liquid Cylinders which have all piping run through a single head boss, bulk tanks are loaded with line penetrations. None of these issues are overly challenging for a capable investigator using helium mass spec equipment. But they do help explain why those not performing full investigations can get a good vacuum pulled on a tank and leave believing the tank is fixed.

We go back to size and semi-permanent installation. Unlike a liquid cylinder it is a huge undertaking to remove a bulk tank, send it in for vacuum investigation and restoral and reinstall. And, there is typically not a ready supply of spares to pop in place while a bulk tank is being repaired. Hence- It is almost always easiest to send 4L- Liquid Cylinders in for repair while it is frequently justifiable to perform bulk investigations in the field. Justifiable…… but often costly nonetheless making it all the more critical that the right tools and right people are used.

Cryogenic Bulk Tanks- Vacuum & Leaks (c)

How do bulk cryogenic vacuum investigations differ from liquid cylinder vacuum investigations?

The principle differences relate to the size of the vessels and the more permanent nature of bulk cryogenic tank installations. There is also an issue with added penetrations and connections on a bulk tank which mean more potential leak points. There are also a couple of other nuisances related to probe tubes, lift plates, vacuum valve and perlite insulation. First- The principles of helium mass-spec leak detection are the same for almost all double-walled, vacuum-insulated cryogenic liquid storage vessels and include:

A) A vacuum evacuation port of some type must be installed on the outer vessel allowing a vacuum pump to be connected to pull molecules from the annular space. These are specialized connections capable of pulling down to very low atmospheric (high vacuum) levels without leaking past. On smaller 4L-DOT type vessels this is typically a port and plug assembly that are pulled on using a fixture that allows the plug to be pulled and replaced under vacuum. A larger vacuum diaphragm valve is used with bulk tanks

B) A helium mass-spec leak detector is set up on a slip stream of the vacuum line to allow sampling for helium molecules. The leak detector can only be used effective after vacuum has been pulled down far enough to get a helium reading. If the vacuum will not come then the leak will have to be found by other means and some repair performed prior to performing the full helium mass spec leak investigation. Vacuum valves, vacuum probe tubes and probe tube isolation valves are often replaced prior to performing an investigation due to their propensity for being large leak points. It is also common to break the vacuum seal on a vessel and reseal lift plates where present (including o-ring replacement and vacuum lube addition). Perlite is also added at this point for perlite insulated vessels. It is worth noting that breaking vacuum improperly can be a major source of moisture contamination and can also cause permanent damage to the vessel.

C) The initial leak investigation consists of spraying helium molecules around the outside of the vessel and all penetration points. This process can be painstakingly slow and tedious as a leak can both provide a positive indication and flood the annular space with helium that can take hours (or days) to evacuate. Also- getting a positive reading is only a start. It is often necessary to work through a series of tests where small portions of the vessel seams or other penetrations are masked off to ultimate isolate the leak point. And- repairs requiring welding will likewise require careful breaking of the vacuum, completion of the repair, and then pulling the vacuum back down on the vessel to start testing all over again.

D) Once the outside of a vessel has been determined to be leak-free then helium is added to the inner vessel and some pressure added behind it to look for possible inner leaks. Fortunately, inner leaks are not that common on cryogenic bulk tanks- especially stationary tanks- since they are not subjected to the kind of rough handling that 4L Liquid Cylinder and smaller open top nitrogen dewars are. I say “fortunately” as isolating and repairing inner leaks is most complicated and worthy of another full set of articles.

But what about the differences between Liquid Cylinder and Bulk Tank vacuum investigations?

We’ll hit more on this next.