Are Bulk Cryogenic Spot Drops a Good Thing?- Part II – Supplier Perspective

In the last episode it was determined that it is costly for cryogenic bulk transports to return home with any of the liquid they departed with. One way to make it home empty is to drop off any liquid remaining after scheduled deliveries at some other customer tank that has some room available. Ideally for the supplier, this would convert the left over liquid from a cost to income. It was asked, “Is this a good thing?” First, we’ll look at the supplier side with the question, “Did the revenue generated offset the cost of an 800 gallon delivery considering that Company X typically hates to deliver under 1500 gallons at a time?”

Here, again, comes The Millennium Answer. The Millennium Answer came into vogue shortly after some high placed U.S. politico said something to the effect of “It depends on your definition of the word ‘is.’” Ever since then it seems everything is contingent. i.e. “It depends.” In this case- It depends on the cost of getting to a drop location and making the fill compared to the revenue that might be generated. Pretty simple, eh? But, not necessarily as simple as it appears on the surface and especially when asking about dropping off 800 gallons where 1500 is preferred.

The dependant aspect of whether 800 gallons is a good drop or not relates to whether it is the (first/only) drop or whether it is the last drop. 800 gallons as a first or only drop is not necessarily a profitable proposition for a bulk supplier. Costs associated with running a 4000 or 6000 gallon transport out on a unscheduled single drop delivery might just exceed any revenue that could be made. This is especially true with lower priced products like liquid nitrogen.
On the other hand, delivering 800 gallons (or even significantly less) as a convenience drop at the end of a route is markedly different. In this case, the costs associated with getting the transport loaded and out into the market place have already been incurred and the liquid is out there. Now, there is just the incremental cost of getting to another location and offloading versus the revenue that could be generated from the drop. Playing to the profit side of this equation are the opportunity costs of not doing the delivery:

- Liquid that would just vent off if left in the transport or be partially lost transferring back in and out of plant storage;
- Slightly higher fuel costs with the load,
- The need to return to the convenience drop site sooner by not having made the drop and not having enough liquid to completely fill the tank when the delivery is made.

All things considered-convenience drops are usually good for the bulk cryogenic liquid supplier as long is the drop is within relatively close proximity of the last scheduled stop or the return route home.
But then……. Are convenience drops good for the customer?

Golf as a Metaphor for Cryogenic Liquid Delivery

Are Bulk Cryogenic Spot Drops a Good Idea?

For the sake of collective sanity- Let’s agree that business profits are good and necessary. Bulk Cryogenic Liquid Suppliers have a number of challenges to overcome in order to turn a profit at the end of the day. Others will be explored over time, but one that is universal is transportation costs. One element of this is how many miles must be traveled to deliver a given quantity of liquid oxygen, nitrogen or argon. For more effort than most of us can imagine goes into trying to optimize this ratio.

Yesterday a good friend used a golf metaphor for business that applies. To wit- He wants his business to operate like a golf ball. When you hit a golf ball out there it stays out there and doesn’t come back. All returns are costly and one of the most important things that can be done with cryogenic liquid delivery is to be sure that all of the liquid that leaves the plant stays out.

One way that delivery companies help assure they are able to do this is to identify bulk tanks that can be used as field receivers for liquid that is left in a truck at the end of its route. So, for instance, a liquid nitrogen truck drives out to a suburb area and delivers 5200 gallons of its 6000 gallon load to clients. The 800 gallons that might be returned to the plant is now a liability. To avoid returning it, the driver might go to a client that did not call in for delivery, but has a 9000 gallon tank that always has some room in it and drop off his remaining liquid He now comes back empty and converted the 800 gallons he had from a cost to revenue.

Is this a good thing?

Did the revenue generated offset the cost of an 800 gallon delivery considering that Company X typically hates to deliver under 1500 gallons?

Is this a good thing for the client that received this drop?

Manana (later).

DOT 4L- 292 Liquid Cylinders with 230 Reliefs?

At the end of the last episode the client had run out of 4L-200 liquid cylinders and was wondering if they could put 230psi reliefs on some of the 4L-292 oxygen liquid cylinders they had remaining in stock to get them through for a few days until their regular delivery. This left the questions of:

- Is this OK?
- Why or why not?
- What other considerations might there be?

First, the fact that the vessels are oxygen is irrelevant to the issue of the pressure relief setting. The important issue in all this is the DOT 4L designation.

What matters is the fact that the maximum allowable relief setting on a 4L-200 is 230psi and it is 350psi on a 4L-292. Technically, it is OK to de-rate a vessel by putting a lower pressure relief than is allowed. So “yes” this is OK.

The other consideration, though, is where the rub comes in. If you look at the factory setting for the pressure builder (PB) regulator on a 4L-200 you’ll find that it is 125psi in most cases. The factory setting for the PB regulator on a 4L-292 is more typically about 300 psi. The problem then with putting a 230psi relief on a 4L-292 cryogenic liquid cylinder is that the pressure builder is set at a level higher than the relief. So, the liquid cylinder will try to build pressure to the PB set point, but constantly vent causing the vessel to exhaust itself. If you want to switch out the relief to 230psi on a 4L-292 you need to remember to reset the PB.

It is common for people to put 230 reliefs on 4L-292s without taking the PB setting into consideration. Likewise, checking the PB setting is one of the trouble-shooting steps to do when a liquid cylinder is reported as “bad” (constantly venting). The liquid cylinder might actually just be doing what it is set up to do.

www.westcryogenics.com

DOT 4L Cryogenic Liquid Cylinder Pressure Relief Change

A large production and research facility has multiple uses for cryogenic liquid cylinders and keeps an inventory of DOT 4L-100, 4L-200 and 4L-292 vessels on site. The 4L-100s are set with 22psi reliefs and installed in labs and a few other locations where they are used strictly for liquid withdrawal. The 4L-200 “medium pressure” vessels are the most commonly used liquid cylinders throughout the facility and are fitted with standard 230psi reliefs. There are also some higher pressure applications at the site where 4L-292 vessels fitted with 350psi reliefs are needed.

Liquid nitrogen, oxygen and argon vessels are normally delivered to this site every Thursday. Mid-morning one Tuesday, they empty a 4L-200 oxygen liquid cylinder at a location that has a maximum feed pressure of 260psi. On arrival at the inventory area they find that their supply of 4L-200 (230psi relief) liquid oxygen cylinders has been exhausted. There are, though, a few 4L-292 (350psi relief) liquid cylinders still on hand. They call to find out if they can take a 230psi relief off an exhausted 4L-200 and put it on a 4L-292 in order to use the 4L-292 at the process area that cannot exceed 260psi.

What is the answer?

Why?

Are there any other questions or considerations that need to be reviewed related to this answer?

Tune in next time…….

Temperature Effects on Gas Pressure

It is often hard to comprehend just how big an impact increased temperature can make of the gas pressure within a cryogenic liquid cylinder or bulk tank containing oxygen, nitrogen or argon.

My good friend Greg Cain at Oxylance provided the following information which is just slightly edited:

“One of the things that you may want to put in there to show people the gas volume / temperature is as follows.

Take a plastic bottle. The 1 liter size makes a bigger impression but a 16 or 20 oz will also work.

Get it warm and dry and put the top on it very tight. Stick it in the freezer for about 15 minutes and pull it out. As the air inside the bottle cools down the air molecules become smaller (more condensed) and the bottle will pull a vacuum on itself and when you take it out it will be half its normal size. The temperature difference will only be about 40 degrees (from 70 down to 30).

Now let the bottle warm back to room temperature by taking the lid off and get the bottle out to its normal size. Put the top on it tight and try squeezing it and see how soft it is. Remove the top and put the warm bottle and top back in the freezer. Leave it in there for 15 minutes. Reach in the freezer and put the top back on very tight and set it out in the sun. After it warms up try squeezing it and see how stiff the bottle is. A difference of 40 degrees will make the bottle so stiff you can’t squeeze it. Now think about how much difference it would make if you were going from -296 to +70 degrees.”

This last sentence is in reference to liquid nitrogen, oxygen or argon which have boiling points nearly 400 degrees F from what we consider to be room temperature.

Thanks, Greg!

Two Secrets to Business Success

Long ago I was told of the young man who was taking over ownership of a business after mentoring for many years at the right hand of the coumpany's founder. On the day the founder was leaving for retirement he asked his successor if he had any other questions.

“Just one,” said the younger man. “Could you just summarize for me what you consider to be the keys to business success?”

“Of course, that’s easy. There are two simple things,” replied the founder. “First, keep whatever commitments you make to a client, no matter the cost or time involved.”

“And the other?”

“Don’t make too many stupid commitments.”

I mention this in lieu of a new product announcement that needs a little more work prior to release. But- as my buddy who spent way too much time on the islands always says “Soon Come.”

Cryogenic Liquid Cylinders- Safe Handling

I recently wrote about safety concerns related to lifting cryogenic liquid cylinders overhead. A number of questions have been received related to safe methods for moving and handling liquid cylinders. Rightfully so as there are a lot more liquid cylinders moved along the ground than lifted overhead. In turn, there is a lot more opportunity for injury and damage resulting from improper handling.

What are the risks related to moving liquid cylinders?

- Back, muscle and joint strain
- Broken bones
- Crushed toes, feet, fingers and hands
- Cuts from cracked or broken handling rings and site glasses.
- Damage to liquid cylinders that are dropped or tipped over including broken necks and inner leaks
- Broken site gauge and covers
- Damage to other equipment or fixtures hit by a dropped liquid cylinder

There are a number of resources for information on proper care and handling of liquid cylinders including manufacturer’s operating instructions and CGA Publication P-30 which can be purchased and downloaded on line. We’ll also continue to hit items here.

One for today is the suggestion that cryogenic liquid cylinders be moved using a safe cart or carrier. This is especially true for full liquid cylinders that commonly weigh from 650 to over 1000 pounds. Carts designed specifically for moving liquid cylinders have a hook that catches the hole in the handling ring support bracket. They also have wheels that the liquid cylinder rests on when tilted back to avoid reliance on brute force to keep the cart from dropping.

Nothing is ever a problem until if becomes a problem and then it is usually too late to get the toothpaste back in the tube. I get enough calls on this issue to know it is a frequent issue. This might be the best week yet to go do a little audit of how your folk are handling liquid cylinders and what improvements you might be able to make in your methods.