Freezing pins

[Mike L]

Here and there I’ve seen snippets of guys with homemade setups using liquid nitrogen to freeze pins before installation. I’d like to build one but not sure where to start. Can’t find any of the pictures I’ve seen but it was basically a box with the nitrogen pumping into it. I guess I’m trying to figure out the details. How much pressure, safety measures, etc. does anyone know about this stuff or has anyone ever built or used one?

 

[mg2361]

Up there in Maine....just put it outside. Isn't it colder than nitrogen up there?

 

[Mike L]

Haha! -2 this morning.

 

[Vetech63]

Ive never used liquid nitrogen.....I guess I haven't had anything quite that tight. I use dry ice and an ice chest.

 

[Jonas302]

Love using liquid nitrogen put pin in stryrofoam cooler pour nitrogen over when it quits bubbling drop pin in hole the bigger the pin or bushing the more it shrinks

Only problem is I don't use enough to keep it around have to drive an hour to town to get some but that is the same and only source of dry ice also

First time we used it to do bucket pins on a 980 my helper caught the bushing on the other side when I threw it into the boom hole it slide right though Cost was around $100 probably more now

 

[treemuncher]

When I've had to shrink bushings or pins, my go-to is propane (-42 C boiling point) because I always have some around the shop. Certainly not as safe and not as cold as nitrogen but it works in a pinch. All you have to do is flip the tank upside down to get liquid out. If you are dumb enough to do what I do, the liability is all on you. This is only for informational purposes of theoretical uses of a cold liquid.

My simple system is a small propane bottle refill adapter that is designed for refilling 1 lb propane bottles from 20 lb propane tanks with a piece of small air line tubing pushed onto the tip of the 1 lb side of the adapter - basically the nipple that you see on the pic above - and cold liquid propane will come out the hose. Flip the tank upside down, balance tank on the handle assembly, hold onto the hose with welding gloves (the hose will whip wildly if you don't hold it down by hand or fixture) and open the valve to control the flow of liquid. Spray the liquid onto the parts to be shrunk. For efficiency, keep the parts on a thermally insulated surface like Styrofoam. SAFETY GLASSES - LONG SLEEVES - WELDING APRON - NO SPARKS OR FLAMES - STAY UPWIND AND DON'T BREATHE THE GAS.

I'm pretty sure you could do much the same with a nitrogen tank and get liquid out. You will just need different fittings and hosing that can handle the much colder temps. Nitrogen's boiling point is -196 C and non flammable. It's the safer choice for sure.

Sometimes the McGuyver in me makes a faster work around when needed at the price of safety.

 

[Nige]

We once made a box for shrinking pins/bushes with LN2. It was made from 1/8” plate IIRC and fitted inside a wooden box that was 2” bigger on all sides. The space in between the two boxes was filled with fine sand.

As Jonas says you can use a styrofoam cooler but in my experience they are generally a one use only deal because the cold cracks the cooler. Still gets the job done though.

I guess it all depends on how often you’re freezing stuff as to how much effort you think needs to be put into making a container.

Let me see if I have a photo of the container I last used for freezing pins. I may be able to get some details of it.

 

[kshansen]

Back when we were doing Allison transmissions often I built a box out of plywood and lined it with foil backed 1 1/2 foam insulation. Made it just a bit bigger than the blocks of dry ice the place we got it for sold. Then again the planetary pins in those transmissions were about 1 1/2 inch by 2-3 inches, not big pins like bucket pins. Did use that box to shrink bucket bushings a few times.

Another option used at times for the planetary pins was to heat the housings in an oven and install the pins at room temperature. Forget what temp we heated them to, maybe 450ºF. That oven also was handy for installing bearings on shafts, like the old Mack Quadra-Plex units we had many of in those days!

Do recall the time the guys assembling a shaker screen with bearing that must have been 10 to 12 inch ID. They heated oil in a cut off oil barrel to 350ºF then lowered the bearing in using a nylon sling. Yea! That did not work too good! I think nylon melts at a bit over 425 but sure gets weak at 350ºF! After a bit they managed to get a chain through the bearing and get it out to install.

 

[Nige]

Here you go. A bit on the big side (and probably overkill) for what you're wanting though.
https://worthingtonindustries.com/g...587e/WI_443__K_Series_Manual_09012017_Web.pdf

 

[Delmer]

Liquid nitrogen is transported and stored in a vacuum insulated container, most common is a semen tank for storing cattle semen for artificial insemination. There is no pressure involved, the high pressure nitrogen cylinders are gas only, there may be large stainless vacuum containers for liquid nitrogen like liquid oxygen, I've never seen one that's mobile. If you're not looking to store liquid nitrogen, just one time use, then you could get a cracked semen tank cheap and take it directly from the supplier to your site. The tank won't be worth the risk to a farmer who may have his life's work invested in the genetics in a couple tanks full of semen and embryos.

Another option is dry ice/CO2, you can turn a CO2 tank on it's side and shoot out liquid that immediately turns to snow, put that in a container with your pin and some kerosene or gasoline or liquid propane to improve heat exchange, or wait longer for the pin to cool with just the dry snow. Or buy the dry ice, it's not hard to handle, good winter gloves are plenty, bare hands only if they're dry and tough. Don't move it in a car without all the windows down and moving.

 

[John C.]

One of my customers just kept a big bottle like an oxygen size bottle of CO2 with a hose for shrinking pins and bushings. They did a lot of 560 Hough center joints which required a tight fit. They filled a cardboard box with the snow, dropped the piece in and kept it covered in snow for a fair bit of time and then installed the part when they figured it was cool enough. I never messed with it because I had enough porto power jacks to force the part in before they could get the pin or bushing cold enough. I did use nitrogen one time on a track pin for 455 Komatsu dozer. Didn't work! Pin got half way in and froze solid. I couldn't move it with a 200 ton press so had to hot wrench it out and start over.

 

[JD955SC]

We get a big liquid nitrogen tank from our welding supplier looks like a big stainless steel propane tank, about 5 feet tall. I think it just vents the boiling liquid nitrogen to atmosphere slowly. It works well for shrinking bearings. We also have a freezer that goes to like -80 Celsius. The liquid nitrogen workes better, usually just have to drop the race or bearing in whereas you’ll still be driving it much of the time with the freezer.

 

[Coaldust]

Cat dealer I worked at had like a 600 size container of LN2 with a regulator and a hose that went to the top of a 36” wide x 24” 1/8” metal box. Put your parts in it and let er’ rip.

For smaller items like bearing races, a coffee can could be filled the same way. Then, you could carry the cold parts to your job on the other side of the shop before the magic liquid disappeared.

The issue is LN2 doesn’t store very well in a bottle of any type. It disappears. It gets expensive, unless you have a high production shop and regularly consume it.

When I need it for a job, I get a 4.5 liter flask from Airgas and pour it into a coffee can or a metal pail to shrink my parts.

 

[Truck Shop]

Used dry ice for dry liner installation on Perkins, better have the oak block and sledge handy though.

 

[Tyler d4c]

Used dry ice for dry liner installation on Perkins, better have the oak block and sledge handy though.

I broke one of those one day in a little kubota I was about 13 stacked alot of hay bales to rebuild that one.

 

[terex herder]

Liquid nitrogen is a cryogenic liquid at atmospheric pressure. It can be stored in large vacuum flasks with the top simply capped with a loose! fitting Styrofoam plug. You can pour it into most any container. At a previous shop to use the nitrogen we had a store bought container which was double walled thin stainless steel with a fancy insulation in between. When that wasn't large enough, we had a couple of different size coffee cans with the styrofoam packing peanuts between the cans. After you are done shrinking the parts, pour the left over nitrogen back in the vacuum bottle.

We had a shop truck driver that wasn't the sharpest knife in the drawer. He had to go to the welding store for gas anyway, so was told to check the nitrogen tank and see if it needed refilled. He pulled a piece of about 1/2" diameter tubing about 10' long out of the metal rack and used it like a dipstick. Well, the boiling nitrogen inside the tubing carried some of the liquid nitrogen out the top of the tubing, so driver was getting a shower of small balls of liquid nitrogen. He was steppin' and fetchin' and jumpin' and had no idea what to do. I guess one of the guys watching went over and pulled the tubing out of the vacuum flask. I wasn't there to see the affair, but when I got back from the other shop about an hour later nobody could tell the story without laughing so hard tears came out.

If you are fast and tough, you can pick small parts out of the liquid nitrogen with your bare hands. DO NOT try to pick small parts out of a dry ice/acetone (or gasoline, or alcohol) bath. Even though the dry ice bath is warmer, it will frost bite you instantly.

 

[JLarson]

I worked with an outfit that did a run of parts that needed a shrink fit so they had their packing guys build a nice box and they insulated it with their expando foam packing setup. They had an onsite gas plant so storage of the dewars wasn't a problem for them. I've done similar with that pink insulation foam board, but I don't bother storing a dewar here.

As far as PPE you can get cryo ppe kits from like Airgas or lab supply places with gloves/sleeves, aprons for handling the cold goods lol

 

[Mike L]

So here is the picture I was thinking of. It’s not a homemade box like I had thought but this is what I have in mind

 

[funwithfuel]

Usually, liquid N is in a double insulated vat. That appears to be Nitrogen gas for charging accumulators and purging vessels. I don't think that's gonna get it.

 

[funwithfuel]

What I do, I place the male part (pin) in dry ice till the screaming and wailing stops. At the same time i have a torpedo heater blasting the female (receiver) this gets her all hot. Then you shove the frozen pee-pee in the hot hole.