Coldtrap absolutely necessary?

#22

capturing minute residuals before entering your pump.

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#23

It’s just a glass coldtrap filled with dry ice. I’ll take a pic when my phone charges a bit if you need.

#24

Just dry ice or are you also putting solvent in there?

#25

Remember the best part about using two cold traps.

One of then is doing the bulk of the work bringing the vapors down.

The second is doing the sop is making sure to keep the vacuum pathway dry.

Think of it like that. You can use one trap, but everything always hers better with two traps.

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#26

Just dry ice

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#27

hate to agree with spddude

but he is insurmountably correct on the benefit of two traps over one.

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#28

You need to use solvent in the cold trap for effective heat transfer. Next time fill it with an alcohol/dry ice slurry.

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#29

I’ve been di only in my cold trap. I’ll have to try out the iso/di next time

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#30

I usually run 2-3 traps on 1st pass and only 1 on 2nd. I always use a trap and the still dont het everything. I run a roughing pump until about 160 c or so while my precision pumps are warming up

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#32

I don’t know if anyone has asked, but why would you want to get rid of the cold trap to begin with? To improve vac depths, or?

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#33

Sick of having to drive to get dry ice in the morning before I can start my day

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#34

Buy in bulk

#35

That ain’t a good enough reason to not use a cold trap imho, the cost of a vacuum pump rebuild or a whole new pump outweighs the inconvenience.

I don’t know if you can store dry ice in an ultra-low freezer (-80C) but if so, buy in bulk as Magister said if you have one

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#36

Uhhhhh

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#37

Yeah, a quick google search says DO NOT store dry ice in a freezer. So I don’t know what to tell ya about bulk storage of dry ice

#38

I’ve stored dry ice in ultra freezers, we can usually store 200lbs for the week this way. I’ve replaced many dry ice applications with mechanical and LN2 so our ordering went down but ultra freezers work well enough. What I’ve seen though is operators placing solutions in the same freezer and there will be dissolved CO2 in the solution the following day.

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#39

I definitely would not store it in a regular freezer though

#40

1 lb of dry ice sublimates to ~250 Liters of gaseous CO2, so if it’s stored in a non-ventilated area (like a -80) booooom.

Non the ignitable, flammable kind of boom, but one that could potentially bust the doors off a freezer and / or release enough gas to asphyxiate operators in the area fairly quickly.

At -80C, you could expect a bit of the dry ice to sublimate to vapor—not as quickly as it would at room temp, but still enough to warrant a safety concern.

#41

Absolutely true, it be willing to bet the used freezers ours were stored in do not have a perfect seal on the doors. Stored dry ice this way for 3 years without incident, but someone else’s mileage would definitely vary. The large coolers will keep it for a few days, I’m assuming they’re made of HDPE or something resistant to becoming brittle.

Edit: large plastic coolers such as the type dry ice is typically delivered in.

Edit 2: dry ice storage is one of the main reasons we switched to mechanical and LN2 traps.

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