Cascade filter/dryer question

[Gray Mole]

Well I'm sure I'll ba answering my own question tomorrow when I replace the filter, but thought I'd ask about it if it's a known issue that I didn't know about ;)

I've made 3 cascades now, and though the first one was a little messy, and the High stage had some brutal startup issues that led me to do a complete new setup, it worked and held load as normal.

In the 2 subsequent ones, including the current one I'm working on and will get pics of as soon as I get my camera USB cable back, I've had some serious blockage problems.

In my first cascade, I used bullet dryers. Spun copper etc etc and it never had a blockage at all.

In my second that I've still got, I always had a blockage. It would clear after a while if I let the HX heat up a bit, but it would be blocked when frozen. I flushed it, vacced it, changed the filter 3 or 4 times, and eventually gave up and set it to the side to come back to.

In this one (2x3/4HP rotary, TEV w/00 orifice, 2.1m .031" cap on Low stage) I'm getting blockages again. I installed a new filter and triple vacced, then replaced the filter and triple vacced again, just to be sure after all the problems again. No luck, it built up a blockage as well.

So I've been using Solid core dryers of a few types on both the low and high stages, and the high's have been fine, but the Low stages get blockages and no matter what I do, they always come back.

So Is there a problem with using solid core dryers(like sporlan 'catch-all' and such) at the liquid temps that come out of the HX? I made sure that the filter was further from the HX this time to see if it was a problem with the filter getting too cold. They're rated for operation at -50, but I'm starting to wonder.

Anyways, if anyone has thoughts on whether or not solid core dryers are normally ok for the Low stage, can you let me know?

I'm picking up some more bullet dryers tomorrow and will see if it fixes things up.

On the plus side, when the blockage started to get worse, I got to see -117 on R23 before it stopped it completely, which was kind of cool :rolleyes:

Cheers

Gray

[hatemi]

Why not place the second stages drier between desuperheater and HX ;) That way it would be roughly at room temp all the time, so they might work better.

[Gray Mole]

Hmm that's a very interesting thought. The solid core dryer's I've got are meant to be liquid line, but would that honestly be all that bad?

I know that the filter is there to protect the metering device for the most part, but if it's filtered at some point, and it worked...

Don't know if I want to test that theory or not. If something did happen to come off the part of the system after the filter, like a little bit of slag or anything, it'd definitely block the captube.

Maybe I'll try it tonight. Guess the worst case really is that I'd have to redo the captube and such, and I've been thinking of going cpev anyways. Not that much to redo the captube either way I suppose.

Gray

[Unknown_road]

are you sure the oil-sep works well? And what kind of vacuum pump do you have?

[_HL4E_HalfLife_]

I think ur TEV is closing up on you. A 00 orifice is ment for a 1/3hp system not a 3/4 ,a 01 works well with a 1/2hp system, a No.2 works with a 3/4hp system and a No.3 is for a 1hp system. I would try a No.2 orifice on it see how it works.

Ps. These orifice sizes are based on R12,R22,&R502 systems.

[Gray Mole]

Hey guys :)

My vac pump is a Yellow Jacket 2cfm 15 micron. I've had no issues on anything single stage, so I'm sure it's working fine.

Vacuum is 'normal' until it hits the blockage, then it pulls further and further to 25inHG and beyond. High pressure rises accordingly until it runs out of refrigerant then it stops rising. Vac is normally at about 10-15inHG no load once it's charged when it's not blocked.

Nice to know on the TEV, and I did struggle to hold load with the 00, but was thinking that 700w should cover it. (That's the rating on 00 with the TEV I'm using) so when I put it back together it'll get the 01 or 02, as I've got both. I'm pretty sure the 01 will work as I can get it to hold the second stage running, but only barely and it's obviously struggling to keep the HX frosted. It's frosting back with no load, but once the loadtester is on it's slowly rising temps.

I tried that out, Hatemi, and it worked. Too late I'm afraid though, as I'm just running out of R23 now. Not a big deal as I've found some good contacts along the way, so I can afford to get more at some point soon.

I ran the captube straight out of the HX with no filter and put another new solid core filter after the desuperheater and guess what? No blockage at all.

I don't know if it's normal, cos most of the guys are just using the copper bullets, but I'm never going to use a solid core again on the Low stage, obviously there's a problem with them, but I wish I knew.

At least now I can redo the other cascade with a copper bullet once I get more R23 and I can be reasonably certain it's gonna work now.

I didn't recover the R23 into a separate bottle as I thought there must be some kind of contamination in it, but now I wish I had. It's in the spare R23 bottle, but there's a couple other gasses in there, which may have been contaminated as well.

I almost got a full charge of R23 into the cascade and topped it up with 402a to get it running, and it still got no load temps under -100c, I think about -102 was about the best, but once the load was on it held about -65 or so until the high stage started to warm up too much.

Can't complain though, the R23 I had was close enough to free that it may as well have been, so now that I've learned so much form working with it, I'll be a lot more prepared for the next one(s) I'm still not sure if I'll get more R23 or wait out the account to get some Ethylene, but there will be more Cascade action in the New Year for me :toast:

Cheers for the input guys, and thanks HL, that's some good info.

Special thanks to Hatemi for giving me a way to prove what I already was thinking, and yet another tool for more work in future, knowledge :)

Gray

[wdrzal]

Build a clean & dry system and don't use a filter;) , sounds like oil loggingf if it happens at the same temp all the time.

[Gray Mole]

Hey Walt :) Whether clean or not, I'm still nervous about running no filter before the captube. I suppose if there were anything in there, it would have been caught up in the other filter I took out, but still...I looked into the filter inlet, and it looked fairly clean, so my brazing and purging skills must be getting better ;)

I was thinking oil myself for the longest time, but it just didn't make sense. Why was my first cascade ok (at least where freezing up was concerned) and these all had the same problem? I tested the oil sep and it was ok, the oil sep is a different one on this one and it's the same problem as the other one that's complete. Both Henry float sep's. One way valve installed. besides, mineral oil is good to -50 anyways, at least -40. My liquid line temps on average are about -20 to -30 at any give time, though I didn't check 'em on this one tbh, Was just trying again to see what else it could be as oil just didn't add up.

Only thing that seems right is the filter. They're all rated to -50, but there must be something about it that they don't seem to like.

I'll recheck the operation tomorrow on this one, and see if it starts and runs as normal. If it does it pretty much confirms my theory.

Either way, I'll just use bullets from now on in the Low stages. Not worth the risk if there's even a chance. I've already wasted too much time and money on 'em, so I'll just try that and see.

Gray