Just Chillin Cascade

[wdrzal]

You know to only static charge with 1150. That means both stages are off and completely warmed to ambiant.............

your correct: keep the 1150 liquid line small Diameter and short as possible.

[{.bLanK} GoD]

My H2 regulator has only 120psi max outlet pressure.
So static charging is not possible.

Close attention was payed to static pressure right up to ambient. As I said earlier on after the first test run, static was way too high, I had to vent 1150 @ 390 psi.
With liquid line much shorter and the new expansion tank being an extra 300cc bigger, static pressure is down to a safer level.

Static pressures @ 20°C are 145 psi on the 1st stage and 190 psi on the second stage.

[{.bLanK} GoD]

Electrics are finished. Second stage is still on manual control. Next week I will purchase and install a thermostat. (350psi HPCO and 400psi pressure release valve are installed, so it's not going to blow up).
Going to bring the label maker home from work tomorrow and label everything.

[n00b 0f l337]

After looking at your pictures, it appears your blow off valves appear to be blow through, if thats right why not plumb them back into the low side?

[godmod]

After looking at your pictures, it appears your blow off valves appear to be blow through, if thats right why not plumb them back into the low side?

How do you see that?

[n00b 0f l337]

Under that cap looks like theres a fitting, could get the right female for it and pipe back into your low side. Sure a blow off is "safe", however I don't think blowing off ethylene is safe

[godmod]

Yeah, thought you might mean this. I think it is just a "normal blow off", like the refco one.

[{.bLanK} GoD]

Yes I have thought about this, the top of the release valve does have a female pipe thread, but if I was going to plumb it back into the system or another tank, I would only do it if it made it safer than it is now.
HPCO is pre set to 350psi, release valve is 400psi. So assuming the (brand new) HPCO works, (It does as I have tested it) the discharge should never get above 350psi (+/- 5psi).
First job for the release valve is a second safety for if the HPCO fails.
Second job is to release pressure if static was to exceed 400psi.
I have the R1150 static down to 190psi now @ 20°C so the only reason the static would get over 400psi now is if the cascade was exposed to a fire.
In that scenario I would rather it blow off a bit of gas than keep building up.
To do it the way you mentioned totally safe, I think the release valve would have to be plumbed to a designated tank which would also have it's own release valve.
It must release to atmosphere under worst case scenario.

[n00b 0f l337]

Yeah I think if you plumbed it into an expansion tank though with its own pop valve you could separate off charge in a worst case scenario.

[{.bLanK} GoD]

Yeah I think if you plumbed it into an expansion tank though with its own pop valve you could separate off charge in a worst case scenario.

Yip but that's another $50 or whatever the valve costs (I can't remember off hand) when the valve that's there now will probably never trip.

EDIT:The extra tank would need to be vacuumed through a separate dedicated port and then filled to 0-5psig with the ultra low temp of your choice. In my case ethylene.

[Xeon th MG Pony]

Put a balloon over the release valves to monitor for leakage, Obviously it will work with the balloon there, it just tells you if you have a small leak.

[{.bLanK} GoD]

Put a balloon over the release valves to monitor for leakage, Obviously it will work with the balloon there, it just tells you if you have a small leak.

Maybe, maybe not.
Remember that helium will slowly leak through a balloon skin. Maybe ethylene will, maybe it wont. But until I know for sure, it's not a guaranteed leak test.

Hey Xeon, did you get your Bennigans voucher and free bubblegum?

[Xeon th MG Pony]

?

Works well to alert you to seepage during running cycles and off cycles for small leaks. Lets just say the ones used in the field are made of latex and where never designed to be used for leak testing, it works well!

As they age the springs get weaker and they start to seep when the pressure gets no where near the set range.

[wdrzal]

Thoughts on relief valve.
1: First remove that red cap,if it pops off @ 400 psi that will be a bullet,even that it has a low mass weight (the plastic cap) it will take a eye out easily.

2: If left to vent to Atmosphere,just plumb a copper tube to a safer discharge direction,usually down /away in a position no one can every be standing. and away from contacts and switches.(all electrical contacts/switches/breakers )spark when the open & close . Totally sealed ones are available. They are whats being used on HC compressors in the EU but they are expensive. In the states there NEMA ratings, but not sure that will mean much in a worldwide forum. In short,if there ever would be a emergency over-pressure release you don't want flammable refrigerant/oil filling a case or pointed toward switches/contacts that create the ingnition source..

This is just a general safety concerns for everyone.

[Xeon th MG Pony]

The ones Walt is talking about are called Rupture disk, they are the best as they do not seep as they age, down side is they are all or nothing, once it goes you must get a new one, but remember the concept? It should never have to go!

[DetroitAC]

EDIT:The extra tank would need to be vacuumed through a separate dedicated port and then filled to 0-5psig with the ultra low temp of your choice. In my case ethylene.

That's a new one to me, please explain

[wdrzal]

After looking at your pictures, it appears your blow off valves appear to be blow through, if thats right why not plumb them back into the low side?

He's not static charging,he's adding gas while unit is on/cold which is/can be dangerious..... you just don't know what the static will be when unit warms up, Unless you did all the engineering and know the system volume and can very accurately measure the gas added.......not likely for most to do. But he has safety's in place to prevent a rupture.still not a good idea IMO.get a regulator with a higher secondary side discharge pressure. you can just change the inlet stub on a N2/helium regulator

plumbing back to the low side will cause a rupture in this case because the same amount of gas will still be in the system..

Where talking about static pressures when the system if off and warms up.

[n00b 0f l337]

Right Walt, however the point of a blow off normally isn't for static, since you normally charge a cascade from static. Thus it must be for when its running if the cut off fails to stop the pressures from rising. Plumbing it back into the lowside will equalize your pressures rapidly and should lower the high unless your low side is above 400 psi

[begrip]

very very good work!

[DetroitAC]

For me the point of a pressure relief valve or PRV (what we call them in automotive) is that sh$t happens and things can terribly wrong. People monkey with their cars, they bypass control devices, they overcharge, unexpected failures and consequences do happen.

You can either have a psssst of refrigerant that is puzzling, or you can have ruptured components, collateral damages, and hurt people. You're going to loose the refrigerant either way. I wouldn't design a system that my child may someday drive that doesn't have a PRV (not that anyone would let me do it anyway).

I think the way blank god's doing it is just what ASME or his NZ equivalent would demand for a pressure vessel. A PRV that pops at or below the rated working pressure of the various pressure vessels, and vents to atmosphere.

[n00b 0f l337]

Again I understand completely, and I understand the arguement for one.
However I think one that vents to the low side, and have designed the unit with a static pressure that works, is 1000x better then a release of ethylene (and possibly liquid ethylene) into your work area. After having tested a few types of pop off valves they don't psssst, at least mines don't, they just blow, one was insanely loud too. If no ones around or a units outside, sure, perfect, but for a cascade like ours I think its not an appropriate safety measure.

[DetroitAC]

However I think one that vents to the low side, and have designed the unit with a static pressure that works, is 1000x better then a release of ethylene (and possibly liquid ethylene) into your work area.

That would work fine if you could specify in advance all the crazy things that will go wrong. You see, you're assuming that the machinery is not warmer than ambient when things go wrong. Failure modes and bad circumstances can happen at the same time.

I don't think it would be a problem to have a PRV plumbed to the low side that is set to blow at slightly below the main PRV, but for the complication why not a HPCO?

I don't think you entirely get it (even though you've assured me you do!). I also don't think you're talking about safety, I think you're talking about the pain and cost of recharging ethylene.

If a PRV blows there is something seriously wrong with the machinery. This should be a very rare occurence, although there's a good chance it will happen when you're commisioning and debugging a new system.
A PRV should be set to a pressure that protects pressure vessels from rupturing. In reality pressure vessels have a good factor of safety built in, but if there's no PRV, a fouled up system will eventually burst the weakest vessel. You don't want to burst a pressure vessel + ethylene into your work area!
When we are testing automotive systems on the bench and we know they are going to pop off the PRV (investigating an issue that causes PRV to pop on a current production model), we rig up a water bath for the gas/oil to go into. Maybe you should do that until you get a system properly debugged so that the HPCO will work properly to control high pressures.

I suppose you can do it however you like. After 300 years of all kinds of vessels bursting and killing people, ASME says you need a PRV to protect pressure vessels, but BAH! those guys aren't xtreme!

[A/\/\/\C]

what kind of pressures are on your low sides when the system will be running ? cos if the prv,s are,nt designed to be piped back to the low side the low side pressure will have an influence on the prv,s spring and opening pressure ie if the lowside was in vacum it would assist the prv to open early if there was say above vaccum this would resist against the opening of the prv make sure that you are sure of the prv,s outlet design before you repipe it back to the lowside if its was only designed to vent at atmospheric pressure then dont pipe it back to the low side as this would affect the valves working pressure
Great Stuff there nice job

[Sam__]

Wow.. thats very nice... i love it. very clean job.

[wdrzal]

After having tested a few types of pop off valves they don't psssst, at least mines don't, they just blow, one was insanely loud too. If no ones around or a units outside, sure, perfect, but for a cascade like ours I think its not an appropriate safety measure.

Again Like DetroitAC said ,PRV's are not about protecting the charge,They are about Protecting Human Life.

Each State has a Bureau of Pressure vessels and laws to govern their use,so do the Feds. The stricter always supersedes.

Spend some time,Ahh correction (a lot of time) reading/studying Mechanical Engineering 101 instead of what "you think or tested". We are just trying to assure you your logic is Flawed. Xeon posted a R-22 pressure vessel failure and it has a much higher LFL,not to mention the chemical energy of Ethylene.

I hope it doesn't take quite a few years on Rikers Island (prison) for Manslaughter or Risking a Catastrophe or Assembling a Explosive Device or a few dozen of other vilotions you can be charged with.......No,it's a refrigeration Device to cool CPU's,your Honor....... The only difference is if it Explodes or has the potential to Explode. Not to mention civil fines & penalties that can be levied.