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Dacosta
11-02-2010, 06:38 PM
Crunching number on a R-507 – CO2 cascade system. I am showing there may be a potential installed costs advantage. The old school’ers are telling me to stop due to the higher pressures of the CO2 side. But if I design the CO2 side with CO2 rated components and compressors, rather than standards components for ammonia or halocarbons, what’s the big deal? What is with the high pressure scare, that make everyone not even consider this?

What am I missing?

lowcool
12-02-2010, 12:59 AM
check out its static pressure at 40 deg C if your cu pipe and fittings can handle it go for it

desA
12-02-2010, 04:17 AM
Crunching number on a R-507 – CO2 cascade system. I am showing there may be a potential installed costs advantage. The old school’ers are telling me to stop due to the higher pressures of the CO2 side. But if I design the CO2 side with CO2 rated components and compressors, rather than standards components for ammonia or halocarbons, what’s the big deal? What is with the high pressure scare, that make everyone not even consider this?

What am I missing?

High pressure blow-outs can have different consequences - depending on liquid, or vapour release.

For refrigerants, a sudden liquid blow at very high pressure could cause some personal damage, I'd expect. A sudden vapour blow could be at fairly high velocity (supersonic), I'd think. Try by putting a piece of lint (not your fingers) in front of the blow - it may surprise you.

For reference, high-pressure steam blowouts (160 bar) can cut a man in half, if he gets hit. It depends on the energy released.

charlie n
12-02-2010, 11:44 PM
You're not missing anything. Take care & design for the pressure & you'll be fine.
If Wilbur & Orvil Wright listened to the "old School'ers" we'd still be on the ground looking up.

desA
13-02-2010, 03:37 AM
The 'old-schoolers' are precisely that, because they have used their sense over the years, to stay alive. :D

I happen to like CO2, but, the high pressures do bother me.

damo567
13-12-2010, 08:40 AM
I just think it's what you are used to, I used to work on 4000PSI compressed air systems but with the right training ad a healthy dose of respect you will be ok!

NoNickName
13-12-2010, 03:16 PM
There's a risk in everything we are up to. It much depends on weighing it against the advantage.
Driving a car is a risk, but can you afford not driving it?

chilliwilly
13-12-2010, 06:25 PM
I can't see the big deal neither, if a system is designed to take a certain pressure, it will be tested to at least twice its highest working pressure.

They've been using co2 on marine/trawler refrigeration for quite some years now. And the people that I have met, that work with it can't see why there are problems elsewhere. Except for poor guidance and lack of information relating to its application.

Most new Coca cola machines are nearly all co2 these days, and its often found in fire extinguishers. Which I'm sure we have all used at least once. I've worked on some hydraulic systems that have a working pressure of around 3000-4000 bar, along with water jet cutters.

:off topic:

I've only ever seen one hazardous occurence with the hydraulic system where a pipe from a charge pump burst. Luckily no one was hurt, just some general damage to the surrounding machinery. This was due to a pipe not being replaced after upgrading the plant to work at a higher working pressure.

The new MD of the factory where I worked, thought he was being schmozzled so he wouldn't agree to it. Despite being told from the people in the know, that it would fail in the near future. Despite passing a pressure burst test, he would not listen to the fact it had signs of fatigue and corrosion. In the long run it cost him more than a short peice of pipe.