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fridge-spark
22-11-2010, 08:33 PM
What will happen if I do not pump down a CO2 evaportor prior to venting the CO2 from the evaporator?

I have been told it will go bang and I may even die :eek:
Is this true?

coolhibby1875
22-11-2010, 09:19 PM
with the greatest respect, the fact your asking this question means you havent been trained to use it, therfore you shoulnt touch it, also your employer should not be sending you to supermarkets that use co2, there are plenty of training courses out there on co2 which your employer should get you on, but judgin by your title your a ELECTRICIAN therfore should not even be touching any refrigerant!!

Colin G
22-11-2010, 10:18 PM
Well one way or another it will 'vent' You may also vent into your underpants!

Silhouette
23-11-2010, 06:52 PM
It may take a few minutes or tens of minutes but the evaporator or one of it's components will eventually rupture causing catastrophic failure:eek: As already advised this may also cause you to vent in your underwear and possibly a few others persons nearby with you!!

supermarketguy
23-11-2010, 08:11 PM
Training is the key to all systems, just finished doing a Tesco C02 site and been to a M&S C02 install tonight, both diffrent, but the same safety rules apply when working on them. What type of system are we talking about ?

bembem
25-11-2010, 06:29 PM
Well one way or another it will 'vent' You may also vent into your underpants!


hahahhahahaha

yeah co2 very high pressure be very careful

fridge-spark
25-11-2010, 11:47 PM
with the greatest respect, the fact your asking this question means you havent been trained to use it, therfore you shoulnt touch it, also your employer should not be sending you to supermarkets that use co2, there are plenty of training courses out there on co2 which your employer should get you on, but judgin by your title your a ELECTRICIAN therfore should not even be touching any refrigerant!!

If you read my user name it is fridge-spark. Yes I am a ELECTRICAN and a refrigeration engineer with NVQ 3 and 2079

I was just asking a simple question to see what would happen if a evaporate was isolated incorrectly.

fridge-spark
25-11-2010, 11:55 PM
Training is the key to all systems, just finished doing a Tesco C02 site and been to a M&S C02 install tonight, both diffrent, but the same safety rules apply when working on them. What type of system are we talking about ?

Hay supermarketguy, thanks for the reply.


The evaps are supplied for a compounded dual (HTLT) pack that can operate both sub and transcritical.

coolhibby1875
26-11-2010, 10:24 AM
If you read my user name it is fridge-spark. Yes I am a ELECTRICAN and a refrigeration engineer with NVQ 3 and 2079

I was just asking a simple question to see what would happen if a evaporate was isolated incorrectly.

you are either a spark or a fridge engineer, have you done 2 apprenticeships?

i have 2nd year trainees with 2079 and the Scottish equilvent of the nvq3 which is a svq, that dont make them fridge engineers!

supermarketguy
26-11-2010, 11:01 PM
Coolhibby, i would have thought that someone that has been involved in this industry, would never judge a book by its cover. Nobody choses this as a career, they generally fall into it.:)

I have over the years found that good electricians, make good refrigeration engineers. and this issue should be on another thread and is :off topic:

Regarding C02 on a case, the rule of thumb is not to trap liquid and if you have been through any of the courses, they would stress this to you. Ball valves should be colour coded, yellow= Liquid Blue=vapour.

If shuting down a case and isolating the liquid to defrost, take solenoid coil off and fit mag valve lifter to stop liquid trap between solenoid and ball valve, thus avoiding trapping liquid. If shutting down case completly, shut liquid fit mag valve liquid and pump down, shut suction and bleed off via guages, so you are in control. Once work is completed, vac and open suction ,open liquid and refit solenoid coil. If both valves were closed, then depending on coil rating and ambient would determine if case would go BANG!!!

Hope this helps,

Supermarketguy

coolhibby1875
27-11-2010, 03:58 PM
Coolhibby, i would have thought that someone that has been involved in this industry, would never judge a book by its cover. Nobody choses this as a career, they generally fall into it.:)

I have over the years found that good electricians, make good refrigeration engineers. and this issue should be on another thread and is :off topic:

Regarding C02 on a case, the rule of thumb is not to trap liquid and if you have been through any of the courses, they would stress this to you. Ball valves should be colour coded, yellow= Liquid Blue=vapour.

If shuting down a case and isolating the liquid to defrost, take solenoid coil off and fit mag valve lifter to stop liquid trap between solenoid and ball valve, thus avoiding trapping liquid. If shutting down case completly, shut liquid fit mag valve liquid and pump down, shut suction and bleed off via guages, so you are in control. Once work is completed, vac and open suction ,open liquid and refit solenoid coil. If both valves were closed, then depending on coil rating and ambient would determine if case would go BANG!!!

Hope this helps,

Supermarketguy

I wasnt trying to put the guy down,just making a point, if you haven't been trained to work with co2 then dont touch it, again i have to say this trade is full of to many people that have changed a fan or probe then start calling themselfs fridge engineers, i knew a guy thats a plumber to trade, helped a fridge engineer out for 6 months whilst out of work, he is now got his own company (1 man band) in refrigeration, he has all his gas cert's ect, yet the guy hasn't got a clue, if its not a fan motor or thermostat or needing topped up with gas he walks away!! now i know plenty of compedent sparks out there that know there way around a fridge, but when a a8 valve on a hot gas defrost pack decides to fail at 10 pm on a friday night would you want a spark or plummer standing in front of a store manager trying to explain whats wrong, and why his ice-cream is running out the door?

750 Valve
28-11-2010, 09:42 AM
Don't forget we all started somewhere, over here I commissioned 3 Co2 subcritical liquid recirc sites before any such course even existed. A little research, common sense and a keen ability to keep an open mind can go a long way.

supermarketguy
28-11-2010, 09:52 PM
Hi Coolhibby,

As 750 Valve has said, people within this trade have come from all walks of life and i have came across some good and some bad, but just because you have done a apprenticeship and got all the tickets dosent make you a good engineer.

What makes you a good engineer is the appatite to learn from the day you start, till the day you go to the big chill in the sky, if you have that you will always learn.

I appreciate that when working on any system can be Hazardous C02 or any other and courses are required, but if somebody is questioning something, its better to try and put them right and make sure they are safe, than tell them nothing and they put themselves in harms way.

this industry is short of good engineers, that is why we have such a varied workforce from diffrent back grounds and any that do take an intrest should be encouraged.

To be honest it just sounded as if, just because he had a diffrent back ground that he should not be enquiring on the subject matter, it is better to point people in the right direction than not at all.

I have been through the star e-learning course and have done diffrent practical courses, for diffrent retailers. Ideally there should be a course that covers all systems and should come under the new f-gas 2079 regs, but at present it dosent. But all c02 courses do have a lot in common and you take the best from them and learn

This forum is here to help people not discourage :D

Cheers

Supermarketguy

fridge-spark
06-12-2010, 01:58 PM
I wasnt trying to put the guy down,just making a point, if you haven't been trained to work with co2 then dont touch it, again i have to say this trade is full of to many people that have changed a fan or probe then start calling themselfs fridge engineers, i knew a guy thats a plumber to trade, helped a fridge engineer out for 6 months whilst out of work, he is now got his own company (1 man band) in refrigeration, he has all his gas cert's ect, yet the guy hasn't got a clue, if its not a fan motor or thermostat or needing topped up with gas he walks away!! now i know plenty of compedent sparks out there that know there way around a fridge, but when a a8 valve on a hot gas defrost pack decides to fail at 10 pm on a friday night would you want a spark or plummer standing in front of a store manager trying to explain whats wrong, and why his ice-cream is running out the door?#

Sorry I have upset you in some way, I really must stop trying so hard to learn and improve myself.

In answer to your qustion I would have to tell the Manger that his A8 valve had failed the same as you would. Prior to telling him is valve had failed I would have carried out some checks to make sure it had failed.

Is there a dif across the valve when required (defrost) depending on the plant layout i would guess around 20 to 30 psi. It may just require adjusting.

Is the sol coil working, check power from the controller and to the coil. Repace the coil or controller if required.

Is the sol valve stuck or blocked, pump down the pack reclaim the gas into the nearest pack and strip the vavle.

Yes your right its broken time to talk to the Manager

"Hello Manager your A8 vavle has failed thus there is no differance in pressure between your hot gas and liquid. With out the differance in pressure hot gas can not flow in to the evaporator , reject it heat, melt the ice and condense ending up as a liquid in the liquid line. Sorry you don't give a sh*T when will it be fixed. The parts are next day befor 12:00"

Sorry if I missed any checks I'm just a sparks.

Any way this is all :off topic:

fridge-spark
06-12-2010, 02:17 PM
This was indeed a little research before my CO2 training which I have now completed and I can now see why people were so concerned. Thank for all your replys.

coolhibby1875
08-12-2010, 12:00 AM
#

Sorry I have upset you in some way, I really must stop trying so hard to learn and improve myself.

In answer to your qustion I would have to tell the Manger that his A8 valve had failed the same as you would. Prior to telling him is valve had failed I would have carried out some checks to make sure it had failed.

Is there a dif across the valve when required (defrost) depending on the plant layout i would guess around 20 to 30 psi. It may just require adjusting.

Is the sol coil working, check power from the controller and to the coil. Repace the coil or controller if required.

Is the sol valve stuck or blocked, pump down the pack reclaim the gas into the nearest pack and strip the vavle.

Yes your right its broken time to talk to the Manager

"Hello Manager your A8 vavle has failed thus there is no differance in pressure between your hot gas and liquid. With out the differance in pressure hot gas can not flow in to the evaporator , reject it heat, melt the ice and condense ending up as a liquid in the liquid line. Sorry you don't give a sh*T when will it be fixed. The parts are next day befor 12:00"

Sorry if I missed any checks I'm just a sparks.

Any way this is all :off topic:
you are just not getting it are you? i was not having a go as i have alreay explained, so why the silly response and sarcastic explanation, not bad for just a spark eh!! gotta love google.

fridge-spark
09-12-2010, 12:07 AM
you are just not getting it are you? i was not having a go as i have alreay explained, so why the silly response and sarcastic explanation, not bad for just a spark eh!! gotta love google.

I do get it. Engineers enter the trade get there tickets and think they can do it. My sarcastic response is because you have put me in this category by my user name. Then assume I google my answers to your prior comments. I have been in the fridge trade for 8 years and an electrician for 6 years prior. So I hold my head up high when I call myself a electrician and fridge engineer.

coolhibby1875
09-12-2010, 03:03 PM
i give up!!!

cold.man
10-12-2010, 04:58 PM
be carful when working with co2 these systems demand alot of respect well any system does for that matter.
i have worked on several co2 systems star packs and space advancer packs.

as every trained refrigeration engineer within the industry knows there are plenty of limited trained people in are game but thats the employers fault not the persons as i do agree everyone has to start somwhere but not put in harms way by there employer.

now co2 is entereing the supermarket industry unfortunatly it will be one of these individuals that does injure themselves with this stuff.

if you are not trained to work on co2 systems please for your own and other peoples sakes dont be a hero.

TriplepointPerk
16-12-2010, 06:34 PM
Hi Coolhibby,

As 750 Valve has said, people within this trade have come from all walks of life and i have came across some good and some bad, but just because you have done a apprenticeship and got all the tickets dosent make you a good engineer.

What makes you a good engineer is the appatite to learn from the day you start, till the day you go to the big chill in the sky, if you have that you will always learn.

I appreciate that when working on any system can be Hazardous C02 or any other and courses are required, but if somebody is questioning something, its better to try and put them right and make sure they are safe, than tell them nothing and they put themselves in harms way.

this industry is short of good engineers, that is why we have such a varied workforce from diffrent back grounds and any that do take an intrest should be encouraged.

To be honest it just sounded as if, just because he had a diffrent back ground that he should not be enquiring on the subject matter, it is better to point people in the right direction than not at all.

I have been through the star e-learning course and have done diffrent practical courses, for diffrent retailers. Ideally there should be a course that covers all systems and should come under the new f-gas 2079 regs, but at present it dosent. But all c02 courses do have a lot in common and you take the best from them and learn

This forum is here to help people not discourage :D

Cheers

Supermarketguy

City & Guilds are currently working on a C02 qualification!! :-)

tug1980
07-03-2011, 11:12 AM
Fridge-Spark do not listen to that clown he is one of them fridge engineers who thinks it is some sort of black magic that only he knows about. I did 13 years in the Royal Navy as an engineer and loved working on refrigeration so I left and im now working on the Tesco systems, I thought i knew alot about refrigeration but I dont and have a keen desire to keep learning. The key rule to CO2 systems is that the liquid in the system must not be trapped or it will solidify and rupture components and pipework, I maintain two co2 plants that have not gone bang and i am still waiting to do the course but i have pestered other engineers for knowledge and it has kept me safe up to now.

michaelm
07-03-2011, 03:51 PM
BH
Tug1980,
<O:pWhat is your opinion, would Tesco continue with CO2 or would look for the alternatives.

mecks
08-03-2011, 05:11 AM
Guys
I am an academic with a lot of respect for you techies who are practical and down to earth. Please believe me, knowledge of a bit of thermodynamics wont hurt you guys. Its not full of difficult equations and snake like integrals.Its just formalisation of commonsense which you have aplenty.

Now, coming to CO2. Its triple point pressure is 5+ atm. When you vent the evap full of Liquid CO2 under pressure what you are doing is throttling it down to nearly 1 atm. There it can be only solid or vapour. There is nothing like liquid CO2 at 1 atm!! So the solidification (formation of dry ice) is so fast that it would choke the tubes. The vapour has no where to go and like a cornered thief, will break what ever sees to escape! This is peculiar only to CO2. Other refrigerants you guys handle dont have that problem. Their triple point pressures are so low that you never get there.

Next, CO2 to be made popular, you must operate it in transcritical mode. Not much of knowledge is available on this. First, there is nothing like condensation there. Second, the pressure and temperature are independent of each other (unlike 134a or 507a etc where the high side pressure is fixed by the condensing temeprature). In fact this is beneficial because we can choose them as we like to get the best out of it.

The biggest problem we have today is the high pressure and what happens if there is power failure? If we can overcome these two we have cracked it. Honestly, how many installations you guys have seen? You can count them on finger tips. The Japanese havent even touched it. Business sense requires that, if the Japanese dont consider it worthwhile, it is not worth touching with a barge pole- bottom line and period.

coolhibby1875
08-03-2011, 10:05 AM
Fridge-Spark do not listen to that clown he is one of them fridge engineers who thinks it is some sort of black magic that only he knows about. I did 13 years in the Royal Navy as an engineer and loved working on refrigeration so I left and im now working on the Tesco systems, I thought i knew alot about refrigeration but I dont and have a keen desire to keep learning. The key rule to CO2 systems is that the liquid in the system must not be trapped or it will solidify and rupture components and pipework, I maintain two co2 plants that have not gone bang and i am still waiting to do the course but i have pestered other engineers for knowledge and it has kept me safe up to now.

it seems your the clown for working on these systems without the training, i would not shout to loudly about this, as Tesco and all supermarkets for that fact DEMAND that the engineers working on thier CO2 systems have completed the training, its people like yourself with the gung ho attitude that will be your downfall!! if something god forbid goes wrong im sure the hse will be satisfied that you have pestered other engineers for their knowladge, i have completed the 3 day training course on the above, and if an engineer phoned me from a co2 site asking what to do, i would in the politest way tell him to leave alone and not touch it, not because i wouldnt think they are not capible, but because if something went wrong i would not be wanting anything to do with the fall out of the aftermath, and also would not be able to sleep at night if someone got hurt!!
When we go out to work its really important that we return home to our loved one's in piece, but more importantly its your employers DUTY to make sure this happens.

keep safe is the message

tony--1
08-03-2011, 06:38 PM
Fridge-Spark do not listen to that clown he is one of them fridge engineers who thinks it is some sort of black magic that only he knows about. I did 13 years in the Royal Navy as an engineer and loved working on refrigeration so I left and im now working on the Tesco systems, I thought i knew alot about refrigeration but I dont and have a keen desire to keep learning. The key rule to CO2 systems is that the liquid in the system must not be trapped or it will solidify and rupture components and pipework, I maintain two co2 plants that have not gone bang and i am still waiting to do the course but i have pestered other engineers for knowledge and it has kept me safe up to now.

you need to go and get the training . b4 you hurt yourself or others

cold.man
22-03-2011, 09:00 PM
why not pump the evap down?
you should have a liquid line ball valve and a suction line ball valve at the fixture?
if you pump down the coil you can then vent of vapour using correct venting procsedures obviously?
there should be a connection on the coil to connect co2 gauges.
once work carried out pull vac and re charge with vapour to desired pressure approx 8 to 10 bar then reopen liquid ball valve.
build up vapor pressure using suction ball valve.

mad fridgie
23-03-2011, 12:05 AM
I have work with CO2 for many years (production off, more than as direct refrigerant) primarily liquification and dry ice production. The working pressures of CO2 in both critical and transcritical are high, so care should be taken, without being afraid. No cutting corners on material selection, ie wall thickness. However the service side that you guys are undertaking does give concern, especially sublimation "solid CO2 formation "dry ice"" This can form instantlly as the pressure drops (as fine powder to start with), as it travels it compacts and can form solid plugs, especially is tight elbows. (major concern if main lines are shut at the compressor set) I would recommend that when purging you attempt to keep you pressure within the pipework above 6bar for as long as possible whilst trying to introduce energy into the pipework (for example on a evap coil leave the fans on) effectively the pipework becomes a vapouriser, boiling of any remaining liquid, then reducing the chance of any dry ice formation. On an insulated piece of pipework, i would look at introducing some high temp CO2 vapour at the opposite end to where you are purging, again attemting to keep the pipework pressure above the tripple point.
When you add heat you will see the pressure rise if there is liquid, open your purge line to a point where the pressure is stable above the tripple point, when the liquid amount starts to reduce, the pressure will start to reduce, throttle back you purge line still keeping above tripple point. The final remnences of liquid will vapourise and pressure will then drop. Very simple really it is all about time, the longer it takes to purge the less likely you will get dry ice formation

Blueboy
15-05-2011, 09:25 PM
I know of many Transcritical CO2 systems running now in leading supermarkets in the UK. There seems to be two main systems the one that runs the liquid at 30-38 Bar with brazed copper pipe between the cases and the pack. The other one that runs at above 55bar and is used by the biggest supermarket this use a mechanical jointing system.

Both systems are good. They have a couple of interesting ways to hold on to the charge at a power down situation. I have to say I have not personally tested either however I know people who have and advise that they have contained some or all of the CO2 for up to 6 hours.

Another system i saw recently uses a R290 power chiller to cool the CO2 that is pumped through the cases. This solves two problems Pumped CO2 is efficient due to the partial phase change and pumped CO2 is run around 30 Bar. The other thing is it uses a lot less energy that current systems

So with the greatest respect I think your conclusion is TOSH. Just because Japan aren't leading the field probably means that will wait for some else to do the R&D then jump in afterwards. I think a combination of Transcritical and Pumped CO2 and Hydrocarbon is probably the answer for supermarkets for the next 20 years

monkey spanners
15-05-2011, 10:52 PM
Just stumbled upon this thread, think the point Coolhibby was making, and one i agree with, that its best not to work on CO2 systems based purely on advice gained from an internet forum... and not that people who originally trained in other trades can't make very good fridgies.

Jon :)

dirk
23-05-2011, 05:01 AM
Any co2 plant that is correctly designed will have bypass check valves and pressure relief valves installed so that there is no chance off trapped liquid or vapour co2 anywhere in the system reaching critical pressures. the consequences of trapping co2 are to dangerous to allow the possibility of trapping through human error.
Its as simple as that.

Blueboy
26-05-2011, 07:14 AM
Any co2 plant that is correctly designed will have bypass check valves and pressure relief valves installed so that there is no chance off trapped liquid or vapour co2 anywhere in the system reaching critical pressures. the consequences of trapping co2 are to dangerous to allow the possibility of trapping through human error.
Its as simple as that.

I am so sorry to tell you that you may be right in NZ , but in the UK we are not afforded the luxury and expense of bypass or blow off valves on every coil. Trapped liquid is a major concern particularly when working on Evaporators on the shop floor. Special care must be taken. The following is my usual procedure.

1) Place a Solenoid magnet on the EEV in place of the electro magnetic coil ( SOL VALVE COIL).

2) Shut the liquid IN valve before the solenoid valve.

3) Now it's time for a cup of tea ( Coffee if not English) take your time 10minutes is plenty

4) Put your specialist C02 Gauges on the access valve on the evaporator coil.

5) You should be seeing the suction pressure now (10 -13 BAR LT or 25-28 HT )

6) Now shut the gas out valve.

7) Blow the coil down through your gauges - There is no need to reclaim this gas it is not an FGAS

8) Now you can strip down the EEV or take off the coil should you wish to.

This is my procedure others may have different idea's. This is an example not a manual. It MUST be stressed that Training is the Key and when unsure stop and get help and advice.

"IT'S AS SIMPLE AS THAT"

Blueboy
26-05-2011, 07:23 AM
Guys
I am an academic with a lot of respect for you techies who are practical and down to earth. Please believe me, knowledge of a bit of thermodynamics wont hurt you guys. Its not full of difficult equations and snake like integrals.Its just formalisation of commonsense which you have aplenty.

Now, coming to CO2. Its triple point pressure is 5+ atm. When you vent the evap full of Liquid CO2 under pressure what you are doing is throttling it down to nearly 1 atm. There it can be only solid or vapour. There is nothing like liquid CO2 at 1 atm!! So the solidification (formation of dry ice) is so fast that it would choke the tubes. The vapour has no where to go and like a cornered thief, will break what ever sees to escape! This is peculiar only to CO2. Other refrigerants you guys handle dont have that problem. Their triple point pressures are so low that you never get there.

Next, CO2 to be made popular, you must operate it in transcritical mode. Not much of knowledge is available on this. First, there is nothing like condensation there. Second, the pressure and temperature are independent of each other (unlike 134a or 507a etc where the high side pressure is fixed by the condensing temeprature). In fact this is beneficial because we can choose them as we like to get the best out of it.

The biggest problem we have today is the high pressure and what happens if there is power failure? If we can overcome these two we have cracked it. Honestly, how many installations you guys have seen? You can count them on finger tips. The Japanese havent even touched it. Business sense requires that, if the Japanese dont consider it worthwhile, it is not worth touching with a barge pole- bottom line and period.

Hi

I know of many Transcritical CO2 systems running now in leading supermarkets in the U K (100 + sites). There seems to be two main systems the one that runs the liquid at 30-38 Bar with brazed copper pipe between the cases and the pack. The other one that runs at above 55bar and is used by the biggest supermarket this uses a mechanical jointing system.

Both systems are good. They have a couple of interesting ways to hold on to the charge at a power down situation. I have to say I have not personally tested either however I know people who have and advise that they have contained some or all of the CO2 for up to 6 hours.

Another system i saw recently uses a R290 powered chiller to cool the CO2 that is pumped through the cases. This solves two problems Pumped CO2 is efficient due to the partial phase change and pumped CO2 is run around 30 Bar. The other thing is it uses a lot less energy that current systems

So with the greatest respect I think your conclusion is TOSH. Just because Japan aren't leading the field probably means that will wait for some else to do the R&D then jump in afterwards. I think a combination of Transcritical and Pumped CO2 and Hydrocarbon is probably the answer for supermarkets for the next 20 years

I posted this a second time to stress my point

chillled
13-06-2011, 09:06 PM
The key to holding on to the refrigerant in any co2 system is to keep it cool, in two ways this is achieved, first by shutting down valves,fans,defrosts etc to evaporators to not add any more heat then secondly by cooling it with a small fractional horsepower condensing unit powered from an essential supply with generator backup. if these systems are in place all refrigerant can be kept in the system indefinitely.

Janaina
16-06-2011, 11:20 AM
Hello!

I am researching CO2 refrigeration in supermarkets around the world in the hope of creating an online map of CO2 supermarkets and was eager to gather information from the users of this forum. Also, any advice on other information sources would be greatly appreciated!

Thanks for you consideration!

headgasket
19-06-2011, 07:24 AM
Last week I had two Co2 gas leaks in two different stores, one on a straight coupler on top of a HT case the other on a tee reducer in a warehouse, personally I like working on CO2 systems I think it will weed out the the crap engineers in the trade by natural selection ( bang), my only worry is the fittings on the pipe work, the straight coupler that failed was 7/8” what a mess, luckily no one was hurt, both of these incidents were kept out of the news. The H&S investigator from this well know supermarket chain, said that the pressure in the pipe work runs at a max of 10 Bar, when informed it was 30 Bar plus was surprised.

750 Valve
19-06-2011, 09:54 AM
They need to stop using mechanical pipe jointing or stop using Co2 if they MUST use that jointing method!

In all seriousness the money saved over the life of a supermarket JUST by using Co2 as the refrigerant far outweighs the cost to install the system properly, design engineers at major chains need to pul their heads in and realise this. Thankfully we won't see too much transcritical down our way so stupid decisions such as using mechanical jointing will not have any affect down here.

mad fridgie
19-06-2011, 10:25 AM
They need to stop using mechanical pipe jointing or stop using Co2 if they MUST use that jointing method!

In all seriousness the money saved over the life of a supermarket JUST by using Co2 as the refrigerant far outweighs the cost to install the system properly, design engineers at major chains need to pul their heads in and realise this. Thankfully we won't see too much transcritical down our way so stupid decisions such as using mechanical jointing will not have any affect down here.
What savings are made over the life time just by using CO2, because it is not power.?

Plank!
19-06-2011, 12:26 PM
They need to stop using mechanical pipe jointing or stop using Co2 if they MUST use that jointing method!

In all seriousness the money saved over the life of a supermarket JUST by using Co2 as the refrigerant far outweighs the cost to install the system properly, design engineers at major chains need to pul their heads in and realise this. Thankfully we won't see too much transcritical down our way so stupid decisions such as using mechanical jointing will not have any affect down here.

The Vulcan Lock-Ring fittings we use on CO2 are essential to many of the jobs.
We've used them extensively on under-desk cooling projects with CO2 and seamless stainless steel tube.

They are certainly not fitted for cost reasons - we use the same coded welders/pipe fitters to install the lock ring fittings - some of the larger 3" couplings cost around 350 each and must be fitted using the correct tooling and hydraulic pump set. Doing the same joint, with the same men using a TIG welder would cost less in time and component cost.

That said, installing pipework in a riser containing 4000+ data cables, in a trading bank, excludes the use of any welding plant. Likewise when we use pumped CO2 to cool blade servers in data halls.
Once the joint is fitted - assuming the pipe specification is correct - they do not leak!
They form a permanent joint, capable of the same loads as a welded joint. Like a welded joint they have to be cut out to remove them.
Please don't confuse these joints with flare nuts or other mechanical joints that can loosen with time.

My understanding is that the joint failed due to a material problem (tho I only have that on hearsay) the same kind of failure could affect a butt-weld or socket welded joint.

The mere fact that the joint was of a mechanical nature was not the reason for the failure.

regards
Steve

padraic
19-06-2011, 04:11 PM
What will happen if I do not pump down a CO2 evaportor prior to venting the CO2 from the evaporator?

I have been told it will go bang and I may even die :eek:
Is this true?

i have to say fareplate of you for asking.. the day you stop asking questions your not going anywhere and i dont care how stupid a question is i will still ask... 16 year as frig engineer myself and a day doesnt go by i dont question something.. doing co2 nearly a year now and loving it and done all the courses but no matter what course you do there is still of alot of learning... good man yourself and keep asking..!

as they said above..pumping down properly is the trick.. close your liquid and keep you akv valve open go for a cup of tea and when you come back close suction and vent vapour.. vac it when finished and open suction first then liquid and away you go..!

joe-ice
19-06-2011, 05:18 PM
what happens if its the main liquid line you have to carry out a repair on .are you venting the entire charge? (assuming theres no backup cooling on the receiver and the repair takes couple hours)

750 Valve
20-06-2011, 11:23 AM
What savings are made over the life time just by using CO2, because it is not power.?

Refrigerant cost!

R404a is set to spiral in cost, even R134a will be expensive, consider annual leakage rates and it makes sense just as a refrigerant based on cost.

750 Valve
20-06-2011, 11:28 AM
The Vulcan Lock-Ring fittings we use on CO2 are essential to many of the jobs.
We've used them extensively on under-desk cooling projects with CO2 and seamless stainless steel tube.

They are certainly not fitted for cost reasons - we use the same coded welders/pipe fitters to install the lock ring fittings - some of the larger 3" couplings cost around 350 each and must be fitted using the correct tooling and hydraulic pump set. Doing the same joint, with the same men using a TIG welder would cost less in time and component cost.

That said, installing pipework in a riser containing 4000+ data cables, in a trading bank, excludes the use of any welding plant. Likewise when we use pumped CO2 to cool blade servers in data halls.
Once the joint is fitted - assuming the pipe specification is correct - they do not leak!
They form a permanent joint, capable of the same loads as a welded joint. Like a welded joint they have to be cut out to remove them.
Please don't confuse these joints with flare nuts or other mechanical joints that can loosen with time.

My understanding is that the joint failed due to a material problem (tho I only have that on hearsay) the same kind of failure could affect a butt-weld or socket welded joint.

The mere fact that the joint was of a mechanical nature was not the reason for the failure.

regards
Steve

The fact that there have been several mechanical joints fail to date to me, means they should be looked at for appropriate use of this method. Weld the pipe or don't use Co2 at those pressures, install a low pressure pumped system instead. There are engineering solutions to most problems, I am a big fan of using Co2 but you have to learn from mistakes.

Unfortunately for the industry there is only speculation surrounding the failures so we can only have a somewhat uninformed opinion, here is hoping they write a white paper or something similar on it for others to learn from.

mad fridgie
20-06-2011, 11:38 AM
Refrigerant cost!

R404a is set to spiral in cost, even R134a will be expensive, consider annual leakage rates and it makes sense just as a refrigerant based on cost.

Thank you, CO2 should only be few cents a kg

Plank!
20-06-2011, 01:24 PM
The fact that there have been several mechanical joints fail to date to me, means they should be looked at for appropriate use of this method. Weld the pipe or don't use Co2 at those pressures, install a low pressure pumped system instead. There are engineering solutions to most problems, I am a big fan of using Co2 but you have to learn from mistakes.

Unfortunately for the industry there is only speculation surrounding the failures so we can only have a somewhat uninformed opinion, here is hoping they write a white paper or something similar on it for others to learn from.

I think we may have to look at quality control.
If we built the same system with welded steel or stainless steel pipework, we would be required to carry out NDT testing of 10% of the welded joints.
As the same rules do not apply to the mechanical / lockring joints we are more than likely missing the chance to find material defects.

I like the lockring joints only because they can be fitted without hot-work permits or risc to data in cable risers or data halls. I'd rather see all CO2 systems installed using TIG welded stainless steel pipework, sadly most customers will not wear that expense.
My work is industrial, CO2 and Ammonia, so my experience is with steel/stainless steel rather than copper. I've never used lockrings on copper pipe.

CJG21
23-06-2011, 02:05 PM
Thank you, CO2 should only be few cents a kg

We are paying up to 3/kg, it certainly isn't as cheap as people think

sundancekid1980
14-07-2011, 08:59 PM
The Vulcan Lock-Ring fittings we use on CO2 are essential to many of the jobs.
We've used them extensively on under-desk cooling projects with CO2 and seamless stainless steel tube.

They are certainly not fitted for cost reasons - we use the same coded welders/pipe fitters to install the lock ring fittings - some of the larger 3" couplings cost around 350 each and must be fitted using the correct tooling and hydraulic pump set. Doing the same joint, with the same men using a TIG welder would cost less in time and component cost.

That said, installing pipework in a riser containing 4000+ data cables, in a trading bank, excludes the use of any welding plant. Likewise when we use pumped CO2 to cool blade servers in data halls.
Once the joint is fitted - assuming the pipe specification is correct - they do not leak!
They form a permanent joint, capable of the same loads as a welded joint. Like a welded joint they have to be cut out to remove them.
Please don't confuse these joints with flare nuts or other mechanical joints that can loosen with time.

My understanding is that the joint failed due to a material problem (tho I only have that on hearsay) the same kind of failure could affect a butt-weld or socket welded joint.

The mere fact that the joint was of a mechanical nature was not the reason for the failure.

regards
Steve

Tell me steve, what happens when one fails? how does the service engineer replace it? It is more time consuming and flawed than brazing. Hence all the current changes etc in Tescos.Correct me if I am wrong but from what I understand Tescos have now put their future CO2 store installations on hold, with these failures playing no small part in their decisions. Proof of this is the fact that Sainsbury's have experienced none of these kind of failures (Brazing), and are full steam ahead in CO2 installations!

coolhibby1875
18-07-2011, 10:26 PM
Last week I had two Co2 gas leaks in two different stores, one on a straight coupler on top of a HT case the other on a tee reducer in a warehouse, personally I like working on CO2 systems I think it will weed out the the crap engineers in the trade by natural selection ( bang), my only worry is the fittings on the pipe work, the straight coupler that failed was 7/8” what a mess, luckily no one was hurt, both of these incidents were kept out of the news. The H&S investigator from this well know supermarket chain, said that the pressure in the pipe work runs at a max of 10 Bar, when informed it was 30 Bar plus was surprised.

So engineers that dont or haven't worked with c02 are crap engineers!! i know loads of folks working on these systems who arent engineers or never will be engineers, and by the sounds of a few have posted on this thread!!, the problem seems you get a couple of people who change a fan on a cabinet that runs on co2 and hay ho they are the dogs bollocks and are now co2 experts, and whilst they are at why not ask for another 1.50 an hour!!