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Terp
14-06-2006, 09:08 PM
I'm looking for info on plants that use gas driven recirculation, like the Phillips controlled pressure receiver system. Is anyone here currently operating one of these? I'd like to find some examples of who's using them, how old they are, what tonnage, etc. Also, I would appreciate your thoughts on the advantages and disadvantages vs. pumps for liquid overfeed.

Thanks!

US Iceman
15-06-2006, 01:09 AM
Hi Terp,

Welcome to the RE forums.

The gas driven pumper systems have many different configurations, i,e., Single drum, dual drum, low pressure receiver and controlled pressure receiver to name a few.

The constant pressure and thermal cycles the transfer drums go through can be quite high. My opinion is this is a problem from a mechanical integrity standpoint.

The biggest problem with these are the check valves. The check valves have on occasion broken open and create quite a mess with an ammonia release.

The second issue is the gas driven aspect of these systems. Due to the need for high pressure gas to displace the liquid the discharge pressure will have some lower limit to maintain a constant circulation rate. If the discharge pressure decreases too low the transfer cycle can slow down.

On the ones using a CPR (controlled pressure receiver) the CPR pressure will usually limit the reduction in discharge pressure.

You do not have any of these problems with mechanically pumped systems.

The worse problem with a mechanically pumped system is the pump selection. Too many pumps are selected with little regard for the net positive suction head requirements and how the system curve is affected by the pump curves.

Myself... I will take a mechanically pumped system anytime over a gas driven system.

bruceboldy
15-06-2006, 01:27 AM
I agree with the entire work of iceman
used both systems for many yers, I would always go back to the pump systems.

There are papers on the subject, about efficiency of one over the other, but the pumps beat the numbers every time

have become quite a fan of the sealed opumps on the market today over the open style also. The prices are much closer to each other then they used to be a few years ago.

Bruce

US Iceman
15-06-2006, 02:27 PM
There has been a big "push" to use hermetic pumps in the last few years to get away from pump seals.

The hermetic pumps are fine if they are installed properly and... if they do not experience cavitation. This is hard on the carbon bearings.

I also think the hermetic pumps may require more NPSH than the open pumps for the same impeller size and speed.

Either way, the critical task to determine the NPSHA is greater than the NPSHR of the pump.

Oh, make sure the hand expansion valves are not too far open also.;)

Terp
16-06-2006, 07:10 PM
I understand that from an efficiency standpoint, especially as overfeed increases, that the pumps beat the gas transfer systems. But there's still a bunch of these gas pumpers operating, aren't there? Some mechanics seem to prefer them, but maybe they're just old. :rolleyes:

Iceman - can you point me to some info on problems with these systems? Info seems sparse on the subject in general. Thanks!

Josip
16-06-2006, 08:14 PM
Hi, Terp

take a look on this drawings, showing one still working plant here in my country.

http://www.refrigeration-engineer.com/forums/attachment.php?attachmentid=831&d=1142020983
http://www.refrigeration-engineer.com/forums/attachment.php?attachmentid=832&d=1142020999

Anyhow I agree with guys regarding pump recirculation. Gas driven recirculation is not cheap because you need a lot of controls.

Best regards,

Josip :)

US Iceman
16-06-2006, 08:24 PM
But there's still a bunch of these gas pumpers operating, aren't there?

Quite a few unfortunately. I'm not a big fan of these, but then I don't sell them either.;)


...can you point me to some info on problems with these systems? Info seems sparse on the subject in general.

I have not seen anything either. The usual stuff in sales literature, but never any information about problems. I guess this means there are none.:rolleyes:

If you want... send me your contact info in a PM and I can give you a call to discuss.

Terp
20-06-2006, 09:45 PM
Thanks, Josip! Nice drawings. Appears to be in the "Liquid Line Transfer" style, based on a paper I have from James Wright. The economizer seems to be an update to the original. Can you translate "Zvijezda tvornica ulja" for me? Google doesn't seem to do Croatian!

Josip
20-06-2006, 10:18 PM
Hi, Terp :)

Zvijezda(Star) tvornica(Factory) ulja(Oil)
(edible oil please ;))

Star Oil Factory

Best regards,

Josip :)

Terp
21-06-2006, 11:01 PM
Zvijezda(Star) tvornica(Factory) ulja(Oil)
(edible oil please ;))


What's cooking, Josip? Soy? Rapeseeds? Sunflowers perhaps?

:)

US Iceman
22-06-2006, 12:37 AM
Hi Josip,

Terp asks a good question. How is refrigeration used to make edible oil? What type of heat exchangers are used and how low of temperature is required?

Thanks,
US Iceman

Josip
24-06-2006, 11:19 AM
Hi, guys :)


What's cooking, Josip? Soy? Rapeseeds? Sunflowers perhaps?

This is kind of factory secret. I do hope that oil is not coming from GMO seeds ;) I think they use all of them to make a different oil, but mostly of sunflower, at least on the bottle is sunflower picture :rolleyes:


Terp asks a good question. How is refrigeration used to make edible oil? What type of heat exchangers are used and how low of temperature is required?

Yeah, sorry I made mistake. That factory produce edible oil, but from that oil they also produce a different kinds of margarine and for that process they need refrigeration plant.

Here are something more about margarine:

http://www.margarine.org/historyofmargarine.html

http://www.newstatesman.com/200003270047

Here you can see more or less complete process.

http://www.naturalandtasty.co.uk/margarine_process.htm

Extrusion machine is pipe in pipe ammonia cooler and depending on amount of added hydrogen before, cooling temperature and time you can produce margarine with diffrent melting points (32-44C or higher) depending on use.

For food we can use only types with melting points from 32C - 36C, otherwise we cannot digest it ;) . To make sweets we use types with higher melting temp due to cooking process under high temperatures around 200C.

Best regards,

Josip :)

US Iceman
24-06-2006, 05:19 PM
Hi Josip,

Thanks for the information. It sounds like scraped surface heat exchangers are being used.

Josip
27-06-2006, 11:56 PM
Hi,


Thanks for the information. It sounds like scraped surface heat exchangers are being used.

Yes,

inner pipe is actually a pump pipe. Inside is a rotor with some kind of blades for homogenisation of margarine.

There is another name for those machines used by workers in factory but...I do not remeber that (working there before 10-11years :) )

Best regards,

Josip :)

Andy
28-06-2006, 09:48 AM
Hi,



Yes,

inner pipe is actually a pump pipe. Inside is a rotor with some kind of blades for homogenisation of margarine.

There is another name for those machines used by workers in factory but...I do not remeber that (working there before 10-11years :) )

Best regards,

Josip :)

wouldn't be a Gersternberg and Agger by any chance:)

We fitted two drums on a Grasso 10 plant, just about the time I started with Cross Refrigeration.

I have two spare secondhand plants from the same customer sitting in our yard at work, both perfectly good, but manual control and not compatabile with modern automated production lines;)

Kind Regards Andy:)

Terp
12-07-2006, 06:15 PM
Jossip -
Thanks for the margarine info! Very funny. Makes me want to run out and eat a tub right now! :D