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What do DDC pump springs do?

post #1 of 15
Thread Starter 
there are 4 springs within the DDC...........


attachment.php?attachmentid=207510&stc=1&d=1303788257

attachment.php?attachmentid=207511&stc=1&d=1303788257

attachment.php?attachmentid=207512&stc=1&d=1303788257
post #2 of 15
Interesting, looks like you have one of the volume compensator pump varieties. Most DDC pumps do not have the lowere compensator portion. I believe those only came in the mac G5 computers, but I've never seen one myself.

If it is a compensator, they are supposed to help smooth flow by giving a flexible cushion of sorts.

You might have something different there though..I'm not sure never having one before...
    
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post #3 of 15
Thread Starter 
Quote:
Originally Posted by Martinm210;13273618 
Interesting, looks like you have one of the volume compensator pump varieties. Most DDC pumps do not have the lowere compensator portion. I believe those only came in the mac G5 computers, but I've never seen one myself.

If it is a compensator, they are supposed to help smooth flow by giving a flexible cushion of sorts.

You might have something different there though..I'm not sure never having one before...

I don't know where it originally came from. It's a second hand pump.

What does "volume compensator pump" "lowere compensator" mean? confused.gifconfused.gifconfused.gif

This pump is thicker than my old PMP-400, and most third party tops work. But the length of screws is a problem --- I don't have appropriate screws.

What else does this pump feature?
Edited by c14c13 - 4/25/11 at 9:19pm
post #4 of 15
Quote:
Originally Posted by Martinm210;13273618 
Interesting, looks like you have one of the volume compensator pump varieties. Most DDC pumps do not have the lowere compensator portion. I believe those only came in the mac G5 computers, but I've never seen one myself.

If it is a compensator, they are supposed to help smooth flow by giving a flexible cushion of sorts.

You might have something different there though..I'm not sure never having one before...

It looks like that to me as well. From what I understand though is that the diaphragm can split and leak though and was a problem with these pumps.

It's this correct? http://www.oberread.com/laing_ddc_exp.htm

Also this is the supposed benefits:


Benefits of the volume compensator expansion chamber

Pulsation/Vibration Damper
Pulsation dampers are normal applied immediately downstream of reciprocating, positive displacement (PD) pumps. With each pulsation comes a resultant pressure peak. These pressure peaks typically aren’t desirable in a given piping system, therefore the need for pulsation dampers. Generally, the application of pulsation dampers is based on one or more of the following criteria: * to prevent potential pipe hammer / vibration * to reduce the load on the pump itself * to minimize or eliminate pulsations for the benefit of downstream instrumentation

Surge Absorber
Pressure problems in cooling systems can occur on pump start-up or shut-down when a corresponding change in velocity introduces a rapid pressure rise. Besides the nuisance of pipe hammer, these surges can cause considerable damage to cooling lines, O-rings and other seals, etc. Surge absorbers take into account system pressures, volumes, acoustic velocities, and flow regimes.

Thermal Expansion Compensator (aka Blow out prevention)
A volume of liquid trapped in an enclosed cooling system has the potential to expand with a corresponding rise in temperature. Volumetric expansion in an enclosed system necessarily means that the pressure in that line must also rise. Thermal Expansion Compensators capture thermal expansion volume and limit the rise in pressure to prevent a catastrophic blow out.

Edited by Forsaken_id - 4/25/11 at 9:22pm
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post #5 of 15
Thread Starter 
very useful info, Forsaken_id, thx.

Hahaha, looks like I got a nice baby. hmmm, even if it is Martinm210, he never owned this one...

I'd rather show off....
Edited by c14c13 - 4/25/11 at 9:41pm
post #6 of 15
I have two without the compensator, but they have been modified and removed prior to my ever seeing the workings of the compensator itself.

I'm not entirely sure what sort of application those would be of benefit, but DDC pumps are used in a lot more than watercooling, so there is probably something out there that needs the smoothing of flow I guess.

I found this old snip from one of the old brochures:
volumecompensator.jpg

When testing these pumps, you do see tiny little bumps in pressure and flow now and then, so I imagine the compensator would just absorb those bumps and make the flow and pressure more smooth. This is probably something for the medical field I would guess, but Mac for some reason decided to go with them as well in the G5s.

I want one...not that it'll help performance any, but just to complete my little DDC historical museum..lol!
Edited by Martinm210 - 4/25/11 at 10:08pm
    
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post #7 of 15
I ordered one of these DDC-3.2VC's from diyinhk's ebay store. He has a few more left if I'm not mistaken.

I figured that it doesn't hurt to have the Compensator and if needed, I can always remove it and plug up the channels leading from the pump to the chamber.

Is this a black or blue impeller? I believe I ordered a blue one...

*Edit* I just had a thought, would that chamber below the pump aid in keeping the PCB cooler than if it were just covered by mounting foam?
Edited by whiteslashasian - 4/26/11 at 9:00am
    
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post #8 of 15
Quote:
Originally Posted by Martinm210;13274307 
I'm not entirely sure what sort of application those would be of benefit, but DDC pumps are used in a lot more than watercooling, so there is probably something out there that needs the smoothing of flow I guess.

aquariums and fountains would be my guess, you want a steady flow of water if you are going to hear the water running
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post #9 of 15
The G5 self containing WCing system had to be pressurized to ensure that the performance never dropped off from day one to about seven years later. No matter what cooling loop anyone builds, permiation will allow the loop to under perform in time without topping off the RES.

A pump with a volume compensator allows the loop to have a constant internal pressure to the outside pressure. The four springs are rated to ensure the pressure plate keeps things near equal. Over the course of time, the DDC-1VC will eventually run out of compensation fluid reserve.

As for owning a DDC-1VC pump, they are bigger, bulkier, and run a salted saline coolant solution. If the pumps were run in this fluid and then parts pulled, chances are, that coolant solution exposed to the air will become corrosive and contaminate your loop in a short time. There are plenty of G5 owners who have had leaks with their water blocks and the nasty corrosion taken place. It's worse than a bad vehicle full of rust. The G5 WCing loop has nearly all aluminum and plastic parts with the pump's stainless cup impeller. Taking that pump and placing into our loops with copper will be a dreaded experience.

The DDC-1VC pumps that have been contaminated with the salted saline coolant can never be flushed well enough since the coolant solution impregnates the pump plastic over time. Many of the leaks are with the pump gaskets or the water block gaskets. The salted saline coolant somehow manages to leak around these gaskets over time with the loop under pressure and under thermal loads.

Personally, I would NEVER use a DDC-1VC that was pulled from a G5 period.

See this link for the horrors of the G5 corrsion leaks ...
http://rknochenmuss.ch/G5leak/G5.html

5305771588_ba92e824aa.jpg

powermac-g5-coolant-leak.jpg
Edited by bmaverick - 4/26/11 at 11:11am
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post #10 of 15
I'll give it a whirl, won't have my loop put together until I build a brand new system though...

Assuming the pump is well cleaned, o-ring replaced with a high quality one, and an anti-corrosion additive is used, I think that should help to minimize the complications...
Edited by whiteslashasian - 4/26/11 at 7:53pm
    
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