P trap correct installation

[simon sheppard]

Hi,

Im currently installing some large DX comms room units.

I have a riser lift of about 8m to 10m, and have been specified to install p traps and oil traps for the remote condenser pipe work.

Can any one specify the correct way of performing this, as several ways have been brought to my attention.

Basically i have a 8 to 10m riser and i would like to know whether i put traps on both discharge and liquid? p traps at the bottom and oil traps half way up??

people are confusing me on the correct way?????


would appreciate some ones advice??


thank you

[Brian_UK]

If you want to get really technical have a look at this pipe guide from McQuay, PDF

http://www.mcquay.com/mcquaybiz/literature/lit_systems/AppGuide/AG_31-011_120407.pdf

[hyperion]

Great information Brian, thanks.

[chemi-cool]

Thanks Brian for a useful link.

I saw somewhere[cant remember where], from the bottom of the U trap, 3\8 tube going up to the top of the riser. For my my question how does that help, i was answered that the pressure in the small tube is a bit higher then the large suction pipe and it takes the oil much better up.

Of course a good oil separator is required.

[coolhandlew]

I was told by Emerson for a similar job; traps on discharge pipework at bottom of all rises and 6M intervals.
For example, the system i installed was thus; the pipework ran under computer floor and then up the internal wall for 2M (TRAP INSTALLED AT BOTTOM), pipework exited through wall and ran laterally along wall for 12M where it then ran up the wall (TRAP INSTALLED AT BOTTOM). There was then a rise of 10M to roof level (TRAP INSTALLED 6M FROM BOTTOM).

[Josip]

Hi, simon sheppard :)

check this link ... maybe you can find some good info for you....

http://www.refrigeration-engineer.com/forums/showthread.php?t=4392

also, searching RE forums maybe you can find more information ...


Best regards, Josip :)

[nike123]

While we are at traps, what would be better, trap made of fittings with smallest dimensions as possible like with 2 45° and one 90° elbow or trap made with bending tools with required minimum bending radius? And what are aceptable dimensions?
Is it same for normal and inverted trap at top of riser?

[Brian_UK]

I would have thought that a pulled bend would be better due to the reduction in pressure drop.

[rk tigere]

Thanks Brian for a useful link.

I saw somewhere[cant remember where], from the bottom of the U trap, 3\8 tube going up to the top of the riser. For my my question how does that help, i was answered that the pressure in the small tube is a bit higher then the large suction pipe and it takes the oil much better up.

Of course a good oil separator is required.
:) Hi Simon I also read in a Trane Manual excerpt where they pointed out that when using unloading compressors you use this double riser system on the discharge line .The larger pipe goes up to the top of the hot gas line through an inverted trap; so that during the low load conditions the oil in this larger riser will not enter into the smaller riser which will be solely carrying the gas flow.:):) I hope this helps !

[nike123]

..............................

[rk tigere]

:D.....oooh I see thanks for the correction Nike123

[nike123]

:D.....oooh I see thanks for the correction Nike123
It was misunderstanding from my part!;)

But smaller riser will not carry only gas. It will still carry oil with refrigerant and with sufficient speed at low load condition because trapped oil in P trap act as plug in bigger pipe.
Problem with this is that if it is lot of P traps (and they are not small as possible), high amount of oil is trapped in these P traps during low load condition (and not returning in compressor).

http://books.google.hr/books?id=gniJE5lK0YAC&pg=PA493&lpg=PA493&dq=refrigeration+double+riser&source=bl&ots=Bh2xAGxYYS&sig=GkrmfHGrPR27tu8N6TPpoYCobm8&hl=hr&ei=D7iYS-eDA8mi_Ab2k52oCw&sa=X&oi=book_result&ct=result&resnum=5&ved=0CCIQ6AEwBA#v=onepage&q=refrigeration%20double%20riser&f=false

[nike123]

Thanks Brian for a useful link.

I saw somewhere[cant remember where], from the bottom of the U trap, 3\8 tube going up to the top of the riser. For my my question how does that help, i was answered that the pressure in the small tube is a bit higher then the large suction pipe and it takes the oil much better up.

Of course a good oil separator is required.

I don't see how pressure in small pipe cold be higher with "connected vessels" (what is correct term?) law in mind.
Only capillary action comes to my mind.
http://www.fas.harvard.edu/%7Escidemos/NewtonianMechanics/CapillaryAction/CapillaryAction04.jpg

[nike123]

I would have thought that a pulled bend would be better due to the reduction in pressure drop.

I have read somewhere, that with arrangement like this:

http://i39.tinypic.com/333bifm.jpg

oil in trap is better mixed and carried with refrigerant because of turbulence in sudden change in direction with 90° short radius elbow.
Pressure drop could be compensated with bigger lines diameter at horizontal lines.
Also, that way oil in trap is minimal as much as it could be (and cannot be "minimalier":p) as oppose to this arrangement:
http://i50.tinypic.com/307yx5t.jpg

Also, I would like to know equivalent length of standard P traps.

[nike123]

Here is what I found on that subject:
http://i42.tinypic.com/34ik4y1.jpg
http://i43.tinypic.com/w2hhzq.jpg
http://i39.tinypic.com/slqm15.jpg
http://i42.tinypic.com/drbm20.jpg
http://i39.tinypic.com/2yo7l9v.jpg
http://i42.tinypic.com/s612mh.jpg
http://i43.tinypic.com/23u79ra.jpg
http://i42.tinypic.com/210x349.jpg

[Brian_UK]

Good set of images, thanks.

[Josip]

Hi, nike123 :)

really good one, thanks for efforts,

waiting now for original poster;)

Best regards, Josip :)

[chemi-cool]

Good info Nike, I will give it a try on my next installation.

Too bad copper is not transparent, I would like to see how it works inside.