Oil Lines

[Blueboy]

Today I was told to use a 1/4 copper line for the oil preasure conection between the compressor and the oil switch instead of the plastic make your own line stuff used on the rest of the plant switches. I ask why and was told the oil line needs to be a bigger bore and false trips will occur if I use the plastic. I just wondered if any new if this is true

[chemi-cool]

Nonsense, I use copper cap tube and never had any problems.

Chemi

[Andy]

Hi Blueboy welcome to RE.

1/4" copper for oil lines, well I suppose the bigger bore will give a more accurate reading, a small line may block, but I would say this choice is down to personal preferance.
I use make up lines, but the bore is 8mm, I would find on discharge lines a bit of fluttering on recips with this line, sometimes it is advisable to fit a small (1mm/40thou") oriface to discharge pressure couplers, and on JE Hall compressors I have even seen orifaces in suction pressure coupler lines.

Kind Regards. Andy

[chemi-cool]

Hi Andy.

For the record only. Danfoss used to make oil differential pressure controls ( and also other companies) that come with fixed cap tubes.

Cap tubes with 1/4 nuts are sold for connecting pressure controls.

Because there is no flow in them, I dont see how they can get blocked.

Have you ever had a problem with blocked cao tube connected to a pressure control?

Chemi

[Andy]

Hi Andy.
Have you ever had a problem with blocked cao tube connected to a pressure control?

Chemi

None for certain, but I could see it happening on ammonia with carbonised oil.

Why did danfoss stop making the oil diff switch with capillaries, cost if a capillary broke, or maybe that were blocking just a thought. Anyway capillaries are not the thing for Industrial Refrigeration with all the vibration that goes on.

Kind Regards. Andy

[chemi-cool]

[QUOTE=Andy] Anyway capillaries are not the thing for Industrial Refrigeration with all the vibration that goes on.
QUOTE]

Hi Andy.

Too much vibrations? check the balance. There is no need for big machines to vibrate.

Something must be wrong.

Chemi

[Andy]

Hi Chemi
vibration is probably not the best term, resonance would be better. With larger plant comes possible operation at part load. All compressors run less balanced at part load, screw or recip. With a recip you will also have gas pulsation at capacity reduction.
From my experience all large scale industrial refrigeration plant has guage lines fitted in either solid hydralic tubing, flared copper/stainless tubing or flexible connections, made out off hydralic hosing or refrigerant grade high pressure hosing.

Kind Regards. Andy.

[chemi-cool]

Hi Andy.

I had once a problem of resonance in a large Melons cooling cold storage.
there were four 40 HP carrier compressors and pipes used to break there all the time. After sitting there and watching the plant and how it works, I was amazed by the " humming and busing" of the whole steel construction that held the compressors.

What I did there was to change the rotation direction of every other compressor and change the springs under the compressors to special rubber plates that absorb vibrations ( tight connection) and the plant went almost completely quite.

I should have used also flexible pipes but that will be installed next time.

Chemi

[Peter_1]

Just picked up this old thread:

As Chemi said, there is no flow in the lines to every pressure switch.

But futhermore, have you looked inside the 1/4 HP connection of some brands? They sometimes have a restriction with a screw fitted in it. Some sort of orifice/restriction.

This is to avoid that the pulsation of the pistons should brake the bellow in the switch, so a smaller tube will do exact the same.