vibration loops????

[nickjh]

Vibration loops for small high pressure HC lines????

At first i thought these were just a rubber damper but i am beggining to thing these may be someting bent into the pipe itself. Does any one know which of the two is correct and anywhere where i can see an example of these.

[Toosh]

Hi I think a diagram would help coz I ain`t got a clue what you talking about

[US Iceman]

The only place I have heard this term was in regards to the small capillary off of pressure switches.

When a pressure switch is installed you unroll the capillary away from the switch bellows, just a small distance.

Then at the other end of the capillary by the flare connection (or what ever the connection is) you again unroll the capillary away from the middle of the capillary.

What you should have as an end result is a nice round coil spring made from the capillary in between the pressure switch and the connection point for the pressure switch.

This vibration loop allows the capillary to move without breaking. You need to space out the coils on this little "spring" so that the capillary does not rub against itself anywhere.

I have seen some use silicone caulking on this "coil" to keep the coil separated also.

[taz24]

Vibration loops for small high pressure HC lines????

At first i thought these were just a rubber damper but i am beggining to thing these may be someting bent into the pipe itself. Does any one know which of the two is correct and anywhere where i can see an example of these.


They are used a lot on small commercial systems. They are used on pipes 1/4 and 3/8, only the small stuff.
They are simply a coil put into the line (most often as part of a bend) to alow the comp to vibrate.
They are used mainly to connect to pressure switches but are often put in the discharge line between comp and cond.
http://www.astra.dp.ua/upload/ca/1223_s1.jpg http://www.heatcraft.com.au/products/images/he_kirby.jpg


They are used because they are cheaper than vibration eliminators (anacondas)

Cheers taz.

[US Iceman]

Taz,

I see what you are describing and I have seen a lot of those but... my impression is these "loops" as shown in the pictures you posted are more for expansion control.

Here's my thought on this. As copper warms and cools, it expands and contracts. If the piping/tubing is ran straight from point to point, it is fixed. Any expansion and contraction occur between two fixed points in a straight line. In this case, something will eventually break.

If you notice the piping in the pictures, the tubing is ran in several directions, horizontal, vertical, and another change in direction.

I think what you are describing is for flexibility in the tubing to prevent leaks caused by expansion and contraction, not vibration.



...vibration eliminators (anacondas)


The vibration eliminators reduce some of the transmitted energy. But I think these are more prevalent to "eliminate pipe movement" when a spring mounted compressor is used.

I guess what I'm trying to say is, I think there are several mechanisms we need to address; vibration, flexibility, expansion/contraction, and restraining pipe movement.

But then again... That's just what I think.;)

[taz24]

Taz,

I see what you are describing and I have seen a lot of those but... my impression is these "loops" as shown in the pictures you posted are more for expansion control


But then again... That's just what I think.;)

You could be right. I'd not given it much thought untill now:).
I assumed they dealt with the vibration and expansion, both together part and parcel of the same problem. I'd not isolated expansion from vibration and you do have a point.

On larger systems I have seen elbows fail due to constant expansion and contraction from hot gas defrost gases being sent down them.

Cheers taz.

[US Iceman]

On larger systems I have seen elbows fail due to constant expansion and contraction from hot gas Defrost (http://www.refrigeration-engineer.com/forums/glossary.php?do=viewglossary&term=14) gases being sent down them.


One thing for sure is... Piping systems are just as much an art as a science. Peter talked about this in one much earlier post about oil return in parallel compressor systems.

Hot gas systems can be difficult. Expansion and contraction on a frequent and regular basis is a sure recipe for things to go wrong. And these are the easy things!

[The MG Pony]

when I make small condencing unites I all ways put in one larg radious loop to help minimize vibration and allow the compressor some woble ability at start up, just due to its vibration dampening it allows for thermal contraction/expansion.

[US Iceman]

...put in one large radius loop...


OK, but... you have to be careful of the orientation of the loop. A pipe loop in a horizontal plane is OK, but a pipe loop in a vertical plane could create a trap. :eek:

This may have unintended consequences at a later time.:o

[The MG Pony]

on the discharge ;) on such small systems the gas pulsations and velocity keep things moving along nicely, that and the heat keeps things nice and runny.

Suction lines a serpentine some where along the route tends to do nicely for flexibility.

larg is not that big when dealing with small systems, say to the order of 5 or so inch. depends on how much kick the compressor has and space avalible.

[US Iceman]

I'm just offering general comments for things to be careful with. One statement made does not apply to every refrigeration system.

I have seen liquid form in discharge lines and oil pockets created because the piping did not account for these.

Size does matter, as does the application, operation, and location of the equipment. I just don't want anyone to take a general comment and think it applies to everything. That is a gross assumption.

[Brian_UK]

One thing with these 'anti-vibration' type loops is that they should be in the correct orientation in relation to the compressor rotating shaft.

Now, unfortunately, I can't for the life of me remember which way it should be.

[The MG Pony]

Ah K good point US, I am very guilty of expecting most to use common sense <_< seems to be my down fall most the time too!

[US Iceman]

Now, unfortunately, I can't for the life of me remember which way it should be.


Parallel to the crankshaft and anchored at the point away from the compressor (downstream on the discharge side, upstream on the suction side).

This is to limit the flexing of the piping, so that the absorber "absorbs" all of the movement, not the piping.

[US Iceman]

MG,

I don't think I would call it common sense. These are things someone has to learn and it's similar to experience.

Common sense is knowing not to stick your finger in a fire. Not knowing what fire is, is something different. That is where the experience becomes a factor.

This falls into the same category of "rules-of-thumb". One size does not fit all situations, so you have to know what the differences are.

This is why it is so hard to answer some questions here on RE. You have to keep digging for information until you get everything you need to answer.:cool:

[The MG Pony]

well by common sense I meant "Not all problems belong to one answere" every situation is unique to its self.

[nickjh]

US iceman, on loop size, is there any specific radius requirements??? Also not even sure if the requirement below applies or not in my situation, the piping im changing is to add a liquid reciever to the condensor. On the piping there is a High pressure relief valve, and a ball valve/shrader valve combination. Are these classified as cut outs???

The requirement im trying to meet is for a ship enviroment is as follows

"Small lines to fitted gauges, high-pressure and low-pressure cut-outs and oil safety switches and similar shall be installed with vibration loops to absorb vibration. Care should be taken where vibration loops are created on small lines to prevent pipes rubbing through, and to support the weight and forces developed in the vibration loop."

Is this relevant to me??

[US Iceman]

Hi Nick,



"Small lines to fitted gauges, high-pressure and low-pressure cut-outs and oil safety switches and similar shall be installed with vibration loops to absorb vibration. Care should be taken where vibration loops are created on small lines to prevent pipes rubbing through, and to support the weight and forces developed in the vibration loop."


That is exactly what I thought you were talking about. They way I used to do this was to have a 3" diameter for the loop, and the individual loops (of the same tubing or capillary) might stack up to about 2-3 inches so that the whole thing looked like a coil spring.

I adjusted the "coil" so that there was always gravity drainage from the top to the bottom. If the "coil" is installed horizontally, the tubing can trap liquids. It seems to me this was mentioned in one manufacturers instructions (for pressure switches).

You can also use some silicone caulking (on two sides of the coil 180° apart) to hold the coils apart and prevent them from running together. After the silicone dries, it acts as a rubber dampener to absorb vibration and maintain the spacing of the loops in the coil.

The term cut-out is what I would refer to as safety switches (typically pressure or temperature). high-pressure, low-pressure, oil safety, etc.

[momo]

You can also use some silicone caulking (on two sides of the coil 180° apart) to hold the coils apart and prevent them from running together. After the silicone dries, it acts as a rubber dampener to absorb vibration and maintain the spacing of the loops in the coil.
Rubber and "pitch" are often found around capillaries and pipes on A/C condenser splits where noise and vibrations are of concern, as are "unexplained" extensions and changes of direction of pipes... the only irritation is the manfacturers drive to "plant the trees" (pipes) too close to each other which makes servicing near impossible without MAJOR surgery! :mad: