Bond between PU and copper cooling pipes
Bond between PU and copper cooling pipes
(OP)
Hi there,
We have some cooling pipes where we continuously have leak problems.
Attached a picture to show the setup; A barbed stainless steel nippe - A PU pipe - A barbed copper nipple.
PU pipe has an outer diameter of 10 mm, inner of 8 and length of 55 mm. It goes on the the barbed fittings and we have clamps to tighten it.
We use ethanol at -25ºC (-13ºF) as a coolant. Sometimes when we mount we have leaks but we can solve this by playing with the clamps, the problem is when we cool down (in order to cool down we close the system and we can not see any more). Also we cool, back to room temperature, cool... so this also creates problems.
How can we fix this PU pipe not to have leaks?
We don't need to remove the PU pipe so we could use some permanent fixed solution. In my mind I think about gluing the barbed area with the PU pipe but I am afraid the ethanol will eat the glue.
Thanks
regards,
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We have some cooling pipes where we continuously have leak problems.
Attached a picture to show the setup; A barbed stainless steel nippe - A PU pipe - A barbed copper nipple.
PU pipe has an outer diameter of 10 mm, inner of 8 and length of 55 mm. It goes on the the barbed fittings and we have clamps to tighten it.
We use ethanol at -25ºC (-13ºF) as a coolant. Sometimes when we mount we have leaks but we can solve this by playing with the clamps, the problem is when we cool down (in order to cool down we close the system and we can not see any more). Also we cool, back to room temperature, cool... so this also creates problems.
How can we fix this PU pipe not to have leaks?
We don't need to remove the PU pipe so we could use some permanent fixed solution. In my mind I think about gluing the barbed area with the PU pipe but I am afraid the ethanol will eat the glue.
Thanks
regards,
http://files.engineering.com/getfile.aspx?folder=1...
http://files.engineering.com/getfile.aspx?folder=f...
http://files.engineering.com/getfile.aspx?folder=2...
http://files.engineering.com/getfile.aspx?folder=b...





RE: Bond between PU and copper cooling pipes
RE: Bond between PU and copper cooling pipes
https://www.swagelok.com/downloads/webcatalogs/en/...
RE: Bond between PU and copper cooling pipes
do you have a diagram or photo of the "barbs"
Some form of factory fitted braided hose with metal screw connectors would seem better than this rather homemade looking affair.
You're right to question the solubility of any glue.
A little search shows that the minimum temperature for PU varies quite a lot. -25C is quite low and the PU you're using could jst become quite brittle and hard and unable to cope with any vibration.
Why is this flexible coupling here? what level of forces does it have or vibration?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Bond between PU and copper cooling pipes
Example is Legris, but there are other brands (just like Swagelok is not the only competent mfg of OD comp fittings)
Make sure the o rings are good for cold and with ethanol. Otherwise, Swagelok, but with an ID insert to give the ferrules something to deform against- same as is required when using PVC tubing with OD compression fittings.
RE: Bond between PU and copper cooling pipes
Bimr, in a first look it seems Swagelok fittings are too long, we only have 55mm and we need two of them (copper-PU and PU-SS), I'll check in detail
LittleInch, stainless steel and copper have an OD of 8, this is also the inner of the PU. I don't have a photo of the open system, but look like something like this:
http://www.brewshop.co.nz/media/catalog/product/ca...
The clamps go at the base of the fittings (not right on the barbed part)
The problem about metal fittings on the plastic pipe is again the space.
We use these PU pipe in order to insulate electrically the system. The system is static and there are no vibrations. Also we need something flexible which can bend in order to mount it.
Moltenmetal, Legris looks promising, I'll dive in their catalogue deeper
thanks all!
RE: Bond between PU and copper cooling pipes
If you clamp the hose on the non-barbed part of the fitting then fluid pressure will tend to expand the tube and lift it off the barbs. Then the seal will be solely due to hose clamp pressure on the smooth part of the fitting. This effect is counteracted by the pressure also tending to stretch the hose axially. If your fittings are fixed in location then there is no stretch due to pressure.
RE: Bond between PU and copper cooling pipes
so we have to put the clamps on the barbed section
good to know!
thanks
RE: Bond between PU and copper cooling pipes
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Bond between PU and copper cooling pipes
One would think that you would be able to make a pipe loop so that your best option would fit easier.
Maybe it would help if the connection had more flexibility in it.
RE: Bond between PU and copper cooling pipes
About the loop we don't have space, but I have ordered from Legris (Parker) some Push-In fittings
Thank you everybody