CR4 - The Engineer's Place for News and Discussion ®


Previous in Forum: I Want To Mfg This Part But Dont Know How If Any Have Idea Than Plz Guide Me.....   Next in Forum: SS 347 Weld Overlay Defects After Gasket Face Machining
Close
Close
Close
34 comments
Member

Join Date: Dec 2013
Location: Bangalore, India
Posts: 5

Brazing Heating Coil with Nickel Pipe

05/06/2016 3:44 AM

I want to braze 1.4 mm (od) heating coil around a Nickel 200 pipe of about 30 cms length. The sheath of the heating coil is also made of Nickel. Insulation between the sheath and heating wire core is MgO.

Can anyone suggest the brazing paste to be used and the highest temperature that can be safely reached during the brazing process ?

__________________
Regards Pubs
Register to Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 26292
Good Answers: 690
#1

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 4:15 AM

Yes. The manufacturer of the heating coil can. Pick up the phone, and ask.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru
United States - Member - New Member

Join Date: Mar 2010
Location: In the pool because it is too hot.
Posts: 3017
Good Answers: 141
#2

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 4:47 AM

Please come up with more details.

Size: length of heating coil, size and schedule of pipe?

What is under the nickel?

Is this heated electrically? Up to which temperature?

Depending on the temperature, I should start with soldering since your heating coil might not survive a brazing process.

Will the wire (heating coil) be wrapped firmly around the pipe?

__________________
Plenty of room here
Register to Reply
Member

Join Date: Dec 2013
Location: Bangalore, India
Posts: 5
#5
In reply to #2

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 5:57 AM

Dimensions are yet to be worked out. But following can be firmly assumed.

- The heating coil is electrically heated

- and is meant to prevent icing inside the tube through which air passes (sometimes of sub zero temps).

- The heating coil's unwound length likely about 4 metres

- The nickel pipe will be about 30 cms in length with a od of 2.5 cms and wall thickness of 1.5 mm.

- Skin temp of heating coil when energised should not exceed 350 deg C

- There has to be firm contact between tube and coil throughout the length of coil and hence the brazing requirement. Soldering appears not feasible.

__________________
Regards Pubs
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 26292
Good Answers: 690
#6
In reply to #5

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 7:42 AM
  • Why is icing a problem?
  • Temperatures?
  • Pressures?
  • Flowrates?
  • Air dewpoint?
  • The heating coil raises the temperature of the air - from what to what and why?
  • Etc.
__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru
United States - Member - New Member

Join Date: Mar 2010
Location: In the pool because it is too hot.
Posts: 3017
Good Answers: 141
#13
In reply to #5

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 12:41 PM

You need to know the heat transfer (here cold) of the medium through the pipe and check if your coil can produce enough to compensate for the freezing,

Air moisture content and flow will be crucial to make your system work.

Since brazing happens to need more than your 350 degrees Celsius, your idea may be

compromised and your heating coil mantle melted down.

You could better bring the coil IN the pipe and coil it up with bringing the ends to the outside using e.g. Swagelock connectors of the right size.

Insulate the pipe on the outside (what you need to do anyway) in each case.

__________________
Plenty of room here
Register to Reply
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 4386
Good Answers: 158
#17
In reply to #5

Re: Brazing Heating Coil with Nickel Pipe

05/07/2016 10:50 AM

What skin temperature is permitted when NOT energized? I suspect that the 350°C limit is based on heat transfer from the heating wire to the skin/sheath, to guarantee not melting the heating wire during operation. Since MgO is a much poorer conductor of heat than nickel, the heating wire will be MUCH hotter than the skin/sheath of the heater coil during operation. During brazing, the opposite is true; the heating wire will be much cooler than the skin.

As at least one person suggested, if you have to do the attachment at or below 350°C, then by definition you are soldering, not brazing.

With an OD of only 1.4mm, that nickel heater sheath has to have a very thin wall thickness. Since it appears that an aggressive flux is required for soldering nickel, it will be important that both the pipe and the heater be very clean just before doing the brazing, and that the brazing be accomplished quickly, with the excess flux removed immediately as soon as it has cooled sufficiently. Otherwise, the combination of flux and solder/braze alloy may dissolve that thin skin.

If this is a one-off item, it would be very expensive, but vacuum brazing with an appropriate braze alloy could eliminate the requirement for flux. Even then, the amount of braze alloy and the time at braze temperature should be carefully limited to avoid the braze alloy dissolving the skin/sheath.

__________________
Teaching is a great experience, but there is no better teacher than experience.
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 26292
Good Answers: 690
#3

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 5:11 AM
  • Cyanoacrylate adhesive?
  • Epoxy resin adhesive?
  • Duct tape?
  • Heating rate?
  • Why does it need to be attached, if there is insulation going over the outside of everything?
  • Temperatures, pressures and flows in the pipe?
  • What is in the pipe that needs keeping warm? Why does a mere 300 of 200 pipe need keeping warm? Why does the remainder of the installation not need keeping warm?
  • Etc.
__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru
United Kingdom - Member - New Member

Join Date: Aug 2010
Location: Resting under the Major Oak
Posts: 4242
Good Answers: 173
#4

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 5:45 AM

Sounds like he's using something like a pyrotenax heating coil. I'm basing that on the MgO insulation.

__________________
Pessimists are rarely disappointed.
Register to Reply
Guru
Canada - Member - If there is a way to screw someting up, there is someone to do so! Safety - Hazmat - New Member

Join Date: Mar 2007
Location: Iqaluit, NU. Canada
Posts: 1789
Good Answers: 134
#7

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 10:05 AM

Knowing nothing about the process other than what you have offered... but, one would think that you need to heat the air before it gets to this section of pipe.

If you are bound and determined to do it this way, why not abandon the idea of an exterior to the pipe heat source and look into "skin effect" heating instead. That way... the pipe itself is the heat source.

__________________
Joe Contractor to Electrical Inspector, "What do you mean you are going to make me follow the code?".
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 11229
Good Answers: 133
#8

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 11:02 AM

Why can't you sleeve the pipe with another pipe to contain the heating coil, and use heat transfer medium (heat transfer oil, or even propylene glycol) to maintain thermal contact?

Use the lowest temperature nickel brazing rod you can find, but you should be talking to the respective OEMs on this to see what they can tolerate.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 26292
Good Answers: 690
#9

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 11:17 AM

A simple domestic hair dryer blown onto the outside surface of the pipe would work, given the absence from this thread of any contextual information apart from there being air inside the pipe that is below its dewpoint.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 11229
Good Answers: 133
#10
In reply to #9

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 11:41 AM

True that.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 19765
Good Answers: 740
#11

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 11:55 AM

What keeps the nickel pipe from short-circuiting the heating coil?

__________________
In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 11229
Good Answers: 133
#12
In reply to #11

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 12:02 PM

The MgO insulation inside the heating coil (tube) to be wrapped around the pipe and brazed on, or 86 the whole idea, and make the pipe be in contact with other thermal supply (hair dryer).

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 19765
Good Answers: 740
#14
In reply to #12

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 12:57 PM

I'm trying to imagine what size of wire fits into a 1.4 mm tube with also a layer of insulation.

__________________
In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 11229
Good Answers: 133
#15
In reply to #14

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 1:04 PM

Probably single strand Nickel chromium wire. Maybe the outer casing of the heat coil is for ground current?

He best just wrap the coil around the pipe that is coated in heat transfer paste, sheath it, and insulate and call it "George". At least if he names it, he will own it.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru

Join Date: Mar 2007
Location: at the beach in Florida
Posts: 17970
Good Answers: 1037
#16

Re: Brazing Heating Coil with Nickel Pipe

05/06/2016 5:19 PM
__________________
Life is like riding a bicycle. To keep your balance you must keep moving. A.E.
Register to Reply
Power-User

Join Date: Sep 2007
Posts: 146
Good Answers: 15
#18

Re: Brazing Heating Coil with Nickel Pipe

05/07/2016 12:45 PM

Unless you are dealing with cryogenic-level temperatures why not just use heating tape like that sold to protect outside water pipes in winter? What heat transfer rate BTU/min) and total heat (BTUs) do you need? Do you plan to have continual heat transfer (heater always on) or on-demand heat transfer (temperature-controlled on/off). If this is a single point problem and not in an unusually harsh environment, it seems that your solution is overly complex and difficult.

Register to Reply Score 1 for Good Answer
Guru
Hobbies - DIY Welding - New Member

Join Date: Sep 2007
Posts: 1593
Good Answers: 57
#19

Re: Brazing Heating Coil with Nickel Pipe

05/08/2016 4:31 PM

Easy-Flow 45 is my go-to brazing material for these applications.I highly recommend it unless there is a reason not to. It is a fairly good color match for nickel, is available in many forms, uses conventional flux and heating methods. It contains some cadmium and is forbidden under some codes, but there are Cd free versions available. Try it-you'll like it.

Register to Reply
Member

Join Date: Dec 2013
Location: Bangalore, India
Posts: 5
#20
In reply to #19

Re: Brazing Heating Coil with Nickel Pipe

05/09/2016 6:26 AM

Thanks to all for the prior tips . I am afraid most not workable.

Reason: This pipe is intended to sit on a Drone to sample the incoming air for its speed and pressure. Hence icing just not acceptable. In fact the heating coil has to be brazed to the inner walls of the tube to maintain the aerodynamic finish on the exterior of the pipe. I have the process figured out except that I need to know the brazing paste which enables nickel to nickel brazing at the lowest temperature yet have an extremely good flow after melt. Please note I can apply the flame to the exterior of the tube only.. So the good flow characteriscs hopefully will ensure an effective bond between the tube's inner surface and the nickel sheath of the heating element all along its coiled length. So my question remains same.........the best brazing paste for nickel to nickel brazing at the lowest temperature possible to make the process as benign as possible to the items being joined.

__________________
Regards Pubs
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 11229
Good Answers: 133
#21
In reply to #20

Re: Brazing Heating Coil with Nickel Pipe

05/09/2016 8:17 AM

Sounds to me like you have no idea about aeronautical instruments. What you are proposing to do will have more effect on the measurements you are attempting to make than the aerodynamics (if the heater were outside the tube) of the pipe. In fact, you could make it far easier on yourself (and us too) if you would simply consider carrying a small bottle of alcohol on board the drone, and spray it into the tube periodically to prevent/remove any icing.

Another thought: how much current is this heater supposed to take, and how much is it going to actually heat the air traveling through this tube? Why not just use pressure sensors and pitot tubes of the correct dimensions?

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru
Hobbies - DIY Welding - New Member

Join Date: Sep 2007
Posts: 1593
Good Answers: 57
#22
In reply to #20

Re: Brazing Heating Coil with Nickel Pipe

05/09/2016 9:36 AM

I don't understand why Easy-Flow 45 won't perform your task exactly as described. If you want a higher temperature material, you can use the silver-copper eutectic 72/28 at 780C. I can provide you with literally hundreds of braze options, but am suggesting the simpler and less expensive ones first. You may also consider replacing the heating coil with a lower voltage/higher current electrical arrangement that would permit you to heat the nickel tube directly thus eliminating the need for a heating coil.

Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 11229
Good Answers: 133
#23
In reply to #22

Re: Brazing Heating Coil with Nickel Pipe

05/09/2016 10:29 AM

Or he could take the guts out of a hair dryer, and insert them in the leading edge of his sensor pipe, although this will perturb any measurements so badly, the data will be absolutely useless and without merit.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 4386
Good Answers: 158
#24
In reply to #20

Re: Brazing Heating Coil with Nickel Pipe

05/09/2016 10:37 AM

It would have saved a lot of time if you had given these details in the original post, but either: A) there are other required details that you still haven't mentioned, or B) JS is right.

If you only want to measure speed and pressure, there is no reason for the device to have such a large OD. As JS implied, turbulence inside the tube is much more of a problem than turbulence on the outside, in terms of accurate measurements. It would be much easier to guarantee good brazing and thermal contact if the heating coil is on the outside of the tube; the remaining indentations between coil turns could easily be filled with a wide variety of possible materials to provide external aerodynamics.

You say this is to be placed on a drone, so weight is obviously a major factor. 1.5 mm wall thickness for the main tube is way too heavy for this job! For an OD of 2.5 cm, a wall thickness of 0.4mm should be plenty. If you reduce the diameter to something closer to that of standard pitot tubes, say 5mm, then you should be able to use a wall thickness of around 0.1-0.2mm.

At that wall thickness, the resistance of the tube should be high enough for you to simply use a relay or solid state device to connect a single cell to the two ends of the tube as required and heat the tube directly. You would thus reduce the weight of the device to a very small fraction of the original, and can thereby allow a much larger battery for heating.

__________________
Teaching is a great experience, but there is no better teacher than experience.
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 11229
Good Answers: 133
#25
In reply to #24

Re: Brazing Heating Coil with Nickel Pipe

05/09/2016 4:18 PM

Any battery he puts on this drone (unless this is Military grade stuff and largely powered by something other than battery) will kill the payload availability and flight time for the drone.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 4386
Good Answers: 158
#26
In reply to #25

Re: Brazing Heating Coil with Nickel Pipe

05/09/2016 5:45 PM

Drones com in a W I D E range of sizes, with all sorts of propulsion systems, from batteries to small jet engines. You're right - I was assuming battery power for the heater, but "it ain't necessarily so".

In reality, the fact that this thing is to fly where icing is a concern means either high altitude or high latitude. I don't think this is your consumer grade quadcopter...

__________________
Teaching is a great experience, but there is no better teacher than experience.
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 11229
Good Answers: 133
#28
In reply to #26

Re: Brazing Heating Coil with Nickel Pipe

05/10/2016 8:15 AM

IF the thing is powered by a small (or large) jet engine, hot bypass air could be used for the same job, with a mere sleeve around the sensing tube. Let the thing be pressed.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 4386
Good Answers: 158
#30
In reply to #28

Re: Brazing Heating Coil with Nickel Pipe

05/10/2016 11:12 AM

Absolutely true! In fact, our company has a novel 3-layer sandwich that has been used to produce a similar tube with integral passageways for heating/cooling gas/fluid, and is indeed currently being tested for use in some critical applications.

__________________
Teaching is a great experience, but there is no better teacher than experience.
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain, and now disconnecting as Little England and Wales (not too sure about Wales bit, either). Kettle's on.
Posts: 26292
Good Answers: 690
#31
In reply to #20

Re: Brazing Heating Coil with Nickel Pipe

05/12/2016 11:44 AM

Next time, please put all the relevant information in the original post. It saves readers going off chasing wild geese and enables a solution to be determined much quicker, leading to a reduction in annoyance for all involved.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru
Technical Fields - Technical Writing - New Member Engineering Fields - Piping Design Engineering - New Member

Join Date: May 2009
Location: Richland, WA, USA
Posts: 19765
Good Answers: 740
#27

Re: Brazing Heating Coil with Nickel Pipe

05/09/2016 6:01 PM

Perhaps it is an omen that the OP's avatar is the same as Kulas's.

__________________
In vino veritas; in cervisia carmen; in aqua E. coli.
Register to Reply Score 1 for Good Answer
Guru
Hobbies - DIY Welding - New Member

Join Date: Sep 2007
Posts: 1593
Good Answers: 57
#29

Re: Brazing Heating Coil with Nickel Pipe

05/10/2016 10:19 AM

It finally occurred to me that you may not recognize the names of the alloys because of your location. This should get you on the right track. http://www.lucasmilhaupt.com/en-US/products/fillermetals/silverbasedcadmiumbearingfillermetals/9/

Register to Reply
Member

Join Date: Dec 2013
Location: Bangalore, India
Posts: 5
#32

Re: Brazing Heating Coil with Nickel Pipe

05/18/2016 4:40 AM

Thanks for all the inputs guys.Thanks specially to 'Welderman' for pointing me to the right direction............. a suitable braze alloy for my application. Thanks again.

__________________
Regards Pubs
Register to Reply
Guru

Join Date: Mar 2011
Location: Lubbock, Texas
Posts: 11229
Good Answers: 133
#33
In reply to #32

Re: Brazing Heating Coil with Nickel Pipe

05/18/2016 8:54 AM

Go forth, and do not put your eye out.

__________________
If it ain't broke, don't fix it. Just build a better one.
Register to Reply
Member

Join Date: Dec 2013
Location: Bangalore, India
Posts: 5
#34

Re: Brazing Heating Coil with Nickel Pipe

05/19/2016 2:41 AM

Thanks again. Signing out from this discussion thread.

__________________
Regards Pubs
Register to Reply
Register to Reply 34 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

dkwarner (4); dvmdsc (2); Graycav (1); James Stewart (9); North of 60 (1); Pubs (4); PWSlack (5); SolarEagle (1); TonyS (1); Tornado (3); welderman (3)

Previous in Forum: I Want To Mfg This Part But Dont Know How If Any Have Idea Than Plz Guide Me.....   Next in Forum: SS 347 Weld Overlay Defects After Gasket Face Machining

Advertisement