Induction heating flat spiral springs

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Summary
is it possible to heat a coiled spring
Summary: is it possible to heat a coiled spring

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If I had a spirally coiled spring like inserted pic, spiral coiled spring approx. 300mm dia and spring section +-12mm dia with +-1mm gauge wire, with a total length of spring approx. 4mtr-6mtr , is it possible to heat this with induction heating generator, say similar to an induction geyser system? would the coil heat up evenly, if possible? can it be heated from one side of the coil or would you need 2 induction elements one either side or is it just not possible? any assistance with clearing this up will be appreciated.
 

jrmichler

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We learned where I used to work that heating bearings in an oven worked much better than by using an induction bearing heater. This was an assembly of 8 bearings up to about 250 mm OD, where the entire assembly was about the size of a basketball. With bearings inside of bearings, and precision fits and tolerances, the standard induction bearing heater would not heat the bearings and parts evenly enough to assemble them. So we brought in an oven (it was an old beat up kitchen oven somebody borrowed from their deer camp), and used that. It worked very nicely.

From that experience, I recommend that you look at an oven instead of induction.
 

berkeman

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Summary: is it possible to heat a coiled spring

is it possible to heat a coiled spring
I'm no expert in induction heating, but as I understand it, induction heating works via eddy currents generated in the metal object by the AC induction field. You need a contiguous piece of metal to get such currents, or else you need to use frequencies that are high enough to induce significant eddy currents in the smaller features of the work piece.

So it would seem that if you want induction heating to work with a spiral work piece, you will need to electrically connect the start and end of the spiral, and use an AC field that couples into the coil directly (the B-field would be orthogonal to the plane of the coil spring). Does that make sense? Can you try that?

 
I want to place the coil spring in a copper pipe and heat water. I wanted to use a spring for the surface area and ease of inserting the spring into the copper pipe
spiraled
coiled . the spring is still one single piece but you say it won't generate eddy current?
 

jrmichler

Science Advisor
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Do I understand correctly that you want to use the spring as a heater? If so, you are far better off to go to a company that builds heaters than to reinvent the wheel by designing your own. A good source is www.omega.com. They specialize in selling small quantities to end users. Their catalog has all the information you need to choose the best heater for your application, plus they have technical people you can call for help.

I recommend them because of previous experience. In fact, I am running a test right now of one of their differential pressure sensors. Waiting for the test to finish, so surfing PF to kill time. Edit to add photo showing high tech experimental setup:

P6100007.JPG
 
Last edited:

Baluncore

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Induction heating is used to very quickly heat the surface of metal objects that can then be rapidly cooled to give a glass hard surface. The inside of the metal object is not heated significantly so it retains it's structural properties and the object does not distort.

A spring must be heated equally throughout the full depth as it is shaped. It will usually then be taken through a second heating to temper the material.

The spring form you are considering is called a clock spring or a power spring.

You could heat the spiral by running a high current through it while it is dry.

But whatever you do you will be left with problems.
1. Without water to keep it cool the spring will overheat, lose it's temper and distort.
2. With water you will have insulation problems, between adjacent coils, to the outer jacket, and to the water.
3. With water you will have a corrosion problem.
 

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