Need help in creating a tech article..measuring heat question
 

A while ago I asked if anyone had access to a pyrometer so I could borrow/rent for a tech article. Pretty much went bust.

I want to compare two or three inexpensive torches as I believe the results would benefit many DIYers here.

Here's where I need help: Does anyone have an idea on how to measure the heat generated by a torch? Perhaps between 1000 to 2500+ degrees. I'd like to get as accurate as possible and keep cost down as this will most likely be the only time I'll use such an instrument.

To compare the temperatures produced by different torches, you could round up samples of different metals with known melting points.

For something less crude, I'm sure you can buy a thermocouple for high-temperature ovens and use a DMM to get a better measurement of the termperature. It shouldn't be that expensive if you already have a multimeter accessible.

/ J

J,

Thanks for the response. Any particular type/size/style of thermocoupler?

Check out Omega Inst. site - they have charts that will help you.

Be sure to get the same part of the flame for each - you are going to have methodological problems....

I'm trying to map out a test plan....from different gasses to using same-batch metal for testing. I'd rather not reuse a test piece as the properties may be changed from a previous test. I'll most likely test at different locations of the flame.

I'm not a scientist but I think I can cover most of the bases relevant to us DIYers.

Suggestions are welcome, Randy.

Doesn't the temp have less to do with the torch than the gas you are using?

There is a chart of flame temps for different gasses here:

http://www.torchcutter.com/fuelprop.htm

The coolest of the bunch is Propane, which burns at only 4580ºF. Acetyline is hottest at 5600ºF.

Tom

Rick,

What kind of torches do you want to measure? Propane, MAP gas, other? Or are you looking at oxy-acetylene torches?

A Chromal-Alumel, Type K thermocouple is great for measuring propane temperatures but it has a limit. The thermocouple junction can be formed at oxy-acetylene temperatures. These Type K thermocouples are readily available in the auto repair industry (Snap-On, etc.) and are not expensive.

Your temperatures are right in the border of more specialized equipment.
Omega is the company that wrote the book on all this technology. You need to research this site:
http://www.omega.com/

Here is a basic outline of thermocouples:
http://www.omega.com/prodinfo/thermocouple.html


I have rolls of Type K thermocouple wire with fiberglass insulation and with ceramic insulation. I use an oxy-acetylene torch reducing flame (rich) to form the junction. These use the yellow connectors. The wires are yellow and red. The ceramic insulation in necessary for exhaust gas temperatures. Fiberglass works OK for everything else. Neither of these insulations is very mechanically durable so I use SS braid on the ceramic and heat shrink on the fiberglass.

Post more after you have been in the Omega site (it is huge.)

Best,
Grady

I may have a surprise....

Grady, Thanks for your wisdom. I'll be sticking to the Propane and Mapp gases as they are within reach of all our budgets.

I'm leaving the office now and will check the Omega site out within the next few days. Please keep the ideas coming. If anyone has a technique or product to trow into the mixfeel free to share.

"Does anyone have an idea on how to measure the heat generated by a torch?"

Although not high tech, a barbeque thermometer might provide enough of a range to give you some answers. Bolt it onto a piece of metal, then with torch adjusted, heat the metal X inches away for X seconds. Repeat test with different torch, use same exact test method. Record temp, then compare. Repeat the tests a few times to minimize test variables.

Mr hi-tech,
Sherwood

I think you should talk to a consulting engineer at Omega.... thermocouples are most accurate at certain temp. ranges (I am a type T man, myself). Type K is nice as you can just read it with a multimeter.

The best thing would be to use a thermal imaging system -- they are a lot cheaper now (they used to only be owned by USAF and traveled on the back of a semi-truck flatbed). Still too spendy w/o a big grant. But maybe you could rent one. I'm still unclear on what you want to do or why, so it's hard to give advise. Just be aware of the way T varies in different parts of the flame.