Process Qualification - Heat Treatment Process Furnace - What is Thermal Mapping?

[dr madhavan]

What is Thermal Mapping? Are there any standards or codes of practices for conducting this with reference to the Heat Treatment Process Furnaces? How frequently is it to be conducted?
Is it to be comparable to 'calibration' requirements?

[Geoff Cotton]

Are you taking about establishing the temperature profile / heat zones within a belt furnace?

We check our belt furnace using a thermocouple a couple of times a year, compare the results to the temperature charts and previous readings.


Hope that helps

[dr madhavan]

I am referring to 'Measurement of uniformity of Temperature across the cross-section as well as in the depath, particularly in 'PIT TYPE' Heat Treatment Furnaces -say, a Gas Carburising Furnace or even a Salt bath furnace.

[lday38]

The thermocouples then are not used every time but are used to verify that the heat is consistent throughout the furnace. Is that correct?
When you say you compare them to the temperture, I believe your saying the gage outside of the furnace.
Have you ever heard of someone using the thermocouples for each lot during processing?
Where can I find out more about process controls for the heattreating process?
I understand that some suppliers use graphs? I would suppose the graph is a picture over time. Is that correct?

Thanks
Linda

[Marc]

Originally Posted by lday38

The thermocouples then are not used every time but are used to verify that the heat is consistent throughout the furnace. Is that correct?

It depends upon what your purpose is. I have seen processes where thermal profile devices go through with every lot, but that's not typical.

Thermal Mapping is taking an oven or furnace and profiling the temperature at different locations. If it's a long furnace line, you would choose multiple 'essential' points and monitor the temperature at each point. If it's a temperature chamber (such as a closed oven) you measure different points within the oven.

Some threads here: Thermal Profiling

Some other Thermal Profile resources.

[lday38]

Thank you , Marc
Yes, they are putting the thermocuple (3 of them) through each lot. The product is a shaft for a blender blade. Having never seen a thermocouple, I would think that it is recording the temperture in the differant locations. Right?
I am hearing that we will get charged more for charts , whch makes some sence. However, I would think they are recording data off these thermocouples that should be available for past lots if there is an issue.
Linda

[Marc]

Are the 'thermocouples' traveling on the belt through the furnace, or are they measuring 3 points in an oven (i.e.: three places along the oven, as I assume this is a long belt oven)?

A thermocouple is two pieces of special wire which are welded together. There are different types each of which is for a specific temperature range. The ends of these wires are attached to a measurement device which measures electrical potential. Some people call the wire and the measurement device a 'thermocouple', but I'm from the old days where a thermocouple was the welded wire junction.

Thermocouple

There are devices which are a compact, single 'box' which can be run through an oven with a lot which internally records, or transmits to an external analyzer, the temperature as the device proceeds through an oven with a lot.

I need more specific information on what you're referring to - Spot measurements at places in an oven, or a device which actually goes through the oven with the lot.

** I assume this is a belt oven (long oven). Or, is this one big stationary oven?

[Marc]

From an email: Hi there
Big statinary oven , atmospherically controlled.

Linda

In those you decide where you want thermocouples, but again it depends upon the oven design. Is it gas or electric? Is there an air mover which keeps air circulating or is it a 'static' oven?

I'm not sure what you mean by atmospherically controlled.