Measuring "Heat Input" for weld procedures 1

[JStephen]

ASME B&PV Section IX, 409.1, lists "Heat Input" as a supplementary essential variable, and lists two or three different ways of measuring, with the limitation that the qualified heat input can't be exceeded in production welding. With manual flux-core welding, what is the normal procedure for measuring this?

The first option involves monitoring travel speed, which implies someone sitting there with a ruler and a stopwatch. The second option involves calculating bead size, which implies measuring actual weld gap and bead depth to calculate the area. Last option is measuring electrode usage per length of weld, which would be awkward with a wire-feed welder. So in practice, what is actually done?

I assume from a brief search, that it is heat input per pass which is considered, as opposed to cumulative.

 

[DVWE]

For FCAW, the best would be V*A*60/Travel Speed. I believe this is the most widely used method, for any process.

The third option works well for SMAW or GTAW, where the electrode is a standard length. It's just a comparison to your deposited bead length.

IMO, the second option only works well for automatic welding, after the piece has been sectioned and etched at the given V and A settings. How else can you adequately measure thickness?

 

[GenB]

Is it recomended then to qualify to a higher heat input to
meet Sect IX rules?
heat input: is it not the relationship V/A in your machine?
fairly new machines have gages to read both V/A and if your machine gages are accurate there is not reason for not using them for the purpose of complying with the Code.

 

[SJones]

You could always stick an arc monitoring device on the equipment.

http://www.tvcalx.co.uk/ALX.htm

Strictly, V*A*60/Travel Speed (distance per minute), is the 'arc energy' and not the "heat input".

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[Ballbearing1]

SJones,
Not sure where you are getting your information but ASME IX QW 409.1 states "Heat Input = Volts x Amps x 60 divided by Travel Speed."
AWS D1.1 Table 4.6 states exactly the same thing.
Cheers,
BB

 

[SJones]

Indeed they do and, for the purposes of those standards that is acceptable. However, on a strict technical basis, arc energy is adjusted by a thermal efficiency factor to get heat input. See, for example, ISO TR 17844. Also strictly, AWS A3.0 would define the result of the formula as 'heat input rate' and not 'heat input' (at least my 2001 version would!).

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[JStephen]

GenB- they intend to measure heat input per inch of weld, not heat input/ second. And you'd want to qualify this at least as great as any production welding.

SJones- I don't think the distinction on the efficency would matter, because we're welding the qualification test with the exact same equipment we'll be doing production welding. It doesn't matter at all to us what the absolute number is, just so we don't exceed it in production.

On the monitors, I don't see that there's a way to adapt them for semiautomatic (IE, handheld) welding, which is the problem.

 

[Ballbearing1]

JStephen,
Your amps, vots and travel speed will be recorded on the PQR.(Amps / Volts should be recorded with an ammeter/voltmeter, not reading what is showing on the machine)
The travel speed is usually recorded with a tape measure, usually 15 seconds and then multiplied by 4 to give you a speed per minute.
From that you can calculate your heat input (J/in - J/mm or Kj/in - Kj/mm)
Your minimum and maximum heat input will then be a known figure that will be listed on your WPS.
If you are in a workshop environment it is quite easy to set all the machines (volts and wire feed speed)and then you just have to ensure that none of the welding operators weld any slower than the slowest travel speed on the WPS.
Finally, remember if the work you are doing does not require impact testing then heat input is not an essential variable.
Hope that helps,
Cheers,
BB

 

[SJones]

I don't see that there's a way to adapt them for semiautomatic (IE, handheld) welding

You don't have to. Look at the datasheets in the link that I posted. The monitors are fully applicable to semiautomatic FCAW

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[JStephen]

Do they measure travel speed of handheld welding equipment? That's what I'm not seeing. I'm assuming the travel speed monitoring capability is assuming a more automated process.

And thanks for the input, everyone.

 

[SJones]

Ok - that's clearer. Generally, the length of the weld run will be manually measured and input into the datalogger by the welding inspector or other 'trusted party'.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04