"Heat input" 3

[MG79]

I'm looking for definition of "lowest & highet heat input".

What is best of national standard... ?

Please advice to me.


Best regards
MG

 

[cloa]

lowest and highest heat input for what?

 

[stanweld]

Assuming you are asking for welding heat input, the equation is:
60 X Volts X Amps devided by the travel speed. This is defined in ASME IX and by the AWS.

 

[MG79]

Sorry for lack of explanation.

I'm going on welding procedure qualification base on part of ISO 15614-1.

 

[SJones]

As per EN 1011-1, the referenced standard for computing heat input, a process dependent thermal efficiency factor, k, is used with the above formula. It also requires the units of kJ/mm so multiply by 10^-3.

However, I suspect that the question relates to the practice of welding two test pieces to qualify a range of heat input and how to cope with the two sets of data generated and then the tolerances to be applied. Oh the arguments that will ensue!!!

I don't know of any standard that dictates the specific rules for this approach. My experience has been that it's all down to a bunfight between the client and the contractor.


Steve Jones
Materials & Corrosion Engineer

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

 

[Kiwi2671]

MG79,
As an example we will use a PQR with the following:
Amps = 120
Volts = 13
Travel Speed = 80 mm/min

120 x 13 x 60 = 93600
93600 divided by 80,000 (Travel speed x 1000)= 1.17
Heat input = 1.17 Kj/mm

WPS is now written with +/- added.
110 - 130 amps
12 - 14 volts
70 - 90 mm/min travel speed

Take your lowest amps / volts (110 and 12) and highest travel speed (90 mm/min)and use the equation above.

Lowest heat input = 0.88 Kj/mm

Now take your highest amps / volts (130 and 14) and lowest travel speed (70 mm/min and use the equation above.

Highest heat input = 1.56 Kj/mm

Hope that helps,
Regards,
Kiwi

 

[SJones]

Kiwi,

Here is where you get to the bunfight as you now have a heat input tolerance of - 25% +33% that not a lot of end users are going to accept, let alone the applicable standards. The first issue generally crops up in establishing what exactly the 'PQR parameter values' are, since it's very rare to see single values quoted from the as run parameters. The 'cheeky' contractors quote the as run range and then try to put +/- tolerances on top and then the disgruntled end user tries to whittle that range down tighter. And so on, and so forth.

I always try to get an arc monitoring system involved for qualification as it makes the number crunching for the bunfight arguments a whole lot simpler.

Steve Jones
Materials & Corrosion Engineer

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

 

[Kiwi2671]

Steve,
With all due respect I totally disagree.
I am using ASME IX as my example as it is what I work with the most but every code I have ever worked with (American, British/European and Australian) all allow a range for parameters.

ASME IX - QW 409.1 has an increase in heat input as a supplementary essential variable - that means it is only essential if the fabrication code requires impact testing.
So if you are not welding low temperature piping/vessels etc changes in heat input are not essential variables. Even if you are you can still decrease your heat input and still be code compliant.
QW 409.8 lists a change in the amperage / voltage range as a non essential variable.

How can you say the contractor is "cheeky" by putting a range (+/-) on the WPS.
I have reviewed welding procedures as the clients representative for some of the worlds largest oil and gas companies - if I do not see a "practical" range in parameters listed on the WPS I will reject it.Singular figures are for the PQR - the WPS is a working document and needs some flexibility.
Different welders have different techniques - some like to weld hot and fast, some like to weld cold and slow. If you do not write a WPS that covers (as much as possible) these differences you have written a worthless document that may as well stay in the QA manual.
Regards,
Kiwi

P.S Have a look at AWS D1.1 - it actually lists the allowed % increase and decrease in amps, volts, travel speed and heat input

 

[SJones]

We are talking ISO 15614-1 which deals with + and - tolerances for toughness and hardness considerations respectively (which will generally apply to the majority of oil company welding requirements). Seeing a single parameter value quoted on the PQR, particularly for pipeline test welds, has not been my general experience. More often than not, it is quoted as a range and then tolerances are applied to this range to try and extend it further for the WPS. The original post is aimed at the practice of running two test welds for a PQR: a 'high heat input' weld and a 'low heat input' weld. A commonly adopted approach has been to try and tolerance the low heat input weld downward further and the high heat input weld upwards further, whereas another approach could be to use the two welds as setting the absolute parameter limits for the WPS, i.e. the 'bunfight'

Steve Jones
Materials & Corrosion Engineer

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

 

[Mr168]

My experiences are very much in line with Steve's, albeit with the power industry.

If I see a PQR with a single value, especially when run manually or semi-auto, I take it with a large, boulder-sized grain of salt. PQR's are for recording actual values, and you will most certainly see a variation in volts, amps, and travel speeds, regardless of how slight they may be.

How exactly does one recording these parameters make the decision of which value they "witnessed the most", or take an "average", and deem that the actual value? Pulsed power supplies? Add some more grey. Pulsed waveforms? Throw "true power" or "true energy" values into the mix, especially when dealing with antiquated and impractical codes, and you've stumbled upon more shades of grey than the Valspar, Behr, and Sherwin Williams catalogs put together.

This is becoming a very hot topic in new power plant construction as of late, particularly as it pertains to the welding of duplex steels and the associated ferrite numbers.

 

[metengr]

Regarding the power industry, most of the heat input data are single values recorded because when it comes to welding the typical power plant ferrous materials (Cr-Mo and CS), heat input is not an essential variable.

Creep strength enhanced ferritic steels in addition to duplex and stainless steels should be added to the list regarding careful review and providing some specified range for heat input.