Dear Sirs

Pls explain

17 ) - An increase or decrease in the wire feed speed for each electrode diameter  (if not amperage controlled) by:

What does it mean by "if not amperage controlled" by   ?

Thanks

Hello Nalla;

First of all one must remember anything in clause 4 means the WPS is qualified by testing because the conditions of clause 3 for prequalification cannot be met. The assumption is there is an existing WPS that is qualified. All the elements listed by table 4.5 are changes that can be made to the WPS. If the change is within the permitted ranges, a revision is all that is needed. If the change exceeds the permitted range listed, the WPS must be requalified by testing.

Specifically, you are asking about item 17:
"An increase or decrease in wire feed speed for each electrode diameter (if not amperage controlled) >10%"

All the items listed by Table 4.5 are essential variables similar to ASME Section IX, only more extensive.

Assuming you are using a constant voltage power supply, there are three variables that are "constants" when setting the power supply up for welding. The three constants are:

Voltage - the power supply is self regulating. That is it will always try to return to the voltage set on the control panel as the remaining two parameters change.

Electrode extension (contact tip to work distance) - the distance from the contact tip to the arc (distance from the contact tip to the work piece) representing resistance in the electrical circuit. As the EE is increased; more resistance and a corresponding reduction in welding current in accordance with Ohm's Law.

Wire feed speed - typically set at the wire feeder. The WFS for the traditional wire feeder is a constant that does not change whether one is welding or holding the gun in the air.

Trying the set up a FCAW or GMAW system using current is the most unreliable method of setting up the machine. Amperage is a variable that is dependent on the electrode extension. A small change in EE will cause a large increase in the current and stability of the operation. So, I often put tape over the ammeter so the welder is left with no alternative other than to use WFS to set the machine.

Amperage and voltage is a quick means of determining whether the welder is using the proper settings. Some machines have tachometers to measure WFS, but how many are accurate?

If the three constants listed are within the proper operating ranges, i.e., V, EE, and WFS, the amperage will be sufficient and in accordance with the manufacturer's recommended range. So, all four parameters must be in balance in order to obtain the optimum operating conditions, but the one variable that is most difficult to control is amperage.

If you've read my previous posts on the presentation of welding parameters you will recollect I use a graphic approach so that the welder can see the relationship between V, EE, WFS, and A. If the welder has the V and EE correct, but the WFS is low, amperage will be low. If C and WFS are correct, but the EE is too short, amperage will be too high. As can be observed, the value of amperage is a function influenced by both WFS and EE. The graphical representation delineates the proper setting for the variables and provides an easier way for the welder to properly set the machine.

Back to your question, notice electrode extension is not a variable that is considered by D1.1, ASME Section IX, or other welding standards. Unfortunately, most committees are composed of individuals that have little if any experience behind the welding helmet. Omission of EE as a parameter is a ghastly oversight by the committees governing what must be included by the WPS and PQR. However, any change in EE will result in corresponding change in A, but the welder can change the WFS to get the right A and still have unsatisfactory operating conditions and will result in frustration by all. It is just one more reason not to use the preprinted forms provided by AWS or ASME. Given, D1.1 lists contact tube to work distance on their form found in Annex N. However, it is a value rather than a range and it is not an essential variable. Another tragic oversight by the committee. The term CTWD is inconsistent with AWS A3.0 which considers CTWD to be a nonstandard term  and the term CTWD is not included in Annex K terms and definitions.

So, in a long winded way, I'm finally responding to your inquiry, both amperage and wire feed speed need to be recorded by the PQR and addressed by the WPS. However, one should also add the electrode extension to the data collected and recorded on the PQR. The WPS must list all the variables included by Table 4.5, because all are considered to be essential variables by AWS D1.1 (the new Farm Code). If either WFS or amperage exceeds the range permitted by Table 4.5, the WPS will have to be requalified.
   
Hope this was useful.

Al

Hi Friends,

I am using AWS D1.1 Code for construction, we have LPT and MPT to test in the welding Joints,but in AWS D1.1 They did not provide the acceptance criteria for these two methods,for procedure it says we need to refer ASTM E165 for LPT,So for this what should i do???

Thanks in advance..

Naga
QC Engineer