ASME WPS help!

Date 02-26-2003 14:45

HI, I know this is a AWS site but there seems to be great deal of procedure knowledge here. I have posted these same questions on the ASME forum but I have not had any replies.
I am currently updating and rewriting all our ASME weld procedures. Over the years several persons using different formats, have written procedures and we are currently seeking a Certificate of Authorization for pressure piping.
I have encountered two problems for which I can not find a acceptable technical answer.
#1 A SMAW WPS using a E7018 electrode.
Table QW-253(Section 9) designates I & E range as nonessential and there is no link or reference to the typical ranges given in Section 4. According to QW-200.1, a completed WPS shall describe all of the essential and nonessential variables. Therefor on the WPS does one specify the actual PQR values or maybe the electrode manufacturers recommended range?
#2 Is there a section or rule of thumb regarding the maximum width of a groove weld cap, before stringers should be used? A change from weave to stringers is considered essential and therefore depending on the groove angle it may limit the thickness qualified. I have been reading for hours I must have missed it. I checked ASME Sections 9,8,2 & B31.1&.3.

Any help would be greatly appreciated, thankyou.
Malcolm Hart

By GRoberts (***)

Date 02-26-2003 15:49

#1. The WPS should specify the ranges that are allowed to be used in production. It is considered good practice if the variables used on the PQR fall within the ranges listed on the WPS. The manufacturers data on I & E ranges is a good place to start, but do not fit all aplications.

#2. Changing from a stinger bead to a weave is a non-essential variable for the arc processes for joining, but addition or deletion of oscillation is an essential variable for overlaying. What type of welding are you asking about, and with what process?

By mhslfab (*)

Date 02-26-2003 19:31

I guess this is a case of which comes first the chicken or the egg. Personally I like to write the WPS without parameters. I then write and perform the PQR using welding parameters which fall within the maufacturer recomendations. The PQR then specifies the actual singular (not ranges) weld parameters, I then calculate a ± 10% (most codes)
and specify these ranges on the WPS. If tavel speed is a essential varible I then caculate the volume of weld metal and use deposition rates to calculate the theoretical travel speeds to see if actual and theoretical compare.
The process is a tig root and stick filler. I have finished the PQR and have singular amperage and voltageg values. According to the welding varible parameter tables for SMAW and GTAW given in ASME Section 9, QW254, I & E are considered nonessential for both processes,but referance is made to section QW409.8 for both processes. QW409.8 does not specify a typical range. There are various ranges specified throughout section QW409 but none can be referenced directly to these welding processes. What ranges should one use?
Regarding stinger to weave , you are right it is nonessential, my mistake. Still it seems strange to me there is no restrictions regarding maximum widths an electrode can be manipulated, I have read resrtictions in other codes. Normally I specify layer and pass configuration in 1/16 increments throughout the qualified thickness but without this information I will have to be more general.

By Niekie3 (***)

Date 02-27-2003 19:23

Hi mhslfab

You must understand that the "preliminary" WPS that is typically made out, to help the welder during the test, is not the WPS that the code is referring to.

The WPS that the code is referring to is a document that is there "to give guidance to the welder" during the production welding. As such, the non-essential variable listed on the WPS needs to be values that will typically be used in production welding. In the case of SMAW, this means that the current range on the WPS will typically be as given by the manufacturer of the filler metals. In the case of SMAW, stating a voltage has little value, because this is determined by the arc length maintained by the welder. As such, you can make it a nice wide range to ensure that all welders are catered for.

Just remember that an increase in heat input is a supplementary essential variable. If impact properties are therefore required, the picture changes. Then you need to be more carefull regarding the amperage and voltage and speed requirements. (or weld bead unit volume deposited)

The whole string / weave issue is a hotly debated issue. This is so because it is possible to deposit a weld bead that is very wide without actually "weaving", while it is also possible to deposit a relatively narrow bead while "weaving". What is the real issue here? Is it about weaving, weld width, volume of weld metal deposited or what? I believe it is about weld width. For this reason I record the maximum weld width when qualifying a procedure and then restrict the WPS weld width to this value + 20% or so.

Hope this helps

Regards
Niekie Jooste

By mhslfab (*)

Date 02-28-2003 17:39

Thankyou for your reply Niekie & GRoberts.