Bevel angle tolerances 1

[faizal8009]

hi,

for bevel angle tolerances . is it any code in BS standard mention for the tolerances.( en 13445, PD 5500, eemua)

 

[johg]

Hi faizal8009,

The tolerances on bevel angles are mentioned in standard only by exception. The API has some tolerances on bevel angles. If you weld the bevels yourselves, you will have some own tolerances (+/- 1°). If bevels are end preparation normally you should ask your client or make a proposal.

Johg

 

[racookpe1978]

Physically, the weld prep bevel angles are only for access BY the individual welder (whether machine or by hand) to get the rod and the tungsten (or the arc source if not GTAW) into the very bottom of the first weld prep zone with enough of an angle into the base metal (both sides!) of the weld to "melt" that exposed metal.

Once that first pass is complete, or more accurately, the root pass and first and second pass, the remainder of the bevel is "wasted" effort" because it requires ever larger and larger amounts of filler metal, time, and money to fill back into the final weld geometry. But, realistically, that first (deepest) part of the joint is also the most critical and is the source of most of the problems with fitup, cleanliness, heat, deposits of inclusions, etc. It has to be right.

But, notice that the bevel itself is melted when you get through. In fact, it had better be completely melted when you get through! So, realistically, is there a point when a bevel angle is wrong and ust be rejected? Yes.

What is that point? At the angle where the man doing the job at that specific location using his specific tools and setup and gas flow and electrode diameter and rod diameter and welding current cannot perform a satisfactory weld.

Will one degree ever matter? Realistically? No. (The first straw never broke a camels back.) The first +/- 1 degree on a weld prep never will interfere with his root pass. In many cases, around much of an ordinary PV circumference weld, a good welder will not need the "drawing perfect" weld prep angle either. Probably not even 7 or 8 degrees of the drawing specific angle. But 5, 6, 7, 8, or 9 degrees? Maybe, most likely too limiting for some welders, not for others. At some point, every welder will begin failing by trying to force a bad bevel. At some particular location (around a nozzle or manhole or instrument fitting) even the best welder may really need MORE than the nominal bevel, but can "work around it" by changing position or by changing welding heads, or by "forcing it" by skill and artistry. Or you may have a whole bunch of "nearly bad" welds he never told you about - but that's a different story.

Don't guess - You are probably asking because you have an out-of-spec condition, or an inspector found an out-of-spec conditin who is challenging your procedures and your QA because he (she ) does not know enough to make an informed decision. Neither do you or I frankly - neither of us is doing the welding.

You ARE in a position to write an "exception memo" or note or letter to the company/customer/QA dept allowing a out-of-spec bevel AFTER you check with the welder (his foreman or GF or lead welder really) to verify this particular case is manageable under this particular condition.

Now, look at the other direction. If your supplier is sending bevels that are too wide, HE is forcing YOU to spend a LOT of extra time and money filling in HIS error. THAT, you need to recover as soon as possible and get that problem in HIS production line corrected as soon as possible.

 

[faizal8009]

Good Day,

Thanks racookpe1978 for your explanation.