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In Misunderstanding Welding Symbols Part I, we discussed a few common confusions people have when reading a print covered with welding symbols. As promised, we’re back to tackle five more misunderstood symbols. Included in this set are a few misconceptions about nondestructive examination symbols. Let’s pick up right where we left off, shall we?
Mistake No. 6: Fillet Weld in a Hole vs. Partially Filled Plug Weld
It’s important to note that a fillet weld in a hole is not the same as a partially filled plug weld. What’s the difference? A fillet weld in a hole covers the perimeter of the hole. A partially filled plug weld, however, fills the bottom of the prepared hole completely, but does not reach the top of the joint. The image below shows a cross section view of a fillet weld in a hole versus a partially filled plug weld. Notice the difference? A fillet weld symbol is used to communicate the first example and a plug weld symbol is used to denote the second.
Mistake No. 7: Stacking Dimensions
A single symbol can communicate a lot about a weld including such as size, pitch, depth of filling, number of welds, angle of countersink, and so on. In many cases, these dimensions are placed above or below the weld symbol depending on the location of the weld symbol itself. Now, when numerous dimensions are to be placed above or below the welding symbol, it’s important to know their proper order. The included dimensions can vary from weld to weld. As an example, let’s take a look at slot welds, which can have upwards of 4 pieces of information looming above or below its weld symbol. In the case of slot welds, the depth of filling dimension is placed within the weld symbol itself, the angle of countersink is then placed just outside of the weld symbol, followed by the number of welds. After this, any necessary contour is noted along with the finishing method should postweld finishing be required. All of these dimensions may not always be present, so if you’re ever unsure as to what a particular dimension is, always reference AWS A2.4, Standard Symbols for Welding, Brazing, and Nondestructive Examination.
Mistake No. 8: Staggered Intermittent Welds
There are a few different types of intermittent welds: intermittent, chain intermittent, and staggered intermittent. Chain and staggered intermittent welds occur when intermittent welds are located on both sides of the joint. There is often confusion when people first encounter a pair of fillet or edge weld symbols offset on a reference line. Well, this offset is what sets a chain intermittent weld apart from a staggered intermittent weld. You see, the offset is meant to mimic the pattern that a staggered intermittent weld forms on a joint. Now, which side of the joint begins with a weld and which begins with an unwelded gap? Well, the offset squelches that concern as well. The side of the reference line that has the weld symbol closest to the arrow is the side that begins with a weld bead while the other side begins with a gap.
Mistake No. 9: Extent of Nondestructive Examination
Symbols aren’t just used to offer details about welds. They are also used to outline nondestructive examination requirements. While nondestructive examination symbols follow rules similar to those of a standard welding symbol, they do retain a few rules and nuances of their own. For example, if you need to indicate the extent of examination, you’ve got two methods of doing so. You can specify the exact length of the area to be inspected or you can note the percentage of the part to be examined, as we mentioned in Welding Symbols Demystified Part I. In both situations, the number is written directly to the right of the abbreviation for the chosen examination method. The difference here is that one is more specific than the other. Though giving an exact length dimension offers more specificity, it is important to note that the dimension alone will not provide someone with enough information to inspect the joint or part. Instead, a drawing with dimension lines must be included in order to specify the exact location of the examined length, which can fall to the right, left, or center of the part.
Mistake No. 10: The Examination Combination
Unlike welding symbols, which can contain only two weld types on a single reference line, examination symbols can contain three or more! These examinations can take place on the arrow side, other side, or have no side significance at all. Let’s take a look at how to communicate this.
As always, arrow side examinations are indicated below the reference line and other side examinations are indicated above the reference line. When there is no side significance or preference as to which side the examination takes place, the letter designation for the test is centered on the reference line. However, unlike welding symbols, a portion of the line is eliminated in order to make room the for the letter designation. As we mentioned, one symbol can be used to indicate more than two tests. This includes multiple tests to take place on one side of the reference line. If more than one test is required on the same side of the reference line or if more than one test is centered on the reference line, they are simply separated by a plus sign as shown here.
That concludes this series! Remember, to get better acquainted with the rules governing these symbols, you can always check out our course, Understanding Welding Symbols. Within the course, we cover all the mistakes that we’ve discussed in this blog series in addition to the rules that apply to all other welding symbols. AWS A2.4 contains a wealth of information that can seem confusing at first. However, with Understanding Welding Symbols at your disposal, reading prints will come to you as easily as reading a book or even this blog.