Welding symbols are a smart way to save time and space on an engineering drawing. It is an effective and concise way of communication between an engineer and a welder to accurately understand how different welds need to be done. Being able to understand and interpret the welding symbols is important if you want to know how to make welds accurately without making any mistakes. Otherwise, it’s going to cost you not just time and effort but extra money as well. Before getting into anything, read the guides to become a welder.
While the welding language might seem overwhelming and strange at first glance, there is absolutely no need to panic. What you need to do is, learn the basics and then understand one symbol at a time. Gradually, with time and practice, you will be able to do it smoothly and easily if your basics are well-learned and strong. Go through this detailed guide about the basics of how to read welding symbols, and you might end up reprimanding yourself for thinking of it as difficult as you did.
How to Read Weld Symbols
A welding symbol constitutes a number of different parts or elements, all of which have different meanings and indications. It’s important to understand all these elements to get the meaning of a welding symbol fully. These parts include the reference line, the arrow, and the tail. Let’s go through what each of these means separately, and then a few other important things to understand.
The Reference Line
The reference line is the most basic and primary part of any welding symbol. It is basically a straight horizontal line with which all the other symbols or parts are connected in order to specify or form a certain welding action. All the information about a weld is conveyed through the symbols drawn around a reference line.
A reference line is drawn on the specific joint for which it is drawn or close to it. Normally, an arrow is connected to it on one end of the line. The instructions about the direction where the arrow points to are given below the reference line, and those about the other side of the line are given above the reference line.
Sometimes, there are multiple operations that are required and have to be indicated for a single weld; a single reference line is not enough for that. For such operations that have to be sequential, a multiple reference line welding symbol is used. For that, multiple reference lines are drawn connected to a single arrow; the closest reference line to the arrow indicates the first welding operation, then the one that comes after that, and so on.
The arrow is another basic part of a welding symbol. The arrow points in the direction of the joint that is to be welded. It is attached to a leader line, which is the stem of the arrow and not a horizontal line. This leader line, in turn, is attached to one side of the horizontal reference line. The side to which the arrow points is referred as the ‘arrow side’ of the joint, while the side opposite to that is referred to as the ‘other side of the joint.
To save up space on the drawing, since there are so many welding symbols to be drawn, a single welding symbol can be drawn for multiple joints. This can be done when there are multiple joints that require exact same welding operations and in the same sequence. Only more than one arrow has to be used, each arrow pointing at the direction of one of the joints.
Then comes the tail, the third most important element needed to understand a welding symbol. It is connected to the other end of the reference line, the ‘other side’ of the joint, opposite to the arrow. It forms a fork, pointing in two directions, or a greater-than ‘>’ or less-than ‘<’ sign. The tail is an optional part, needed only if there are some further special instructions to be given for a weld.
Any further instructions that remain and that are not specifically meant to be conveyed through any of the other parts of a welding symbol are written around any side of the tail. If there are such extra specific instructions to be given, the tail is not used in the welding symbol. Mostly the instructions given at the tail of the symbol are about the approved welding procedure specifications (WPS).
Information about the welding process that is to be used is often specified, like which welding process should be used; the engineer might convey that to the welder. Typically, for a welding symbol to be complete, a reference line, a leader line, an arrow, and a tail are all that is required if WPS is specified in the tail. Since WPS contains all the information, there is about welding a joint. That is if there is any special information remaining to be given; otherwise, the reference line, the leader line, and the arrow are sufficient.
A Weld symbol can either be a geometric shape or parallel lines that indicate a certain type of weld. The Weld symbols are placed at the center of the reference line of a welding symbol, either over it or below it. They indicate the type of weld that needs to be done for the project, while the rest of the welding symbol gives instructions on how to do that specific weld.
If the weld symbol is placed below the reference line, the weld needs to be done on the side of the joint where the arrow is pointing. If the weld symbol is placed over the reference line, the weld has to be done at the side opposite to where the arrow is pointing on the joint. Suppose there are weld symbols placed at both sides of the reference line that indicates that the weld has to be done on both sides of the joint. There are many weld symbols that symbolize different types of welds; some of the common ones are fillet weld, groove weld, and plug or slot weld. Since there are so many of them, it is important for welders to memorize all the symbols for accurate welding.
Angles and Dimensions
The angles and dimensions include the length, width, depth, or angle of a weld or whether it should be mirrored or offset. All this information is an important part of welding specifications indicated by a welding symbol. Mostly, the width or diameter of the weld is mentioned in inches on the left side of the welding symbol.
The length is also mentioned in inches and on the right side of the symbol. If any specific length is not mentioned, that means that the weld has to be carried out from one end of the joint to the other. As per the rule, the dimensions mentioned below the reference line are for the side of the joint where the arrow points. Dimensions written above are for the side of the joint opposite to the arrow.
If dimensions are given on both sides of a reference line, both of them are for the respective sides of the joint. Angles are also mentioned with a welding symbol, the root opening or root face of a weld. This is also important to consider; it specifies the beveling required for starting a weld. This is mostly done if the base metal that is being welded is thicker than ¼ inch.