[Music] knowing why two fails and what to do about it is important because it is essential that failures be repaired what we’re going to do now is take a look at some ways of fixing boiler tube failures all the repairs will be dealing with require welding in a boiler this work must be done by a certified welder however as a maintenance person you may have to assist a certified welder and you will need to know how the repair is done remember to review welding safety precautions before work is started there are special hazards involved with welding these hazards include intense ultraviolet light from the electric arc fumes from the welding itself and danger from hot Sparks and molten metal make sure that you keep safety in mind at all times there are several precautions that must be taken to protect against hazards caused by welding first the welder and his helper must be protected from the electric arcs intense light by welding shields these shields have special glass lenses that filter this light to keep it from damaging the eyes second the area where the welding is done must be well ventilated because of the harmful fumes produced by welding in a confined area it may be necessary to set up a portable fan to get adequate ventilation third the welder must wear gloves and heavy clothing to protect him from sparks and molten metal some companies have even more safety requirements check for these in your safety manual the manual will also list precautions that must be taken when working inside a boiler the actual repairs you’ll be involved with will be done inside a boiler but in order to clearly demonstrate the procedures will be working on individual boiler tubes in the shop each of the repair procedures we’ll talk about will be demonstrated this way the first method of tube repair is the replacement of a section of tube here the length of tube containing a failure is cut out completely and replaced by a new section of 2 replacement of an entire tube section can be done to repair any kind of tube failure replace tubes are as good as new ones you can replace every tube in the boiler or as much of one tube is necessary the problems with replacement of a tube section are that it is time-consuming and expensive still it is sometimes the only procedure that can be used because the damage is too severe to be repaired by any other method when getting ready to assist in a repair be sure you’re thoroughly familiar with the procedure if your plant has a written procedure read it over carefully and be sure you understand it if there are no written procedures talk the process over with an experienced welder also make sure that you know the materials equipment and working methods that apply specifically to your boiler the type of metal that the tube to be repaired is made of and the type of weld rod used for the job are both important considerations there are a lot of different kinds of weld rod available and there are a variety of metals used in boiler tubes the type of tube metal and the type of weld rod must be compatible if the wrong kind rod is used the weld made with it is very likely to fail for this reason the foreman or an experienced welder usually chooses the type of welding rod in addition to the welding rod you’ll need a replacement to the new tube must be the same type of tube as the one that failed it has to be made of the same type of metal and its dimensions have to be identical your manufacturers manual will tell you what metal the original boiler tubes are made of using the right replacement tube is very important before starting the job get all of the equipment you’ll need to do the work first of all you’ll need a welding machine if there is a written procedure it may call for a particular type of welding machine the tools that are needed include a rod holder which is also called a stinger a grounding cable a slag hammer a wire brush a saw to cut the tubes and a grinder before they’re used check the tools to ensure they’re in good condition for example make sure that the welding cables are not frayed or broken once preparations and precautions are finished the procedure begins by cutting out the damaged section of tube here we’ll do the cutting with a saw now this type of saw is attached to the tube that will be cut this is done by attaching a clamp to the tube and then attaching the saw to the clamp cutting is done with a saw rather than a cutting torch to avoid getting slag inside the tube two cuts must be made to the damaged tube section one above the failure and one below when the damaged section has been removed the remaining two bends are prepared for welding both free ends must be beveled beveling or scarfing as it’s sometimes called is the process of tapering the end of a tube this is done with a grinder you may need ear protection when this is done particularly if the grinder is driven with an air motor next the distance between the free ends of the tube is carefully measured it’s important to get an accurate measurement so the replacement section can be cut to fit in the available space space is left for the beveling that is done to the free ends of the tube and to the replacement section the replacement piece may be cut on a saw in the shop the ends of the replacement section must also be beveled this can be done in the shop before the replacement section is taken to the boiler once the ends are prepared the replacement section must be tack welded in place to hold the replacement piece while it is being tacked welded a brace like the one you see here is sometimes used tack wells are small spot wells that are made to hold the replacement section in place while the final welds are being made the final welds must be made by a certified welder as a weld is made an impurity called slag is produced slag must be removed this is done by chipping it off with the slag hammer to remove any remaining slag a wire brush is used once the welds have finished the repair is complete a repair like this is usually tested by pressurizing the boiler this is called a hydrostatic test and it’s done to make sure the welds don’t leak that completes the procedure let’s sum up the key points the material and equipment you need for replacing the section of tube are weld rod a replacement tube a welding machine a rod holder a grounding cable a slag hammer a wire brush a saw and a grinder there are five steps for the repair cut out the damaged tube section bevel the remaining ends cut the replacement tube to size and bevel the ends tack weld the replacement section in place and weld the replacement section to the original tube take some time now and clear up any problems or questions