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Recommended Installation Procedures Merit Weld -Miser Tee -Let Welding Outlet Fittings are designed B and manufactured to reduce the cost of installation from both the standpoint of labor required and energy consumed. In addition, by following the recommended installation procedures, many of the problems associated with installing welding outlet fittings on standard weight or light weight pipe are eliminated, including burn through and excessive shrinkage resulting in pipe distortion. Recommended Hole Sizes The hole cut in the branch or header pipe can be cut prior or subsequent to attachment of the Tee -Let. One advantage of cutting the hole after welding is that the pipe is left intact during welding thereby reducing shrinkage and possible distortion. If holes are cut prior to welding, as some codes require, then the following hole sizes are recommended. Note that the same hole diameter for a given outlet size is required for both Type A and Type C Tee -Lets 1-1112'larger. 112, 3/4 & 1 Outlet 1 %4- 21Y2 Outlet Recommended Welding Procedures Merit Weld -Wiser Tee -Lets are designed to be installed on standard weight or light weight pipe with one weld pass on Type A outlet sizes from 112 through 21/2 inclu- sive, and on Type C outlet sizes through 4". Moreover, the wall thickness at the weld end of the fitting approximately matches standard weight pipe. Accordingly, heat setting can be made to optimize penetration on both the fitting and the pipe which it is being welded. Aside from reducing the likelihood of burn through and distortion resulting from excessive heat, the amount of weld required for adequate penetration is significantly reduced. Merit Tee -Lets are manufactured from continuous cast aluminum killed steel with a carbon range of from 0.05 to 0.25. Merit specifies that residuals, such as chrome, nickel and other metals resident in the scrap used for production of the steel be reported and kept to a minimum. On the other hand, certain grades of carbon steel pipe are manufactured from skelp whose chemical composition is not speci- fied. When the metal inert gas shield (MIG) welding process is employed, certain residuals may cause excessive porosity, spatter or lack of penetration. Specifically, gases released during the welding process do not escape before the molten puddle sets up. When porosity or lack of penetration occurs, one approach is to slightly increase the heat in order to give the gases time to escape from the puddle. A flux cored wire can also be used. This wire contains scavengers which allow gases in the molten weld puddle to escape before the weld solidifies.The following recom- mended settings for welding therefore may need to be adjusted slightly higher if any of the above mentioned adverse conditions exist. As a general rule, the weld should be only as hot as required to allow the weld to penetrate the materials being welded while concomitantly allowing gases developed in the welding process to escape. Every effort must be made to avoid welding too hot or overheating both the pipe and the Tee -Let. Excessive heat may cause the wrench tight threads (those in the bottom of the Tee -Let near the weld zone) to distort while also causing the branch pipe to bend. It should be noted that Merit Tee -Lets have been subjected to exhaustive testing and evaluation, and only negli- gibly distort when subjected to excessive heat. The threads, on the other hand, may not return to their gauged form after cooling if excessive heat causes them to expand. The following is intended only as a guide, and assumes that the welding equipment is properly calibrated and functioning normally and the operator is qualified. MERIT® Weld-MiserTm Tee -Let® Installation (coat.) Welding Outlet Fittings Outlet A B Size In./mm In./mm In./mm Yi /4 /6 13 7 6 / �/ /6 19 7 5 1 �/ /6 25 7 5 1'k /4 /6 31 7 5 1i/ /6 / 38 8 7 2 /6 �/ 50 8 7 2�,L /6 1/463 8 7 3 /e /6 75 10 5 4 / /6 100 10 5 RECOMMENDED HOLE SIZES Tee -Let Size Type Fecotl Hollee Size ize In./ram Yi Type A s/e 13 16 2/4 Type A '/e 19 22 1 Type 1Ye 25 28 1Y4 Type 11/ 31 38 1Y4 Type 12/e 31 35 1i/ Type AorC 11/e 38 41 2 Type AorC 2 50 50 2Yi Type AorC 2�/6 63 61 3 Type AorC 3 75 75 4 Type AorC 4 100 100 Holes may be cut employing mechanical means -Including hole sawing, mechanical flame cutting (oxy-acetylene or propane), and air plasma cutting (constricted tungsten arc) machines. Merit offers a simple approach to cut- bng the hole. Hand-held templates are sized to match your plasma cutter. AMBtar- Merit -1.10 — 9 — fireN ua% pvivan ar Mvil Inttmananal