Industrial Machinery Repair Episode 2 Part 10 pot

V-Belt Drives 459 ● Check sheaves for wear. Use a sheave gauge to ensure the sheave is not worn. If worn, write a corrective maintenance work order to change the sheave at a later date. Risk if the procedure is not followed: HIGH. Belts will slip (even though you may not hear the slippage), thus resulting in equipment not operating to specifications. 24 Maintenance Welding Introduction An important use of arc welding is the repair of plant machinery and equip- ment. In this respect, welding is an indispensable tool without which pro- duction operations would soon shut down. Fortunately, welding machines and electrodes have been developed to the point where reliable welding can be accomplished under the most adverse circumstances. Frequently, weld- ing must be done under something less than ideal conditions, and therefore, equipment and operators for maintenance welding should be the best. Besides making quick, on-the-spot repairs of broken machinery parts, weld- ing offers the maintenance department a means of making many items needed to meet a particular demand promptly. Broken castings, when new ones are no longer available, can be replaced with steel weldments fashioned out of standard shapes and plates (see Figure 24.1). Special machine tools required by production for specific operations often can be designed and made for a fraction of the cost of purchasing a standard machine and adapting it to the job. Material-handling devices can be made to fit the plant’s physical dimensions. Individual jib cranes can be installed. Conveyors, either rolldown or pallet-type, can be tailor-made for specific applications. Tubs and containers can be made to fit products. Grabs, hooks, and other handling equipment can be made for shipping and receiving. Jigs and fixtures, as well as other simple tooling, can be fabricated in the main- tenance department as either permanent tooling or as temporary tooling for a trial lot. The almost infinite variety of this type of welding makes it impossible to do more than suggest what can be done. Figures 24.2 through 24.5 provide just a few examples of the imaginative applications of welding technology achieved by some maintenance technicians. The welding involved should present no particular problems if the operators have the necessary training and background to provide them with a knowledge of the many welding techniques that can be used. A maintenance crew proficient in welding can fabricate and erect many of the structures required by a plant, even to the extent of making structural Maintenance Welding 461 Original casting Properly designed weldment Not needed Figure 24.1 Figure 24.2 steel for a major plant expansion. Welding can be done either in the plant maintenance department or on the erection site. Structures must, of course, be adequately designed to withstand the loads to which they will be sub- jected. Such loads will vary from those of wind and snow in simple sheds 462 Maintenance Welding Figure 24.3 Figure 24.4 to dynamic loads of several tons where a crane is involved. Materials and joint designs must be selected with a knowledge of what each can do. Then the design must be executed by properly trained and qualified welders. Structural welding involves out-of-position work, so a welder must be able to make good welds under all conditions. Typical joints that are used in welded structures are shown in Figures 24.6 through 24.9. Maintenance Welding 463 Figure 24.5 Standard structural shapes, including pipe, which makes an excellent struc- tural shape, can be used. Electrodes such as the E6010-11 types are often the welder’s first choice for this kind of fabrication welding because of their all-position characteristics. These electrodes, which are not low-hydrogen types, may be used providing the weldability of the steel is such that neither weld cracks nor severe porosity is likely to occur. Scrap materials often can be put to good use. When using scrap, however, it is best to weld with a low-hydrogen E7016-18 type of electrode, since the analysis of the steel is unlikely to be known, and some high-carbon steels may be encountered. Low-hydrogen electrodes minimize cracking tendencies. Structural scrap frequently comes from dismantled structures such as elevated railroads, which used rivet-quality steel that takes little or no account of the carbon content. Shielded Metal Arc Welding (SMAW) “Stick Welding” Shielded metal arc welding is the most widely used method of arc welding. With SMAW, often called “stick welding,” an electric arc is formed between a consumable metal electrode and the work. The intense heat of the arc, which has been measured at temperatures as high as 13,000 ◦ F, melts the 464 Maintenance Welding (A) (B) (C) Section YϪY Milled C C Y Y 14 68WF 14 136WF 33 220WF 16 40WF 16 40WF Bar 6ϫ 7 — 16 5 — 16 5 — 16 3 – 8 1 – 4 1 – 4 1 – 2 PL.15 ϫ1 ϫ1'Ϫ5 3 – 4 1 – 4 PL.6ϫϪ6ϫ2' 3 – 4 3 – 4 PL.8ϫϪ3ϫ1' 3 – 8 1 – 2 PL.8ϫϫ8 1 – 2 PL. 15ϫ1ϫ1'Ϫ5 Figure 24.6 electrode and the surface of the work adjacent to the arc. Tiny globules of molten metal rapidly form on the tip of the electrode and transfer through the arc, in the “arc stream,” and into the molten “weld pool” or “weld puddle” on the work’s surface (see Figure 24.10). Within the shielded metal arc welding process, electrodes are readily avail- able in tensile strength ranges of 60,000 to 120,000 psi (see Table 24.1). In addition, if specific alloys are required to match the base metal, these, too, are readily available (see Table 24.2). Maintenance Welding 465 Field weld A 1/4" for 8",10",12",14", 8/16" beams. 5/16" for beams larger than 16" Standard connection for simple beam-to-beam framing L Seat 1 – 2 L Seat T Seat or half I beam Stiffened L Seat Stiffeners Plug welds Column Figure 24.7 466 Maintenance Welding a a a b bb F. W . F. W . F. W . F. W . F. W . S.W. S.W. S.W. S.W. Half I-beam seat Half I-beam seat Seat made from I beam or T “m” (F.W.) F. W . F.W. = Field weld S.W. = Shop weld F. W . F. W . F. W . F. W . F. W . S.W. T S.W. d c c b F. W . F. W . S.W. d Figure 24.8 Flux-Cored Arc Welding (FCAW) Flux-cored arc welding is generally applied as a semiautomatic process. It may be used with or without external shielding gas depending on the electrode selected. Either method utilizes a fabricated flux-cored elec- trode containing elements within the core that perform a scavenging and deoxidizing action on the weld metal to improve the properties of the weld. FCAW with Gas If gas is required with a flux-cored electrode, it is usually CO 2 or a mixture of CO 2 and another gas. These electrodes are best suited to welding rela- tively thick plate (not sheet metal) and for fabricating and repairing heavy weldments. FCAW Self-Shielded Self-shielded flux-cored electrodes, better known as Innershield, are also available. In effect, these are stick electrodes turned inside out and made into a continuous coil of tubular wire. All shielding, slagging, and Maintenance Welding 467 Tie plate Butt weld Hook bolts Crane girder Plate Stiffener Bracing rod slot Lower col. section Connection plate/ shop-welded to girder. No holes in girder itself Girder stiffener Girder Beam Upper column section Figure 24.9 deoxidizing materials are in the core of the tubular wire. No external gas or flux is required. Innershield electrodes offer much of the simplicity, adaptability, and uni- form weld quality that account for the continuing popularity of manual welding with stick electrodes, but as a semiautomatic process, they get the job done faster. This is an open-arc process that allows the operator to place the weld metal accurately and to visually control the weld puddle. These electrodes operate in all positions: flat, vertical, horizontal, and overhead. The electrode used for semiautomatic and fully automatic flux-cored arc welding is mechanically fed through a welding gun or welding jaws into the arc from a continuously wound coil that weighs approximately 50 pounds. 468 Maintenance Welding Electrode Molten pool Extruded covering Gaseous shield Arc stream Base metal Slag Figure 24.10 Table 24.1 AWS classification Tensile strength, min. psi Yield strength, min. psi E6010-11 62,000 50,000 E7010-11 70,000 57,000 E7016-18 70,000 57,000 E8016-18 80,000 67,000 E9016-18 90,000 77,000 E10016-18 100,000 87,000 E11016-18 110,000 97,000 E12016-18 120,000 107,000 Note: E6010-11 and E7010-11 are cellulosic electrodes. All others are low- hydrogen electrodes and are better suited to welding higher-strength steels. Only the fabricated flux-cored electrodes are suited to this method of welding, since coiling extruded flux-coated electrodes would damage the coating. In addition, metal-to-metal contact at the electrode’s surface is necessary to transfer the welding current from the welding gun into the electrode. This is impossible if the electrode is covered. A typical application of semiautomatic and fully automatic equipment for FCAW is shown in Figure 24.11. For a given cross section of electrode wire, much higher welding amperage can be applied with semiautomatic and fully automatic processes. This is because the current travels only a very short distance along the bare metal electrode, since contact between the current- carrying gun and the bare metal electrode occurs close to the arc. In manual welding, the welding current must travel the entire length of the electrode, [...]... 150–30 02 160– 320 2 21 0–40 02 320 –51 02 400–60 02 0.035 0.045 1/16 3/ 32 0.9 1 .2 1.6 2. 4 150–300 20 0–400 25 0–450 350–550 0. 020 0.030 0.035 0.045 1/16 0.5 0.8 0.9 1 .2 1.6 – – 100 –160 150 26 0 100 –400 0.030 0.035 0.045 0.8 0.9 1 .2 – – – 0. 020 0. 025 0.030 0.035 0.045 1/16 5/64 3/ 32 7/64 8 0.5 0.6 0.8 0.9 1 .2 1.6 2. 0 2. 4 2. 8 3 .2 – – 75–150 100 –160 140– 310 28 0–450 – – – – ERAZ92A ERAZ92A EREZ33A EREZ33A ERCuSi-A... range Amperes 0. 020 0. 025 0.030 0.035 0.045 0.0 52 1/16 5/64 3/ 32 1/8 0.5 0.6 0.8 0.9 1 .2 1.3 1.6 2. 0 2. 4 3 .2 – – 40 -22 0 60 -28 0 125 -380 26 0-460 27 5-450 – – – 0.035 0.045 1/16 5/64 3/ 32 1/8 5/ 32 0.9 1 .2 1.6 2. 0 2. 4 3 .2 4.0 60 -28 0 125 -380 27 5-450 – – – – 2 Spray transfer mode 3 Trademark-International Nickel Co Table 24 .4 Shielding gas Advantages Argon 25 % argon + 75% helium 0 to 1 in (0 to 25 mm) thick:... E7 020 -G E9018-Mc E10018-Mc E 1101 8-Mc E 120 18-Mc E 120 18-M1c E7018-Wg E8018-W1g – 1.00 min f 0 .10 0 .10 0 .10 0 .10 0 .10 0. 12 0. 12 0.60–1 .25 0.75–1.70 1.30–1.80 1.30 2. 25 0.80–1.60 0.40–0.70 0.50–1.30 – – 0.80 min f 0.50 min f 0.30 min f 0 .20 min f 0 .10 min f 0.030 0.030 0.80 1.40–1.80 0.15 0.35 0.030 0.030 0.60 1.40 2. 10 0.35 0 .25 –0.50 0.030 0.030 0.60 1 .25 2. 50 0.40 0 .25 –0.50 0.030 0.030 0.60 1.75 2. 50... ER 1100 or ER5356 ER5554, ER5356 or ER5183 ER5556 or ER5356 ER4043 or ER5356 ERAZ61A, ERAZ92A AWS Electrode diameter filler metal specification Current range (use latest in mm Amperes edition) A5 .10 ERAZ61A, ERAZ92A ERAZ61A, ERAZ92A ERAZ61A, ERAZ92A A5.19 0.030 3/64 1/16 3/ 32 1/8 0.8 1 .2 1.6 2. 4 3 .2 50–175 90 25 0 160–350 22 5–400 350–475 0.040 3/64 1/16 3/ 32 1/8 1.0 1 .2 1.6 2. 4 3 .2 150–30 02 160– 320 2 21 0–40 02. .. E7015-C1L E7016-C1L E7018-C1L E8016-C2 E8018-C2 E7015-C2L E7016-C2L E7018-C2L E8016-C3c E8018-C3c 0. 12 1 .25 0.03 0.04 0.05 1 .25 0.03 0.04 0. 12 1 .25 0.03 0.04 0.05 1 .25 0. 12 0.06 0.08 0.50 2. 00 2. 75 2. 00 2. 75 – – – – – – – – – 3.00–3.75 – – – 0.03 0.04 0.60 0.80 0.50 3.00–3.75 – – – 0.40–1 .25 0.03 0.03 0.80 0.80–1 .10 0.15 0.35 0.05 Continued 470 Maintenance Welding Table 24 .2 continued AWS Classificationa... Table 24 .2 Chemical composition, percentb AWS Classificationa C Mn P S Cr Mo V – 0.40–0.65 – – 0.40–0.65 0.40–0.65 – – 1.00–1.50 0.40–0.65 1.00–1.50 0.40–0.65 – – – – – 1.00–1.50 0.40–0.65 2. 00 2. 50 0.90–1 .20 2. 00 2. 50 0.90–1 .20 – – – – – – 2. 00 2. 50 0.90–1 .20 – 1.75 2. 25 0.40–0.65 – 0.40–0.60 1.00–1 .25 0.05 Ni Si Chemical composition, percentb E7 010- Al E7011-AI E7015-AI E7016-Al E7018-Al E7 020 -A1 E7 027 -Al... S Si Ni Cr Mo V 0.05 0.40–0.65 0. 02 – Nickel-molybdenum steel electrodes E8018-NMd 0 .10 0.80–1 .25 0. 02 0.03 0.60 0.80–1 .10 Manganese-molybdenum steel electrodes E9015-D1 0. 12 1 .25 –1.75 0.03 0.04 E9018-DI E8016-D3 0. 12 1.00–1.75 0.03 0.04 E8018-D3 E10015-D2 0.15 1.65 2. 00 0.03 0.04 E10016-D2 E10018-D2 0.60 0.80 0.60 0.80 0.60 0.60 0.80 – – 0 .25 –0.45 – – 0.40–0.65 – 0 .25 –0.45 – – All other low-alloy steel... 473 Table 24 .3 Recommended electrode Base metal type Aluminum and aluminum alloys Material type 1100 3003, 3004 50 52, 5454 5083, 5086, 5456 6061, 6063 Magnesium AZ10A AZ3IB,AZ61A, alloys AZ80A ZE10A ZK21A AZ63A, AZ81A, AZ91C AZ92A, AM100A HK31A, HM21A, HM31A LA141A Copper and Silicon Bronze copper Deoxidized copper Cu-Ni alloys alloys Aluminum bronze Phosphor bronze Electrode classification ER 1100 or ER4043... ERCuA1-A1, A2 or A3 ERCuSn-A Nickel and nickel alloys Monel3 Alloy 400 ERNiCu-7 Inconel3 Alloy 600 ERNiCrFe-5 Titanium and titanium alloys Commercially pure Ti-0.15 Pd Ti-5A1 2. 5Sn Use a filler metal one or two grades lower ERTi-0 .2 Pd ERTi-5A1 2. 5Sn or commercially pure Austenitic stainless steels Type 20 1 Types 301, 3 02, 304 & 308 Type 304L Type 310 Type 316 Type 321 Type 347 A5.7 ER308 ER308 ER308L ER 310. .. argon + 25 % CO2 Less than 1/8 in (3 .2 mm) thick: high welding speeds without burn-thru; minimum distortion and spatter More than 1/8 in (3 .2 mm) thick: minimum spatter; clean weld appearance; good puddle control in vertical and overhead positions Deeper penetration; faster welding speeds 75% argon + 25 % CO2 CO2 Stainless steel 90% helium + 7.5% No effect on corrosion resistance; small argon + 2. 5% CO2 heat-affected . ERAZ61A, ERAZ92A 1/16 1.6 21 0–400 2 ZK21A ERAZ61A, ERAZ92A 3/ 32 2.4 320 – 510 2 AZ63A, AZ81A, A5.19 1/8 3 .2 400–600 2 AZ91C ERAZ92A AZ92A, AM100A ERAZ92A HK31A, HM21A, HM31A EREZ33A LA141A EREZ33A Copper. 100 –160 Type 310 ER 310 A5.9 0.045 1 .2 140– 310 Type 316 ER316 1/16 1.6 28 0–450 Type 321 ER 321 5/64 2. 0 – Type 347 ER347 3/ 32 2.4 – 7/64 2. 8 – 8 3 .2 – 474 Maintenance Welding Table 24 .3 continued Recommended. – 3/ 32 2.4 – 1/8 3 .2 – Steel Higher strength ER80S-D2 0.035 0.9 60 -28 0 carbon steels and ER80S-Nil 0.045 1 .2 125 -380 some low alloy ER100S-G 1/16 1.6 27 5-450 steels A5 .28 5/64 2. 0 – 3/ 32 2.4 – 1/8