Bolted joints

Cooling tower Threaded pipe joints Bolts, nuts, washers Partially exfoliated coatings Lap joints in sheet metal Between bushings and shafts on pumps Pump gaskets... 

Dia., in. Fittings Flanges Trims Hang. Supp. Welds Shop Field Joints Bolt ups... 

Stacks are designed to vent exhaust gases from industrial processes. If the gases are combustible, flare stacks may be used to burn the exhaust gases before they are vented into the atmosphere. In the case of combustible gases, operational procedures should be used that prevent the infiltration of oxygen into the stack where it could mix with the exhaust gases and cause an explosion. Stacks should be built with welded seams rather than bolted joints. Bolted joints, especially joints... 

Structurally bolts act as backup elements—in an intact joint, bolts carry no load... 

Joints Bolted or joints Bolted or joints, but require special tool to open... 

Relaxation is an important example of a creep phenomenon encountered in practice. Bolts, studs, flanges, and springs of all kinds are subject to relaxation when used at high temperatures. These members are loaded to a stress that must be maintained for proper functioning. If relaxation occurs, the stress decreases. Thus bolts can become loose so that bolted joints develop leaks after operation at elevated temperatures. 

Transition Joints. Use of explosion-clad transition joints avoids the limitations involved in joining two incompatible materials by bolting or riveting. Many transition joints can be cut from a single large-area flat-plate clad and deflvered to limit the temperature at the bond interface so as to avoid undesirable diffusion. Conventional welding practices may be used for both similar metal welds. 

Ma.rine. In the presence of an electrolyte, eg, seawater, aluminum and steel form a galvanic cell and corrosion takes place at the interface. Because the aluminum superstmcture is bolted to the steel bulkhead in a lap joint, crevice corrosion is masked and may remain uimoticed until replacement is required. By using transition-joint strips cut from explosion-welded clads, the corrosion problem can be eliminated. Because the transition is metaHurgicaHy bonded, there is no crevice in which the electrolyte can act and galvanic action caimot take place. Steel corrosion is confined to external surfaces where it can be detected easily and corrected by simple wire bmshing and painting. 

Bolting Bolting requirements for ANSI flanged joints are pre-... 

Bolted joints are friendlier than quick-release couplings. The former are usually dismantled by a fitter after issue of a permit to work. One person prepares the equipment and another person opens it up the issue of the permit provides an opportunity to check that the correct precautions have been taken. In addition, if the joints are unbolted correctly, any trapped pressure is immediately apparent and the joint can be remade or the pressure allowed to blow off. In contrast, many accidents have occurred because operators opened up equipment which was under pressure, without independent consideration of the hazards, using quick-release couphngs. There are, however, designs of quick-release couphngs which give the operator a second chance. 

Random checking of bolted connections for proper jointing and tightening... 

Extra care needs be taken on the quality of fasteners and the method of jointing and bolting. 

For busbar joints we have considered 8 Numbers bolts of size M-10 (diameter of bolt shank, 10 mm), as in Figure 29.4. As the size of these fasteners is greater than that of the busbar supports, their suitability is not determined separately. 

The contact resistance can be minimized by increasing the pull of the fasteners. Increasing the area of overlap may not reduce the contact resistance, unless the number of fasteners is also increased. It is mandatory to maintain a certain minimum contact pres.stire per unit area of the joint overlap. An average contact pressure at around 40-55 kg/cm is considered adequate. For the purpose of easy application, it is expressed in terms of bolt torque, depending upon the area of overlap and the number of fasteners, as specified in Table 29.1. 

Make the joint by using the correct size of bolts, nuts and washers. Refer to Table 29.1 for the recommended number and size of fasteners for different widths of bus sections and Table 29.2 for the recommended size of washers for different sizes of bolts. See also... 

Use a torque wrench to tighten the fasteners to ensure correct surface-to-surface contact of the current-carrying parts (Figure 29.2(c)). The recommended values of bolt torque are given in Table 29.1. A pressure that is too high may eause relaxation of the joint by cold flow and must be avoided. 

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