Types of Joints

Strength relies on the adhesion to the substrate - which is heavily influenced by the surface preparation of the adherends. Thick or rigid adherends are required to avoid distortion under load, leading to peel stresses on the joint. 

Whole of bond area is used to resist the applied load. This is the most common general type of adhesive joint, and the most efficient Practical joint designs must avoid the tendency of adherends to distort and peel. 

Inefficient because the bond area is not fully used for load distribution. Peel-type loading at the opening edge causes very high stress concentrations in this area. 

Very inefficient because ail of the load is borne by a narrow strip along the opening edge of the bond area. 

Torsional shear may be an acceptable loading mode, but adhesive butt joints should be generally avoided because the strength relies heavily on the properties of the adhesive, the bond area is often restricted and joints tend to be prone to off-axis loads. 

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The selection and appHcation of an expansion joint is not as simple as selecting a pipe fitting or a valve and requires a sound understanding of the joint s capabihties and limitations. Improper appHcation of any type of joint can result in serious or damaging effects. However, when properly selected and integrated into the piping system, satisfactory service and safe operation can be expected. Selection and appHcation of beUows expansion joints require special attention to design and installation. 

When both components of a threaded joint are of weldable metal, the joint may be seal-welded as shown in Fig. 10-130. Seal welds may be used only to prevent leakage of threaded joints. They are not considered as contributing any strength to the joint. This type of joint is limited to new construction and is not suitable as a repair procedure, since pipe dope in the threads would interfere with welding. This method provides tight joints with a minimum of welding labor. When threaded joints used to join materials with widely dinerent coeffi-... 

Manufacturers offer flanged-end pipe in only a few metals. Otherwise, flanges are attached to pipe by various types of joints (Fig. 10-133). The lap joint involves a modification of the pipe which ma ... 

E = joint efficiency, see Table 12-4 (Most vessels are fabricated in accordance with Type of Joint No. 1.)... 

Tubes may be inserted into a tubesheet, and packing may be added between them and the tubesheet. A threaded ferrule is inserted to tighten the packing. This type of joint is used only for special expansion problems. 

Tubing is classified according to the outside diameter, the steel grade, unit weight (well thickness), length and type of joints. The API tubing list is given in Tables 4-161 and 4-162. 

The type of jointing may be restricted by the grade of pipe used. For example, some grades of steel pipe are... 

Figure 44.3 illustrates a typical double-pivot universal joint. This type of joint, which is similar to those used in automobiles, generates a unique frequency at four times (4x) the rotational speed of the shaft. Each of the pivot-point bearings generates a passing frequency each time the shaft completes a revolution. 

The next type of joint is weld overlays, which are often utilized to eliminate the need for costly thrust blocks [Fig. 4-2(p)]. In designing the pipe an analysis was made to ensure that it possessed sufficient longitudinal strength. It makes sense, then, to make the weld joints be at least as strong as the longitudinal strength of the pipe rather than just as an internal pressure-seal pipe. 

When the joint is to be made using a bench torch it will usually be found easier to work so that the glass is blown through the smaller of the two tubes, when the joint is more easily visible. If the larger tube is used for blowing, the joint may be screened from view by it. When the novice starts trying to make this type of joint with a bench torch, difficulty may be experienced in rotating the two tubes of different... 

The waU thickness of the taper produced by drawing down the larger tube can have an effect on the profile of the finished joint (Figure 23). If this taper has a wall thickness about the same as the unworked tube it will tend to retain its profile in working, but if it is thin-walled the joint will tend to have a rounded profile. This provides a method of controlling the type of joint produced. A rounded profile can be produced by starting with a uniformly thick rounded end. 

The only difference between this type of joint and a normal butt joint is in the preparation of the capillary tube first the end of this is sealed off and a small fairly thin-wall bulb btown equal in diameter to the hole in the wide tube. The end of this bulb is then blown out and the joint made by the normal method. The flame must be directed so that the capillary is not collapsed. If the capillary has a very fine bore some difficuhy will be found in blowing through it. This may be overcome by connecting it to a compressed air line while the smaU bulb is btown the end of the bulb can then be pulled out with a rod and cut off to give the prepared end. 

The strength of a welded joint will depend on the type of joint and the quality of the welding. 

Table 13.3. Maximum allowable joint efficiency Type of joint Degree of radiography...

The preferred types of joint, and recommended designs and profiles, are given in the codes and standards. 

The choice of the type of joints to be used depends on the dimensions and on the requested vacuum level. 

No. Type of Joint Type of Seam Examination Factor, 5... 

Spot radiography for longitudinal groove welds required to have a weld joint factor, ), of 0.90 requires examination by radiography in accordance with para. IP-10.5.2 of at least 300 mm (1 ft) in each 30 m (100 ft) of weld for each welder. Acceptance criteria are those stated in Table IP-10.5 for radiography for the type of joint examined. 

The study of joint toxic effects originated with the analysis of the effect of two compounds in binary mixtures. Plackett and Hewlett [344] identified four types of joint effects as follows ... 

If the response of the organism is produced by a combination of the two compounds, then they are said to exert joint action. This joint action can be further classified into simply additive, more than additive (i.e., synergistic), and less than additive (i.e., antagonistic). When this scheme is applied to multicomponent mixtures present in leachates of solid wastes, the analysis becomes more complex because the joint actions of different compound pairs may fall into different types of joint action. In the next section, three different modeling schemes are presented. 

Using the TU concept, alternative schemes have been proposed to characterize the degree of joint action of multiple compounds acting together. In the first scheme, the sum of the TUs of the components M (i. e., M = 2 TU,) is used as an index to categorize the type of joint action as follows ... 

Suspect pipe integrity due to age, materials of construction and /or type of joint... 

A vacuum adapter is used to connect two different sizes (or types) of joints together, and it often has a vacuum valve between its two ends (see Fig. 18.5). For example, the glass joints of the vacuum manifold and solvent reservoirs are... 

A. Standard Taper and Ball Joints. These joints (Fig. 8.1) have been used for many years on vacuum and inert-atmosphere systems, and the availability of a variety of synthetic greases and waxes has extended their utility. Of the two, the ball-and-socket joint permits more flexibility in the orientation of the two halves. When this flexibility is important, this type of joint is obviously to be preferred, even though the ball joint is somewhat more prone to leak than a standard taper joint. Both metal ball joints and metal standard taper joints are available,1 and these items provide one means of joining metal and glass apparatus. 

Fig. 8.3. Cross-section of a Urry type glass O-ring joint and two types of screw clamps, (u) An O-ring. b) Cross section of a Urry-typc O-joint. Note the ridge which is tooled into the groove, (c) Two types of joint clamps. The upper one is manufactured by A. H. Thomas Co., Philadelphia, PA 19105.

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