Branch Connections

Where a branch connection is connected to a main run of pipe, it is necessary to specify the type of fitting required. ANSI B31.3 provides a 

API RP 14E recommends that no reinforcement be used and presents a typical branch connection schedule (Table 15-6) to provide more mechanical strength than is required by ANSI B31.3. Most onshore operators use integrally reinforced branch-connection fittings or tees inter-changcalil, . 

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Tees Tees may be cast, forged, or hot- or cold-formed from short pieces of pipe. Though it is impossible to have the same flow simultaneously through all three end connections, it is not economical to produce or stock the great variety of tees which accurate sizing of end connections requires. It is customary to stock only tees with the two end (run) connections of the same size and the branch connection either of the same size as the run connections or one, two, or three sizes smaller. Adjacent reducers or reducing elbow fittings are used for other size reductions. Branch connections (see subsection Joints ) are often more economical than tees, particularly when the ratio of branch to run is small. 

The niles provide that a branch connection has adequate strength for pressure if a fitting (tee, lateral, or cross) is in accordance with an approved standard and is used within the pressure-temperature limitations or if the connection is made by welding a coupling or half coupling (wall thickness not less than the brancn anywhere in reinforcement zone or less than extra heavy or 3000 lb) to the run and provided the ratio of branch to run diameters is not greater than one-Fourth and that the branch is not greater than 2 in nominal diameter. 

Openings in closures over 50 percent in diameter are designed as flanges in flat closures and as reducers in other closures. Openings of not over one-half of the diameter are to be reinforced as branch connections. 

FIG. 10-166 Typ es of reinforcement for branch connections. (From Kellogg, Design of Piping Systems, Wiley, New York, 1965. )... 

FIG. 10-168 Moments in branch connections. (Extracted fom the Chemical Flant and Fettoleum Refiner Fiping Code, ANSI B31.3—1976, with petmission of the publisher, the Ametican Society of Mechanical Engineets, New York.)... 

Acceptable comprehensive methods of analysis are analytical, model-test, and chart methods, which evaluate for the entire piping system under consideration the forces, moments, and stresses caused by bending and torsion from a simultaneous consideration of terminal and intermediate restraints to thermal expansion and include all external movements transmitted under thermal change to the piping by its terminal and intermediate attachments. Correction factors, as provided by the details of these rules, must be applied for the stress intensification of curved pipe and branch connections and may be applied for the increased flexibihty of such component parts. 

Imperfection f When required examination is Girth and miter-joint hutt welds Longitudinal hutt welds Fillet, socket, seal, and reinforcement attachment welds Welded branch connections and fabricated laps... 

Figure 15.19 Examples of crack patterns due to stress-corrosion cracking and corrosion fatigue in branch connections and vessel or pipe support attachment welds. (Reprinted with permission from Helmut Thielsch, Defects and Failures in Pressure Vessels and Piping, New York, Van Nostrand Reinhold, 1965.)...

A. 2-(Trimethtjlsiloxymethyl)allyltvimethylBilane. An oven-dried (Note 1) 2-L, three-necked, round-bottomed flask is equipped with an air-tight mechanical stirrer (Note 2), a 500-mL pressure-equalizing dropping funnel (Note 3), and a reflux condenser. The top of the condenser is connected to a three-way stopcock with one branch connected to a nitrogen source and the other to a variable pressure oil pump with a dry-ice trap (Note 4). The apparatus is flamed dry under a steady stream of nitrogen. The flask is... 

Use completely welded full wrap-around reinforcement pads at branch connections with pad thickness equal to header wall thickness. 

An integrally reinforced branch connection fitting that has been pres sure tested (weld-o-let type) is used. 

Sweepolet is a contoured, integral r r, rr butt-weld branch connection with a low intensification factor for low stresses -fatigue life. The attachment weld is easily amined by radiography, ultrasound and other standard non-destructive techniques. 

Insert Weldolet" is another contoured butt-. .. branch connection used in less critical >r. tions. Like the Sweepolet, the attac i are easily examined by radiography, ultrasou, and other standard non-destructive techn ... 

Figure 2-10. Branch connections for welding openings into steel pipe. See Figure 2-4C for alternate welding fittings. By permission, Bonney Forge Corp., Allentown, PA.

Vibration Frequency, Hz Note Indicated vibration iimits are for average piping systems constructed in accordance with good engineering practices. Make addi-tionai aiiowances for criticai appiications, unreinforced branch connections, etc. 

Branched-chain alkane (Section 3.2) An alkane that contains a branching connection of carbons as opposed to a straight-chain alkane. 

Weldolet" an economical butt-weld branch connection, is designed to minimize stress concentrations and provide integral reinforcement. 

Thredoletr utilizes the basic Weldolet configuration, provides a threaded outlet branch connection. 

Acceptable Detail for Branch Connection of Pipe Fitting. .. Acceptable Details for Branch Attachment Suitable for 100%... 

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