Fittings reducing elbow

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. 

Reducing elbow fittings permit change of direction and concentric size reduction in the same fitting. 

REDUCING ELBOW - A fitting that makes an angle between two joints of pipe and that decreases in diameter from one end to the other. 

Enough space must be available to properly service the flow meter and to install any straight lengths of upstream and downstream pipe recommended by the manufacturer for use with the meter. Close-coupled fittings such as elbows or reducers tend to distort the velocity profile and can cause errors in a manner similar to those introduced by laminar flow. The amount of straight pipe required depends on the flow meter type. For the typical case of an orifice plate, piping requirements are normally Hsted in terms of the P or orifice/pipe bore ratio as shown in Table 1 (1) (see Piping systems). 

The simplest method of reduciag stresses and reactions is to provide additional pipe ia the system ia the form of loops or offset-bonds. When physical limitations restrict the use of additional bends, a multiple arrangement of several small-size pipe mns may sometimes be used. Owiag to stress intensification, the maximum stress generally occurs at elbows, bends, and Ts. Thus, heavier-walled fittings may reduce the stress without significantly impairing flexibiUty. FiaaHy, effectively located restraints can reduce thermal effects on the equipment. 

Compared with elbow fittings, bends with a centerhne radius of three or five nominal pipe diameters save the cost of joints and reduce pressure drop. Such bends are not suited for instaUation in a bank of pipes of unequal size when the bends are in the same plane as the bank. 

Current designs for venturi scrubbers generally use the vertical downflow of gas through the venturi contactor and incorporate three features (I) a wet-approach or flooded-waU entry sec tion, to avoid dust buildup at a wet-dry pmction (2) an adjustable throat for the venturi (or orifice), to provide for adjustment of the pressure drop and (3) a flooded elbow located below the venturi and ahead of the entrainment separator, to reduce wear by abrasive particles. The venturi throat is sometimes fitted with a refractoiy fining to resist abrasion by dust particles. The entrainment separator is commonly, but not invariably, of the cyclone type. An example of the standard form of venturi scrubber is shown in Fig. 17-48. The wet-approach entiy section has made practical the recirculation of slurries. Various forms of adjustable throats, which may be under manual or automatic control. 

Any obstruction to flow will generate turbulence and cause a pressure drop. So, pipe fittings, such as bends, elbows, reducing or enlargement sections, and tee junctions, will increase the pressure drop in a pipeline. 

For the smaller sizes in nominal pipe diameters with coned -and- threaded connections it is usual to design the pipe-work with standard fittings such as crosses, unions, bulk-head couplings, reducers, adapters, elbows and Tees (for some examples see Fig. 4.2-4). These fittings are normally in cold-worked austenitic steel (e.g., 1.4571 or AISI 316Ti), but features with inserts of other more corrosion-resistant materials are available. 

Pipe fittings such as elbows, tee-pieces, reducers, expanders, valves, etc. can all alter the symmetry of the flow profile. MlLLER(2) has listed the following effects ... 

The additional frictional losses due to pipeline fittings such as elbows may be added to the velocity head loss N = 4fL/DH using the same velocity head loss values as for incompressible flow. This works well for fittings which do not significantly reduce the channel cross-sectional area, but may cause large errors when the flow area is greatly... 

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