Piping equivalent length

TABLE 3—DETERMINATION OF LIQUID OUTLET PIPING EQUIVALENT LENGTH ... 

The flow resistance of pipe fittings (elbows, tees, etc) and valves is expressed in terms of either an equivalent length of straight pipe or velocity head loss (head loss = Kv /2g ). Most handbooks and manufacturers pubHcations dealing with fluid flow incorporate either tables of equivalent lengths for fittings and valves or K values for velocity head loss. Inasmuch as the velocity in the equipment is generally much lower than in the pipe, a pressure loss equal to at least one velocity head occurs when the fluid is accelerated to the pipe velocity. 

Although it has been common practice to specify the pressure loss in ordinary valves in terms of either equivalent length of straight pipe of the same size or velocity head loss, it is becoming more common to specify flow rate and pressure drop characteristics in the same terms as has been the practice for valves designed specifically for control service, namely, in terms of the valve coefficient, C. The flow coefficient of a valve is defined as the volume of Hquid at a specified density that flows through the fully opened valve with a unit pressure drop, eg, = 1 when 3.79 L/min (1 gal /min) pass through the valve... 

Product Plastic pellets, Vn-in (3.2-mm) cubes, 30-lh/ft (481-kg/nd) hulk density equivalent length of system, 600 ft (183 m) f 1995 costs. Equipment includes motor and blower package, cyclone receivers, railcar-unloading connections, high-level interlocks for stopping the motor and blower combination when the silos reach a full level, and all necessary piping. Installation is not included. 

Total equivalent length of pipe (assuming that every fitting has an average 5 m of equivalent pipe length, to account for friction) = 1000 + 25 X 5... 

Tlie following table gives equivalent lengths of pipe for various fittings. 

Lj = Faetor for friction in fittings, equivalent length in pipe diameter per unit length of pipe (1/ft)... 

The equivalent length of the main flare header is then calculated from the flare stack to the last safety valve, taking into consideration the straight length of the pipe and approximate equivalent lengths for bends, etc. If the achial location of the flare stack is not known by that time, it maybe assumed to be 500 ft from the last piece of equipment. Later on, even if it varies from 500 ft, it will not affect the pressure drop calculation at all compared with the entire length of the pipe. 

The head losses calculated using K coefficients by these figures can be added directly to the total friction head loss for the straight pipe portions of a system. When equivalent lengths are determined, they must be added to the straight pipe before determining the total head loss, as shown in the example calculations for a water system. 

Lp is the equivalent length of pipe size d, length L , after conversion to basis of reference diameter, d . 

Tabulate the summation of equivalent lengths of straight pipe, valves, fittings, entrance/exit losses as presented in earlier sections of this chapter. 

L(,q = Equivalent length of pipe plus equivalent length of fittings, valves, etc., ft. 

L = equivalent length of pipe, ft BC = tube length for sensible heating. Figure 10-110, ft CD = tube length for vaporization, ft. Figure 10-110 G = mass velocity, lb/ (sec) (ft )... 

AZ = height of driving leg for thermal circulation, ft Wx = mass rate, Ib /sec, total flow, or W Wj = shaft work done by system, ft liquid A = change from one condition to another AL[ = change in equivalent length of pipe, ft, inlet piping system... 

L = equivalent length of pipe, ft 7 = acceleration loss group, dimensionless... 

L = length of straight tube for heat transfer (or, nominal tube length), ft or, length of path, ft or, length or thickness of coil or jacket, ft or, superficial liquid mass velocity, lb/ (hr) (ft ) or, equivalent length of pipe, ft or, thickness of insulation, in. 

Representative Equivalent Length in Pipe Diameters (L/D) of Various Valves and Fittings [1]... 

Nominal pipe bore (mm (in)) Equivalent length of fitting ... 

Figure 2-21. Equivalent length of fittings for pipe systems. Note preferred use for VA in. and larger pipe butt-welded or socket-welded connections (this author). By permission, Tube Turns Div., Chemitron Corp. Bull. TT 725,1952, reference now to Tube TUrns Technologies, Inc.

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