Length, equivalent

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

GPSA Engineering Data Book, Gas Processors Suppliers Association, 10th Ed. 1987. 

Branan, C. R., The Process Engineer s Pocket Handbook, Vol. 1, Gulf Publishing Co., p. 6, 1976. 

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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... 

Equivalent Lengths for Multiple Lines Based on Panhandle A... 

Find the equivalent length in terms of single 12-in. ID line. 

D = Header diameter, ft f = Moody friction factor L = Header equivalent length, ft M2 == Mach number at the header outlet Pi,P2 = Inlet and outlet header pressures, psia... 

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. 

An 800-gal reaetor eontaining a styrene mixture with a speeifie heat of 0.6 eal/gm °C has a 10-in. rupture disk and a vent line with equivalent length = 400. The vessel MAWP is 100 psig and the rupture disk set pressure is 20 psig. The styrene mixture had a self-heat rate of 60°C/min at 170°C as it is tempered in a DIERS venting test. Determine the allowable reaetor mixture eharge to limit the overpressure to 10% over the set pressure. 

Constant friction method. The principle is that the friction losses per meter run of the duct are taken as being constant. Values in the 1 to 5 Pa/m range are typical. The friction losses of connecting elements are expressed as an equivalent length of the straight ductwork runs. This is a simple method. It is ideally suited as a preliminary design method where it is combined with another approach. 

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. 

From Figure 2-20 or 2-21 determine the equivalent lengths of all fittings, valves, etc. 

If a line is made up of several different sizes, these may be resolved to one, and then the equation solved once for this total equivalent length. If these are handled on a per size basis, and totaled on the basis of the longest length of one size of line, then the equivalent length, L, for any size d, referenced to a basic diameter, d. ... 

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

The calculations can be based on diameter d. and a length of all the various L, values in the line plus the length of line of size d., giving a total equivalent length for the line system. 

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