Sample Problem – Equivalent Length Calculation for Piping Fittings

Tutorial for equivalent length calculation

This tutorial uses sample calculations to demonstrate how to calculate equivalent length for piping fittings, joints and valves.

Problem Statement -

Calculate the equivalent length and combinedK-factorfor following set of fittings,90⁰elbows - 5 nos. 45⁰elbows - 2 nos.Gate valves - 3 nos.Ball valve - 1 no.Check valve - 1 no. The line size is 6 inches while there is a 8"-6"reducerat the beginning of the line.

The 6" line with 'STD' schedule handles 100,000 kg/hr of water. Approximate length of this line is around 200m. This water stream is available at 5 barg pressure and 30⁰C.

Solution -

This sample problem is solved in following 3 basic steps.

Step 1.

第一步解决这个示例的problem requires determination the important physical properties of given fluid (water) at given temperature and pressure conditions.

UsingEnggCyclopedia's Liquid Density Calculator, water density at 30⁰C =993.41 kg/m³

UsingEnggCyclopedia's Liquid Viscosity Calculator, water viscosity at 30⁰C =0.81 cP

FromEnggCyclopedia's standard pipe dimensions calculator, for 6" pipe with STD schedule, internal diameter is 154.1 mm.

Step 2.

Total K factor for the set of fittings can be calculated usingEnggCyclopedia's K factor calculator.Refer to the screenshot below for demonstration of use of this calculator.

Step 3.

In the third step of solving this sample problem, inputs from steps 1 and 2 are fed toEnggCylopedia's equivalent length calculatorto get equivalent length for the given set of fittings. Refer to the screenshot given below for guidance to use the calculator.Thus the set of fittings in given 6" line are equivalent to 60.36 m of that line. Along with the original 200 m of straight pipe, the total equivalent length of the given 6" line becomes 260.36 m. This length can be used to quickly calculate variation of pressure drop for minor variations in the flowrate, usingEnggCyclopedia's pipe pressure drop calculator. For manor variations in the flowrate, the Darcy friction factor and hence the equivalent length has to be recalculated.