Pipe Fittings Loss Calculations with K Factors

Pipe fittings, valves and bends usually have some associated K factor or local loss coefficient, which allows the calculation of the pressure loss through the fitting for a particular fluid flowing at a specified velocity. Manufacturers of pipe work fittings and valves often publish a fitting's associated 'K' factor.

Pipe Fitting Loss Formula

Example pipe fitting symbols Fluid head loss through a fitting can be calculated by the following equation:

h = K x v² / 2g

where
h = pressure loss in terms of fluid head, i.e. fluid head loss
K = manufacturer's published 'K' factor for the fitting
v = velocity of fluid
g = acceleration due to gravity

Where the length of the pipe is relatively long, the effect of the fitting losses are usually considered as minor losses, and are often ignored during initial analysis of the pipe system.

If the piping design contains a partially open valve then the effect and head loss through the valve should always be included since the valve head loss may turn out to be significant.

Pipe Fittings and K factors database

Our Pipe Flow Expert software has a database that contains the K factors for many different types of valves and fittings. It also has special wizard helpers that can calculate the K factor for special types of fittings such as:

Addition information about losses through pipe fittings is published in 'Flow of Fluids through valves, fittings and pipe' - Crane Technical Paper No. 410.

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