Tuesday, 15 December 2015

MAJOR AND MINOR LOSSES IN PIPES

MAJOR AND MINOR LOSSES IN PIPES

We were discussing in our previous post about the pump performance curve and we have also seen the difference between positive and non positive displacement pumps.

After completing my engineering, i had joined an organization and that organization was in chemical manufacturing business. I was assigned there to analyze one pipe flow problem and to produce the outcome in front of the team leader and i had recalled the concept of head losses in pipe flow at that time to produce the required details.

Today we will see here the head losses in pipe flow. Determination of head losses is very important in pipe flow problems and also in designing of a pumping system. So if you need to calculate the head losses in pipe flow, this post will be a very important key for you.

There are two types of head losses in pipe flow system i.e. Major head loss and Minor head loss.

Head loss in pipe flow system due to viscous effect i.e. due to friction will be termed as major head loss and will be indicated by h L-Major.

Head loss in pipe flow system due to various piping components such as valves, fittings, elbows, contractions, enlargement, tees, bends and exits  will be termed as minor head loss and will be indicated by h L-Minor.

Therefore, complete head loss or pressure loss in pipe flow will be summation of major head loss and minor head loss and will be indicated by h L.
= h L-Major + h L-Minor

Major Head loss

 
Major Head losses in pipe flow problem will be calculated with the help of Darcy-Weisbach formula as mentioned below and this Darcy-Weisbach formula will be used to calculate the major loss in pipe flow, it does not matter that pipe is horizontal, vertical or on inclined plane.
Friction factor as mentioned above will be determined on the basis of type of flow i.e. Laminar flow, Transition flow and turbulent flow. We can refer below equations in order to determine the friction factor.

Minor Head loss

As we have discussed above minor head losses are pressure losses in pipe flow system due to various piping components such as valves, fittings, elbows, contractions, enlargement, tees, bends and exits.
Where K is termed as minor loss coefficient and values of minor loss coefficient, K for various piping components or fitting are mentioned in following table.

Type of Piping Components or Fittings
Minor loss coefficient, K
Tee, Flanged, Dividing Line Flow
0.2
Tee, Threaded, Dividing Line Flow
0.9
Tee, Flanged, Dividing Branched Flow
1.0
Tee, Threaded , Dividing Branch Flow
2.0
Union, Threaded
0.08
Elbow, Flanged Regular 90o
0.3
Elbow, Threaded Regular 90o
1.5
Elbow, Threaded Regular 45o
0.4
Elbow, Flanged Long Radius 90o
0.2
Elbow, Threaded Long Radius 90o
0.7
Elbow, Flanged Long Radius 45o
0.2
Return Bend, Flanged 180o
0.2
Return Bend, Threaded 180o
1.5
Globe Valve, Fully Open
10
Angle Valve, Fully Open
2
Gate Valve, Fully Open
0.15
Gate Valve, 1/4 Closed
0.26
Gate Valve, 1/2 Closed
2.1
Gate Valve, 3/4 Closed
17
Swing Check Valve, Forward Flow
2
Ball Valve, Fully Open
0.05
Ball Valve, 1/3 Closed
5.5
Ball Valve, 2/3 Closed
200
Diaphragm Valve, Open
2.3
Diaphragm Valve, Half Open
4.3
Diaphragm Valve, 1/4 Open
21
Water meter
7

Values of minor loss coefficient K for various piping components or fitting, as mentioned in table, have been taken from www.engineeringtoolbox.com

Do you have suggestions? Please write in comment box.

Also Read

Archivo del blog

Copyright © HKDIVEDI.COM | Powered by Blogger | Designed by Dapinder