Adding Minor Losses to Pipes

Product(s): WaterCAD, WaterGEMS, Hammer
Version(s): CONNECT Edition, V8i
Area: Modeling


WaterCAD, WaterGEMS and HAMMER have the ability to model multiple minor losses in a single pipe. This TechNote explains how to do it. 


WaterCAD, WaterGEMS and HAMMER won't calculate the losses automatically if you place pipe bends, etc. You must account for these losses by using minor loss coefficients if you would like to. In some modeling cases, it might be necessary to represent multiple minor losses in a particular pipe. For example, if there are multiple bends throughout the pipe, plus a gate valve.

However, many modelers will choose to omit minor loss details (since as the term implies, they should be minor compared to other losses). If you find that minor losses as having a significant impact on pressures, it could be due to large velocities in the pipes. Headloss from minor loss coefficients is equal to K * V^2/2g.

Pipe vs. Valve for Minor Losses

A minor can be used on both a pipe as well as on a valve. They both use the standard minor loss equation where Hl = K*V^2/2g. With the valve, you can use a different diameter to impact the velocity and with a pipe, the velocity is based on the pipe diameter. The other difference is in the layout and visualization. If you want to see the head drop at a node, use a TCV. If you are OK with distributing it over a length of pipe, use the pipe. Using the TCV also has the benefit of being able to see it visually in the drawing and account for it in the FlexTables.

Adding Minor Losses

Single Minor Loss

If you want to include a single minor loss, you can set Specify Local Minor Loss to True. You can then enter a minor loss value or click the ellipsis (...) button in the cell to open the Engineering Library. The Engineering Library includes a number of potential minor losses that can be applied to a pipe or valve.

Multiple Minor Losses

In the Pipe Properties window, set the Specify Local Minor Loss field to False. This will enable the field for Minor Losses.

Click inside the box for the Minor Losses field and click the ellipsis (...) button to bring up the Minor Losses window for that pipe:

Click in the Minor Loss Coefficient box to bring up the ellipsis button like in the screenshot above. Then click the ellipsis (...) button; this will bring up the Minor Loss Coefficients window:

You'll notice that the Minor Loss Coefficients window is currently empty. Click on the down arrow next to the book and you'll get the following menu:

Click the Import from Library option. This will open the Minor Loss Engineering library:

Click on the + sign in front of the Minor Loss Libraries entry and then the MinorLossLibrary.xml entry to list all of the minor losses currently in this library.

Click on one of the minor loss entries to highlight and select it:

With the minor loss entry highlighted, click the Select button and this will add the minor loss to your Minor Loss Coefficients window.

If you have multiple minor losses, you will need to repeat steps 4-8 again to add the other minor losses to this same window-in the screenshot below, I have added 2 more minor losses to this window:

Click the Close button to close this window.

Next, back on the Minor Losses window, click on the dropdown box in the Minor Loss Coefficient column and you should see all of the minor losses that you had imported into the Minor Loss Coefficients window in steps 4-9 (in the case of this example, the 3 minor losses I had added show up):

Select the appropriate minor loss for this particular pipe. If there are multiple minor losses, add each minor loss onto a separate line:

Set the Quantity field to the appropriate number of occurrences of that minor loss in that pipe. After all of the appropriate minor losses have been selected, click the OK button to close this window.

Back on the Pipe Properties window, the Minor Losses field value will update to list the correct number of minor losses that was added (3 items in the case of this example) and the Minor Loss Coefficient (Derived) field should update to the correct composite minor loss value.

Adding multiple minor losses to multiple pipes at one time using Modelbuilder

1) You will need to have a spread sheet with 3 columns: a) Label b) Minor Loss Label c) Quantity  

This is a sample of what your worksheet might look like Minor Losses worksheet for Modelbuilder

Note: The minor loss label will be the exact label name that you have listed in the minor loss coefficients manager  

2) Create a selection set of pipes that you are going to be adding a collection of minor losses for.

3) Open your flextable based on that selection set  . Edit the flextable and add the column titled "Specify Minor Loss Coefficient?" then set it to "False", which is a blank checkbox.

4) Open ModelBuilder (Tools > Modelbuilder) and start a new run.

5) In step one choose the appropriate Excel datasource, which will likely be "Excel 2013 / 2010 / 2007 (12.0)" and click the Next button twice

6) On step 3 make sure your options are set up as shown below and click the Next button twice

 7) Set the Table Type to "Pipe, Minor Losses" (blue box) and the Key Field to "Label" (red box). In the field mapping steps below (green box) match the Minor Loss field to the "Minor Loss Coefficients (Label)" and the Quantity field to the "Quantity". Click Next when done.

 8) When asked in the last Modelbuilder step if you'd like to build a model choose "Yes" your information will be imported. Double check to make sure the information is correct on a few pipes.

See Also

Product TechNotes and FAQs

OpenFlows Methods Product Tech Notes And FAQs

General WaterGEMS V8 FAQ  

Hydraulics and Hydrology Forum