My co-worker Paul produced this blurb, on request from a customer who was attempting a Velocity Pressure calculation (a **velocity pressure** calculation is required by NFPA when designing Fixed Spray deluge systems). This type of calculation requires the use of the **Input Types** field, discussed in this post a ways back: Why Use Input Types?

For this kind of calc, The program needs to know which pipes are perpendicular at pipe intersections. The perpendicular pipe is where the velocity pressure is used to determine the flow into the pipe.

You can use any of the default **Input Types** from in the selection box, in this example we have used the Letters **A B** & **C** as the Input Types for clarity

All of the pipe where the flow goes straight through must have the same Input Type. Outlet pipes where the flow is determined by the velocity pressure must have a different Input Type.

In addition to the perpendicular pipe outlets the velocity pressure is also used to determine the flow at a K-Factor where a sprinkler head is directly connected to a pipe. (The sprinkler is the perpendicular outlet).

We used **A** for the Input Type from the remote sprinkler back to the supply point. We used Input Type** B** for the pipe that comes off perpendicular to the Input Type **A** pipes and Input type **C** for the pipe that comes off perpendicular to the Input Type **B** pipes.

Based on this, the program knows where all the perpendicular pipe locations are and can calculate the velocity pressures correctly.

Below is a flow diagram showing all of the **B** Input Type Pipe Marked in Yellow and all of the **C** input Type Pipe Marked in Pink. The pipe not highlighted is Input Type** A** pipe.

The Velocity calculation is performed at the intersection of the different Input Types and the K-factor location.

This link will get you the example job used for this post. We suggest you place it in your **\HES\HydraCALC\Ver50\Data\Jobs\Example Jobs** folder. Velocity Pressure.WXF

*Illustration for labeling Input Types*

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