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Standalone HydraCALC (Location)

Button: Print Final Function: Results Error Type: Discrepancy

Description:

Reviewing the results you notice a discrepancy between the k-factor of an equivalent k versus a sprinkler head using that equivalent k-factor

 

In the example below, EQ02 has a k-factor of 5.37.  Reference point 1 is supposed to use the k-factor of EQ02 (5.37) but in fact is using a different value (5.36).

 

Solutions:

1.
Cause:

Elevations were used in the Equivalent K Piping tab of HydraCALC
Solution:

It is not recommended to enter elevations in the Equivalent K Piping tab. 

 

In this case the sprinkler is at 8'-4" and the branchline pipe at 7'-10". 

 

 

Remove all elevations plus the blank row references to EQ01 & EQ02 in the 3rd and 5th rows.

 

In the System Piping tab, enter the sprinkler elevation as the elevation for node 1, not the branchline elevation.

 
2.
Cause:

The program is using a rounded flow to establish the k-factor for an equivalent k, but the actual flow to establish the k-factor for the flowing sprinkler.
Solution:

While very rare, this rundown will explain how this is possible...

 

When calculating the equivalent k, the formula of [k √ p = Q] is used;

 

5.6 * sqrt(7) results in a flow of 14.816207 gpm at SP02, or rounded to 14.82 gpm.  

 

At EQ02, a new pressure of 7.627 psi is calculated and with the rounded flow of 14.82 gpm, we have a new k-factor of 5.37 psi

 

The k-factor at reference point 1 is calculated based off the same pressure of 7.627 but the non-rounded flow of 14.816207.  This results in a k-factor at node 1 of 5.36.

 

 

The formulas below demonstrate this;

 

 
Updated: Sept. 19, 2022, 2 p.m. Created: April 13, 2022, 4:21 p.m.