6.5 Hydraulic Calculations
Automist is a pre-engineered system with a maximum total hose length of 60m. All fire tests were performed with the worst-case scenario; 60m total hose lengths with 20m of 1⁄4” and 40m of 5/16”. This causes the maximum acceptable delay in water discharge of, 21 seconds, and pressure loss for the system’s water flow.
To determine the pressure losses and flows on the hoses specified by Plumis, measurements were carried out, given the lack of accurate data available for internal pipe surface roughness the hoses used in the Hazen–Williams and Darcy–Weisbach methods. The following key parameters have been measured for the Automist hoses through experimentation:
|
Parameter |
1/4" hose |
5/16" hose |
Spray Head |
|
Pressure loss (bar/m) |
0.2165 |
0.0866 |
|
|
Time delay (s/m) |
0.25 |
0.40 |
|
|
Pressure loss (bar) |
|
|
3.5 |
|
K factor |
|
|
0.62 |
Maximum high pressure hose length when:
- Both 5/16” and 1/4” hoses are used
|
Max. 1/4" hose length (m) |
Max. 5/16" hose length (m) |
Total hose length (m) |
|
20 |
40 |
60 |
- Only 5/16” hose is used
|
Max. 1/4" hose length (m) |
Max. 5/16" hose length (m) |
Total hose length (m) |
|
0 |
50 |
50 |
Below are the hydraulic calculations for the most unfavourable spray head configurations:
|
1/4" hose |
5/16" hose |
Total hose length (m) |
Pressure loss (bar) |
Time delay (s) |
Flow Rate (l/min) |
Pressure at |
Pressure at |
|
20 |
40 |
60 |
11.29 |
21 |
6.02 |
105.67 |
94.38 |
|
0 |
50 |
50 |
7.8 |
20 |
6.07 |
103.68 |
95.85 |
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