## Manual calculation example (16.02.17) ...

I am sometimes asked by Email to show how my programs will get the same answers as a manual calculation done with a pocket calculator, so here is an example to explain the various formulas and equations used for just 3 heads being supplied by 25, 32 and 40 mm pipes along a branch line / range. . 1) Assume a sprinkler head "K" factor of 80 on an Ordinary Hazard scheme where the density is 5 mm/min and the area covered per head is 12 sq.m, so we just have a minimum flow rate Q of 5 x 12 which is 60 L/min, but what is the pressure? . 2) Using the formula Q = K x square root of P (the pressure in bars), we need to transpose this to give P in terms of the known K and Q so is Q / K all squared which comes to 0.5625 bars. . 3) If we assume a nominal 25 mm diameter pipe of type M to BS10255, the actual internal bore is 27.35 mm and the Hazen-Williams "C" factor is 120, so what would be the pressure drop of a 4 m length (the reducing elbow at the head is included in the "K" factor) run flat with no change in elevation? . 4) Using the Hazen-Williams pressure drop formula :- . 1.85 605000.0 x L x Q Pressure drop = ---------------- 1.85 4.87 C x D . 5) We have L = 4.0 m, Q = 60.0 L/min, C = 120 and D = 27.35 mm so this works out to be 605000 x 4 x 1947.959007 / 7022.395823 / 9953646.213 which equals 0.06744157 bars. . 6) The pressure at the second head is therefore this value plus 0.5625 bars which is 0.62994157 so giving a flow Q of 80 x square root 0.62994157 ie. 63.49508682 L/min (about 3.5 more than the end head because it is nearer to the source). . 7) So the flow Q in the second 32 mm pipe is now 60 + 63.4950862 = 123.4950868 L/min along with L = 4.0 m, C = 120 but D is now 36.05 mm bore. The new pressure drop is 605000 x 4 x 7405.457734 / 7022.395823 / 38205743.91 which equals 0.066796438 bars. . 8) The pressure at the third head is therefore this value plus 0.62994157 bars which is 0.696738008 so giving a flow Q of 80 x square root 0.696738008 ie. 66.776667 L/min (again about 3.5 more than the previous head). . 9) So the flow Q in the third 40 mm pipe is now 123.4950868 + 66.776667 = 190.2717538 L/min along with L = 4.0, C = 120 and D = 41.95 mm. The new pressure drop is 605000 x 4 x 16475.6476 / 7022.395823 / 79929053.53 which equals 0.071034263 bars. . 10) The pressure at the start of this pipe is this value plus 0.696738008 which comes to 0.767772271 bars at a flow rate of 190.2717538 L/min. . 11) So although we have 3 heads of nominal flow of 60 L/min, the actual flow rate is just over 190 L/min (not 180) and the pressure needed is 0.768 bars (not 0.56). . 12) Perhaps this will demonstrate why nobody but nobody would ever produce such hydraulic calculations manually - you are just bound to make an error somewhere so getting the WRONG answer! . 13) May I suggest you now download and run my very simple AACALC10 program and check the above calculation is the same. You need to select "New" and type in 3 pipes as follows, pressing {TAB} to replace the spaces below :- . 100 110 41.95 120 4.0 0.0 0.0 80.0 60.0 110 120 36.05 120 4.0 0.0 0.0 80.0 60.0 120 130 27.35 120 4.0 0.0 0.0 80.0 60.0 . 14) It will only take a minute or two to type these values in, noting each time that the hydraulic calculations are repeated so that you see, on the top line :- . Source duty = 190.3 L/min at 0.768 bars (ie. the same as above). . 15) If you think that the 36.05 and 41.95 mm pipe sizes are too big [as they are], then you simply redo the manual calculation steps (7) to (10) and see how long it takes you. . 16) So for 27.35, 27.35 and 36.05, the source is 198.8 L/min at 1.048 bars and for 27.35, 27.35 and 27.35, the source is 198.8 L/min at 1.505 bars - is this what you calculated? . 17) If you still have AACALC10 open, then you only need change the pipe sizes and the calculations are done instantly.

18) If AACALC10 is too complicated for you, then my AACALC8 will repeat the same sums for a complete range from "page 2" simply by setting K = 80, density = 5 and area to 12 - thats all. You can even do 2 pipe friction loss calculations at the same time ...

19) I have also provided FIRSTHCP where DEMO 3 is this exact example to help you learn hydraulic calculations.

20) I can also suggest that you download the complete source code of FREESPRAY for a real example of how such calculations are carried out for complete sprinkler systems, not just for 3 heads along a single branch line / range! .

Alternatively, just CLICK HERE to download my suggested hydcalc.ods file of the above arrangement.

[27.07.17] If you want your own, free, personalised hydraulics calculator and/or have not used a "spreadsheet" type program before, then just download LIBREOFFICE onto your computer. I suggest you do this via www.ninite.com (it is on the far right hand side and you may want some of the other items listed). It only takes a few minutes so then run the LIBREOFFICE program, select LIBRECALC and type the first 5 numbers and [Enter] in the cells A1 to A5.

In A6, type = 60500*SQRT(A4*A4+A5*A5)*A1^1.85/A3^1.85/A2^4.87 [Enter] . If you don't want the sloping length to be used, then just type A4 instead of the SQRT( .. ) part. . In A7, type =A5*0.098 [Enter] . In A8, type =A6+A7 [Enter] . In A9, type =A1/(0.04712*A2*A2) [Enter] . and as you do so, those values will be calculated and shown. You can then enter the text items in B1 to B9 as needed and can format the rows / columns with the required font, size, number of decimal places as desired and SAVE it. That's all.

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## These are the hydraulics programs you have been looking for ...

For the **EN12845 RULES** used throughout Europe, there are the
AACALC7,
CAD2ENRULES,
EASYSHP,
VSHP,
HYD,
IPDS43 and AAVIEW7 programs.

For the **NFPA 13/15 + FM GLOBAL RULES** used worldwide, you can choose
FREESHP,
CAD2HCP,
FIRSTHCP,
ISO2HCP and
AACALC9 with a CAD program for Pipe Schedule systems called
AACALC12 plus
FREEWATERMIST for **NFPA 750** water mist systems.

For **BOTH the above sprinkler rules**, I offer AACALC8,
AACALC10, AACALC11 and my latest
FREEHC software packages.

For the **BS9251:2014** systems, you can use NEW3RD.

All these are in **METRIC** units only, except FREEHCP
which is in the **AMERICAN** units of feet, inches, gpm and psi.

The **5 programs I added in 2017** were FIRSTHCP,
CAD2HCP, CAD2ENRULES,
ISO2HCP and FREEHCP so perhaps
you should try those first. If you want me to review your very first job done with
any of my programs, then you can Email the corresponding data file.