Let is say, a 1000-meter long PN 10 pipe with a diameter of 110 mm is to be used for moving water to a height of 15 meters at 10m / sec speed. Is the pipe pressure we choose suitable to do this job?

Here Q = 10 m/sn, L = 1000 m, Hg = 15 m.

1.The table shows J = 0,0135 for a10 m/s flow rate in 110 mm PVC pipe.

Head loss in 1000 meter pipe; H1 = 1000x0, 0135 = 13,5 mss.

2. If we take the head loss in the additional parts as 5% of the pipe, 13,5 x 0,05 = 0,68 mss

3. By adding the water column head to the head losses caused by the elevation difference of 15 meters;

the operating pressure inside the pipe: 13,5 + 0,68 + 15 = 29,18 mss = 3 ATM is calculated.

4. Let is calculate the effect of the water hammer on the pipe;

Based on the table on the side page a/g = 34.55 and V=1.23 for PN 10 pipe diameter of which is 110 mm.

Water Hammer = a/g.V = 34,55. 1,23 = 42,5 mss = 4 Atm.

Total pressure that will affect the pipe is calculated as 3 + 4 = 7 ATM.

In other words, our pipe will be subject to a maximum pressure of 7 bar (suppression state). Our pipe will not explode because we chose 10 ATM at the beginning of our pipe. In the case of depression, that is, the lowest pressure that can occur in this system is 3-4 = -1 ATM. The result is negative. The difference in pressure due to the water hammer will overcome the pressure that the pipe can withstand and strech the pipe inward. That is to say, our pipe will strech in this case. So it is understood that we did not select the correct pressure for the installation.

A pipe pressure with which either the total suppression pressure will not be higher than the selected pressure or the minimum pressure at depression will turn out to be positive should be selected.

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