Closing or opening valves quickly - or starting the pump stop - can cause pressure transients in pipes known as outbreaks or air -blows.
One "ARIETE BLAR ” or ” Hydraulic Hammer ” In the pipe or tube is a peak pressure caused by the sudden variation of the flow rate.
ARIETE blows can be created if:
- Valves opens or closes fast.
- The pumps stop or start suddenly.
- PARTS OF THE PUMPING SOURGE.
And speed energy is converted to pressure energy. As the flow of water is restricted inside a pipe, a shock wave will travel back and forth through the incompressible water in the pipe, diverting everything in its way.
As liquids have a very low compressibility, the resulting pressure energy can be very high. If the intensity of the shock wave is high, physical damage may occur to the system.
The pressure peak of the airway blow to a piping caused by closing or opening a valve can be estimated as:
D p = 0.070 ΔV l / d t (1)
Where
Δ P = Increased pressure - Pressure peak (psi)
Δ v = change in flow speed (ft/s)
Δ T = valve closure time (s)
L = upstream tube length (ft)
- 1 pel (pure) = 0.3048 m
- 1 pé/s = 0,3048 m/s
- 1 psi (lb/in 2 ) = 6894,8 Pa (N/m 2 )
Example - Single -generated air -closing scam
The peak pressure (sap of acet) in a water tube of 100 feet where the speed of water flow is reduced from 6 pumps/s to 0 pump/s When a solenoid valve closes in 0,1 s - It can be estimated as:
Δ p = 0.070 ((6 pounds/s) - (0 pits/s)) (100 pits)/(0.1 s)
= 42 0 (psi)
With a closing time of 1 s (solenoid valve with shock absorber) - The peak pressure peak (air -sample) can be estimated as:
Δ p = 0.070 ((6 pounds/s) - (0 pits/s)) (100 pits)/(1 s)
= 42(psi)
To avoid that ARIETE BOLDS damage piping systems.
- open and close the valves slowly
- Use Soft Starters to Start/Stop Bombs
Source: https://www.engineeringtoolbox.com/water-hammer-d_966.html
