When air is admitted into the pipe, an in “Air Pocket” is created in the local high points where the Air / Vacuum valve is located. The returning flow re-fills the “pocket”. Too-high velocity of the approaching water column may generate a pressure surge when it reaches the valve.
Operation of the SA addition
The Surge Arrestor addition of “DAV-M” valves limits the air outflow, when the escaping air velocity exceeds a threshold value.
This optional addition creates a temporary, slow closing “Air Cushion” that decelerates the water velocity, preventing water hammer effect.
Adjustment of the air outflow can be done by plugging or un-plugging a set of bores in the SA adjustment plate (see pictures right side).
Vacuum Breaking (Air Intake)
Decrease or the pressure in the system to negative value and the simultaneous drainage of the valve chamber, forces the floats down, allowing the admittance of air into the pipe. The SA disc is in its low position, allowing unrestricted air flow into the system.