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DAV-M-SA Triple-function air / vacuum valve equipped with surge-preventing device

DAV-M-SA Triple-function air / vacuum valve equipped with surge-preventing device

Overview

The DOROT DAV-M-SA valves were designed allow air flow into the pipe when it is draining, preventing the risk of excessive negative pressure that may cause collapse of the pipe.
The valves will also enable drain of small quantities of air- which tend to accumulate in the elevated locations during normal system operation, reducing the effective cross-section of the pipe, thus damage the hydraulic performance of the network.
The outflow of the air is restricted, so in the case of fast filling-up of the pipe by water, which forces the air out- it a not escape at the same rate as the water flow, consequently a "temporary air cushion" is created, absorbing the kinetic energy of the approaching water mass. The flow of the air is adjustable by the user.
All the valve components are included within a sturdy, tamper-proof body.

Features & Advantages

•    Surge Arresting – Automatically prevents water hammer pressure surges associated with air release valves operation.
•    Optimum performance – Air outlet can be adjusted according to surge analysis results, on site to a required aero-dynamic performance. The SA addition is assembled on user selected valves only (at local high elevated points). The flow through other valves remains unrestricted. 
•    Simplicity – Can be easily assembled on any of Dorot’s DAV-M series air valves. Reliability – Simple, durable mechanism, fabricated from high grade materials. Can be serviced without having to put the air valve out of service.

 

Function

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

• Air venting  - 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.
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