Thursday, 13 February 2014

Comparision of Surge Systems

Comparison of Surge Systems

Surge-Anticipating valve
Air vessel
Negative pressure
Requires design of proper air valves and/or one-way filling tanks.
Very large capacity may be required for the pipe filling stage and local high points.

Does not require any external additions except a drain pipe to the sump.
Requires compressor, backup compressor & sophisticated control systems to maintain the proper water volume in the tank
Check valve
Prevents mechanical slam to the check valve.
Increases mechanical slamming to the check valve.

System Cost
Low-cost for larger systems - valve size is reduced, mostly, as the pipe is longer. (longer pipes have a higher friction, and returning flow is smaller)
Very high cost for large systems. The tank size increases with capacity of the pipe, so longer pipes require larger vessels
Expensive, not practical for small networks (up to 8")
Low cost for small system protection
Low-cost and easy maintenance - only periodical testing required.
High maintenance costs: Compressor, control system and micro-crack detection
Enables periodical operation tests  without stop of pumping.
Does not allow a test without completely stop of pumping.
Requires minimal space
Requires large space
Relief function
 High Pressure Relief function is added as a standard feature of the valve
Not included, cannot prevent abnormal high pressure in the network during pumping
Protection of raw-water & sewage system
Included in the standard valve. Same protection. No additional parts. Clean or filtered media is required.
Makes the maintenance even more difficult & expensive task. Not recommended.

Though air-vessels are the most common method of surge-protection used nowadays in design of pumping system, it is our opinion that using Surge-Anticipating Valves should be seriously  considered due to its low cost, ease of maintenance (cost of ownership) and reliability.

Combination of Air Release Valves with Surge-Anticipating valves, if properly sized and adjusted, will supply an equal level of protection for large systems, at a much lower cost and smaller footprint.

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