Comparision of Surge Systems

Comparison of Surge Systems

Item	Surge-Anticipating valve	Air vessel
Negative pressure prevention	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.
Accessories	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 slam	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
Maintenance	Low-cost and easy maintenance - only periodical testing required.	High maintenance costs: Compressor, control system and micro-crack detection
Testing	Enables periodical operation tests  without stop of pumping.	Does not allow a test without completely stop of pumping.
Footprint	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.

Summary

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.