Surge Protection System 

Compressor type

Are commonly arranged with compressors, to p​rovide additional air in to the tank if the liquid level rises above the normal condition. 
The change in level is detected by a level instrument, which may be a simple bypass level gauge containing a magnetic float which rises and falls with the liquid level activating magnetically sensitive switches attached to the level gauge or a more advanced level instrument, such as a radar or ultrasonic level detection instrument.
The surge tank will be fitted with level switches and instrumentation to enable level detection and control actions to be 
taken.

Surge Protection System

Dip Tube Type

As there is no bladder in the vessel, the connection pipe is completely open and there is absolutely no risk of obstruction if used in a sewage system. With this surge vessel there is absolute control of the amount of air as it is renewed at any pump stop, and therefore no need for a compressor.

On the top of this vessel the dip tube is connected with one Air valve(Single) or

two Air valves(Twin) .

This type of device is recommended  for relatively flat profiles with low geometric head.