What does the surge valve do?

surge valve

The Surge Valve element encompasses both a Surge Anticipator Valve (SAV) and Surge Relief Valve (SRV). You can configure the valve to act as one of these types or both. When the pressure at an SAV valve falls below the threshold value, it opens up to the atmosphere, in anticipation of a subsequent upsurge (high pressure.) The SRV opens up to the atmosphere when the pressure at the SRV rises above the threshold pressure and closes immediately after pressure drops below this setting.