We've had a lot of questions about how to use this device. First, please be aware that we don't have a lot of experience using spunding for pressure ferments but here are a few notes. You can use this device to check and/or vent a keg that has had the gas source disconnected. If you want to just use it to check pressure, turn the PRV all the way clockwise so that it doesn't vent and then connect to the keg's gas post. If the pressure is higher than you wanted, turn the PRV counterclockwise to allow venting.

In order to set the PRV pressure for venting during fermentation, it's best to pressurize the keg first to just over your desired vent pressure, rotate the PRV clockwise nearly all the way and then attach the spunding valve to the keg. Rotate the knob counter-clockwise slowly until it begins venting. Find the spot where it vents down to your desired pressure and then stops. To check that you've set it properly, remove the spunding, repressurize the keg to a few PSI above your set pressure and then reattach the spunding to watch for appropriate pressure venting.

This process sounds tedious but gets much easier after you've done it once or twice. You can also save gas by connecting the spunding directly to a gas source using our ball lock jumper post. If you don't have a CO2 source, it would be best to start using the spunding until after fermentation has become quite active.
That way it will be building pressure while you are working on adjusting the knob

Warning:We recommend using a vessel with an overpressure vent in ADDITION to using the spunding. It's always better to have redundant overpressure protection when fermenting in a pressure vessel. It is safer to use an open blowoff device for the front end of a fermentation and then switch to spunding when krausen has subsided.