X. Over Pressure for O2 first stage

MX Rebreather - Over Pressure for O2 first stage

When using an offboard O2 bottle as both the rebreather O2 feed and OC deco bailout, the cylinder valve must be turned on to supply gas to the MX rebreather. However, as discussed earlier, to reduce risk, we shutoff the 2nd stage regulator with an isolator. In normal OC operations the second stage acts as an over pressure relief valve, and if the first stage was to have a creep or allow greater than 165psi/11b +/- pressure down the LP hose this 2nd stage would release that pressure. However because it is now isolated, or off, we need to add an OPV (see images above) on the first stage, much like on our argon system. This will activate or release pressure in the event of an IP creep or first stage failure.