Central LP port of the MK25

[scubadada]

What's with the warning sent with my newly purchased MK25 DIN/S600, "Don't connect a R-series second stage or ocotpus to the central LP port in the first stages equipped with a swivel turrent since the axial-direct High Flow could make your R-series second stage not work properly"

Thanks and good diving,

Craig

 

[tstormdiver]

It is because the air flowing through the central port it a straight shot. Very little, if any, turbulence to slow the flow down. The "R" series 2nd stages & most Octos are unbalanced 2nd stages. That high velocity flow can cause a freeflow condition. On the side ports, there is usually enough turbulence to slow the flow & makes it possible to properly use an unbalanced 2nd stage on the 1st stage.

 

[scubadada]

Thanks tstormdiver, appreciate the information. I have one R series regulator, a 109. Unlikely I would run it off the central port but I will keep this in mind

 

[herman]

This is more sales BS than physics. The problem is the air velocity or flow is not going to be any greater in normal operation than in any other port unless the port is wide open and under full flow. The hose, connectors and the LP seat itself are going to keep flow way below what any of the ports are capable of and as long as IP stays up, the HP seat will remain in a throttled position which limits both flow rate and velocity. Also, the cavity that the piston dumps into is going to act as an expansion chamber, slowing the air as it exits the piston stem....which is way smaller than any port. Makes a nice sales pitch for those who don't understand how regs work..

 

[SCUBAPRO Harry]

Given that the MK25 has a enormous gas flow rate to the second stages, the "in-line" or straight LP port has an even slightly higher flow value since there is no 'turn' for the air to take. In some circumstances, this high rate of gas flow has made the 'unbalanced' second stages flutter or "pop" as this flow pushes against the LP poppet/spring. Your old 109 can be upgraded to a Balanced 109 which I recommend to most since it improves its performance significantly.

 

[JulesSCUBAPRO]

The R series regs usually coupled with longer hoses, demonstrates an undesirable hammering of the piston in the first stage when connected through the central lp port of the first stage.