Scubapro HP Coupling

[mahjong]

Hi. I use the SP high pressure coupling to swap easily between gauges and computers. This is the two-piece coupling where one piece (male) attaches to the HP port of the first-stage and the other piece (female) screws onto the end of the HP hose--the latter then screws into the former. There is also a cap (non-water-tight--it's just a dust cap) that protects the male part attached to the first-stage when the HP hose is disconnected. My question regards rinsing after the dive: Can I rinse the first stage and the HP hose/gauge/computer with the coupling disconnected? Will water enter either or both ends? If water were to enter the HP hose, then I suspect my gauge or computer would explode the next time hooked up the reg and opened the tank valve.

Posted on "Gauges" as well--not sure exactly where this belongs.

Many thanks,

mahjong

 

[mahjong]

Hi. I use the SP high pressure coupling to swap easily between gauges and computers. This is the two-piece coupling where one piece (male) attaches to the HP port of the first-stage and the other piece (female) screws onto the end of the HP hose--the latter then screws into the former. There is also a cap (non-water-tight--it's just a dust cap) that protects the male part attached to the first-stage when the HP hose is disconnected. My question regards rinsing after the dive: Can I rinse the first stage and the HP hose/gauge/computer with the coupling disconnected? Will water enter either or both ends? If water were to enter the HP hose, then I suspect my gauge or computer would explode the next time hooked up the reg and opened the tank valve.

Thanks,

Mahjong

 

[DA Aquamaster]

The first stage side of the coupling is a glorified schrader valve. It is sealed by spring pressure and the valve is opened when the valve is depressed when the two pieces of the coupling are threaded together. The cap is consequently both a dust cap and insurance against the valve being unintentionally depressed.

The hose side of the fitting provides a pin to depress the first stage side of the valve.

Only the first stage side of the valve would be sealed. However sealed or not, both sides trap water droplets and theoretically a small portion of the water droplets present when the two are reconnected could find its way into the system. I am always very careful to ensure both sides are completely dry when I reconnect them.

Rinsing the first stage with the fitting disconnected or even diving with it disconnected would not be a problem, especially with the dust cap in place to ensure the pin is not depressed. Just be sure the fitting is completely dry before connecting it to the hose.

Rinsing the hose end of the fitting is something I would avoid on general prinicple as it woudl potentially allow water into the HP hose. Besides, it can easily be done before you disconnect the two parts of the fitting - the outside of the fitting needs rinsing, not the inside.

If water enters the high pressure hose, nothing will explode but it will move down the hose and then enter and corrode the internal parts of the SPG or computer on the end of the hose.


I have three of these fittings and while I like the ability to move the same computer from double tank to single tank to double hose regulators. I use them very carefully. The high pressure connection between the two ends of the fitting is made in the last 1 1/2 turns of the fitting. If the fitting begins to unscrew itself during the dive (which can happen if the fitting is not very snugly assembled due to torque applied to the hose from rotating/looking at the SPG or computer) it will disonnect itself causing the SPG reading to freeze at whatever pressure is trapped in the hose. If the diver does not notice the unchanging air pressure reading, they could end up in an OOA situation.

Hand tight is not quite enough, especially since it is a left hand thread and helpful dive boat staff "checking" the connection may apply enough normal "righty tighty" pressure to remove much of the snugness. Whenever possible I will use a wrench applied to the small flats below the knurled portion of the fitting to snug it very very slightly past hand tight.

Edited: To reflect much appreciated input from AWAP who pointed out a couple of crucial errors.

 

[DA Aquamaster]

After consulting with AWAP it is apparent I erred in that the hose end of the fitting is not sealed at all. The above post has been edited to reflect how it actually operates in order to avoid any confusion.

In light of how it actually operates, I replicated the air trapping issue but had to work very hard to do it. I found it occurred during only a very small range of travel as the fitting disconnects and did not occur with all of my fittings.

The bad news is that the hose end of the fitting itself is totally unsealed. Getting water on the inside of that end of the fitting would be very, very bad for the long term health of your SPG or computer.

Similarly, having the fitting unscrew to the point where the spg reading drops to zero would essentially open the hose/SPG/computer to the surrounding water.

So...it is doubly important to rinse the hose side of the fitting only while it is connected and to ensure everything is dry when it is re-connected.


And...per your request the thread in the regulators section has been merged into this one.

 

[mahjong]

Thank you so much for the detailed reply, DA. I had been happily using my couplings to swap between an SPG and computer on different dive days and never had any worries. Esp given that the hose end is totally unsealed, you would think that the coupling instructions would make a "warning" point about rinsing. Equally important--it seems a "warning" point in the instructions is also in order about making sure the coupling is good and tight so as to avoid disconnection and an OOA situation. I had been hand tightening mine, and not at all very tightly, assuming that once 3000 psi shoots through it would effectively be locked.

Many thanks again!

Mahjong