SP MK16 vs. MK25... and for fun S550 vs. S600?

[redacted]

wch once bubbled...
How strong a current would it take to depress the cover of either? Has this happened to anyone?
Bill

Currents can hit 4 to 5 knots in some sections. If I grab something & become stationary in current that strong I often have to adjust the knob on my G500 to eliminate a very mild FF.

The knob is also useful if you soak your gear while it is not pressurized. By tightening the knob all the way you reduce the likelyhood of watrer getting into the LP hose around the LP seat.

I believe all of the SP balanced barrel poppet reg share the "anti-set" design. It come with the balance feature.

 

[undah20]

awap, you should avoid using this practice.

By cranking in upon the adjustment knob, you are only increasing the spring tension upon the poppet and it's seat upon the knife edge. Simply causing more tension for teh edge to dig into teh seat - premature aging. The chances of water getting is are limited and the next time placed upon a tank would blow out any water.

False, on all the balaced designs having the antiset feature. Only the S600 and G250HP, and even your G500. The previous G250 did not have the antiset feature, neither does the D400 or S550, R380, R190.

 

[redacted]

That soaking procedure is recommended in the SP user's manual.

I'm fairly sure that the relationship between the S600 (G500) and the S550 is the same as that between the G250 and the G200B. Basically they differ by the user adjustable knob which provide some "field adjustment" on the spring tension in the balance chamber. And the anti-set feature simply is that the spring tension pressing the LP seat against the orifice is minimal since it does not have to overcome the force of the IP gas pressing against the LP seat. This force is offset by the balance chamber. With unbalanced seconds, the spring tension on the LP seat must be high enough that it can maintain a seal with IP gas acting on the upstream side and only ambient pressure on the downstream side. If I've got this wrong, I sure like to learn. I'm not a tech, just some poor DIY diver who had too many bad experiences with bad service techs.

 

[undah20]

Okay, take your G500 when the knob is completely turned out (max performance) and not connected to a tank. Shake it....hear that? That's the lever moving inside. Take the S550, shake it, hear nothing right? Okay, "ANTI-SET POPPET"....it means the whole poppet assembly is allowed to move AWAY from the knife edge...not in contact - savign the seating edge. With the S550 design, the chamber keeps presssure on the spring the whole time. Yes, the POPPET is balanced and has a small balaced chamber on the end, but the S600's whole knob is where the balancing chamber is. (Hope this helps)

And the G250 HP, yes, HP is the same as the S600 internally and the relationship between the S550 (G200B) was. But the older G250 - NOT the "HP" version - the G250, G250 Euro, G250 translucent blue), all have the balanced design. But again, it's the ANTI-SET POPPET design that makes the difference.

You're right in that you can crank it in, but the amount of water and the difference it makes (IF - (BIG 'IF' THERE) you are getting it serviced regularly) is nominal.

 

[SeaJay]

...And I'm here in South Carolina, where the tides rise and fall every day sometimes in excess of ten feet!

This creates what I once told someone, "3-4 knot currents." We actually measured the other day from a boat, and upwards of 6 knots is more accurate.

Since we're diving for fossilized megladon teeth, we often dive like this... Dive, hit the bottom, streamline, put a BFK in the ground, and hold on. Drift backwards foot by foot, feeling along the ground for teeth.

I've never had any regulator freeflow while I'm breathing it... And I've never had my R380 backup freeflow while on my necklace.

...And even with all of that current, I don't think I'd ever experience a "spontaneous freeflow" from my reg, even if in 6 knots of heavy, silty, saltwater current.

Me? I prefer the security of the completely sealed diaphragm on both my first and second stages. I also prefer the simplicity of no extra knobs (do you know how many times I've dived a reg, only to find out that I'd have had a better dive if I'd realized that it was totally detuned?)

 

[luvdiving]

On Johnston Atoll (800 miles SW of Hawaii), one of the diving challenges was lobstering. The lobsters spent the day hiding in shallow holes on the barrier reef.

When the surge coming over the reef was bad, you had to hold on to dead coral as hard as you could to avoid being swept off the reef and tumbling through dozens of spiny sea urchins. Boy, those were the days.

If I didn't de-tune the reg somewhat before the dive, I got some nasty free flows. That's about the only time I used the adjustment knob.:boom: