Stone
Contributor
Scubaroo,
I bought my magnahelic directly from Dwyer-inst.com. I think I paid $60 instead of the $100 Scubatools wants. I bought the 5-0-5 (and it works just fine), but I think the 3-0-3 is a better choice.
Reg Technicians - What do you set the cracking effort to?
- Thread starter ElectricZombie
- Start date
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Scubaroo,
I bought my magnahelic directly from Dwyer-inst.com. I think I paid $60 instead of the $100 Scubatools wants. I bought the 5-0-5 (and it works just fine), but I think the 3-0-3 is a better choice.
The "5-0-5" or "2-0-2" notation means the gauge will measure from -5 inches water column to +5 inches water column. Same for the "2-0-2" unit.
Dwyer also makes units in the following ranges:
0.5-0-0.5
1-0-1
From an accuracy standpoint you are always best to pick the unit that has the closest range to the value you are measuring. The unit range value has to be above the measured value, in other words you would not want to use the 1-0-1 unit to measure 1" water column.
The 2-0-2 unit sounds like the best fit to me in this case.
Dwyer also makes units in the following ranges:
0.5-0-0.5
1-0-1
From an accuracy standpoint you are always best to pick the unit that has the closest range to the value you are measuring. The unit range value has to be above the measured value, in other words you would not want to use the 1-0-1 unit to measure 1" water column.
The 2-0-2 unit sounds like the best fit to me in this case.
nickjb
Contributor
For the DIYer is there anything wrong with using a bent tube filled with water, the classic manometer?
Stone
Contributor
Here's a link to an old thread that tells how to order from the Dwyer site: Directions
I think if you use a 2-0-2 you might have a little harder time seeing how close you are since it only goes up (and down)to 2. If you happen to initially set it at 3.5" somehow, then you don't have anything to gauge how much you need to adjust it to get down to around 1.5 or less. with the 5-0-5, I think you can learn how your equipment reacts to adjustment and in the long run, set it up a lot quicker and easier. If it was set at 4 or 5 and we only had a 2-0-2, then it might get a little frustrating if you didn't have a clue how far out you were. I guess you could do a water test to get you in the ballpark and the chances of someone that works on their regs setting the CP to 4 or 5" is probably not that great. Maybe if you really have a lot of experience and do it every day, the 2-0-2 would be an ok choice but again, I don't think there is any real advantage to it. More likely, a good use for the 2-0-2 would be if you had both it and a 5-0-5. Use the 5-0-5 to get it close and then switch to the 2-0-2 for those regs you really want to pinpoint the CP on. Again, I don't think there's anyone out there that can really tell a difference between a cp of .4 and .5" by breathing it anyway.
Stone
Contributor
Jamiei has a point.
On my regs, the pre-adjustment puts me on the "free-flow" side of nominal, so I always increase cracking pressure. I imagine some regs start out "out of range" and you have to decrease cracking pressure before it will even register on the gauge.
In my case, the 2-0-2 or 3-0-3 would always work.
On my regs, the pre-adjustment puts me on the "free-flow" side of nominal, so I always increase cracking pressure. I imagine some regs start out "out of range" and you have to decrease cracking pressure before it will even register on the gauge.
In my case, the 2-0-2 or 3-0-3 would always work.
OP
ElectricZombie
Contributor
When I put the orifice back in the 2nd stage, I barely screw it in so that when I turn the air on, I will always get freeflow. I then use the adjustment tool to move the orifice towards the seat. If you do it in this manner, you won't accidentally set it too hard which cuts into the seat material. You can then do the fine adjustment from the left side. This way, you'll never have the cracking effort above 2.0 or so anyway. A really good reg should be able to be set below 1.0 if desired.
All regs should be able to breath at least a 1.5 - 2.0, anything more and I would consider a rebuild or getting a new reg. A 2-0-2 or 3-0-3 will do everything you need and should be more accurate than a 5-0-5.
Scubaroo
Contributor
Thanks Stone, already found them for around that price at http://www.lesman.com/acatalog/Online_Catalog_Units__Millimeters_of_Water_Column_1233.html
Stone
Contributor
Never want to see a diver pay too much. Some of Scubatools other stuff is pretty reasonable, but the gauges are not.
brian cooper
Contributor
Apeks, in cold water (2 to 4deg C) can be set up exactly as pre Vances book, and correction on his web site (re page198 info..)
9.8 bar IP, chamber sandpapered down to get slight hissing when manual adjuster turned fully out, this stops when turned in by one full turn. cracking pressure 8mm (3/8")to 25mm (1").
IP is NOT critical because 2nd stage is balanced and will not freeflow even when IP is mal-adjusted upto 17 bar, PROVIDED that all seats and seals have been bedded in.
Lowering the IP does reduce the tendancy for 2nd stage freezing but Ihave found thats not a problem on my old T50D.
Having said all that I normally set customer's regs at 30mm (1.25") , it keeps them happy and it well clear of freeflow (the main cause for complaint)
Cheers
Brian Cooper
You must buy THE book and read "Round the Bend"
9.8 bar IP, chamber sandpapered down to get slight hissing when manual adjuster turned fully out, this stops when turned in by one full turn. cracking pressure 8mm (3/8")to 25mm (1").
IP is NOT critical because 2nd stage is balanced and will not freeflow even when IP is mal-adjusted upto 17 bar, PROVIDED that all seats and seals have been bedded in.
Lowering the IP does reduce the tendancy for 2nd stage freezing but Ihave found thats not a problem on my old T50D.
Having said all that I normally set customer's regs at 30mm (1.25") , it keeps them happy and it well clear of freeflow (the main cause for complaint)
Cheers
Brian Cooper
You must buy THE book and read "Round the Bend"
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