DA info/help needed please.

[Bryan]

I’m trying to do an outline for a power point presentation on DA Aqua-Master repair and I’m struggling with part of it……I just can’t find the right words/phrases/sayings/BS, etc….How would you present the reason for setting the IP on a DA with the cylinder pressure at 500psi ? NOT IN ROCKET SCIENCE TERMS…..My description takes a long time and only makes sense in my head and Lord knows that no one wants to go there! Many of you are much more gifted with words than I am…..All advice is appreciated.

[standingup]

Is the IP set with the cylinder pressure at 500 to insure that the IP always remains sufficient even at the end of a dive? What is a power point and where will it be viewed, will it be posted on VDH?

[JES]

... What is a power point and where will it be viewed, will it be posted on VDH?

PowerPoint is a complete presentation graphics package from Microsoft. It gives you everything you need to produce a professional-looking presentation. PowerPoint offers word processing, outlining, drawing, graphing, and presentation management tools- all designed to be easy to use and learn.

Only Bryan knows the answers to the last two questions.

[luis]

The intermediate pressure (IP) increases as the tank pressure decreases, so it is necessary to adjust the IP with a low tank pressure (a tank pressure of 300 to 500 PSI is recommended).
Since the highest possible IP will occur at the lowest tank pressure, this procedure will also ensure that the second stage is properly adjusted to operate at the highest IP without free-flowing.


Does this help?

[simonbeans]

If I understand what you said, it must be written in pure eloquence. And, believe it or not, I got it!!!!! You are most talented. You must have had an education NOT in US public schools.
Allan

[Bryan]

The intermediate pressure (IP) increases as the tank pressure decreases, so it is necessary to adjust the IP with a low tank pressure (a tank pressure of 300 to 500 PSI is recommended).
Since the highest possible IP will occur at the lowest tank pressure, this procedure will also ensure that the second stage is properly adjusted to operate at the highest IP without free-flowing.


Does this help?

It makes more sense that the nonsense way I was explaining it.....Thank you Luis.

The powerpoint is for Portage Quarry. Dr. Miller asked that we start working early on stuff for this year. It may show up on VDH....Depends on how the final product turns out.... I'm coming to Florida to DIVE not to work on regulators!!! From the roster we already have you will be able to get more info about two hoses than you would ever every want. I turn to many of the guys on the list when I get stumped....

[Nemrod]

When ever I have to write something I freeze up.


"Adjust the IP at 500 psi to prevent free flow."

In a tech manual there would proabably be an * with a note at the page bottom explaining that

"with an unbalanced first stage the IP increases as tank pressure falls resulting in a potential for free flow."

You see, techs don't always need to know why, just that it does.

Nemrod

[standingup]

Great info guys thanks

[luis]

The intermediate pressure (IP) increases as the tank pressure decreases, so it is necessary to adjust the IP with a low tank pressure (a tank pressure of 300 to 500 PSI is recommended).
Since the highest possible IP will occur at the lowest tank pressure, this procedure will also ensure that the second stage is properly adjusted to operate at the highest IP without free-flowing.


Does this help?

I would like to add:
The above is specific to the DA Aqua Master and any other un-balanced diaphragm regulator first stage.



For an un-balanced piston first stage the maximum IP occurs at the maximum tank pressure. Many (if not most) un-balanced piston first stage the IP can only be adjusted by adding spacer washers under the piston spring. Therefore, most of the time the intermediate pressure is checked, but it is not adjusted. For this type of first stage the IP should be checked (and adjusted) using a tank at the maximum operating pressure for that regulator.

[SDAquamaster]

It's pretty easy to visualize what will happen to the IP as tank pressure falls on an unbalanced first stage if you think about whether the seat is located upstream of the orifice or downstream of the orifice.

If the seat is downstream of the orifice, as is the case with balanced piston first stages, the IP will decrease as tank pressure falls as the amount of downstream assist helping to open the valve decreases as the tank pressure drops.

If the seat is upstream of the orifice, as is the case with any unbalanced diaphragm first stage, the IP will increase as the downstream force trying to hold the valve closed will decrease as the tank pressure falls.

Given that there have been no unbalanced diaphragm first stages produced in perhaps the last 30 years, any unbalanced diaphragm first stage you encounter will be a vintage first stage.

Of course simpler is probably better for techs who may have limited spatial ability and just advising them to set the IP of an unbalanced diaphragm at a low tank pressure of 300-500 psi and to set the IP of an unbalanced piston regulator at a high tank pressure of 3000-3300 psi may save you a lot of trouble.