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luis
VDH Moderator
Posts: 1655
Joined: Thu Jun 30, 2005 9:28 pm
First Name: Luis
Location: Maine

DA Aqua Master IP change with tank pressure

Sun Jun 30, 2013 10:51 am

I just rebuild an Aqua Master for a friend of mine (who coincidentally is a rep for Aqua Lung).

It has been a little while since I worked on a non-balanced Aqua Master so I decided to publish some of the IP versus tank pressure data. I have taken this data before, but not as precisely and in as many increments.

I have digital pressure gauges for tank pressure and intermediate pressure (IP). They have both been calibrated against a calibration gauge and their maximum error of both was less than 1% (0.62% and 0.74% respectively).

I collected data a couple of times, but I am only including the data after the last IP adjustment. I am also including the cracking effort.

The first few times that I collected data the cracking effort was on average about 0.2inWC lower, but that was without the band clamp. Tightening the band clap (clamping hard on the diaphragm) will raise the cracking effort. After this test I adjusted the band clamp some.

Notice that the IP raises 26.6 psi when the tank pressure drops from 2100 psi to about 300 psi. The pressure change in fairly linear (above tank pressure of 300 psi): approximately 1.48 psi increase per 100 psi tank pressure drop.

Also notice that (approximately) below 300 psi tank pressure, the IP is not linear. At some point (around 145 psi) the first stage just opens and the IP reading is the same as the tank pressure.

If I extrapolate to a full tank (2475 psi), I would say that the initial IP would be around 106 psi. That is an IP change of about 30 psi from a full to an empty tank.

I own one Aqua Master that I will try to take some more data later and I will post it.

I am also posting pictures of my test set up and my regulator work bench. I just redid my work bench, cleaned, and organized a lot of the parts containers, so I decided I needed to take pictures to remind me how it is supposed to look when it is relatively clean. The regulator on the left is a PRAM, not related to this test.

I am using several high pressure hoses in series (and my valve test stand) in order to have a reasonable size pressure reservoir after I close the tank valve. I don’t have a high pressure regulator to set the supply pressure by just dialing a knob, so I just use all the hose length as a pressure reservoir that I can adjust the input pressure for it test data point.

There is about a 5 to 7 psi IP drift from initial IP recovery until it locks. You may notice that some of the initial IP data collection (the red data points in the graph) is not smooth. The reading is constantly changing at that stage; therefore taking some of the initial IP data is not always precise. Once the pressure locks the data (shown in blue) is much more accurate.


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Luis

Buceador con escafandra autónoma clásica.

User avatar
luis
VDH Moderator
Posts: 1655
Joined: Thu Jun 30, 2005 9:28 pm
First Name: Luis
Location: Maine

Re: DA Aqua Master IP change with tank pressure

Sat Jul 20, 2013 12:31 pm

Here is some more data from an Aqua Master that I own.

It is not great looking, but it works well. This Aqua Master is in basically original configuration (except it has a DBE and silicone diaphragm.

The IP data follows the same pattern as the other DA.


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Here are some of the tools that I use for testing regulators.

The “Y” connection with the two IP gauges is what I use to calibrate my IP gauges. The digital gauge was calibrated against a calibration standard gauge.

The unit on the top right is a jig that I use to work on regulators. I can use on any tank and it places the regulator in a comfortable position, while reading tank pressure. After servicing a regulator I always put in on this jig. I close the tank valve and let the regulator sit over night. The next day I open the valve while looking at the needle. If the needle moves, I know there is something leaking.
On the bottom right is an HP calibration gauge.


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This is what I use to do a bubble test to check where a leak could be occurring. I have a couple of different “valve extension hoses” like this that I use for different purposes. It makes it handy to have HP air without lifting the tank or putting it in awkward position.


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Soon I will publish some very interesting data (at least I think it is interesting) on exhaust valve flow resistance.
Luis

Buceador con escafandra autónoma clásica.

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Bryan
Plank Owner
Posts: 5270
Joined: Fri Jun 24, 2005 11:40 am
First Name: Bryan
Location: Wesley Chapel Florida
Contact: Website

Re: DA Aqua Master IP change with tank pressure

Sat Jul 20, 2013 12:53 pm

Luis we need to combine the information with the charts into a PDF for the download section and an anchor link to the technical section.
Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

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captain
Plank Owner
Posts: 1400
Joined: Mon Jul 04, 2005 11:32 am
Location: LaPlace, LA

Re: DA Aqua Master IP change with tank pressure

Sun Jul 21, 2013 9:46 am

I don't own an adjustable HP regulator but what I did to have a continuous 300 psi supply to set DAM's on is shim up IP pressure on an old Healthways piston regulator.
Captain

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