homemade hydrotestor

[sciencediver1]

Ok, Im well on my way to having my own tubbler,which is coming along well but what is the feeling of building my own Hydrotest machine. Has any one tried this, I mean it can't be too hard to put one together given some, pipe capped on the bottom and with a removible lid and a pressure sourse to hold it at test pressure and taking a few measurements in the process is it? I have seen some systems on sale on line. Has anyone tried this? Craig

 

[akscubainst]

Why would you want to? DOT isn't going to certify it so it would basically be worthless.

They require everything to be exactly calibrated and it has to be done frequently.

Even if you buy a complete system, you have to have an independent inspector (of which there are 7 nationwide) come to your site at your expense to test and certify your machine. This has to be done every 5 years. I seriously doubt that one of these inspectors is going to certify a garage built machine.

Hydrotesting isn't something that DOT takes lightly, I've heard of testors being fined hundreds of thousands of dollars for not doing things properly. That testor was in Seattle as a matter of fact.

Stick to visuals and maybe tumbling and leave the Hydros to the guys that are setup to do it.

 

[herman]

Unless I read this wrong, he is talking about a pressure pot for testing depth gauges and the like, not a hydro system for testing tanks. Pressure pots are fairly simple and safe....a home brew tank hydro system is a bomb waiting to explode. Depending on the depth you want to test to, 100psi capacity is plenty. The hardest item is the lid which needs a clear section to view the item under test. You don't have to have a clear section but it's nice to have. Remember the items under test need to be submerged to test it properly. The easiest way to build one is to find a 10 to 12" diameter pipe with flanges on each end and a couple of flange plates.

 

[Charlie99]

Pressure pots are fairly simple and safe....a home brew tank hydro system is a bomb waiting to explode.

A hydro system with no air has very little stored energy and failure is a very unexciting event, even with pressures of several thousand psi.

OTOH, a pressure pot system with a lot of compressed air at 100psi can truly be a bomb.

Keep the amount of compressible gas and materials to a minimum.

 

[DA Aquamaster]

If you are making a pressure pot, you want to be sure to be very conservative in your engineering with at least a 200% safety margin. You will also want to incorporate an automatic over pressure relief valve and you will want to plan on a design that is for the most part water filled. The water in the pot is for all practical purposes not compressible and will not cause an explosion if the pot ruptures so the less air in the pot the better. In addition most depth gauges and computers need to be covered with water when tested anyway to prevent possible damage to the sensors and/or diaphragms and internal parts.

As for home brewed hydro testing - what would be the point. As indicated above, to be of any value you and your system would have to be inspected, calibrated and certified by a DOT inspector something that would probably cost you a minimum of $1500. Plus you have to meet other requirements such as having your pressure gauge recalibrated every 6 months. You'd have to hydro a lot of tanks to save any money over a $15.00- $20.00 hydro at a local facility.

 

[oxyhacker]

There's plans for a pressure pot in Steve's divelight book which is made from a sawed-off junk aluminum 80.

Aluminum tanks are have thick enough walls that you can drill them for 1/4" studs and still have space for an O-ring or gasket seal, so a top can be made of just a piece of 3/4" or 1" acrylic, no machining required other than drilling and tapping few holes.

Unless I read this wrong, he is talking about a pressure pot for testing depth gauges and the like, not a hydro system for testing tanks. Pressure pots are fairly simple and safe....a home brew tank hydro system is a bomb waiting to explode. Depending on the depth you want to test to, 100psi capacity is plenty. The hardest item is the lid which needs a clear section to view the item under test. You don't have to have a clear section but it's nice to have. Remember the items under test need to be submerged to test it properly. The easiest way to build one is to find a 10 to 12" diameter pipe with flanges on each end and a couple of flange plates.

 

[426Scuba]

Why would you want to? DOT isn't going to certify it so it would basically be worthless.

They require everything to be exactly calibrated and it has to be done frequently.

Even if you buy a complete system, you have to have an independent inspector (of which there are 7 nationwide) come to your site at your expense to test and certify your machine. This has to be done every 5 years. I seriously doubt that one of these inspectors is going to certify a garage built machine.

Hydrotesting isn't something that DOT takes lightly, I've heard of testors being fined hundreds of thousands of dollars for not doing things properly. That testor was in Seattle as a matter of fact.

Stick to visuals and maybe tumbling and leave the Hydros to the guys that are setup to do it.

I have rebuilt an old hydro test stand and gone through the certification process. If you would like some help building one I would be glad to help.
FYI the test stand needs to be calibrated every day (it is used) with a calibrated cylinder and pressure gauge. The system must also be calibrated to within 500 psi of the test pressure. When I went through certification I think there was more than 7 inspectors nation wide, but I may be wrong its been a couple of year. FYI most cylinder mfg's have and inspector in house I know PST does..

But as posted above it is far less money to pay some one else to do it for you. And if you want to make a biz out of it spend the money and buy an automated one with a big jacket and multiple head cover.