Question about hydro for HP steel tanks with REE stamp on them

ours are $15/hydro $20 with a VIP sticker. They don't fill however.

 

Do they load a holding pressure of breathing grade air? I'm wondering how the shop doing the fill knows the cylinder is not contaminated?

 

ours don't usually worry about it, but they put about 100lbs of air in there. That said, I will usually drain them and transfill a few hundred pounds in there before taking them to get filled

 

If I could find a $100 viz cert course, I'd go that route too. For $300 it's not clear I'd save any money very soon. Do you ever have trouble getting fills with your self-inspected tanks?

 

elgoog, I would cross my fingers and pray!

Just kidding!

A little background. I run a hydro-test facility in a dive shop and have been involved with testing for over 30 years.

You ask some very good and educated questions. There are a lot of myths around hydro-testing and there is not a lot of information on the net or better said it would take a long time to sort it all out!
First the REE stands for Rejected Elastic Expansion. It is used in different ways depending on the DOT specifications of the cylinder and as for yours, And with out reading the exact document for your cylinders (This should be done by the tester before EVERY test) I will go from memory. In your case the REE will be used for determining the safety of the cylinder. As your cyl has a DOT E rating (E stands for exemption) and is filled to 3442 PSI. In other cases the REE can be used to determine if the cyl can be plus stamped (That means it can be filled to 10% over the rated pressure).

The 90% pre test you mentioned comes from a slight problem with the difference in the base metal and the zink (Galvanized) coating. It stems back to the 60's and Norris cyl's that would commonly fail hydro. The 90% is to pre stretch the zink coating so it will not give a false reading on the base metal. Keep in mind that the hydro-testing process is looking at the elasticity of the base metal. Your cyl will be pressurized to 5250 PSI, held for a predetermined amount of time, measured for expansion and release the pressure and re-measured to make certain it will not burst!!!

I hardly ever (Can not quite say Never) fail steel cylinders during hydro-test. Rust and pitting is the biggest failure of steel.

Now a little personal Blah, Blah, Blah.....

I would like to say that all hydro-test facility's are excellent. (most are) but that is not always the case. Some of them only deal with industrial cylinders and as such are not as concerned with the cleanliness of a breathing cylinder. Ask questions! Who does the visual inspections on your cyl's? Can I see inside? Tell me what I am looking at! I know I personally get excited if a customer wants to know information. I spend more time with them. If nothing else it will make certain that it gets looked at. Ask who your shop is certified through! In years past it has been an industry standard and there where few actual certified inspectors. PSI was one of the first, and now SDI has a great inspection course. I am a visual inspection instructor and I am very anal about the cyl's that go through my shop. As for going to the hydro test plant directly. That would be a good idea if you have the time and want to learn. As for price! You will most likely not get a fill and a visual from the plant and will have to return to the dive shop for those things. Besides why would you not want to support your local dive shop? Develop a good re-pore and better yet GOOD friends??? At the top you might save $10 at the worst you will pay full price and then have to pay the dive shop $17 for a VIS and fill! (Un-less you have a stupid number of cylinders like me Your local shop should be your best friend! END of personal note!

PrffsrE

 

Thank you for writing this up and explaining it to us new individuals in scuba diving it answered a lot of my questions I had already.

 

Just where did this info come from? The round out is not due to it having actual zinc (with a C) on it. It's because the galvanizing process is hot enough (840F / 450C) that hot dipped galvanized cylinders can take a set (aka shape) which is more like a banana than a tube. The pre-stretch protocol is to "round out" the cylinder so that the change in shape (straightening) under pressure is not mistaken for a permanent deformation. Faber's spray on zinc coating (under their paint) is not done at high temperatures and those cylinders don't take a banana shape, so they don't require a round out despite having a zinc coating.

 

I’m learning a lot of important information from all the divers and it’s great to see everyone sharing their knowledge and advice as well and that if there is something that isn’t correct someone will explain it so it’s better understood.
Thank you once again for responding.

 

For any questions on the XS Scuba Worthington X Series cylinders, SP14157, they maintain a page on their site with links for all of the pertinent instructions and documentation. So if your hydro tester does NOT have the necessary info, it is available there.
Changes to the hydro retest — XS Scuba

 

Thank you so much for taking the time posting this information it will be very helpful to have in case my dive shop doesn’t have it. Thanks again for everyone’s help.