Internal rust & flash rust in steel tanks

[dnight]

I flubbed your name! Sorry, Tom, i've always been bad with names.

Thanks again for the assist, the tanks are getting used as much as I can get to dive!

 

[drbill]

I agree with Thomas Ivey that PST has a good reputation, and welcome his participation on SB (more manufacturers should do the same). However my HP120 made by PST for Sherwood in June, 1993, recently failed hydro after only 10 years. Needless to say I was quite disappointed by that failure. I expected at least 15-20 years from that tank.

While I am considering a replacement tank from PST (E8 130 or HP 120), comments here and concern about PST's current situation have me looking at alternatives too.

Again, thank you Thomas and PST for participating on SB.

Dr. Bill

 

[drbill]

I was out at the Casino Dive Park yesterday and it was almost empty (what's wrong with you guys, and especially you ladies... vis is good now). An instructor I hadn't seen in a while was there with his AOW class.

I told him my HP120 had failed hydro and he said one of his students had purchased two PST tanks from Sport Chalet 6 months ago and had them VIP'ed recently. Both showed signs of "rust."

I mentioned to him what tivey said about the discoloration. The diver said it wasn't just a matter of discoloration... there were rust particles on the tank's inside wall and a rust powder at the bottom of the tank. Then he said his brother had also bought two PST tanks and they showed "rust" as well.

He was not a happy camper, although he allowed that the rust could have occured due to fills on a dive boat out of San Diego (he wouldn't mention which boat).

Since I've heard several stories like this after my HP120 failed hydro, I am waiting to see how frequent a problem this is before I purchase a new E-series tank.

Dr. Bill

 

[padiscubapro]

drbill once bubbled...
I agree with Thomas Ivey that PST has a good reputation, and welcome his participation on SB (more manufacturers should do the same). However my HP120 made by PST for Sherwood in June, 1993, recently failed hydro after only 10 years. Needless to say I was quite disappointed by that failure. I expected at least 15-20 years from that tank.

While I am considering a replacement tank from PST (E8 130 or HP 120), comments here and concern about PST's current situation have me looking at alternatives too.

Again, thank you Thomas and PST for participating on SB.

Dr. Bill

Bill
I am assuming that your tanks are hot dip galvanized. I know of several that have "failed" hydro when in reality they were fine.. In one case I know of the hydro facility was forced to purchase new tanks for the person.. the hydro facility condemened the tank by XX ing out the serial number (like he is supposed to) the problem was that the hydro tester did not follow the procedure required for the tanks in question (and didn't even know about it)..

the tester must follow this procedure:
http://www.pstscuba.com/tech.htm


The person had another hydrostation document the procedure and test the tanks... The hydrostation lost on court for 2 new tanks plus the hydro costs(foir other facility) and filing fees.

needless to say the careless hydro facility paid full retail

 

[padiscubapro]

drbill once bubbled...
I was out at the Casino Dive Park yesterday and it was almost empty (what's wrong with you guys, and especially you ladies... vis is good now). An instructor I hadn't seen in a while was there with his AOW class.

I told him my HP120 had failed hydro and he said one of his students had purchased two PST tanks from Sport Chalet 6 months ago and had them VIP'ed recently. Both showed signs of "rust."

I mentioned to him what tivey said about the discoloration. The diver said it wasn't just a matter of discoloration... there were rust particles on the tank's inside wall and a rust powder at the bottom of the tank. Then he said his brother had also bought two PST tanks and they showed "rust" as well.

He was not a happy camper, although he allowed that the rust could have occured due to fills on a dive boat out of San Diego (he wouldn't mention which boat).

Since I've heard several stories like this after my HP120 failed hydro, I am waiting to see how frequent a problem this is before I purchase a new E-series tank.

Dr. Bill

I seen it far too common that operators of compressors don;t have the necessry drier's and other measures on their air stations. with AL tanks you can get away with far more moisture than steels.. Before getting a fill at any station I always request too see their current "air" test data... if they don't have one I definately wouldn't be breathing their gas... To see how dry the gas is look at the dewpoint rating... ideally it should be at least -20f.. Most people can't believe how much liquid you can pull from compressed air..

If you have an ANDI facility near you they have to meet -50f, plus other requirements (quarterly results must be sent to ANDI hq)

Rusting of steels can also happen when people "oxygen" clean tanks... ideally they should be using something like Blue Gold which has a rust inhibitor (and is DESIGNED for oxygen cleaning)too many use things like simple green and other degreasers which MAY work fine for some cleaning.. The tanks are supposed to be degreased and rinsed then dried using NITROGEN gas, letting a steel drip dry or use compressed air causes flash rusting especialy if a rust inhibitor wasn't used.

 

[drbill]

padiscubapro- When my tank failed hydro, I was told about the E9791 DOT exemption and asked the test facility if they had followed it. They assured me they had (and seemed slightly miffed that I even asked). The tank had been taken up to 85-90% TP and brought back down to round it before being tested at full TP.

Dr. Bill

 

[Genesis]

I mentioned to him what tivey said about the discoloration. The diver said it wasn't just a matter of discoloration... there were rust particles on the tank's inside wall and a rust powder at the bottom of the tank. Then he said his brother had also bought two PST tanks and they showed "rust" as well.

It does not take much water being blown into a steel tank to do this. In fact, it takes VERY little.

If you do not trust the fill protocol of the place where you get your tanks filled, don't use them. Fills on a boat deck are suspect at best.

I've had one problem (exactly one) with my PST tanks, and I know how it happened. Nothing a tumble didn't fix, but it still pizzed me off. At least I know where the problem came from, and it WON'T happen again.

 

[drbill]

We don't have a lot of choice re: fill stations out on the island. CDS at the Point and the green Pleasure Pier, and SCUBA Luv ib town.

I take my other tank to the mainland to dive on boats rather than the HP120 that failed.

Dr. Bill

 

[VTernovski]

I don't think it's smart to buy tanks form LeisurePro. They certainly don't do the visual there, and they have no means of filling a tank for you. How do I know? I work across the street from them. So, you will still be forced to bring a tank to your local dive shop. The tanks are brand new, but you never know how long and where it's been sitting. for all I care it could be in their basement full of moisture etc...

dnight once bubbled...
Yep, the vis sticker on the tank says may 2003, so it's been sitting on a shelf unpressurized for 4 months.

Back to leisurepro it goes.

 

[Dan The Man]

Hey Dr. Bill,

That was me you saw at Casino Point. I had 2 relatively new tanks (PST HP100, manufactured 1 year ago, bought 4 months ago) fail visual due to rust. One of them had lots of rust particles inside, the other had no particles, but some rust patches were visible.

My brother has 2 identical tanks (used a bit less frequently than mine) and both of his had flash rust, but no big patches or particles.

We opted to tumble them all, just to be safe.

It is possible that the rust was from boat fills, although I somewhat doubt that. The boat is the "Lois Ann" out of San Diego (I am a pass holder and dive it most every weekend). All the tanks they rent on the boat are steel, and it is easily the nicest boat in San Diego, with a nice new compressor...

I think the more likely source of rust would be the questionable compressor we had to use on our last trip down to Bahia de Los Angeles. Have a look at that compressor and you'll see what I mean.

For the next year I'm going to do a little experiment: 1 tank will be desginated the "clean" tank and filled only by the LDS. The other tank will be the "boat" tank and be used mostly on the boat. (And the next time I go to Baha, I'll take only rentals).

--Dan