Posted by Eric Frasco on August 11, 2002 at 19:55:07:
In Reply to: Question about visual inspections posted by dawhale on August 11, 2002 at 14:53:03:
How often do you take your tanks out on boat trips, and how often do you have them filled only at shops on land?
The reason I ask is due to the fact that the boats just don't do as good a job in giving dry fills as the shops do. I won't go in to the reasons why in this post (I think I did in a post about a year ago) but they are compressing very humid air, which makes it hard to remove all the moisture, and you have dripping salt water everywhere, making it very easy to get a few drops of salt water into your tank when they hook it up to fill it.
So why is this important, you ask? Because tanks you take on boat trips are more likely to need tumbling much more frequently than tanks that are filled at inland pumping stations that have better control over humidity and dripping salt water.
With that said, you should probably dedicate one of your tanks to boat diving. And you should probably expect to have that tank tumbled more frequently than your other tanks.
When I was doing lots of boat trips years ago, I had one tank that I had to have opened up every six months as I could see rust deposits on the inlet filter of the 1st stage of the regulator. Usually it was only a light rust, no heavy pits. Which makes a difference when they tumble it, because the amount of tumbling they do depends on how severe the pitting is.
If you wait six months for this "marginal" visual, the pitting could be more severe. Knowing this, you should take it out and have it tumbled. But have it done by someone who knows what to tell the folks tumbling it so that they do not remove any more of the surface of the cylinder interior than absolutely necessary. If the "technician" can't tell you anything about the tumbling process, then take the tank somewhere where they can tell you just exactly what is going to be done to your cylinder.
This 30 day turn around sounds like they have a central processing facility where they ship the tanks to, then the tank is sent out from the central facility to the place where it will be tumbled, then back to the central facility before being sent back to the shop. Extra turn around times like this really stack up and it takes a long time to get your gear back.
Most places have the tank picked up directly by the testing/tumbling facility on one day of the week (say, Tuesday), and will have it back the next week (probably the following Tuesday, but they will often tell you to come in on Wednesday so they have time to put the valve back in and fill it, etc.). At most, if the testing/tumbling facililty is really busy, it should be maybe two weeks.
And finally, if the tank is not back when promised, a reputable facility will probably offer you the free use of a rental tank to compensate you for the inconvenience.
One really important thing to look out for when you take a tank in for visual is to watch and see whether or not they remove the tank boot. If they don't take off the tank boot for the visual, then take your business elsewhere. The tank boot holds the water (any water your tank comes in contact with, both salt water on your dive, and fresh water at the fill station) in intimate contact with the bottom of your tank, and it doesn't dry well at all. I've seen boots removed that were hiding serious corrosion. The tanks passed internal visual but failed hydro due to the damage to the bottom of the tanks. So if all the technician does is look at the inside, then he's only done half the inspection.
-Eric-