In article , Badger.badger wrote:
rack, we tend to send out several bottles at once. 3 bottle in a rack
provides redundancy better than one bottle of 3 times the volume or
pressure), and redundancy is important [SNIP]

Only 3? We had 12 cyl MCP's until the fire....NOT H2 related BTW.

Multi-Cylinder Packs? Or "gas racks" as they'd popularly be called.
A single cylinder would last a 6 weeks to 2 months of operations, with a
50% cycle of operational / downmanned. Keeping a bigger stock would mean that
the bottles could easily go out of test, or the gas rack. Or the certificate of
conformity on the gas (analytical grade, remember) would expire. And don't
forget the several months the bottles would spend sitting in the gas cage
onshore too.
Actually, the figures I gave were for the system at Major Company, who I
left a good while ago for Small Company. Small Company have a gas system that
only uses H2 for fuel, not for carrier. Consequently the H2 gas requirements
were smaller, and the issues of keeping redundancy at the system level without
having thousands of pounds worth of gas racks and bottles on rental were
paradoxically worse.
Did you use enough gas that it was worthwhile owning your own bottles and
racks? Not us - Linde would send us a nice little (ha, ha!) rental bill every
month, which Muggins had to check to make sure that we didn't go into "rust
penalty" on a bottle.
Yes, we did try to use hydrogen generators. Have you seen the cost of the
ion-exchange filter packs? Bottle gas is cheaper and easier.

--
Aidan
Aberdeen, Scotland
Written at Wed, 06 Dec 2006 09:18 GMT, but posted later.