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Re: Aquatic Plants Digest V4 #660

Operating pressure range and MAWP ( maximum allowable working pressure ) 
are two very differnet parameters of a regulator.  If the tank regulator 
fails ( and they do ) your downstream regulator better be rated for the 
full tank pressure ( 860 psig ).  Either that or you need a pressure 
relief device inbetween them.  What is the design pressure or mawp of 
your ARO regulator?  

I have stated this before, but it warrants repeating.  You have to look 
at your entire pressure circuit and determine your weak link and make 
sure you are adequately protected.  Installing a "cheap low-pressure" 
regulator downstream of a high pressure source is very dangerous.  Most 
cheap low pressure regulators are typically only good for 150 psig or 
less.  A diaphram failure in the high pressure regulator is a very 
feasible event.  860 psig is enough pressure to impart significant 
velocity to regulator fragments........
Again I strongly recommend that you understand your design pressures, 
people have been killed  by overpressurized regulators coming apart.


Aquatic Plants Digest

>I have to disagree with you on your cost projection for the avoidance
>approach.  As I have posted previously, I use a second mini-regulator
>downstream of the primary tank regulator.  You don't need a special
>high-pressure regulator so the mini-regulator is well within its operating
>pressure range to regulate the 35 psig from the tank to 2 psig to the needle
>valve manifold.  The specific equipment I have in use on three systems right
>now is the ARO model #127112820.  Total cost (three years ago) was around
>$30 including the gauge and fittings.  This is MUCH less than $100 - $300.
>I'm sure there are other equally suitable regulators available in a similar
>price range.
>Lyndle Schenck