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An issue for you to ponder

First, an article on the Matheson-TriGas website, titled "Introduction to 
Regulators". Thanks to Andy Galassi for posting the Matheson regulators on 
ebay, which steered me to this site.

http://www.matheson-trigas.com/catalog/ics/ProductPage.cfm?MFRName=0&CAT  
ID=2&SUBID=11&PGROUPID=MG99228001

Note the third paragraph;

"On occasion, an outlet valve is affixed to the outlet port of the 
regulator. This valve is to be used to shut the regulator on or off for 
brief periods of time. It should never be used to throttle or control the 
flow of gas emitted from a regulator. This practice could cause serious 
damage to both the regulator and its operator. Flow should always be 
controlled by some other piece of equipment such as a rotameter or mass 
flowmeter."

Next, a brief introduction to one method of risk analysis. Factoring the 
likelihood of an event occurrence, with the severity of that occurrence, 
yields a risk factor. In other words, an event with very severe 
consequences actually has relatively low risk if the likelihood of it ever 
happening is nearly nil. On the other hand, an occurrence with only 
slightly severe consequences may have a greater risk factor if the 
likelihood is very high. For example; Getting hit by a meteor falling from 
the sky has very severe consequences, but the likelihood is so miniscule, 
no one (at least that I know), worries or even thinks about it. The 
potential consequences of being involved in a serious automobile accident 
are every bit as severe (dead is dead), but the likelihood is orders of 
magnitude higher, thus the installation of seatbelts and airbags into 
modern automobiles (Let's not pursue the political issues involved in 
mandatory seat belt laws here. That is a topic for another list).

Now for my concern. I just recently installed a needle valve rated at 6000# 
onto the outlet port of the dual stage CO2 regulator. I know this valve is 
way overrated for this service, but it was FREE. To the outlet side of the  
 valve, a length of standard aquarium airline tubing was connected via 
another fitting. This allows for a very controllable system.

The previous configuration consisted of an adapter fitting that screwed 
into the regulator, to which a short length of standard airline tubing 
connected. At the end of this tubing, a standard aquarium air valve was 
installed just upstream of the CO2 reactor. While this may not rise to the 
standards of some subscribers to the digest, it performed well for me. I 
installed the high pressure valve because it was there...

I am beginning to believe I should remove the high pressure needle valve 
and revert to the previous configuration. My concern is that if the 
regulator does malfunction, it may present the low pressure (outlet) side 
of the regulator with pressure in excess of it's design rating, resulting 
in rapid, uncontrolled disassembly of the regulator (big bang theory?). 
While the likelihood of this occurring is very low while someone (me) is in 
the damage field, the consequences, if it happens, are potentially very 
severe.

While I must stop short of insisting everyone subscribing to the list 
should remove the valve from the outlet port of their regulator, one of the 
voices in my head insisted I bring this thought to your attention.

Your humble servant,

Douglas Guynn, in west Texas, where the sky is clear, the wind is cold and 
dry, and the water, what little there is, is REALLY hard.

	dguynn at nwol_net
	915.368.5411

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