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End-of-Tank CO2 Dumping

Contents:

  1. Anti Dump CO2 Rewgulator
    by George Booth <booth/lvld.agilent.com> (Thu, 7 Sep 2000)
  2. Compressed Gas Regulators (was: Carbo-Plus vs. compressed gas)
    by Stephen Boulet <stepheb/comm.mot.com> (Wed, 06 Sep 2000)
  3. CO2 miscellany
    by Dave Gomberg <gomberg/wcf.com> (Wed, 06 Sep 2000)
  4. CO2 regulation
    by ()
  5. Pressure Regulator
    by Casey Huang <yhplsing/singnet.com.sg> (Thu, 28 Sep 2000)
  6. My last word on needle valves....
    by Dave Gomberg <gomberg/wcf.com> (Wed, 17 Jan 2001)
  7. "My last word on needle valves..."
    by Paul Sears <psears/nrn1.NRCan.gc.ca> (Thu, 18 Jan 2001)
  8. My last word on needle valves....
    by "Tom Wood" <tomwood2/flash.net> (Thu, 18 Jan 2001)
  9. My last (final) word on needle valves
    by Wright Huntley <huntley1/home.com> (Sat, 20 Jan 2001)
  10. CO2 dumping simulation
    by George Booth <booth/frii.com> (Thu, 21 Dec 2000)
  11. Needle Valves and Nutrients
    by "Schenck, Lyndle" <lschenck/dcscorp.com> (Wed, 13 Dec 2000)
  12. CO2 regulation
    by Dave Gomberg <gomberg/wcf.com> (Fri, 08 Sep 2000)
  13. CO2 Regulators
    by wshimoda/alum.mit.edu (Fri, 8 Sep 2000)
  14. (No Title)
    by ()
  15. CO2 regulation
    by "Tom Wood" <tomwood2/flash.net> (Sat, 9 Sep 2000)
  16. CO2 regulation.
    by Wright Huntley <huntley1/home.com> (Sun, 10 Sep 2000)
  17. CO2 regulation
    by zxcvbob <bob/area51online.net> (Mon, 11 Sep 2000)
  18. Regulator & Needle Valve Specs & Selection
    by "James Purchase" <jpurch/interlog.com> (Mon, 11 Sep 2000)
  19. Regulator & Needle Valve Specs & Selection
    by George Booth <booth/lvld.agilent.com> (Mon, 11 Sep 2000)
  20. Regulator & Needle Valve Specs & Selection
    by Erik Olson <erik/thekrib.com> (Mon, 11 Sep 2000)
  21. CO2 regulators
    by zxcvbob <bob/area51online.net> (Tue, 12 Sep 2000)
  22. Experience and CO2 regulation
    by "Tom Wood" <tomwood2/flash.net> (Tue, 12 Sep 2000)
  23. Re:: Experience and CO2 regulation
    by "Robert H" <robertpaulh/earthlink.net> (Tue, 12 Sep 2000)
  24. Pressurized CO2 Summary
    by "DaTrueDave" <DaTrueDave/earthlink.net> (Sun, 17 Sep 2000)
  25. Aquatic Plants Digest V4 #641
    by Chuck Gadd <cgadd/cfxc.com> (Thu, 02 Nov 2000)
  26. Aquatic Plants Digest V4 #641
    by Dave Gomberg <gomberg/wcf.com> (Tue, 14 Nov 2000)
  27. CO2 dumping simulation
    by Dave Gomberg <gomberg/wcf.com> (Tue, 19 Dec 2000)
  28. CO2 system...
    by "Jeff Bodin" <bodin1/gte.net> (Thu, 2 Nov 2000)

Anti Dump CO2 Rewgulator

by George Booth <booth/lvld.agilent.com>
Date: Thu, 7 Sep 2000

> Date: Thu, 7 Sep 2000 11:35:08 EDT
> From: FocaIPoint@aol.com
> 
> But, why let the tank go empty in the first 
> instance?  Weight it when full with the regulator and hoses attached. Put a 
> piece of tape on the tank and write that number on it. Weigh the tank 
> periodically and when it approaches say 4 pounds or less (for a five pound 
> tank) shut it down and get a refill or replacement tank.
> 
> Or am I missing something here as usual?

You may be missing the high pressure gauge. No need to weigh the tank, just look 
at the gauge once a week or so. While there is still liquid CO2 in the tank, the 
tank pressure stays constant (900 PSI or so). When enough CO2 has been used, the 
liquid is gone and you are left with pure gas. As the gas is used up, the tank 
pressure slowly drops. We change ours when the pressure gets down to 200 PSI or 
so. The folks at the gas store like to have a little left so they can release it 
quickly to chill the bottle (so you get your fair share of fresh). You have 
plenty of time to watch the pressure drop - our ten pound tanks take about a 
month to go from 900 to 200 PSI.  


George Booth in Ft. Collins, Colorado (booth@frii.com)
  http://www.frii.com/~booth/AquaticConcepts 


Compressed Gas Regulators (was: Carbo-Plus vs. compressed gas)

by Stephen Boulet <stepheb/comm.mot.com>
Date: Wed, 06 Sep 2000

James Purchase wrote:

> Dave Gomberg wrote:
>
> "3.  Get a regulator that does not dump when the tank empties  (I am working
> on trying to find these)   OR
> 4.  Include a simple pressure relief device in your system  "
>
> Dave, could you elaborate a bit on these two points, please? What should a
> hobbyist look for in the specs of a regulator which would indicate that it
> won't "dump" when the cylinder is close to empty? Is a "two-stage" regulator
> better for this than a "single-stage" one?
>
> Thanks,
>
> James Purchase
>

I experienced this dumping phenomenem first hand, unfortunately. As the compressed gas container nears empty, it lets off large quantities of CO2 (as much as two or more small air pumps). That killed most fish in my planted tank, including some beautiful adult M. parkinsoni's (good thing I had some fry), SAEs, and plecos.  :(

After that happened (near when I was about to move), I set the tank up again at my new house, but this time with a pH monitor/controller and solenoid regulator in the setup. The controller worked for me when the tank tried to dump again, and all the fish were fine.

Without the controller or some other solution, the best thing to do would be to refill the tank before it gets to the dumping stage. Leaving some margin for error would be wise, I think.

- -- Stephen


CO2 miscellany

by Dave Gomberg <gomberg/wcf.com>
Date: Wed, 06 Sep 2000

At 03:48 PM 9/6/00 -0400, Ivo wrote:
>I thought of another way of avoiding the gas dump. Or, better said, avoid its
>ill effects on the fish. This only applies to sump-based systems. The idea is
>to place the diffuser in the sump. The diffuser could be placed near the
>return pump intake, such that, when it is working under normal conditions,
>the tiny bubbles are sucked by the pump. If there is a suden release of gas,
>most of it will bubble out of the sump and doesn't get sucked into the main
>tank. Does this makes sense ?

Sounds good to me.

James Purchase asked:
Dave Gomberg wrote:
>"3.  Get a regulator that does not dump when the tank empties  (I am working
>on trying to find these)   OR
>4.  Include a simple pressure relief device in your system  "
>Dave, could you elaborate a bit on these two points, please? What should a
>hobbyist look for in the specs of a regulator which would indicate that it
>won't "dump" when the cylinder is close to empty? Is a "two-stage" regulator
>better for this than a "single-stage" one?

I have yet to find a company that makes two-stage regulators (one regulator 
feeding another).   Usually folks are talking about two GAUGE regulators, 
heck you can put 100 gauges on a regulator, they won't affect its function, 
only measure it.  In reply, James said he had found one but I could not get 
their web page to display.

There are charts that SOME manufacturers have that show how input pressure 
affects output pressure at a constant setting.  You want a regulator whose 
output pressure doesn't rise much as the input pressure drops.   I am 
working on making a deal for same as we speak.

- --
Dave Gomberg, San Francisco            mailto:gomberg@wcf.com
NEW Planted Aquaria Magazine:        http://www.wcf.com/pam
- -----------------------------------------------------------------


CO2 regulation

by
To: Aquatic-Plants/actwin.com

Here is just about all I know about managing compressed CO2 (sorry for the 
long post):

In an un-managed configuration, a CO2 tank after a year to ten years of 
faithful service will run out of gas.  When this happens, the regulator 
which has been providing a steady outlet pressure of say 10 or 20 or 30 psi 
(depending on how you have it set up) will suddenly fail and dump the 2-400 
psi gas straight into the appliance (reactor or whatever) that you are feeding.

The purpose of this little diatribe is to tell you all I know about 
avoiding this problem.

There are three basic ways to manage your CO2 system and avoid end-of-tank 
failure.  These are anticipation of end-of-tank, relieving the pressure 
pulse, or avoidance of the pressure pulse.  Anticipation means that you 
track your CO2 usage or pressure and take steps to avoid the end-of-tank 
condition entirely.  Relief of the pressure involves a special device 
designed to relieve the excess pressure during the pulse so that the rise 
at the appliance is small.  Avoidance refers to using a regulator and 
associated control parts so that the pulse does not occur until the tank is 
totally exhausted, at which time the flow will stop.

Anticipation:

Anticipation is the simplest and cheapest solution.  One way to anticipate 
end-of-tank is to weigh the tank regularly.  You can expect it to deliver 
about the announced volume (in pounds of CO2).  If you plot weight versus 
tank age in days it should be easy to guess about when you will have 
reduced its weight by the 20 pounds of CO2 you bought.  If you decide to 
replace it based on low weight, it would be interesting to empty it 
completely by opening the shutoff valve with the regulator removed to see 
(and weigh) how much gas actually remained.

Another way to anticipate end-of-tank is to closely monitor the 
high-pressure gauge on your regulator (if it has one).  The pressure will 
START to drop weeks before an end-of-tank dump occurs.

Once an end-of-tank condition is anticipated, you can simply turn the gas 
off at night and when you are away until you have a chance to refill your tank.

Sadly, anticipation is unforgiving of inattention and if you don't notice 
the end-of-tank a disaster can occur.  If your failure occurs during the 
day when your plants are metabolically active and producing lots of oxygen 
then no problem may ensue.  Or if your tank is open-top, so that there is 
lots of atmospheric oxygen in contact with the water surface you are 
reasonably safe.  But if your top has a tight fitting cover and the dump 
occurs when lights are out and your tank is heavily populated with fish, 
the CO2 in the gap between the water surface and the cover may physically 
drive off all oxygen, at which point your fish can suffocate.

Relief:

Relief is based on the idea that the excess gas that would be delivered 
during an end-of-tank dump is simply vented into the atmosphere 
somewhere.  The most convenient place to vent is usually right near your 
tank, but you can also plumb a plastic vent line to a more convenient 
location if desired.  A relief system should also be tested on a routine 
basis to make sure that it is continuing to provide the protection it was 
designed to give.

Pressure relief devices come in two kinds:  manufactured valves and 
water-head homebrew devices.  Many valve companies make pressure relief 
valves that will trigger at about 20 psi which should suit most users.  If 
you have a higher operating pressure, make sure you select a valve that 
vents at a pressure just a little higher than your norm.  One manufacturer 
of pressure relief valves is Rexarc, you can contact their sales department 
at (937) 839-4604 (info@rexarc.com).

You can also make a pressure relief device at home if you tap your system 
at a point where the pressure is supposed to be low (like right before the 
appliance, after any pressure-reducing check valve).  At this point the 
pressure should be only a few feet of water (2 feet of water is about 
1psi).  Simply take a 6 foot piece of 3" plastic sewer pipe, put a plastic 
cap on one end, set it upright open end up and fill with water to about a 
foot from the top.  Run a long piece of plastic tube or airhose down to the 
bottom of the sewer pipe and connect the other end to your CO2 line.  As 
long as the pressure is less than the five feet of water in the sewer pipe, 
the pipe will do nothing.  When the pressure rises to more than five feet 
of water, the excess gas will vent out thru the airhose, down to the bottom 
of the sewer pipe, and bubbling out the top.  You can enhance this design 
by also capping the top and running a CO2 vent line made of plastic water 
pipe out to a more convenient location if you wish.  Ensure the low end of 
the hose from the CO2 system stays at the bottom of the sewer pipe by 
weighing it down.  Or use a rigid plastic pipe to convey the CO2 down to 
the bottom of the sewer pipe.

Avoidance:

A third strategy for managing end-of-tank failure is avoidance, referring 
to selecting system components so that failure simply does not occur.  This 
can be an expensive strategy but should be considered if the stakes are 
high (such as many tanks or a very expensive setup).  Avoidance strategies 
are like relief strategies in that they involving using different hardware.

One place to attack avoidance is at the regulator.  There are two stage 
regulators (where one regulator feeds another, do not confuse with two 
gauge regulators), down-stream regulators (that regulate based on output 
pressure, not input pressure), and better grade regulators (that undergo 
much less pressure rise as the input pressure falls).  All these strategies 
increase the cost of the system.  Whether they are worth it depends on many 
too many factors for one person to attempt to decide for 
another.  Generally speaking. if you are handy with tools and savvy enough 
to do your own CO2 system design, you should expect avoidance to add an 
extra $100-300 to the cost of your CO2 system.

I had considered the idea of adding a "avoidance" type system to my CO2 
system line.  I researched the issues carefully.  Although I could buy a 
better grade regulator for only about $30 more than a cheaper one, the 
company that made it interprets ISO rules to prohibit making special 
versions of their products (even if it only means omitting parts that are 
normally added at the end).  So I would have had to remove the original and 
build new output plumbing of the regulator myself.  With the labor costs, 
warranty, and liability issues, this just was not practical.  So I dropped 
the idea.  If you want to pursue this idea on your own, call Praxair and 
ask them about a Victor SR253-B320-06 and get out your tool box.



- --
Dave Gomberg, San Francisco            mailto:gomberg@wcf.com
NEW Planted Aquaria Magazine:        http://www.wcf.com/pam
- -----------------------------------------------------------------


Pressure Regulator

by Casey Huang <yhplsing/singnet.com.sg>
Date: Thu, 28 Sep 2000

Hello David,

I don't know whether it is TRUE or not that "When the input
pressure to the regulator decreases, the output pressure
*increases*", but I think your explanation about the principle
of operation of a Pressure Reducing Regulator is wrong. Any increase
in Outlet Pressure will only generate more force by the diaphragm
to push more against the set spring force towards the direction of
closing the valve NOT opening.

When the inlet pressure decreases substantially, the pressure acting on
the diaphragm which is connected to the outlet side will also decreases,
therefore the force generated will not be enough to overcome / counter
the spring force to shut the valve (similar to complete diaphragm failure
- - fail open).

For more explanation, please go to:

 http://www.cashco.com/download/diom.pdf

 (just because it has good explanation and drawings)

You can see the detailed explanation (SECTION III, PRINCIPLE OF OPERATION)
and the internal design of a typical Pressure Reducing Regulator.

"Dumping" is an uncontrolled flow of gas at LOWER than SET pressure. If you
have a flow control valve (needle valve) downstream, it should not cause
an increase in CO2 dosage in your tank (lower pressure, same orifice = less
gas passing through). 


Regards
Casey Huang



>
>Date: Wed, 27 Sep 2000 13:54:27 -0700
>From: "David Ozenne" <dozenne@10fold.com>
>Subject: Re: CO2 discussion
>
>James-
>
>Good post.  But I think you have made a serious mistake.  When the input
pressure to the regulator decreases, the output pressure *increases*, at
least until the output pressure equals the input pressure.  (At that point
the regulator essentially becomes an open valve.)  That is what causes the
"dumping" when your tank runs low.
>
>David Ozenne
>whose CO2 tank reached ~400 psi before he noticed the fish acting funny...
>
>(my apologies for this corporate sig)


- --


My last word on needle valves....

by Dave Gomberg <gomberg/wcf.com>
Date: Wed, 17 Jan 2001

This is a good news/bad news story.

First I should say that as the seller of over 250 CO2 systems, it is my 
guess that my system is the most widely used in this country.  And I am 
concerned that my customers have a positive experience with it.  This does 
require paying attention to end of tank (see 
http://www.wcf.com/co2iron/faq.html#dump  ).

I searched and searched for a proper needle valve that could be used in 
connection with my high-pressure system for those who wanted a more 
belt-and-suspenders approach to end-of-tank management.   And the good news:

I found a terrific valve, the Fabco NV-55 which costs between $15 and 
$20.  You buy one from your local Fabco distributor (see 
http://www.fabco-air.com/distributors.html    ).  It seems to be quite well 
built and to allow you to regulate the flow pretty accurately, even when 
the input pressure to the valve is 30 psi.

Now the bad news:

I left the valve in place overnight.   This AM, the hose connecting the 
regulator to the Fabco valve had blown off the regulator and dumped the 
whole CO2 cylinder.   The bad news of that is that I needed to go get a 
refill, and I may have to rebuild my regulator.  The good news is that no 
fish were killed (because the dump occurred into the room, not into the 
airspace over the tank).

So all in all, I have to say the risks of a needle valve outweigh the 
benefits FOR ME.   And I will not use one.   But you may come to a 
different conclusion.   If you do and if you are a user of my system, send 
an SASE with $.55 in stamps on it to me and I will send you free the 
adaptors to connect your NV-55 to the green hose that comes in my system.

Sorry the news isn't better.     Dave



- --
Dave Gomberg, San Francisco            mailto:gomberg@wcf.com
NEW Planted Aquaria Magazine:        http://www.wcf.com/pam
- -----------------------------------------------------------------


"My last word on needle valves..."

by Paul Sears <psears/nrn1.NRCan.gc.ca>
Date: Thu, 18 Jan 2001

> From: Dave Gomberg <gomberg@wcf.com>
> Subject: My last word on needle valves....
> 
> It seems to be quite well 
> built and to allow you to regulate the flow pretty accurately, even when 
> the input pressure to the valve is 30 psi.
> 
> Now the bad news:
> 
> I left the valve in place overnight.   This AM, the hose connecting the 
> regulator to the Fabco valve had blown off the regulator and dumped the 
> whole CO2 cylinder.

	That (200 kPa) seems a pretty high pressure to leave on a hose.  I use
stainless steel tubing and Swagelok fittings between the regulator and
the needle valve, and that is for a pressure of less than 50 kPa.
It's overkill, I know, but it means I _can_ use much higher pressure
if I want to.

> So all in all, I have to say the risks of a needle valve outweigh the 
> benefits FOR ME.

	I think that is a risk of a _hose_ not a needle valve.


- -- 
Paul Sears        Ottawa, Canada


My last word on needle valves....

by "Tom Wood" <tomwood2/flash.net>
Date: Thu, 18 Jan 2001

G: First I should say that as the seller of over 250 CO2 systems, it is my
guess that my system is the most widely used in this country.

What a tragedy.

G: I searched and searched for a proper needle valve that could be used in
connection with my high-pressure system for those who wanted a more
belt-and-suspenders approach to end-of-tank management.

I doubt that car manufacturers could get away with arguing that adding
brakes to their product after the fact is a belt-and-suspenders approach to
managing their product. Your system is proven to be unreliable. Why not just
be man enough to admit it and stop all this dissembling?

G: I left the valve in place overnight.   This AM, the hose connecting the
regulator to the Fabco valve had blown off the regulator and dumped the
whole CO2 cylinder.   The bad news of that is that I needed to go get a
refill, and I may have to rebuild my regulator.

So now you are suggesting that use of a needle valve will lead to
destruction of your regulator. What rot. A needle valve that screws into the
regulator is the standard installation. Try it, you might like it. Lose the
diffuser, it's an over-priced high-markup piece of equipment that should
never have come to market.

G: So all in all, I have to say the risks of a needle valve outweigh the
benefits FOR ME.   And I will not use one.   But you may come to a
different conclusion.   If you do and if you are a user of my system, send
an SASE with $.55 in stamps on it to me and I will send you free the
adaptors to connect your NV-55 to the green hose that comes in my system.

A defective fix for a defective system. How generous.

And that's all I have to say.

Tom Wood
Austin, Texas, ya'll


My last (final) word on needle valves

by Wright Huntley <huntley1/home.com>
Date: Sat, 20 Jan 2001

> Date: Sat, 20 Jan 2001 07:30:56 -0800
> From: Dave Gomberg <gomberg@wcf.com>
> Subject: Re: My last word on needle valves
> 
> At 03:48 PM 1/19/01 -0500, Chuck Gadd asks:
> >Or was Dave running the
> >regulator output at a higher pressure with the needle-valve?
> 
> Yes, I was running my regulator flat out into the needle valve.  Unless 
> there is quite a pressure drop across the valve, the flow will not go sonic 
> and the valve will not restrict the flow as desired.

I assume Dave meant supersonic, which is the hard, final limit in most
valves, beyond which essentially no additional flow is even possible (aka
the "choke" point). You don't really need that, I think, as any highly
turbulent flow becomes quite non-linear and gives pretty decent flow
regulation. Most valves seem to regulate well enough with only a few psi
across them. I think that's why folks here now refer to them as "low
pressure" systems, as opposed to the Eheim with spring-loaded check valve
that takes 12-15psi just to open it.

I'd bet Dave's experiment did not remove that additional source of (useless)
back pressure, either. I know I left *mine* in while fiddling with various
valves, so I was working up around 20psi and above, while the actual drop
across the needle valve was probably as low as 5 psi. [It's just too much
trouble to get rid of the check valve in a nicely-working setup.]

The blue-green silicone tubing proved too soft to use on bayonet fittings at
much above 10-15 psi. At that level, a twist-tie, as used for plastic bags,
can usually keep it on. At 20-30 psi, I needed more drastic clamping, and I
still don't trust it very much not to blow out. It can balloon ominously at
much above that level. 

I suggest using regular vinyl airline tubing between regulator and needle
valve, with a good wire tie on each end. Otherwise, use polyethylene tubing
for that stretch, with Imperial-Eastman tubing fittings o/e. Some "plastic"
tubing is a good idea to protect the fish against catastrophic regulator
failure. I do not like attaching the valve to the regulator with only metal
tubing unless the needle valve is rated for 1000 psi or above (many are
not).

Now *my* last word on this subject:

I really like the Eheim glass diffuser, even if it may need a "Chlorox" soak
once in a great while. 

I like the flow-regulation provided by a needle valve, but will remove the
Eheim check valve, in the future, so my low-pressure system is really
running at just the pressure drop across the valve. The end-of-tank rise of
a few psi will increase flow a bit, but not nearly as drastically as through
a fully-open check valve.

The sintered glass emitter provides a nice flow of very fine bubbles. If a
few reach the surface, they just increase CO2 concentration there, so little
is probably lost. [My tanks are well covered to keep my killies from trying
to move up the evolutionary ladder.] I also like Tom Barr's safe burping
system, but it is more obtrusive in my smaller tanks, so I'll wait a while
before getting any. The Eheim is so tiny it is hard to find unless the light
catches the bubble stream. That's a huge plus if appearance means anything.

In summary, I'll be using Dave's regulator and Eheim diffuser (sans check
valve), with Anthony's recycled fire-extinguisher tanks, and some kind of
in-hose needle valve to set the bubble rate with 10 psi or so of regulator
output pressure (high enough for proper regulation, anyway). Does anyone see
any fundamental flaw in this plan?

My mind is made up, so please don't confuse me with any additional facts.
;^)

Wright


- -- 
Wright Huntley, Fremont CA, USA, 510 494-8679  huntleyone at home dot com

        Quit bashing Microsoft. They do very good things. They
          hire the handicapped -- for example, utter morons
                 to compose all error messages.

              *** http://www.libertarian.org/ ***


CO2 dumping simulation

by George Booth <booth/frii.com>
Date: Thu, 21 Dec 2000

>Date: Tue, 19 Dec 2000 16:11:17 -0800
>From: Dave Gomberg <gomberg@wcf.com>
>
>The first one is an old
>rebuilt Norgren from many years ago.   It is the regulator I normally use
>and it will dump.  I measured the following (P1 is input pressure, P2 is
>output pressure):
>
>Time  P1  P2
>    0   850   15.1
>50   575   15.2
>60   500   15.2
>57   425   15.2
>65   350   15.5
>69   300   15.6
>73   250   15.2
>78   200   15.2
>82   150   14.8
>87   100   14.0 dropping to zero slowly

So, the 0.5 PSI "spike" is the infamous dump you've been warning us about 
lo these many weeks?

>Then I tried a new Cornelius regulator from the high-pressure system I sell:
>   0   760   15.0
>   2   740   15.2
>   4   700   15.3
>   6   600   16.0
>   7  fall    P2 rose quickly to 22, then dropped almost as fast, diffusor
>bubbling like crazy.
>
>You can pretty clearly see the dump

My lord, Dave, put a darn needle valve on the system and get over it. The 
check valve/diffuser combo is clearly a sloppy and inadequate way to 
control flow. Find a source for something like the $8 NO1 we used to use. 
Stop driving us crazy by calling a minor increase in pressure a "dump" and 
make the system stable the proper way with a flow regulator.

>This again underscores the importance of having a strategy to deal with
>dumping.   I am looking as we speak for a relief valve that can be
>retrofitted into existing systems I have sold since so many folks want
>something more fool-proof.
>
>I am also looking into substituting a regulator that does not dump as
>vigorously as the current Cornelius.   I would like to keep the price point
>pretty much the same tho, so this is a little tricky.

Is anyboby else shaking their heads at the relative nonsense of this all?

George Booth in Ft. Collins, Colorado (booth@frii.com)
"The web site for Aquatic Gardeners by Aquatic Gardeners"
   http://www.frii.com/~booth/AquaticConcepts/


Needle Valves and Nutrients

by "Schenck, Lyndle" <lschenck/dcscorp.com>
Date: Wed, 13 Dec 2000

Dave wrote:  " So some experimentation in this area is required if you wish
to trust your system to a needle valve. If you have a device (such as an
Eheim diffusor) that runs at 15psi (more or less), and you encounter a dump
at end of tank protected by a secondary regulator which has been set to drop
the pressure from say 40psi where your primary regulator is set to 15psi
needed by the Eheim, the input to the secondary will rise from 40psi to
200psi. The problem is we don't know what the effect will be because the
secondary regulator may or may not tolerate 200psi. If it is a natural gas
regulator it may break down. Then it may be worse that with no protection at
all. You must carefully quiz the maker of your secondary regulator to ensure
that the 200psi won't be a problem. I hope this helps clarify just how
complex this issue is. And I hope it saves the fish of someone relying on an
untested needle valve setup. BTW, you can borrow a high output pressure
regulator (one that can go to 400psi for example) and simulate a dump and
test your system's performance under those circumstances. Be sure to take
all necessary safety precautions if you do this tho. "

This is just wrong for Dave's system and for the rest of us that use CO2
service (Beer tap) regulators.  For "Draught beer dispensing equipment and
related components"  pressure relief devices (relief valve) are required on
the outlet side of the regulator.   Dave uses Cornelius Beer Tap CO2
regulators.  They come equipped with a pressure relief valve that "protects
against overpressure" (Rapids Catalog).  Since I use Norgren regulators I
got their spec sheets.  The Norgren regulator has a pressure relief valve
that "will limit the outlet pressure to 70 psi maximum."

So.  With an end-of-tank dump, or even with a catastrophic failure, the
maximum outlet pressure is limited to 70 psi, not 400 psi or even 200 psi.
This is well within the range of almost ANY needle valve or secondary
regulator. 

My end-of-tank dump was on a commercial system (Sandpoint) that used a
metering valve to control the regulator outlet pressure.  It took a while
for me to understand what happened.  My solution was a second regulator AND
needle valves which even I consider overkill.  However if you have a good
needle valve and use the beer regulator factory set pressure (around 50
psi), the maximum pressure you will ever see at the needle valve will be 70
psi.  That difference will cause an increase in flow but not so much as to
crash a system in the short run. 

This is, in my view, a case against high pressure systems (diffusers).  If
the flow is predicated on a set pressure, the effect of a higher pressure
can cause a much higher volume of CO2 to enter the tank.  For low pressure
systems the increase flow is effectively linear (for illustration purposes)
at these pressures, e.g. 50 psi to 70 psi = 20 psi increase will increase
flow by about 40 percent.

Let the flames begin!

Lyndle Schenck


CO2 regulation

by Dave Gomberg <gomberg/wcf.com>
Date: Fri, 08 Sep 2000

OK, now I am mad ;^)>

Actually, some folks have accused me of being mad for a long time.....

Here is just about all I know about managing compressed CO2 (sorry for the 
long post):


In an un-managed configuration, a CO2 tank after a year to ten years of 
faithful service will run out of gas.  When this happens, the regulator 
which has been providing a steady outlet pressure of say 10 or 20 or 30 psi 
(depending on how you have it set up) will suddenly fail and dump the 2-400 
psi gas straight into the appliance (reactor or whatever) that you are feeding.

The purpose of this little diatribe is to tell you all I know about 
avoiding this problem.

There are three basic ways to manage your CO2 system and avoid end-of-tank 
failure.  These are anticipation of end-of-tank, relieving the pressure 
pulse, or avoidance of the pressure pulse.  Anticipation means that you 
track your CO2 usage or pressure and take steps to avoid the end-of-tank 
condition entirely.  Relief of the pressure involves a special device 
designed to relieve the excess pressure during the pulse so that the rise 
at the appliance is small.  Avoidance refers to using a regulator and 
associated control parts so that the pulse does not occur until the tank is 
totally exhausted, at which time the flow will stop.

Anticipation:

Anticipation is the simplest and cheapest solution.  One way to anticipate 
end-of-tank is to weigh the tank regularly.  You can expect it to deliver 
about the announced volume (in pounds of CO2).  If you plot weight versus 
tank age in days it should be easy to guess about when you will have 
reduced its weight by the 20 pounds of CO2 you bought.  If you decide to 
replace it based on low weight, it would be interesting to empty it 
completely by opening the shutoff valve with the regulator removed to see 
(and weigh) how much gas actually remained.

Another way to anticipate end-of-tank is to closely monitor the 
high-pressure gauge on your regulator (if it has one).  The pressure will 
START to drop weeks before an end-of-tank dump occurs.

Once an end-of-tank condition is anticipated, you can simply turn the gas 
off at night until you have a chance to refill your tank.

Sadly, anticipation is unforgiving of inattention and if you don't notice 
the end-of-tank a disaster can occur.  If your failure occurs during the 
day when your plants are metabolically active and producing lots of oxygen 
then no problem will ensue.  Or if your tank is open-top, so that there is 
lots of atmospheric oxygen in contact with the water surface you are 
reasonably safe.  But if your top has a tight fitting cover and the dump 
occurs when lights are out and your tank is heavily populated with fish, 
the CO2 in the gap between the water surface and the cover may physically 
drive off all oxygen, at which point your fish can suffocate.

Relief:

Relief is based on the idea that the excess gas that would be delivered 
during an end-of-tank dump is simply vented into the atmosphere 
somewhere.  The most convenient place to vent is usually right near your 
tank, but you can also plumb a plastic vent line to a more convenient 
location if desired.  A relief system should also be tested on a routine 
basis to make sure that it is continuing to provide the protection it was 
designed to give.

Pressure relief devices come in two kinds:  manufactured valves and 
water-head homebrew devices.  Many valve companies make pressure relief 
valves that will trigger at about 20 psi which should suit most users.  If 
you have a higher operating pressure, make sure you select a valve that 
vents at a pressure just a little higher than your norm.  One manufacturer 
of pressure relief valves is Rexarc, you can contact their sales department 
at (937) 839-4604 (info@rexarc.com).

You can also make a pressure relief device at home if you tap your system 
at a point where the pressure is supposed to be low (like right before the 
appliance, after any pressure-reducing check valve).  At this point the 
pressure should be only a few feet of water (2 feet of water is about 
1psi).  Simply take a 6 foot piece of 3" plastic sewer pipe, put a plastic 
cap on one end, set it upright open end up and fill with water to about a 
foot from the top.  Run a long piece of plastic tube or airhose down to the 
bottom of the sewer pipe and connect the other end to your CO2 line.  As 
long as the pressure is less than the five feet of water in the sewer pipe, 
the pipe will do nothing.  When the pressure rises to more than five feet 
of water, the excess gas will vent out thru the airhose, down to the bottom 
of the sewer pipe, and bubbling out the top.  You can enhance this design 
by also capping the top and running a CO2 vent line made of plastic water 
pipe out to a more convenient location if you wish.  Ensure the low end of 
the hose from the CO2 system stays at the bottom of the sewer pipe by 
weighing it down.  Or use a rigid plastic pipe to convey the CO2 down to 
the bottom of the sewer pipe.

Avoidance:

A third strategy for managing end-of-tank failure is avoidance, referring 
to selecting system components so that failure simply does not occur.  This 
can be an expensive strategy but should be considered if the stakes are 
high (such as many tanks or a very expensive setup).  Avoidance strategies 
are like relief strategies in that they involving using different hardware.

One place to attack avoidance is at the regulator.  There are two stage 
regulators (where one regulator feeds another, do not confuse with two 
gauge regulators), down-stream regulators (that regulate based on output 
pressure, not input pressure), and better grade regulators (that undergo 
much less pressure rise as the input pressure falls).  All these strategies 
increase the cost of the system.  Whether they are worth it depends on many 
too many factors for one person to attempt to decide for 
another.  Generally speaking. if you are handy with tools and savvy enough 
to do your own CO2 system design, you should expect avoidance to add an 
extra $100-300 to the cost of your CO2 system.

I had considered the idea of adding a "avoidance" type system to my CO2 
system line.  I researched the issues carefully.  Although I could buy a 
better grade regulator for only about $30 more than a cheaper one, the 
company that made it interprets ISO rules to prohibit making special 
versions of their products (even if it only means omitting parts that are 
normally added at the end).  So I would have had to remove the original and 
build new output plumbing of the regulator myself.  With the labor costs, 
warranty, and liability issues, this just was not practical.  So I dropped 
the idea.  If you want to pursue this idea on your own, call Praxair and 
ask them about a Victor SR253-B320-06 and get out your tool box.

- --
Dave Gomberg, San Francisco            mailto:gomberg@wcf.com
NEW Planted Aquaria Magazine:        http://www.wcf.com/pam
- -----------------------------------------------------------------


CO2 Regulators

by wshimoda/alum.mit.edu
Date: Fri, 8 Sep 2000

Thanks to George, James, and Dave for their informative posts.

Thought someone might find the following information useful:


(No Title)

by

I also asked an authorized Victor regulator repair person about the differences between the cheap and expensive Victor regulators and he said that the cheaper ones use rubber and fabric diaphragms, while the expensive ones use metal diaphragms, to regulate pressure.  The cheaper diaphragms aren't as durable, so they require more frequent replacement.  He even went so far to say that the cheapest ones aren't even worth servicing.  I suspect the homebrew regulators are similar, although I notice that they sell part kits (which I assume are designed for maintenance by the person making the beer rather than a trained regulator repair person.)

FWIW, our two stage regulator has never "dumped" CO2, even though we let the tank pressure drop until no gas flows.

How we got a cheap, but good two stage regulator (other than the one we got for free.)  Got a Victor catalog explaining the various models (including the type of gas it's configured for, and the operating output pressure range.)  I got it by filling out their online request form.  Went to ebay.  Found some two stage regulators and emailed sellers for model numbers.  If they weren't configured for CO2 or the lower pressure ranges, I asked the Victor repair guy whether or not they could be reconfigured, and for how much.  Bid accordingly.

Don't be shy about calling the regulator repair guy in your area.  Although the guy I dealt with does most of his business with welders, he was so fascinated (amused?) by what I was going to use the regulator for, that after dropping off my regulator (it was a non-Victor medical lab regulator with a medical prescription CO2 fitting that he changed to an industrial fitting) and looking at our aquariums and ponds, he decided not to charge me anything.  (Don't ask me what medical CO2 is though.  All I know is that the elaborate printed lable on the bottle said Carbon Dioxide, and that you needed a prescription to fill it.)

Hope this helps.

Wade Shimoda
Honolulu, HI

Small soapbox:  Was there a reason why this thread changed names so many times?
Some of the names:
Re: Compressed Gas Regulators (was: Carbo-Plus vs. compressed gas)
CO2 miscellany
CO2 Regulators
CO2 Dumping
Anti Dump CO2 Rewgulator
CO2 Regulator
CO2 regulation

All of these are, of course, much better than "Re: Aquatic Plants Digest V4 #nnn"


CO2 regulation

by "Tom Wood" <tomwood2/flash.net>
Date: Sat, 9 Sep 2000

> From: Dave Gomberg
>
> In an un-managed configuration, a CO2 tank after a year to ten years of
> faithful service will run out of gas.  When this happens, the regulator
> which has been providing a steady outlet pressure of say 10 or 20 or 30
psi
> (depending on how you have it set up) will suddenly fail and dump the
2-400
> psi gas straight into the appliance (reactor or whatever) that you are
feeding.
>
> There are three basic ways to manage your CO2 system and avoid end-of-tank
> failure.  These are anticipation of end-of-tank, relieving the pressure
> pulse, or avoidance of the pressure pulse.

There followed a long discussion of these three ways to manage a problem
inherent only in a defectively designed CO2 system. Any end-of-tank failure
is a failure of the design of the CO2 system. A CO2 tank equipped with a
simple $65 dual gauge regulator and a simple $20 needle valve will not ever
experience this imaginary pressure pulse or dumping of any kind. Never.
Ever. The needle valve, also known as a fine metering valve, provides a tiny
gateway through which the gas is metered out. Once it is set to allow the
one or two bubbles per second you want, that is all the CO2 that can get
through at that rate, and the amount of gas in the CO2 cylinder is
irrelevant to the valve performance. The amount of FUD being generated on
this list regarding this issue is beginning to get shameful.

Tom


CO2 regulation.

by Wright Huntley <huntley1/home.com>
Date: Sun, 10 Sep 2000

> 
> Date: Mon, 11 Sep 2000 07:26:09 +1000
> From: "Neil Travis" <travisn@gravity.net.au>
> Subject: Re CO2 regulation.
> 
> It Appear that Gomberg  is on a sell my product line at the moment. As a
> regular contributor to this list all I seem to do is get knocked by him with
> his commercial interests.
> In Australia "Dave states full of bull shit"
> a good regulator costs around $80.00. Say $50.00 US. Not as expensive as his
> dump when the tank gets low type.
> Could you imagine going into a Bar for a beer and as soon as the gas gets
> low the tap explodes?

This provocative way of stating untruths has a tendency to get the more
knowledgeable on this list a bit hot under the collar. I'm going to chime
in, but try to avoid the emotion and get a bit of the air clear. When we
know misinformation is being archived, we have some obligation to respond.
No?

Neil's beer-tap regulators and the ones sold by Dave do not differ in any
functional way, only in the application.

> Not me. I like my beer too much. That is the type of regulator that will do
> the job properly.
> I would suggest that a bit more research is done into gas systems for
> quality and keep away from the rubbish.

The rubbish is entirely Neil's utter failure to understand the operation of
the normal single-stage gas pressure regulator. It *will* have a modest
increase in output pressure as the tank approaches empty. The increase is a
tiny fraction of the initial 900 psi, and can have no serious effect on
pressurized beer that can tolerate the slight increase. You wouldn't even
notice a 40psi to 60 psi change in the foam in your glass.

The high-pressure gauge for most beer regulators has a red zone down around
300-400 psi with a warning to refill the tank. Observing it totally
eliminates the problem, anyway.

> As it so happens I have a reply from Dave on this subject and he openly
> states that for a price he is quite willing to sell rubbish as he says it is
> economically enviable to sell quality as his customers are unwilling to pay
> the price so he sells crap.

I sincerely doubt if you are using Dave's words correctly or in context.
Don't bother to send them to me, tho, for I don't really care.

> Any one wanting a copy is welcome to it.

Why? I know Dave is a retired academic/consultant who pursues the business
as a hobby and not a way to make anything significant, so I may have an
advantage over Neil. I also know that Dave is wise enough to realize that
all the hobby will stand is the price of single-stage regulators. I won't
try to apologize for his astringent way of replying to foolish posts. 

I'm an engineer, and Dave is not. Sometimes I wish he consulted with me on
these things, but he has properly learned to be cautious about my
off-the-cuff responses, too. {Free advice worth every penny, phenomenon.
:-)]

Where Dave, I, and others have been stung is by the apparent simplicity of
directly driving the Eheim diffuser assembly out of a regulator set to
*very* low pressure. We are adjusting the pressure to set the bubble-count
rate. If it changes with pressure, why are we surprised if it changes a lot
when the tank empties and the regulation fails?

Most of the typical 13 psi drop is not across the glass-frit diffuser, but
in holding barely open the heavily spring-loaded check valve that prevents
reverse flow from siphoning water out of your tank. Unfortunately, it
doesn't perform well either as a non-linear flow-regulator, or as a
second-stage pressure regulator. A few psi of increase to it causes a rather
impressive increase in bubble rate. Result? A more-or-less dumped tank, near
the end, with too much CO2 in the aquarium, but not likely to be nearly
enough to cause an atmospheric problem in a normal room.

We are generally trying to reduce the liquified tank pressure to a
manageable and safe level, and then we desire a constant volume/unit time
(number of bubbles/sec). That's best done with a *flow* regulator, and not a
pressure regulator. One time-honored way to get that flow regulation is with
a good needle valve and a constant-pressure source.

Turbulence in the flow through an orfice has long been used to control fluid
flow rate, somewhat independent of input pressure. The non-linearity of the
turbulence means the input pressure can change quite a lot for only a little
change in the flow volume. The needle valve does that rather well, if the
shape of the aperture is such as to be highly turbulent at the terribly low
flow rates we demand. It helps to have sufficient pressure drop across the
needle valve to be in that turbulent condition at all times. That is, run
the input pressure up around 20 psi or more. It's easy to see why it can be
quite thermally sensitive, too.

A number of folks here have reported particular valves they have found to
work well in this application. Modest changes in tank terminal-stage
pressure are not reflected in huge differences in bubble rate, as they have
been when running systems without the needle valve.

Single stage regulators can be used all the way to empty, if the needle
valve acts as an adequate flow restrictor over the modest range of pressures
encountered. OTOH, the Ehiem system also works quite well, as long as the
tank high-pressure gauge is monitored and the tank is refilled when the
liquid is all evaporated (about 500 psi remains). The Eheim system just
isn't tolerant of inlet pressure changes to any significant extent.

The expense of buying multi-stage regulators simply is ridiculous under
those conditions. Who needs them? They do nothing particularly useful for
most aquarists who have to feed the fish and plants a few times during the
month (and can see the gauge).

Neil, I have regulators that came from Liquid Carbonic (our local
beer-vendor supplier) and from Dave. The only significant difference is that
Dave provides some clever fittings that are brutally difficult to find
elsewhere. IMHO, his are, as a result, a huge bargain.

I hope this clears the air without increasing the confusion level.

Wright

PS. I think a good needle valve (and higher regulated pressure) in front of
the Eheim system could be a useful thing to do. I haven't tried it yet, but
will report if it does a good job.

- -- 
Wright Huntley, Fremont CA, USA, 510 494-8679  huntleyone at home dot com

"People constantly speak of 'the government' doing this or that, as they
might speak of God doing it. But the government is really nothing but a 
group of men, and usually they are very inferior men." --H. L. Mencken

               *** http://www.self-gov.org/index.html ***


CO2 regulation

by zxcvbob <bob/area51online.net>
Date: Mon, 11 Sep 2000

Wright Huntley sez:
> We are generally trying to reduce the liquified tank pressure to a
> manageable and safe level, and then we desire a constant volume/unit time
> (number of bubbles/sec). That's best done with a *flow* regulator, and not a
> pressure regulator. One time-honored way to get that flow regulation is with
> a good needle valve and a constant-pressure source.
> 
> Turbulence in the flow through an orfice has long been used to control fluid
> flow rate, somewhat independent of input pressure. The non-linearity of the
> turbulence means the input pressure can change quite a lot for only a little
> change in the flow volume. The needle valve does that rather well, if the
> shape of the aperture is such as to be highly turbulent at the terribly low
> flow rates we demand. It helps to have sufficient pressure drop across the
> needle valve to be in that turbulent condition at all times. That is, run
> the input pressure up around 20 psi or more. It's easy to see why it can be
> quite thermally sensitive, too.

FINALLY! Someone understands that we are trying to regulate the flow
rather than the pressure.  If the CO2 control system fails due to the
normal increase in output pressure as the high side pressure drops, it
is a poorly designed system.  It doesn't matter how cheap nor expensive
the components are;  it either has to tolerate normal pressure
fluctuations or specify a multi-stage regulator so there will be no
significant pressure fluctuations.  

BTW, you can inexpensively achieve two-stage pressure regulation at a
very low output pressure by plumbing a low pressure LP gas regulator in
series with your tank regulator.  Your regulator probably has 1/4" pipe
threads in the body for its output, so you could connect the two
regulators in series with just a short pipe nipple.  The output pressure
will be low enough that just about any metering valve will be sufficient
to adjust the flow rate.  The potential problem here is that the
operating pressure might be too low (11" water column) to overcome the
head pressure in your tank to reach your reactor.

Regards,
Bob


Regulator & Needle Valve Specs & Selection

by "James Purchase" <jpurch/interlog.com>
Date: Mon, 11 Sep 2000

Whew! So much discussion on what some folks say is not "rocket
science"....... but while some posts seem to come close, nobody seems to
have grasped what I think is the problem. Regulators and valves come with
"spec sheets" which describe, in technical terms how they will perform.
While some of you might be familiar with these things, a lot of us are not,
and merely pointing us in the direction of the "specs" doesn't accomplish
much other than increase confusion and anxiety.

Hopefully, if I you can extend your patience just a tad more, I'd like to
present some "specs" and ask some questions which might shed some light on
the issues.

Note: All of the following assumes a setup consisting of a Regulator +
Needle Valve (no solenoid, no automatic timer or controller) and any
responses should be appropriate for either a Sintered Glass Diffusor (like
the Eheim or ADA models) or a regular Reactor (like the Dupla "S"). If
known, any differences applicable to use of either end use appliance should
be outlined.

A. - Gass Grade & Regulator Construction:

On the BOC Gases web site, they have a chart which is supposed to help you
select the correct regulator for different gases. Under CO2, they list three
"grades" of purity and there are two different regulator models recommended,
depending upon the grade of gas you use.

Grade of CO2                                        Regulator Model
Recommended
Research Grade 99.999%                       BHS500/270
Instrument (Coleman) Grade 99.99%      BHS500/270
Bone Dry 99.8%                                    BGS270

The BGS270 is described as constructed from chrome plated forged brass. The
BHS500 is constructed from chrome plated brass bar stock, while the BHS270
is chrome plated forged brass.

Questions:
1. Does it make any difference if the regulator is made from forged brass or
brass bar stock?
2. Is there any specific reason why they would recommend a different
regulator for CO2 of differing purity?
3. Are the "beer tap" regulators so many of you are using capable of being
used with the wide variety of "grades" of CO2 which seem to be available
(i.e. "Industrial/Welding", Medical, Food Grade, etc).
4. Is there a real difference here?

B. Regulator Outlet Pressure Range:

Looking at the information available online from Air Products, their General
Purpose, Single Stage Regulator (dual Gauge has the following specs:

Model                        1         2      3       4        5          6
7        8
E11-215A (CGA)   3000    15    280    85   0-3000  100  0-30     1
E11-215B (CGA)   3000    50    850   250  0-3000  100  0-60      2
E11-215D (CGA)   3000  100  1500  250   0-3000  100  0-200    5
E11-215F (CGA)    3000  250  1950  350   0-3000  100  0-400  10

1 - Maximum Inlet Pressure (psig)
2 - Maximum Outlet Pressure (psig)
3 - Capacity (scfh at Maximum Delivery Pressure)
4 - Relief Valve Setting (psig)
5 - Inlet Gauge Range (psig)
6 - Inlet Gauge Graduation (psig)
7 - Delivery Gauge Range (psig)
8 - Delivery Gauge Graduation (psig)

Questions:
1. Assuming the setup of a Reulator + Needle Valve, which of these models
would be most suitable for our sort of use, and WHY?

C. Needle Valve Specs & Selection:

When I look at the spec sheets of various needle valves, I see  things like
Maximum Working Pressure, Flow Coefficient (Cv) and Stem Taper Angle and
whether or not the valve is capable of cutting off the flow of gas
completely. For example. using the spec sheets for the various valves from
Nupro:

Model             Max Working    Cv       Stem Taper   Capable of Cutoff
Service?
                       Pressure
Nupro 31        5000 psig           0.04
Series Union Bonnet
Nupro BMG     350 psig           0.019     3 degrees metering
Nupro BMRG   350 psig           0.30     20 degrees regulating
Nupro BMW    700 psig            0.019     3 degrees metering
Nupro BMRW  700 psig           0.30     20 degrees regulating
Nupro L          1000 psig           0.15      5 degrees      can be used
for cutoff service
Nupro M         1000 psig           0.03      3 degrees      not designed
for cutoff service
Nupro S          2000 psig           0.004    1 degree        not designed
for cutoff service

Questions:
1. Other than price differences, is there a reason why you would select one
valve over another for our purposes?
2. Which "specs" should we be looking at, and what ranges are useful and/or
practical for our purposes?
3. Are there other considerations that I'm missing?

Thanks,

James Purchase
Toronto


Regulator & Needle Valve Specs & Selection

by George Booth <booth/lvld.agilent.com>
Date: Mon, 11 Sep 2000

> Date: Mon, 11 Sep 2000 11:59:43 -0500
> From: "James Purchase" <jpurch@interlog.com>
> 
> Hopefully, if I you can extend your patience just a tad more, I'd like to
> present some "specs" and ask some questions which might shed some light on
> the issues.

Since you didn't specifically limit input to only those holding a BSVR (Bachelor 
of Science in Valves and Regulators), I'll answer from an Experienced CO2 User 
perspective.  

I'll reverse the order of your questions, since that may help arrive at a 
practical solution.

> C. Needle Valve Specs & Selection:
> 
> When I look at the spec sheets of various needle valves, I see  things like
> Maximum Working Pressure, Flow Coefficient (Cv) and Stem Taper Angle and
> whether or not the valve is capable of cutting off the flow of gas
> completely. For example. using the spec sheets for the various valves from
> Nupro:
> 
> Model        Max Working    Cv    Stem Taper   Capable of Cutoff
> Service?        Pressure
> Nupro 31       5000 psig   0.04
> Series Union Bonnet
> Nupro BMG       350 psig   0.019     3 degrees  metering
> Nupro BMRG      350 psig   0.30     20 degrees  regulating
> Nupro BMW       700 psig   0.019     3 degrees  metering
> Nupro BMRW      700 psig   0.30     20 degrees  regulating
> Nupro L        1000 psig   0.15      5 degrees  can be used for cutoff service
> Nupro M        1000 psig   0.03      3 degrees  not designed for cutoff 
service
> Nupro S        2000 psig   0.004     1 degree   not designed for cutoff 
service
> 
> Questions:
> 1. Other than price differences, is there a reason why you would select one
> valve over another for our purposes?

The end use is the primary concern.  You want low flow, so the valve with the 
smallest Cv is the best, as long as it's not *too* slow. The Cv is like 
resistance - the smaller the Cv, the higher the resistance to flow.  Inlet 
pressure is a concern if you want to avoid the cost of a regulator. Typical CO2 
tank pressure is 950 psi - it goes higher if the tank is warmer. A Max Working 
Pressure of 1000 psi (without a regulator) might be asking for trouble. 

I don't know how the Stem Taper angle affects things buty I would guess a 3 
degree taper is more needle-valve-like than a 20 degree taper. And more 
needle-like seems to give more flow restriction.  

> 2. Which "specs" should we be looking at, and what ranges are useful and/or
> practical for our purposes?

The Nupro M series (Cv=0.03) gives you a max of 1.2 cubic feet per minute 
connected to an inlet pressure of 2 bar (35 psig).  The Nupro S series 
(Cv=0.004) gives you a max of 0.15 cubic feet per minute connected to an inlet 
pressure of 2 bar (35 psig).  I use the M series and that provides a good 
bubbles/sec range. The BMG and S would give a finer range but may cost more.   

Since the flow is spec'ed at 35 psig, I would *assume* that is a good inlet 
pressure to shoot for.
 
> 3. Are there other considerations that I'm missing?

Cost, fitting sizes to match the rest of the plumbing, ease of adjustment 
(vernier or coarse), adjustment locking, corrosion resistance, sensitivity to 
blockage (I would guess most fine valves are *very* sensitive), ease of cleaning 
if blocked, colors avilable to match your other components. 

[Special thanks to Marque Crozman of Australia for providing this detailed info, 
archived on my web site ("CO2/Nupro Valve FAQ").

> B. Regulator Outlet Pressure Range:
> 
> Looking at the information available online from Air Products, their General
> Purpose, Single Stage Regulator (dual Gauge has the following specs:
> 
> Model             1   2     3    4     5      6    7      8
> E11-215A (CGA) 3000  15   280   85  0-3000  100   0-30    1
> E11-215B (CGA) 3000  50   850  250  0-3000  100   0-60    2
> E11-215D (CGA) 3000 100  1500  250  0-3000  100  0-200    5
> E11-215F (CGA) 3000 250  1950  350  0-3000  100  0-400   10
> 
> 1 - Maximum Inlet Pressure (psig)
> 2 - Maximum Outlet Pressure (psig)
> 3 - Capacity (scfh at Maximum Delivery Pressure)
> 4 - Relief Valve Setting (psig)
> 5 - Inlet Gauge Range (psig)
> 6 - Inlet Gauge Graduation (psig)
> 7 - Delivery Gauge Range (psig)
> 8 - Delivery Gauge Graduation (psig)
> 
> Questions:
> 1. Assuming the setup of a Reulator + Needle Valve, which of these models
> would be most suitable for our sort of use, and WHY?

We want around 35 psig on the inlet to the needle valve, so E11-215B looks like 
the optimum. Max flow is irrelevant (the valve max is 70 scfh). The "B" model 
gives us the best low pressure valve resolution. But all would work just fine. 

> A. - Gass Grade & Regulator Construction:
> 
> On the BOC Gases web site, they have a chart which is supposed to help you
> select the correct regulator for different gases. Under CO2, they list three
> "grades" of purity and there are two different regulator models recommended,
> depending upon the grade of gas you use.
> 
> Grade of CO2                           Regulator Model
> Recommended
> Research Grade 99.999%                       BHS500/270
> Instrument (Coleman) Grade 99.99%            BHS500/270
> Bone Dry 99.8%                                   BGS270
> 
> The BGS270 is described as constructed from chrome plated forged brass. The
> BHS500 is constructed from chrome plated brass bar stock, while the BHS270
> is chrome plated forged brass.
> 
> Questions:
> 1. Does it make any difference if the regulator is made from forged brass or
> brass bar stock?

If the other specs are equivalent, I would guess not. Perhaps forged is better 
in a severe environment (rough handling). 

> 2. Is there any specific reason why they would recommend a different
> regulator for CO2 of differing purity?

I guess it has to do with the "impurity". For our use, I would say it doesn't 
matter. I can't see how a few PPM of impurity would affect the regulator unless 
it was corrosive or somehow damaging to the internals.  

> 3. Are the "beer tap" regulators so many of you are using capable of being
> used with the wide variety of "grades" of CO2 which seem to be available
> (i.e. "Industrial/Welding", Medical, Food Grade, etc).

I think most CO2 supply stores use "Food grade". Again, for our use, it doesn't 
matter. 

> 4. Is there a real difference here?

No. 


George Booth in Ft. Collins, Colorado (booth@frii.com)
  http://www.frii.com/~booth/AquaticConcepts 


Regulator & Needle Valve Specs & Selection

by Erik Olson <erik/thekrib.com>
Date: Mon, 11 Sep 2000

On Mon, 11 Sep 2000, George Booth wrote:
> > From: "James Purchase" <jpurch@interlog.com>

> > C. Needle Valve Specs & Selection:

> > Model        Max Working    Cv    Stem Taper   Capable of Cutoff
> > Service?        Pressure
> > Nupro 31       5000 psig   0.04
> > Series Union Bonnet
> > Nupro BMG       350 psig   0.019     3 degrees  metering
> > Nupro BMRG      350 psig   0.30     20 degrees  regulating
> > Nupro BMW       700 psig   0.019     3 degrees  metering
> > Nupro BMRW      700 psig   0.30     20 degrees  regulating
> > Nupro L        1000 psig   0.15      5 degrees  can be used for cutoff service
> > Nupro M        1000 psig   0.03      3 degrees  not designed for cutoff 
> service
> > Nupro S        2000 psig   0.004     1 degree   not designed for cutoff 
> service


Been away all weekend, just read through the 100 postings, a majority of
which were on this whole CO2 dumping regulator problem.  Wright and one
other person had the insight that perhaps explains why people are fighting
here:

THE INCREASE IN PRESSURE AT THE END OF THE TANK IS ONLY A NOTICABLE
PROBLEM FOR PEOPLE USING THE EHEIM OR AMANO SINTERED GLASS DIFFUSERS!

Neil Travis, George Booth, myself and others don't use sintered glass
diffusers.  We use the old needle valve approach.  The needle valve acts
as a flow restrictor.  Some of these valvues (like the Nupro series'
above) can even be run straight from the tank at 800 PSI input pressure!  
I remember someone in this forum speculating about removing the regulator
(essentially a first stage of a two stage system with the needle valve as
the second) entirely.

So what happens?  Let's try some arbitrary numbers -- perhaps someone will
chime in with more realistic ones --- say we set the needle valve to
provide a nominal 1 bubble per second when driven at 20 PSI.  Near the end
of the life of the cylinder, we hit a bump in pressure where it goes up to
200 PSI downside of the regulator.  This then causes the needle valve to
increase its flow by at most a factor of 10 as, aka 10 bubbles per second.  
Annoying, but not catastrophic.  And it happens slowly.

In a sintered glass diffuser, though, that pressure of 200 PSI is going to
"pop" the diffuser and cause the CO2 to vent into the tank as quickly as
it can, which is almost certain to kill the fish.  I've seen a diffuser
pop and spew an entire bottle of CO2 into a tank.
It's not pretty.

My question is, if the only way to avoid this effect is to add a flow
restricter between the regulator and the diffuser, is it really any better
than just going with the traditional reg-needle combination to begin with?

    - Erik

PS: http://showcase.aquatic-gardeners.org (19 days left... blah blah..
great prizes... blah blah... entries starting to pile in... why not finish
YOURS now instead of the absolute last minute!)

- -- 
Erik Olson
erik at thekrib dot com


CO2 regulators

by zxcvbob <bob/area51online.net>
Date: Tue, 12 Sep 2000

Stephen Boulet <stepheb@comm.mot.com> asks:
>
> Can a needle valve be used in front of a sintered glass diffuser like Eheim's?
 
Yes.  It will provide a flow restriction in case the diffuser breaks
or pops off.  You can decide for yourself if it *should* be used.
(IMO, redundancy is good).

Regards,
Bob

"If we don't succeed, we run the risk of failure."
 -- Dan Quayle


Experience and CO2 regulation

by "Tom Wood" <tomwood2/flash.net>
Date: Tue, 12 Sep 2000

It is a tragedy that in our culture the value of experience has been
discounted in favor of easy religion and apparent science. I have learned to
trust my experience in any given discipline over both of the other
scriptures. I have been using a $65 dual gauge (NOT dual stage) beer
regulator and a $20 needle valve on a 5 pound CO2 cylinder for 4 years. I've
never killed a single fish because of too much CO2, and I almost always run
my CO2 cylinder empty. The CO2 is run from the needle valve through a
plastic tubing into the intake sieve of a canister filter. I count the
bubble rate (1-2 per second for a 65 gallon tank) in the intake sieve. A $65
regulator (described by others here as rubbish) and an $20 needle valve
(described by others here as totally inadequate). That is all. Nothing else.
No dead fish. No pressure pulses. No dumping. Happy plants. Healthy fish. My
experience. I don't have a clue what model number any of the equipment is,
it doesn't matter, I am only relating actual experience with modestly priced
equipment. I believe that anyone can do the same thing. The regulator MUST
be rated for CO2 pressures (the seller will know) and the needle valve
should have the finest movements you can afford, $20 will work, $40 is
better, after that you are just trying to impress your friends.

What follows is speculation (based on experience) and is therefore subject
to more error. I never claim expert status in any discipline except that of
being me.

My "cheap" needle valve is admittedly difficult to set because even a
delicate finger touch causes a noticeable change in output. I suspect that a
$40 valve would be at least twice as easy to set if the same finger touch
produces a smaller change in output. The more expensive needle valves cost
more because they are machined in a way that allows our finger movements to
produce a finer motion at the actual valve opening. I also suspect that the
needle valve produces a backpressure that helps the regulator maintain its
output pressure setting. From what I can gather from this discussion, the
CO2 designs that have a free flow after the regulator are the systems that
can't maintain a regulated gas flow when the cylinder pressure starts
dropping. I suspect that the regulators cannot cope with a changing pressure
on the high side AND a free flow on the  low side because the mechanism
interprets the falling pressure on the high side as a higher demand on the
low side and then "dumps" gas to rectify the demand. This is not really a
pressure pulse, but rather a misinterpretation of changing conditions by the
mechanism.

I don't care if it IS made in Germany, if it kills your fish it is still
defective.

I believe that my earlier comment still stands: Any end-of-tank failure is a
failure of the design of the CO2 delivery system.

That should be worth at least 4 cents........

Tom


Re:: Experience and CO2 regulation

by "Robert H" <robertpaulh/earthlink.net>
Date: Tue, 12 Sep 2000

>>A $65 regulator (described by others here as rubbish) and an $20 needle
valve (described by others here as totally inadequate). That is all. Nothing
else. No dead fish. No pressure pulses. No dumping. Happy plants. Healthy
fish. My experience.<<

If it ain't broke, it don't need fixin. My personal experience is as
follows,
Two years ago I bought a german made Aqualine regulator. After two months it
leaked from around the face plate of one of the gauges. I had to return it
to the North American distributor directly instead of Pet Warehouse. The
distributor didnt even have one unit in stock to replace it...and it took
them four months to send me another one. The replacement unit lasted one
month until the cannister fell over and one of the gauges cracked, my fault
I know, but not very durable.  An iosaled experience I am sure, but it
turned me off to Aqualine.

I currently have two of Davids regulators, a Hydrologix, and a Profistar.
The Hydrologix came with a solenoid that stopped working after a month.
Hydrologix immediately sent me another one, which sprung a leak two weeks
ago that emptied a 20# cylinder in two hours. There is some depressed little
hole with a tiny scew in it...thats where the leak was..The needle valve
seemed very difficult to control, and it had some type of control arm on the
front of the regulator that doesnt seem to do anything. It was also
frustrating in that it didnt seem to hold constant flow pressure very well.
I would have to check it and reajust it almost on a daily basis. (before it
sprung a leak, and both units were like this) I had it running with Daves
diffusor, which it didnt seem to run as smoothly with as Daves regulator
does.

I havnt had any major problems with the Profistar. Daves units have been
very reliable. It appears much more solidly built than either the Aqualine
or the Hydrologix. It holds an even, steady output pressure very easily.
What I dont like about it is that you can not do fine control of the output,
and it doesnt have a needle valve... reaching the flow you want can take
some work, but once you are there it stays there. My biggest problem has
been lines popping off valves because of the high pressure. I have six
aquariums tied to one regulator.  I too have let it run empty, and as far as
I know I havnt had it empty anything back into the aquarium (s)...perhaps
because I have a check valve on the line. I also do not have any fish in
these aquariums, so I am not particularly worried about it. (well a few
minnows, but they are just fertilizer!)

So while we debate who has the bigger, better bread box, I am more concerned
with its reliability, construction, the quality of support from the
manufacturer-vendor, its ease, practical use, cost, and longevity. If it
works, I can afford it, and I can set it up and leave it alone without
worrying about it, then I am happy...I am simple that way!

Robert Paul H
http://www.aquabotanic.com


Pressurized CO2 Summary

by "DaTrueDave" <DaTrueDave/earthlink.net>
Date: Sun, 17 Sep 2000

Well, I think I've been able to comprehend most of what was said in
these threads...  I still need to check out some of the websites that
were mentioned.  I was hoping that someone would "break it down Barney
style" for some of us slow learners out here, however...   Here's what
I got out of these discussions  (I'm interested in a "low pressure"
system, so if I leave out some info on "high pressure" please correct
me!) :

A single stage regulator with a needle valve (both of appropriate
quality, application and connected properly) will be sufficient for
any system that we might need.  There were some manufacturers and
model numbers thrown around....

A single stage regulator without a needle valve will work with a "high
pressure" reactor/diffuser, however, the risk of connection failure
exists if the reactor/diffuser should get clogged.

A dual stage regulator that is homemade in Australia will never break,
and will supply a neverending perfect amount of co2 for your plants.
Just kidding...  :-)   I'm actually still a bit fuzzy about the
applications of dual stage regulators for our purposes.  Does a dual
stage regulator eliminate the need for a needle valve in a "low
pressure" system?  I think that someone explained that a dual stage
still just regulates pressure and not flow, so a needle valve is still
needed, yes?  What are the reasons to shell out more dough to get a
dual stage regulator?  Is it just to prevent "dumping"?

"Dumping" occurs when a tank with a single stage regulator gets too
low for the regulator to work correctly.  The tank "dumps" the
remaining co2 quicker than normal.  Solution?  Don't let the tank run
out, OR put a needle valve after the regulator, OR get a dual stage
regulator, OR set up your co2 reactor so that excess co2 is gassed out
of the aquarium.

I'm really interested in seeing someone (more knowledgable than I)
doing up a CO2 FAQ.  I would love to see several model numbers of
hardware and the application of the hardware to be included in the
FAQ.  I'd like to see an explanation of Dave Gomberg's "high" and
"low" pressure concepts.  I'd like to see a range of parameters (that
these regulators and valves might have in their spec sheets) that are
acceptable for our uses.

I don't really expect anyone to jump on this and write it up just
because I asked...  I'm just thinking out loud about what I would like
to see...
~~~~~~~~~~~~~~~~~~~~~
Dave Engle
Jacksonville, NC
Visit the Aquatic Plant Trading Board at:
http://coolboard.homestead.com/myboards.cfm?oid=2018519504483
or (if you can't remember that...)
http://www.PlantTrader.homestead.com


Aquatic Plants Digest V4 #641

by Chuck Gadd <cgadd/cfxc.com>
Date: Thu, 02 Nov 2000

Tom wrote:
> Two words: Needle valve

> two-gauge regulator and a relatively cheap needle valve ($20 at M3 I
> believe) will never, ever, dump CO2 because the needle valve acts as a tiny
> gateway through which only the preset amount of gas can ever pass. That's

Just for fun, I decided to see what my $20 needle valve (from M3) would do
in a dump situation.   I couldn't test it with a massive dump, but I did
crank the regulator from it's normal 4psi setting, up to the regulator max
of 45psi.   The bubble rate probably doubled, from it's normal 2 per second, to
about 4 maybe 5 per second.  That would probably drop my pH, but I'm not sure
how much.   

I'd guess that if you were using the in-line needle valve they sell (with
standard airline fittings at both ends, then if the tank dumped, it might
just pop the airline tubing off somewhere between the tank and needle valve.

- --
Chuck Gadd


Aquatic Plants Digest V4 #641

by Dave Gomberg <gomberg/wcf.com>
Date: Tue, 14 Nov 2000

At 11:53 PM 11/2/00 -0500, Wright wrote:
>CO2 tanks dump, with a single regulator -- some worse than others, but all 
>do it.

Actually, Wright, I believe Neil Travis was right when he said it was 
possible to design a regulator without the helper piston that all of ours 
use.  Such a regulator would be good to the last drop.   Sad to say, 
Cornelius and Norgren, the top two American makers, do not make such a 
model.  Victor makes a regulator with a smaller piston (and less dumping), 
but they claim that since they are an ISO 9001 company they cannot make a 
model to my specs by omitting one part (to permit attachment of air hose) 
and so they are not feasible to use in a production environment like 
mine.  If you don't mind fiddling, get a Victor and try modifying it.

Sidenote to Neil:  If you know of a company that sells a regulator in the 
US that depends only on output pressure for its function I would appreciate 
knowing the brand name and model if you know it.



- --
Dave Gomberg, San Francisco            mailto:gomberg@wcf.com
NEW Planted Aquaria Magazine:        http://www.wcf.com/pam
- -----------------------------------------------------------------


CO2 dumping simulation

by Dave Gomberg <gomberg/wcf.com>
Date: Tue, 19 Dec 2000

It occurred to me this AM that you could simulate an end-of-tank condition 
by shutting off the main control valve atop your CO2 cylinder.   So I did 
this with two different regulators I have.   The first one is an old 
rebuilt Norgren from many years ago.   It is the regulator I normally use 
and it will dump.  I measured the following (P1 is input pressure, P2 is 
output pressure):

Time  P1  P2
   0   850   15.1
50   575   15.2
60   500   15.2
57   425   15.2
65   350   15.5
69   300   15.6
73   250   15.2
78   200   15.2
82   150   14.8
87   100   14.0 dropping to zero slowly

P1 stayed at 100  making me think there is a stop in the gauge that 
prevents the needle from dropping below 100 (or else the calibration was 
off, this test was run at about 63F).

Then I tried a new Cornelius regulator from the high-pressure system I sell:

  0   760   15.0
  2   740   15.2
  4   700   15.3
  6   600   16.0
  7  fall    P2 rose quickly to 22, then dropped almost as fast, diffusor 
bubbling like crazy.

You can pretty clearly see the dump, it is interesting to speculate what 
would have happened with a full tank of gas available to dump, instead of 
the few ccs in the stem from the tank shutoff valve to the regulator body.

This again underscores the importance of having a strategy to deal with 
dumping.   I am looking as we speak for a relief valve that can be 
retrofitted into existing systems I have sold since so many folks want 
something more fool-proof.

I am also looking into substituting a regulator that does not dump as 
vigorously as the current Cornelius.   I would like to keep the price point 
pretty much the same tho, so this is a little tricky.

Stay tuned.


- --
Dave Gomberg, San Francisco            mailto:gomberg@wcf.com
NEW Planted Aquaria Magazine:        http://www.wcf.com/pam
- -----------------------------------------------------------------


CO2 system...

by "Jeff Bodin" <bodin1/gte.net>
Date: Thu, 2 Nov 2000

OK,

So last night, I was a little over-reactive... (understandably so, having to
flush about $500 worth of fish). I also checked around/got feedback and yes,
400 lbs. was low (but I have run the tank empty before without having this
happen, now I know it CAN happen). More importantly, it was a fluke that I
checked the pressure yesterday morning. Because I did and was blowing my way
out of the house late for work, I had every intention of changing the tank
today (Could-a would-a should-a). If checking the tank pressure gauge has to
become a regular thing (every 2-3 days) for people with this type of CO2
system... what a pain!

MY POINT: I cannot stress enough that ANY system sold into this trade should
be safe. The one I bought from a common source was not. I also received a
few e-mails (off-line) from people who obtained the very same system who
have had very similar experiences (expensive fish kills).

I have been raising fish for 15 years, bred Discus and Angels for 5 of them,
and am now in my "plant-phase". In that 20 years time, I have had other
disasters (imagine loosing 12 tanks of breeding Discus because a centralized
system's bio crashed!) and I am sure that this experience wont be my last.
Stupidity is one thing (in the case of the central system failure, another
story for another time), unsafe products (to people OR fish) just plain
should not be allowed. I'd rather be upset with myself for doing something
stupid than to have the kind of thing that just happened happen. (By the
way, cheap heaters that stick also come to mind and yes, been-there, done
that one too...)

How many people buy heating cables, and then six months later they and/or
their fish get electrocuted? They don't (I should hope) because the system
itself has two backups: one because the transformer is low voltage/low
current and is internally fuse protected (C/UL approval ensures this); and
two, because we are all smart enough to know that a tank should ALWAYS be
powered through a GFI (right?).

When I bought the system, the seller NEVER said, "Hey bubba, listen REAL
REAL close. You need to monitor the gauge every other day. When the CO2 tank
starts to lose pressure, change it or the valve will 'explode' and all of
your fish will die."  Had the seller said that, I would have looked for a
different system that was safer and more reliable. IN FACT, the seller even
went as far as telling (bragging was more like it) me how safe the system
was compared to other systems! The fact that I have received e-mails from
others experiencing the same problem with this same set-up indicates to me
that the seller never told these people this could happen either.

Since I am already out $500 in fish (and just bought additional PCs for
$100+ and more plants for another $100) and already have $100+ in the CO2
set-up, the question becomes: How can I make the system I am using right now
safe (without buying a whole new system)? Will a real-good needle valve
help? Or would I still get a dump and blow up the needle valve in the
process (as well as kill the fish)?

At this point, the tank is so far over its monthly budget that my wife is
beyond comprehending my need to spend even more money to "get it right".
Tom. You indicated a first option, but did not expand on it. Please do so.

Stepping down off of the soapbox now. Looking for nirvana, will settle for
safety and reliability.

Thanks,

- - Jeff


Up to CO2 <- Plants <- The Krib
This page was last updated 18 February 2002