Visitors since May 06
This is a Robot Wars / Battlebots inspired collection of information from around the web... an aid to understanding the use of CO2
in powering pneumatics...but the info contained here is also of help in unrelated areas LOOK around ( it's a bit of a mish mash ).
There's info on CO2 ...Filling bottles... Bottle Pressure...Cylinder valve threads ... Flow coefficients ... Valve flow... Valves... BSP Threads etc.
New in pneumatics section ...HERE A very handy conversion utility... Download it ..... you will not be disappointed!
Questions ......Comments ....... EMAIL ....me!
LUXFER Bottle / Cylinder
Extinguishers ,Paintball, etc ....
Sizes C thru to J
CATALINA Cylinders U.S of A HERE
Sizes C thru to J
CO2 CYLINDER VALVES
You'll find the bottle neck thread size by following the Luxfer and Catalina
links above ...
But normally they're M25 X 2mm ...Older
You can purchase a hand wheel valve to replace the std fire extinguisher squeeze valve from :-
European M25 X 2mm pitch only.
Co2 Screw Down Valve (Tapered thread 3/4" BSP )
Throughout the world, carbon dioxide cylinder valves have a special
British BS341 No. 8 European DIN 477 No. 6 and SN 219505 Type 7
French NF E 29-650 Type C Australian AS2473 Type 30
America CGA 320 and Japanese JIS B 8246 CO2 threads are different and are not compatible with each other nor with British/European CO2 threads).
American CO2 Valve Thread Size
Standard cylinder valve outlet connection for pressures up to 3,000 psig for compressed co2.
Cylinder valve outlet thread: .825-14NGO-RH-EXT
Note:- Want to use your U.S.
Regulator on a European bottle?...Simply unscrew the stem and replace the nut.
A regulator nut to fit the European thread can be obtained from www.weldability.com part no:- DACO2NUT
1/2" BSP = CGA 320 .... Well it is the same apart from the thread angle. ☺
A female 1/2" BSP .... British Standard Pipe..... fitting will screw nicely onto the male CGA 320 thread.
Inlet Thread : 5/8-18UNF
Outlet Thread : CGA 320
CGA 320 Thread
Both Paintball and Soda Stream valves have this special
thread specifically for CO2 called a CGA320 thread.
CGA stands for Compressed Gas Association...... and is often called an ASA thread or Air Source Adaptor.
SodaStream adaptors @ craftbrew.com Australia ...type "sodastream" in search for other options
Sodastream to Paintball adaptor from Palmer Pursuit.
SODA CLUB CYLINDER
The NEW Soda Stream ........or Soda Club cylinder has a strange thread ..... 4.4 mm pitch trapezoidal!
It's possible to buy this adapter / adaptor in the USA HERE and HERE
and Europe HERE
Problems re-filling your Soda Club bottle? .....This may well be the result of Soda Clubs special valve.
More info at this blog soadahclub.vox.com
Australia seems to have retained the original SodaStream thread on their new Alco jet bottles
see pic below ......perhaps other countries have as well.
http://www.firekwencher.com 1kg and 2kg Fire Extinguishers also by Soda Club
How to fill
an empty bottle
This is the process used to refill empty or partially full tanks. Using what is normally called a Fill Station, the tank to be filled is connected
to the larger storage tank. Air or C02 is then transferred from the storage tank into your bottle.
For the transfer of air or C02 to take place, the tank you are filling from must be at a higher pressure than the one you are trying to fill.
Standard CO2 cylinders all have liquid in them as long as they are filled but come in two types. Gas and Siphon.
Gas cylinders stand upright and releases gas from the evaporation liquid when the valve is opened - this type of cylinder must be turned
upside down in order to obtain liquid CO2 to refill any cylinder.
Siphon cylinders have a tube from the valve to the bottom of the cylinder so that when the valve is opened liquid CO2 comes out without
having to invert the bottle.
Fire extinguishers are of the Siphon type and Pub Beer Gas Cylinders are of the Gas type.
The measurement of gas in a tank is dependent on the type of gas. C02 under high pressure is LIQUID ...so the
fill is always calculated by weight, never by pressure.
The weight of gas/liquid that the bottle should hold will be stamped on the bottle....NEVER exceed it.
A 2 kg tank is designed to carry safely a maximum of 2 kg of liquid C02.
A pressure gauge on a C02 bottle can never tell you how full it is.
The pressure in the tank is connected to the temperature of the C02....Find out by how much...click here
Air, on the other hand, is measured as a pressure within a fixed volume, the volume of the tank is irrelevant to the pressure you
can fill it to and the maximum fill pressure is always its safe working pressure, printed on the bottle.
W.P. = working pressure (or fill pressure). This is the maximum any bottle should be filled to and should be printed on the bottle.
This will be around 750 p.s.i. as a norm for CO2..........but can rise considerably on a hot day.
T.P. = test pressure. The pressure the bottle is hydrostatically tested too.
You should never try to fill to this pressure. Any burst disks must fail before this pressure.
B.P. = burst pressure… Pressure at which the cylinder will rupture.
This is prevented from happening by a small thin copper disc retained under a plug in the valve called a rupture or burst disc,
this will blow @ around 2,200 psi venting the contents of the cylinder to atmosphere.
You can fill an
empty Fire Extinguisher Bottle in almost the same way. A slightly
different order of valves being turned on and
off is employed.
Connect pipe work - making sure dump tap is off - open valve on Fire
Extinguisher - open valve on donor bottle - wait while
the bottle fills , you should hear the gas going in and can guess-timate when the bottle stops filling - shut both - vent excess
in the pipe by opening dump valve - remove Fire Extinguisher and weigh it.
NOTE BOTTLES MUST HAVE A CURRENT PRESSURE
TEST DATE STAMPED ON THEM.
Technical explanation of the volume of gas in 1kg of liquid CO2
Suppose you have a 1kg capacity fire extinguisher.
That is 1kg of liquid CO2
The weight of a mole of CO2 is 44g so you know that you have 22.7 moles of gas.
At 1.0 atm pressure and room temperature of 298 K, the concentration of an ideal gas is 0.041 mol/L.
So at room temp and pressure those 22.7 moles will occupy 22.7/0.041= 553 liters .
Therefore ....1 kg of liquid co2 will give you approximately :-
36 litre's of gas at 15 bar / 225 p.s.i , 55 litre's at 10 bar / 150 p.s.i. and 81 litre's at 100 p.s.i
Online calculator & info for everything CO2 HERE
A quick conversion for our American friends ....... 1lb of liquid CO2 contains 10.3 moles of gas .......1 mole of gas is 0.86 cubic feet .........So our 1lb of liquid will expand to a volume of around 8.8 cubic feet or 15,000 cubic inches @ room temp and pressure.
Temperature and percentage of fill greatly affects the pressure of co2 in
your bottle (around 750-850 p.s.i. is the norm). See the graph below.
@ 100 degrees F the pressure in full bottle will have risen to 1400 psi ... @ 120 degrees F it's approaching 2000 psi .
If one simply tries to exploit the gaseous phase
existing in the vapor space of the tank for process purposes, what will happen
is that the gas phase inventory may be depleted faster than tank liquid can
vaporize and replace the gas removed. The amount of heat required to
continuously vaporize liquid CO2 is such that external, ambient heat cannot be
transmitted through the tank walls fast enough to makeup for the gas removed.
This results in a decrease of tank vapor space pressure – sometimes down to
very low pressures that approach 5 barg. At this very low pressure, the
corresponding saturated temperature of the tank’s liquid would be approaching
-56.4oC and all the liquid will be solid
i.e. Dry Ice.
The way that the vapor pressure in the tank is kept constant while saturated vapor is withdrawn from the top of the tank is that a liquid vaporizer is employed to generate and replace the withdrawn vapors. The vaporization is usually effected by the use of an immersed electric heater that responds to the action of a simple pressure switch or transmitter that is mounted on the top of the tank. When the pressure decays, the electric heater is activated; when the design pressure is reached, the heater is shut off.
CO2 Phase Diagram.......... above.
The carbon dioxide phase diagram has 3 phases -- gaseous, liquid, and solid. The triple point (pressure 5.1 atm., temperature - 56.4C) is defined as the temperature and pressure where three phases (gas, liquid and solid) can exist simultaneously in thermodynamic equilibrium. Above the critical point (pressure 73 atm., temperature 31.1C ) the liquid and gas phase cannot exist as separate phases. This region, known as the superfluid or supercritical phase, has properties indistinguishable from the liquid and gas phases.
At temperatures below −78 °C, carbon dioxide condenses into a white solid called dry ice. Liquid carbon dioxide forms only at pressures above 5.1 atm; at atmospheric pressure, it passes directly between the gaseous and solid phases in a process called sublimation.
Enthalpy has a lot to answer for and is the cause of freezing.
With a gas fed source as the pressure drops in an orifice, liquid droplets nucleate and the percentage of liquid increases. At the interface between the liquid-gas and gas-solid regions (near 80 psi.), all the liquid converts to solid - yielding about 6 % dry ice. With a liquid fed source as the pressure drops in the orifice, gas bubbles form and the percentage of gas increases until the gas-solid boundary is met. Here, the remaining liquid is transformed into solid - yielding about 45% dry ice.
So.......If you use compressed co2 in liquid form and utilise the gas that boils off from it ...then your containing vessel , bottle or cylinder will get cold .....if you exceed the ability of the bottle or cylinder to warm back up by absorbing heat from it's surroundings then the pressure will drop and the contents may freeze.
A small amount of dry ice or snow can be formed by the gas as it exits the system to a lower pressure and a large amount of dry ice if its liquid exiting to a lower pressure.
The formation of large amounts of dry ice is to be avoided as this can cause a system blockage.
Fire extinguishers do not have this freezing problem .......liquid is ejected to atmosphere so most of the heat/cold transfer happens outside the bottle.
When it comes to using pneumatics the following
Flow = Speed
Pressure = Power
A combination of the 2 gives an effective flipper.
So.....MAXIMISE your possible flow ....
NO restrictions in your pipe work .....
and a decent size buffer tank of around twice your rams volume .
( The buffer tank contains a " head " of gas @ your required pressure.)
Several factors have an impact on the flow coefficient.
o Orifice size (diameter of the piping or opening through the valve)
o Length of piping or opening through the valve
o Turbulence caused by bends or turns in the piping
o Restrictions, or anything that reduces the orifice size or the flow path
o Shape of the orifice
Flow Coefficient Cv and Flow Factor Kv
The flow coefficient - C v - and the flow factor - Kv - are commonly used for specifying the capacities of control valves.
It is often convenient to express the capacities and flow characteristics of control valves in terms of the
Flow Coefficient - Cv
The flow coefficient - C v - is based on the imperial units system and is defined as:
The flow of water through a valve at 60 o F in
flow coefficient is commonly used in the
The metric equivalent of the flow coefficient - Cv - is based on the SI-system and is called the
Flow Factor - Kv
The flow factor is defined as
The flow of water through a valve at 20 o C in cubic meters per hour with a pressure drop of 1 kg/cm 2 (1 bar)
flow factor is commonly used outside
What is the Qn Value?
Qn value is used in pneumatics to define the flow of a valve. It is defined as:
The volume flow in litres per minute of air at a temperature of 20° celcius, with an input pressure of 6 bar and a pressure drop across the valve of 1 bar.
dimensions of Kv values can be transposed by means
of following factors:
Here's a list of definitions & Acronym's pertaining to valves....
"100% Area" (
"Standard Opening" - means that the area through the valve is less than the area of standard pipe, and therefore these valves should be used only where restriction of flow is unimportant.
"Round Port" - means that the valve has a full round opening through the plug and body, of the same size and area as standard pipe.
"WOG" - Water, oil, gas (Cold working pressure)
"SWP" - Steam Working Pressure
"ANSI" - American National Standards Institute
"CWP" - Cold Working Pressure
Note :- Kv quoted in litres/min
Cv Flow Through Orifices
flow rates for servo assisted 2/2 valves.
Info also applies to 5/2 and 3/2 spool valves.
Note that the flow for these is almost 1/3 that of the equivalent size
Or if you like your pipe or tube could flow nearly 3 times more.
PACulatorValve sizing and flow
The answer to your valve flow questions .... CLICK ON THE ABOVE LINK ... remember that the density of CO2 is 1.52
There is a link to this at the top of the page....I really like it....So here it is again Convert.exe DOWNLOAD IT! if you haven't already.
High Pressure & Liquid CO2 Valves ...........HYCONTROL
High Pressure Burkert Solenoid valve
This is the valve used on MANY Full Pressure European Flippers.
This valve only has a pressure rating of 50 bar BUT it has been re-tested and approved for the higher 66 bar ( 1000 psi ) used in Fighting Robots.
Note that over-volting of the std 24v solenoid is necessary for a satisfactory activation at 66 bar OR use a 12v solenoid coil @ 24v.
|The Burkert 5404||The above chart shows American specs for the same valve .... Note:- The Non- UL version has the 50 bar rating|
QEV's Quick Exhaust Valves
These have good flow rates compared to a standard 2/2 or 5/2 spool valve ......perhaps 3 times better.
Consider it's use as an inlet valve instead of an exhaust ☺.
a regulator ..Get the Victor SR310
Take the link TWICE!
Victor® SR-311-320 Carbon Dioxide Regulator
Part No :-
PDF File for the Victor.... HERE