Visitors since May 06
INDEX
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
Manufacturer --HERE
Extinguishers ,Paintball, etc ....
CATALINA Cylinders U.S of A
HERE
UK
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.
Technobots
Co2 Screw Down Valve (Tapered thread 3/4" BSP )
gascylindersuk.co.uk
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Throughout the world, carbon dioxide cylinder valves have a special
thread. In
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). |
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American CO2 Valve Thread Size
CGA 320 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.
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Paintball Valve
Specs:- Inlet Thread : 5/8-18UNF Outlet Thread : CGA 320
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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
Alco2Jet®
SODA
CLUB website
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
Gas Outlet Valve
Threads.... designations and dimension
HERE &
HERE
BSP NPT & Others Screw Threads.
HERE
How to fill
an empty bottle
Decanting
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.
Fills
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 ... only 66% of it's volume is liquid filled.... or if
you like... it's only 2/3rds full of liquid... the "empty " 1/3rd
contains gas and acts as an expansion gap.
Liquid CO2 has the same density as water ... therefore a 2kg
tank has a total volume of 3 liter's consisting of 2 liter's of liquid
co2
and 1 liter volume of expansion gap.
More
HERE
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.
Abbreviations
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.
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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.
PLEASE
NOTE BOTTLES MUST HAVE A CURRENT PRESSURE
TEST DATE STAMPED ON THEM.
Filling kit and "How to" links on another site........
http://www.kegman.net/refilling.html
and
http://www.kegman.net/paintball/pbrefiller.html
Properties of Carbon Dioxide or CO2
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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
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Bottle Freezing
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
applies.
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
difference between the flow coefficient
Cv and the flow factor
Kv.
The flow coefficient - C v - and the flow factor - Kv - are commonly used for specifying the capacities of control valves.
The Flow Coefficient - C v
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
The
flow coefficient is commonly used in the
The Flow Factor - K v
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)
The
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.
Converting between
Flow Factor Kv , Flow Coefficient Cv and Qn
The
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
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Approx
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
ball valve.
Or if you like your pipe or tube could flow nearly 3 times more.
PACulatorValve sizing and flow
calculator
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.
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| 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
☺.
Need
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