Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
(OP)
thread135-111334: Propane/Butane vaporization calculation After reading this thread I wanted to add some basic information and ask for some help.
Pressure and contents in industrial gas cylinders is always calculated at 15 degrees C by the Industrial gas companies.
I am trying to work out the maximum withdrawal rate of LPG from different sized cylinders when used with oxygen/LPG equipment for cutting, brazing, and heating.
Usually for heating and cutting applications I would suggest the use of 45kg LPG cylinders with a "G" sized oxygen cylinder, but I have heard of people using 9kg and 18 kg LPG cylinders.
I would think this is dangerous because a lack of LPG pressure and flow could cause a flashback due to a lack of gas pressure and volume to keep the flame at the end of the tip or nozzle.
Here in Australia most cutting and heating tips use 100-150 kPa of LPG and anywhere between 200-1000 kPa of oxygen, depending on the size of the tip or nozzle.
From information gleaned from an LPG supplier here in Australia I have found out the maximum withdrawal rate from a 45kg cylinder is about 56.6 litres per minute, I am trying to find out the maximum withdrawal from a 9kg & 18kg cylinder at 15 degrees C.
Cylinders for LPG here go 4kg, 9kg, 18kg, 45kg, 190kg
The reason I ask this is due to the issue of withdrawal of acetylene from cylinders which is limited to 1/7th of the cylinder content per hour for intermittent use and 1/10th per hour for continuous use.
All oxygen/acetylene heating torches on the Aussie market grossly exceed the maximum withdrawal rate and often cause flashbacks, this is why I always recommend oxygen/LPG for heating over oxygen/acetylene even though the flame is colder, 2,850 degrees C v's 3,160 degrees C the heating tips for oxygen/LPG are much larger so the calorific energy available is much greater.
Can anyone out there help?
Pressure and contents in industrial gas cylinders is always calculated at 15 degrees C by the Industrial gas companies.
I am trying to work out the maximum withdrawal rate of LPG from different sized cylinders when used with oxygen/LPG equipment for cutting, brazing, and heating.
Usually for heating and cutting applications I would suggest the use of 45kg LPG cylinders with a "G" sized oxygen cylinder, but I have heard of people using 9kg and 18 kg LPG cylinders.
I would think this is dangerous because a lack of LPG pressure and flow could cause a flashback due to a lack of gas pressure and volume to keep the flame at the end of the tip or nozzle.
Here in Australia most cutting and heating tips use 100-150 kPa of LPG and anywhere between 200-1000 kPa of oxygen, depending on the size of the tip or nozzle.
From information gleaned from an LPG supplier here in Australia I have found out the maximum withdrawal rate from a 45kg cylinder is about 56.6 litres per minute, I am trying to find out the maximum withdrawal from a 9kg & 18kg cylinder at 15 degrees C.
Cylinders for LPG here go 4kg, 9kg, 18kg, 45kg, 190kg
The reason I ask this is due to the issue of withdrawal of acetylene from cylinders which is limited to 1/7th of the cylinder content per hour for intermittent use and 1/10th per hour for continuous use.
All oxygen/acetylene heating torches on the Aussie market grossly exceed the maximum withdrawal rate and often cause flashbacks, this is why I always recommend oxygen/LPG for heating over oxygen/acetylene even though the flame is colder, 2,850 degrees C v's 3,160 degrees C the heating tips for oxygen/LPG are much larger so the calorific energy available is much greater.
Can anyone out there help?
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
One source I found said max rate was
47 kg - 2.37 kg/h
19 - 1.32
13 - 1.05
[EDIT] - so for the 47kg one this equates to about 22l per minute so about half of your flow. But it is highly dependant on the air temp and also how much fluid is in the cylinder. The fuller the cylinder the more liquid area there is for heat transfer so the higher the rate of vaporisation.
It's not clear what temperature this was based on though.
But it sounds right - the smaller the tank the greater the surface are to volume is and so the greater the heat transfer per kg of fluid.
So you need to define the air temp and the heat input if it's external to find out max flow.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
What do you know about this device?
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
https://www.ameritempgroup.com/store/p1649/Powerbl...
They're not cheap but you will get a reliable flow.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
For my job I need to know the flow rates of the tips and nozzles of the gas equipment I am supplying and ensure the gas supply system and cylinders can give the required amount of gas, both in pressure and in flow.
Acetylene is simple, I have the details written in my thread at the top.
Oxygen is simple as it's a gaseous gas in the cylinders not a liquid.
I have the specifications of the regulators, hoses, flashback arrestors, blowpipes, cutting attachments, mixers and tips or nozzles, but the maximum withdrawal rates of LPG from the different sized cylinders is difficult to find.
The reason I need this information is if there is not enough gas pressure and flow from a cylinder, it could cause a flashback.
Remember a flashback arrestor won't stop you having a flashback, it will only stop the flame going back into the down stream gas equipment.
I need to be sure the cylinder I recommend is big enough to supply what is needed to the different tips and nozzles.
The ambient temperature for gases should always be measured and calculated at 15 degrees C
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
M = (A/Ao) x Mo
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
Theoretically, you are right. But wall resistance is much lower than inside htc, and hence inside htc is one of the limiting resistances to heat transfer, in addition to external htc. Of these 2 limiting resistances, the external natural convection htc would be much lower than the internal boiling htc. So I've approximated that heat transfer into the liquid from ambient is relatively constant regardless of level in the tank. This approximation helps to enable the linear relationship suggested. An approximation to reality is better than not knowing at all.
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
MJCronin
Sr. Process Engineer
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
RE: Maximum withdrawal rate of LPG from cylinders @ 15 degrees C
See here as an example: https://www.google.com/maps/place/Clairville,+Toro...
There are really long bus ducts that run from the brown roofed 230 kV GIS building to the right and then way, way up to where the line terminals' air-to-gas bushings are. These take multiple cylinders of SF6 gas to fill.
In a similar vein, we electrical operators used to keep our handheld propane torches inside the control building during the winter months, and take them out to our vehicles when going out on a switching run; these torches were invaluable for thawing frozen switchgear locks. One soon learned the value of this the first time one forgot to store them inside; one either had to thaw locks with one's bare hands, or warm the torch cylinder with one's bare hands to scare anything more than a very sluggish flame out of the torch due to near-nonexistent propane vapourization . . .
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]