# 7.2 cubic metres of Nitrogen compressed, will last 30mins-1hr of usage

#### JL3110

Summary
So I am currently looking to work on some projects with my brother.

I have some questions regarding the usage of nitrogen.
We are looking at a 7.2 cubic metre cylinder of Nitrogen Pure compressed and wondering at what rate of pressure will equal roughly 30-60mins of use?

We are still relatively new to this hence why we are seeking all advice, and knowledge before continuing.
So I am currently looking to work on some projects with my brother.

I have some questions regarding the usage of nitrogen.
We are looking at a 7.2 cubic metre cylinder of Nitrogen Pure compressed and wondering at what rate of pressure will equal roughly 30-60mins of use?

We are still relatively new to this hence why we are seeking all advice, and knowledge before continuing.

Related General Engineering News on Phys.org

#### BvU

Homework Helper
Hello JL, & bro, !

7.2 cubic meters is huge ! Size G apparently.

You will need to give more information if you want to calculate a time: the flowrate at delivery pressure, for example

#### JL3110

Great well if the size is huge it should definitely do the job.

What information do you need?

I am not sure what flowrate I will use and what pressure yet, thats what I am trying to determine.
Forgive me, we are still learning to wrap our heads around this.

Kind regards,

Hello JL, & bro, !

7.2 cubic meters is huge ! Size G apparently.

You will need to give more information if you want to calculate a time: the flowrate at delivery pressure, for example

#### BvU

Homework Helper
I am not sure what flowrate I will use and what pressure yet, thats what I am trying to determine.
Makes a difference if you use 0.1 kg/s or 10 !

So: how do you know you need a 7.2 m3 'bottle' ?

In the mean time, study the ideal gas law $pV = NRT$ for estimates.

#### JL3110

im not sure if 7.2m cubic is the right amount, it was just the largest and we figured it should be enough for our projects. We would rather have some left over than have none.
We are filling small tyres, like miniature go carts tyres.

#### BvU

Homework Helper
Way too big. Estimate the volume of a tyre and the desired pressure.

Remember, you get the stuff delivered 200 Bara in e.g an 1.8 m3 bottle .

Say the desired tyre pressure is 4 Bara and a tyre is 0.004 m3. You can fill some $$1.8/0.004 \times 200/4 = 20000$$ tyres

#### BvU

Homework Helper
By the way, a potential supplier should be happy to help you with this !

#### phyzguy

@BvU are you sure you're giving good advice? The volume of these gas cylinders is given as the volume of gas at STP. Since it is compressed to ~150 atmospheres, the volume of the actual cylinder is much smaller. The 7.2 m^3 N2 bottle is a standard gas cylinder, about 6-8 inches in diameter and about 4 feet tall. This size cylinder is used all the time.

BvU

#### JL3110

What would you recommend?
Would this suffice or would 2 be required possibly?

@BvU are you sure you're giving good advice? The volume of these gas cylinders is given as the volume of gas at STP. Since it is compressed to ~150 atmospheres, the volume of the actual cylinder is much smaller. The 7.2 m^3 N2 bottle is a standard gas cylinder, about 6-8 inches in diameter and about 4 feet tall. This size cylinder is used all the time.

#### phyzguy

What would you recommend?
Would this suffice or would 2 be required possibly?
You haven't given enough information to decide. Simply giving the pressure isn't enough. The gas cylinder can supply high pressure indefinitely if you aren't using any volume. What are you attempting to do? Fill tires? If so, what is the volume of the tire, how many tires do you want to fill, and what pressure do you want to fill them to?

#### JL3110

My apologies this is what I am looking to ascertain.

the volume capacity of the bag inside the tyres are 50L.
Roughly got about 16 to fill.
The desired pressure at this stage isnt clear, we will relatively go by test and trial but low pressure is what we are aiming for.

My question i guess was if i had that 7.2 cubic metre cylinder, and i was to use a low rate of pressure release from the cylinder to fill the 16 50L bags how long would it take? Would I have enough nitrogen?

You haven't given enough information to decide. Simply giving the pressure isn't enough. The gas cylinder can supply high pressure indefinitely if you aren't using any volume. What are you attempting to do? Fill tires? If so, what is the volume of the tire, how many tires do you want to fill, and what pressure do you want to fill them to?

#### phyzguy

Well, a liter is 1000 cm^3, and 1 m^3 = (100 cm)^3 = 10^6 cm^3, so 1 m^3 is 1000 liters. So say you want to fill the tires to 4 atmospheres, which is approximately 60 psi or about 4.1 bar. That would use 16*50*4 = 3200 L. So you could do this twice with your 7.2 m^3 cylinder. If you use less pressure, you could do it more times, more pressure would mean less times. Does this make sense?

#### JBA

Gold Member
50 liters sounds like a lot of volume for a go kart tyre. What is your basis for this number i.e. Is this maybe the amount of gas @ atmospheric pressure or is it from an actual dimensional volume of the inner tube in the tyre?

#### JBA

Gold Member
So say you want to fill the tires to 4 atmospheres, which is approximately 60 psi or about 4.1 bar.
The 4 bar pressure was an example pressure in post #6 by @BvU , it is not a stated requirement by OP.

#### BvU

Homework Helper
@BvU The volume of these gas cylinders is given as the volume of gas at STP.
That 's misleading to me -- sorry if I missed that.

Oh well, that's what you get when you look at things as a physicist...

@JL3110 : what's the argument to reject a solution with a simple small and cheap air compressor like my bike repairman uses ?
And: exactly how big are these 'miniature go cart tyres' ? Or is the 50 L at STP too ?

#### Torbert

Nitrogen is used in aircraft tires for a great many reasons, no moisture and large molecules are two. Those big bottles are used with a regulator so the output pressure can be set. At 80 psi an eight wheel aircraft could have all its tires filled one after another without a tremendous change in bottle temperature. Small valve stem diameters limit airflow.
An anecdote about using high pressure nitrogen without the regulator.

A tire not on an aircraft needed to be filled for analysis but the regulator had been sent out for repairs. The mechanic was rather inexperienced and figured on just cracking the valve slightly so just 80 psi would come out of the 4000 psi bottle, saving waiting time.
When the bolts holding the rim together gave out, the half not tied down went through the hanger wall and damaged an aircraft parked outside.

I have not seen mention of a pressure regulator and if the product is to be used in real life, I worry.

BvU

#### phyzguy

I have not seen mention of a pressure regulator and if the product is to be used in real life, I worry.
Yes, @JL3110 , I want to emphasize this point. You absolutely need a regulator for what you are trying to do.

#### bobob

If you are going to fill lots of tires, you would be better off using a liquid nitrogen dewer. Those have gas phase valves that allow you to take warm gas out. Since nitrogen goes from liquid to vapor at an expansion ratio of a little over 600:1, you can pack a lot of gas into an LM2 dewer.

"7.2 cubic metres of Nitrogen compressed, will last 30mins-1hr of usage"

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving