Author Topic: Pumping gas  (Read 20797 times)

Offline Darren

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Pumping gas
« on: January 14, 2009, 04:51:52 PM »
hypothesis:

If one wanted to pump a very low pressure, but infinite volume, of gas from one source into, a bottle to 200 Bar what type of pump would be capable?  :smart:

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bogstandard

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Re: Pumping gas
« Reply #1 on: January 14, 2009, 05:18:07 PM »
Darren, statement just doesn't quite match up.

very low pressure -> to 200 Bar

The pump would have to get the gas to the bottle pressure otherwise it would not transfer.

John

Offline Darren

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Re: Pumping gas
« Reply #2 on: January 14, 2009, 05:31:03 PM »
That's right John,

I was thinking of a diving bottle pump/compressor but threw it out to the crowd in case there might be a better solution.
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bogstandard

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Re: Pumping gas
« Reply #3 on: January 14, 2009, 06:53:36 PM »
Sorry Darren, but still don't understand.

Not about the pump, but the part about the low pressure. Is there a relevance of it being at very low pressure and infinite volume? Why is it at a very low pressure? Does the infinite volume mean it is stored in a massive storage tank, or is it extracted from the atmosphere, or maybe salt water.

Unless of course you mean you just want to pump a gas up to 200 bar. If that is what is required, then other questions come to mind.

Would the gas become volatile at higher pressures?, as in acetylene, which shouldn't be stored above 1 bar unless dissolved in acetone and the cylinder filled with Kapok or other cellular medium.

I know this is getting rather stupid, but if the original question was, 'I want to pump air up to 200 bar, what sort of pump should I use', then I wouldn't be ragging you about it  :bang:


Bogs the stickman  :poke:

BTW, if my final statement about pumping air is correct, then I have no idea, but your diving bottle pump sounds just fine. I just wanted to be a bit of a PITA tonight :lol:

Sorry about that.

Offline Darren

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Re: Pumping gas
« Reply #4 on: January 14, 2009, 08:39:29 PM »
Hi John,

Sorry I was a little vague, that was deliberate on my part. Two reasons, the idea is prob not legal in the UK and it's fraught with dangers.

But what the heck, it's legal in the States and they do it at home.

The idea is to run a car on methane gas, mains gas in the UK. I converted my car 4yrs ago to run on LPG and it's been great. Should be quite simple to convert to methane, only prob is filling the tank to 200 bar. I understand it takes hrs to do this from the mains cos the supply pressure is low and you mustn't suck out your neighbors supply.

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Offline Bernd

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Re: Pumping gas
« Reply #5 on: January 14, 2009, 10:11:17 PM »
Darren,

I have a freind that goes diving. He fills his own bottles. The compressor he uses has I believe three or four stages. It takes him quite a while to fill his diving tanks. Your looking at 2900 psi. (200bar) right?

Of course you know LPG is liguid propane gas right? LNG is liguid natural gas. There buess here in the states that use compressed natural gas. The tanks are made from aluminum and spun fiberglass.

If you want to do a bit of research use Google and do a search on CNG (Compressed Natrual Gas) Close to 300,000 hits.

I have given thought to making methane gas (decomposing garbage, basically plants will give you mathane). Compress it and use it in my vehicle.

I'm liking this subject now that I know somebody else is interested in this.

Bernd
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Offline Darren

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Re: Pumping gas
« Reply #6 on: January 14, 2009, 10:29:52 PM »
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline Darren

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Re: Pumping gas
« Reply #7 on: January 14, 2009, 10:32:07 PM »
btw, I thought LPG was liquid petroleum gas and CNG was compressed natural gas in order to state where their origins.
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Offline Bernd

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Re: Pumping gas
« Reply #8 on: January 14, 2009, 10:36:13 PM »
btw, I thought LPG was liquid petroleum gas and CNG was compressed natural gas in order to state where their origins.

Awwwww right you are.  :bang:

Bernd
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Offline Bernd

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Re: Pumping gas
« Reply #9 on: January 14, 2009, 10:40:03 PM »
Have you seen this Bernd?

http://www.green-trust.org/2000/biofuel/batesmethane.htm

I thought I'd seen that some were. When I got to the bottom I saw it "The Mother Earth News". I used to have a subscription to that magazine.

One problem with all that is the gov doesn't want you using those things because it makes you independent. They can't have that now can they? :D

Bernd
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Offline Darren

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Re: Pumping gas
« Reply #10 on: January 14, 2009, 10:43:56 PM »
Oh you get that problem as well do you.

I thought it was just us brits
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Offline Brass_Machine

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Re: Pumping gas
« Reply #11 on: January 14, 2009, 10:47:35 PM »
A very interesting read. Hmmm...

BTW, isn't like almost 4am Darren??

Eric
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Offline Darren

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Re: Pumping gas
« Reply #12 on: January 14, 2009, 10:50:47 PM »
Yes Eric,

it's this cat thing, say no more

Call me soft if you like
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Offline Brass_Machine

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Re: Pumping gas
« Reply #13 on: January 14, 2009, 10:54:59 PM »
Yes Eric,

it's this cat thing, say no more

Call me soft if you like

Never would I do that, I understand. How about I call you 'human' instead?

Eric

If you are still up, check your PMs in about 10 minutes.
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Offline SPiN Racing

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Re: Pumping gas
« Reply #14 on: January 15, 2009, 12:03:51 AM »
I have a suggestion.. if it helps.

If you are saying that it takes quite some time for the low pressure gas to come into a tank of a given volume and pressure.
Lets say.. you have a big tank in the car. And it holds (I have no idea so Im making this up) 100 Cubic feet of compressed gas at 200Bar.
If you were to compress this from the Mains.. it would take (more guessing) 10 hours to fill.

Wouldnt it be a simpler idea to have a decently large tank buried in the yard or something that holds.. say.. 200 Feet of gas. Then you could let the slow steady pressurization of the tank run on its own. Once fill shut off via pressure switch.
When its time to fill the car, simply connect the two and let it bleed over? Or possibly run a pump for a short time as it would equalise pressure between the two, lowering the overall pressure some.

It would make a re-fill go from a 10 hour ordeal to a few minute process wouldnt it?
SPiN Racing

Offline Darren

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Re: Pumping gas
« Reply #15 on: January 15, 2009, 12:14:27 AM »
Now that's a great idea, I was thinking something similar but hadn't quite thought it through completely as yet.

We can't use the normal LPG tanks fitted to cars as they only take about 20bar and we need 200 bar for CNG. Reason being that it has less energy by volume so we need more of it to get any decent mileage from a tank.

BTW, welding bottles are rated at 300 bar so we could use those and they come in reasonable sizes too.

I was thinking of two bottles, fill one while using the other. Really long trips carry both. But the time spent running a motor to fill will cost. So your idea has merit.
One thing, a big tank will not fill a small tank with enough gas worth having without using a high pressure pump to transfer it over. We need enough pressure to convert the gas into a liquid. I believe this happens at about 1,100 psi.
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Offline SPiN Racing

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Re: Pumping gas
« Reply #16 on: January 15, 2009, 12:36:14 AM »
What type of vehicle you gonna put it in?

If it was a small truck.. or a car with..... Room to be modified.... You could do something like a race team Pit Cart.
They simply have some 1" angle Iron welded onto a small boc frame to keep them from rolling around, and a buss bar with the bottles attached to it.
Then you go down and open the valves and the bar is pressurised. The bottles are stored low in the vehicle, and are surrounded with some angle iron to prevent impacts etc. from blowing a valve off.

If its a car like a S-10 Pickup.. or somethig with a frame.. Realistically you could sneak the bottles up between the frame rails on eather side of the driveshaft.
Granted if its a Pickup.. simply put them in the bed, and hook em up.
OH and to keep officer Law happy.. Paint them Blue and put a No2 sticker on them. :D
SPiN Racing

Offline sbwhart

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Re: Pumping gas
« Reply #17 on: January 15, 2009, 03:38:26 AM »
I've got it in the back of my mind that the nuclear power industry use none mechanical pumps to move gas round, I think they work symilar to a steam injector on Locomotives:- flow through a cone increased velocity increase pressure, bit hazzey I know but may be worth further research.

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Offline Paul Barker

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Re: Pumping gas
« Reply #18 on: January 15, 2009, 04:11:29 AM »
Hello i am a close friend of Darren though we live a 7 hr drive apart.
It is really my question. Darren and I band these things about sometimes our mad professor ideas come to nothing.

By trade
I am corgi registered gas fitter in the UK after Darren's leed I drive an LPG van for my work.

In my work I work with LPG and Methane which we call Natural gas.


Yes I had read the Bates article which is where I discovered that the pump he used was a diving bottle compressor, which seems to be a three stage opposed piston pump. Forgive me I am not a mechanical engineer and dislexic so might get some technical names incorrect.

Reading up on the use of methane in countries where it is in the domestic domain, 200 bar is the usual and I found an old 2002 advert for a domestic garage pump costing $2,000. But I thought that was rather expensive. It also seems that the cost of power to compress the methane is half as much again as the cost of the gas (which in the uk comes out of the meter at 21mbar and you would have to do your pumping at night (which is the practice anyway over 5 hours) because our domestic gas meters are barely sized sufficient to supply the modern appliances. Since our infrastructure was put in at a time people had a cooker and if you were lucky a gas fire running on gas extracted from coal at the electricity generating plants (known as "town gas"). These mains are cast iron and geting on for 100 years old, so the pressure of gas inside them is also very low perhaps on average 30 mbar.

It is quite conceivable that if you sucked gas from your supply at too great a rate you could suck the flame out of your neighbours cooker which has no flame supervision device, hence when you stop your pump and the neighbours supply is back to pressure his kitchen will be gassed up to the explosive ratio of 5 to 15%, in he comes to make his first cup of tea throws a switch and boomb there is a picture of a pile of rubble on your TV AM podcast.

So, there can be infrastructure reasons why this may never be made legal in some countries, our infrastructures for services  being possibly the oldest in the world, and our country being near enough bankrupt and the Victorian work ethic having become undervalued by the grab what you can from benefits mutation of the Bevin Welfare State.

Now that all our products are imported from China and the people with the knowledge are gathering in these forums because industry has spat them out, and the admisnistration of our supply industries is handled by people who have no on the tools experience, we are in a mess. I represent British Gas as a front line fitter geting down and dirty with the stuff but I am managed by people who wouldn't even know the specific gravity of methane or what other gases are contained within it, and why (to control the calorific value). They wouldn't know how to take the case off most domestic boilers (because thankfully the manufacturers make it tricky so that the unknowledgeable (like managers) can't kill themselves or anyone else.

When you get this class of people administering dictating and ordering in an industry you are in trouble. The trouble is inside organisations graduates of nothing useful create for themselves empires and other empires clone around them like in a bubble map and departments are renamed so that they can have more nothing useful degree'd managers etc etc. Disseminate to conquer the poor weighed down bloke on the tools! You wouldn't believe the amount of office numpties from all different departments I have to negotiate like obstacles in a maize to achieve what should be a straight forward objective. Great Britain? It died with Fred Dibnar.

Anyway big storage vessel slow 24hr pressurising of it, and balanced release into vehicle tank sounds great idea, vehicle tank would receive percentage fill big tank contains in quick time. but massive tank cost and still require 3 stage pump which is also massive cost relative to savings.

What are the savings? Well Darren and I differ a little on this but he thinks 50% I think methane off the top of your domestic supply hense at your lowest rate comes out about 1/3rd the price of autogas (Propane in the UK) Insidentally autogas is as cheap a form of Propane here as a 47kg bottled for the domestic market. So no savings to be found searching out other Propane sources.

The problem with Methane is the cost of compressing it to a liquid so that the storage vessel can be appropriate for the use and the mileage sufficient, particularly considering it has to get you to your destination and all the way home since you can never fill up elsewhere in a country where you are the only one doing it..

« Last Edit: January 15, 2009, 04:15:13 AM by Paul Barker »

Offline Paul Barker

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Re: Pumping gas
« Reply #19 on: January 15, 2009, 04:20:59 AM »
You will not understand this next bit but the Triodes Darren is using would bring tears to your eyes if you heard them.

In the Uk these were used in rf (radio frequency) heating more specifically diathermy which is what makes the roast pork smell in an operating theatre (I used to be a nurse).

Offline Paul Barker

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Re: Pumping gas
« Reply #20 on: January 15, 2009, 04:38:38 AM »
Anyway Bates does mention an inflatable dinghy on top of the car, and this is not at all stupid. You could compress at much lower cost sufficient methane for a town car with say the range of a town electric car to a low pressure of perhaps 3 bar with a much cheaper compressor. Basically you just need a simple diaphragm gosvenor (which is all Bates' converter would be) to regulate the flow of gas when it can't get sufficient you are out of methane throw the petrol (which I think you across the pond call gas so this will get confusing) switch.

As far as anyone can see you have a boat which goes down a lot.

So what are the dangers?

The only risk you have with methane is that you must avoid it building up in an enclosed space to a ratio of 5 to 15% with air. More gas than that it will not explode, less gas it will not explode. It actually explodes at 12% every time ask anyone in the coal industry, they run tests all the time and it always explodes at 12% never anything different. I believe we in the gas industry are trained to the 5 to 15% knowledge so that we will be ever vigillant.

There is no poison it contains no carbon monoxide that is a product of incomplete combustion nowadays when we were on coal gas or town gas that did contain C0 which is why people used to put their head in a gas oven to kill themselves. If you did that today you would remain alive until a neighbour came in and switched on the light whence you would both be blown to smitherines. You could put your mouth over a gas supply pipe and breathe it in, you would lack oxygen but nothing in the gas (which is vertually neat methane with a little ethane butane and propane mixed in to ensure consistent calorific value).

So as long as your plant is outisde, zero risk.

We are not worried in the industry  in the slightest whatsoever about gas leaks outside. Methane oozes out of the cast iron mains all over this country.

Inside a dwelling gas is a very serious issue, there is never a minor outcome every so often there is a picture in the paper of a pile of rubble where a house used to be, allow methane to achieve combustible ratio, provide ignition (electrical switch) and it will take the whole house out without question. In the atmosphere it is impossible for it to explode. It might light and burn off but it won't explode.

The issue of monitoring your flow of gas from your supply is a big issue. There are many gas appliances without flame supervision, which in your property or your neighbours would become a bomb if you don't ensure sufficient gas is available to them inspight of what you are doing.
« Last Edit: January 15, 2009, 04:42:13 AM by Paul Barker »

Offline Bernd

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Re: Pumping gas
« Reply #21 on: January 15, 2009, 09:57:46 AM »
Spin,

Think of taking atmosphereic pressure of 14.5 psi up to 3000 psi. The larger the tank your pumping it in the longer it will take. The last piston that gives you the 3000 psi is very small. If I remember right it's about 5." to 1" in dia. Not much volume there only pressure. The pump needs to be saveral stages to get to that high pressure.

It's kind of tough to get your mind wraped around that. If I see the guy that does the diving I'll ask him about his pump and how long it takes.

One other consideration here when squeezing a gas into a more compack container is the heat generated. Get it hot enough and the gas could explode.

Bernd
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Offline Darren

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Re: Pumping gas
« Reply #22 on: January 15, 2009, 12:22:02 PM »
If I understand what you are saying it goes something like this.

1st pump moves a large volume at a relatively low pressure. 2nd pump has a smaller piston moving a smaller amount of gas but at a higher pressure. 3rd pump smaller piston and more pressure.

But all 3 pumps could run from the same power source thereby not having to increase the power required at each stage?
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Offline Bernd

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Re: Pumping gas
« Reply #23 on: January 15, 2009, 01:00:58 PM »
Darren,

Yes close. The pump is as one unit containing 3 or 4 pistons. The first cylinder would take a certain volume compress it into the next cylinder at a higher pressure and so on. Think of a triple expansion steam engine operating backwards. By that I mean take the steam after it has exited the exhust. Now take that steam and send it back through going from the largest cylinder back to the smallest. You'll, theoretically though, end up with the steam pressure that started out in the boiler. I used that example to see if you can grasp what I'm trying to explain.

I tred a Google search. To much info to look through. See if you can find something on high pressure pumps or cng pumps.

Bernd
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Offline Paul Barker

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Re: Pumping gas
« Reply #24 on: January 15, 2009, 01:51:06 PM »
it did occur to me that you could buy two 150 psi compressors and series them, but the components are only designed to withstand 150 psi.

I wonder what the multiplication factor is? If the first compressor liftes pressure by 150 times does the second lift 150 psi X 150? Absolutely not, surely not.

is it essential for the second compressor to be smaller? If you ran the pair off gearing you could simply half the speed of the second one to produce the same effect?