The capacity of a cylinder is easily altered by using different length diameters of standard sizes of materials. Ends will be the same no matter the length of the cylinders.

Spheres would all be different, depending on capacity.

Follow convention. Don't get cute with your design unless there's a legitimate reason.

Thank you for your responde lyn. I should have said earlier, the code sets the capacity at 7,5 liters. I have come up with a list of sets of parameters {diameter, semiellipsoidal height, cylindrical height} that meets the capacity criteria.

In general, you would try to minimize the weight of the steel in each container.

Then, too, packing density needs to be considered - every time an item is shipped or stored, it takes up space. A cylinder is more efficient than a sphere in this regard. For utmost efficiency, you would consider the case size requirement and how it fits on a standard pallet, etc. Generally, space = $. Weight too, of course, in the case of shipping, but you have to consider the trade-offs.

I'm sure there are other considerations as well.

That is a great point. At first, it would seem that a sphere is more efficient, given that for a given volume and a set maximum height, the sphere is the shape with the lowest diameter, so I don't understand how a cylinder would be more effective.

There's another interesting thing about packaging. 13kg cylinders, for example, have a ring at the top, in order to make it easier to handle and to stack vertically. However, I haven't seen any 3kg LPG cylinders with that ring.

True, but have you tried to chase a sphere downhill? Getting serious, it's NOT a good idea to stack items like that vertically, relying on "shape provisions". The existing cylinders use the ring to stand, NOT to stack. S.M.

I don't think I've ever seen a 3kg LPG cylinder. They may be shipped in corrugated cartons designed to support stacking. What is the location?

There's another interesting thing about packaging. 13kg cylinders, for example, have a ring at the top, in order to make it easier to handle and to stack vertically.

Also one of the most important thing the top ring does is to protect the valve assembly.

Now the bottom may have a ring or four flat spots/dimples so the cylinder may sit upright. I don't think the rings are designed for direct stacking. As this could damage the bottom of the top tank or the ring on the bottom tank without a buffer between them.

"for a given volume and a set maximum height, the sphere is the shape with the lowest diameter, so I don't understand how a cylinder would be more effective."

Definitely sphere will have maximum volume with lowest wall surface area, but it' not the everything to be considered for manufacturing. For making spherical container you have to weld two hemishpherical pieces at center. Sperical shape has three disadvantages:

1. It require special order for whole material from hot pressing machine, a costly affair. In case of cylindrical shape standered size seamless pipe of required length can be used and two standard dished ends available in market.

2. It requires longest single weld in C leading to a weaker section.

3. Spherical ones are not easier for packing and taking more space for transportation.

Rings at bottom (for support & keeping it upright) and at top (to handle & protect valve body while handling) are required. Rings at top also help vertical stacking while transportation.

"3kg LPG cylinder manufacturing plant."

Once you have to make a cylinder manufacturing plant, why you are thinking about spheres. Do you want to make "LPG Sphere" manufacturing plant?

"the sphere is the shape with the lowest diameter, so I don't understand how a cylinder would be more effective."

Huh? My geometry teacher would not agree if specific volume is the primary criteria.

Think about it for a while.

You're absolutely right. Thanks

You need to take into account, the safety factor. 20% must be left for expansion and with this, you need to decide what type of thread outlet. They will be left hand thread by standard however will it be a POL fitting?

It sounds be the volumes you are talking about that these bottles will be portable, that is all well and good, and as mentioned earlier, about top rings for stacking, they are also for protection of the valve.

Will your fill valve/outlet valve have the safety bleed built in? Or like some portable cylinders in some countries, will they be separate from each other.

Cylinder material can help with the weight factor as well. There are several companies now making them from heavy gauge aluminium. This does increase the overall dimension by about 25mm, but they weigh much less than their equivalent steel counterparts. This means a saving on fuel costs for delivery, handling costs during manufacture, and time saving during manufacture. By not coating aluminium cylinders, the white oxide that tends to form, is a very good protective coating, so there will be a saving in manufacture there as well.

Hope this helps, and good luck on the thesis

I am not aware of your location, In India, there are small LPG cylinders available in the market some of them are designed and manufactured by good compnies based on standards. The importance of design and features are based on the usage and usefull ness at the end user's place with the ease of handling and safety.

Normally I have not seen upper rings in the small size cylinders but the Burner with stand is fitted on the top of the valve of the cylinder and gas is being used for cooking similarly, lapm post is fitted and the gas it used for lighting etc.

The exsisting 5 Kg cylinder's shape is as below:

You can note the bottom ring for stablising the placement on plateform.

That looks like what we would (in Australia) call a 'Porta-Gas' cylinder. Different thread type altogether, as well as a different pressure rating on the appliances that use this type of cylinder.

These cylinders are mainly used here, for camping purposes and have minimal gas pressure regulating, operating at higher pressures (7 - 12 Kpa).

The standard cylinder here, uses a POL type thread and although the same pressure out, it is regulated down to 2.75Kpa before the connection to the appliance.

You cannot mix the two of these cylinders, ie, run a 2.75Kpa appliance from one of these bottles as the gas would be too high a velocity, and the presssure far too much. In short, it would not be very safe.

If this is the type of cylinder being manufactured, you will not need a top ring (depending upon the handling requirements). If the outlet valve is to be fitted permanently, you will need a top ring to protect the valve.

I used to cook quite often on a gas camping stove. Just one thought, I would like to add. The evaporation surface of the gas is very important, if you like to have some heat in cooking. Also the gas may not get to cold whiles cooking otherwise you will have only a very slow evaporation (and the pressure drops). so make the fluid surface as big as possible, and the tank surface as big as possible.

A quick google search brought up these examples

http://www.alibaba.com/product-gs/237372348/3KG_LPG_Cylinder.html

http://www.alibaba.com/product-gs/325354625/3kg_LPG_gas_cylinder.html

http://www.alibaba.com/product-gs/513187310/3KG_LPG_liquified_gas_cylinder.html

http://www.alibaba.com/product-gs/249560278/LPG_Gas_Cylinders.html

See the attached file at Excel for finding the dimensions required for LPG Cylinder 3 Kg: http://dl.dropbox.com/u/48490928/LPG%20Cylinder%203%20Kg.xlsx

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