helium cost and helium tank question

[solidude]

15 characters dude

[swamidog]

that's like asking: "how fast is a blue car?".

So how much do helium tanks cost on average and how many regular sized balloons can a full tank fill?

[swamidog]

not intending to be rude, but without specifying size of tank and size of balloons, it's kind of a hard problem to solve.

try this:

http://www.balloondealer.com/heliumr...o=pinfo&PID=17

Kind of rude.
Tell me what I need to specify. I thought this could be answered by telling how much regular 9'' balloons a N liter tank can fill.

[Photonbeam]

Volume of tank / volume of balloon = number of balloons filled
Volume of a sphere = 4/3 pi x radius cubed
9 inch dia =0.75ft dia
0.75' / 2 = 0.375' radius
0.375 cubed = 0.053
4/3 x 0.053 = 0.07
0.07 x 3.1416 = 0.22 cubic feet for a 9" dia balloon
A 75 cubic ft tank might fill about 340 nine inch balloons
The balloons are not perfect spheres but this should get you in the ball park.

[mixedgas]

You need to check how the terms are defined on your tank.

Tanks in the US are usually filled to ~100 Bar or more of pressure when full. The Balloon is filled when its a little more then 1 Bar aka 1 Atmosphere. So you have to make sure your 10 Litre tank is not measured as EXPANDED to 10 Litres at STP aka 1 Bar and 0' C. Which is a very small tank, but they do exist (Lecture Bottle). 10 Litres at 100 Bar on the other hand is a lot of gas.( Similar to US Linde Size S or Size P Cylinder) STP is the normalized "Standard Temperature and Pressure" for gas calculations.

The right tank to purchase or rent comes up to about your shoulder in height if your a average height guy in the US.

One other thing you need, a regulator to reduce the 100+ bar down to just above atmospheric pressure. Balloon filling regulators have a rubber cone on them, the balloon slides over the cone when filling. Tilting the cone triggers the low pressure valve.

I don't know where your at, but there will be a national standard fitting on the high pressure tank, and your regulator fitting must match that fitting. Flammable and corrosive gasses get different fittings compared to inert gasses. In the USA, Helium is a CGA-580 fitting. A few types of these fittings need a disposable gasket. Generally it takes a special wrench and a lot of care to change a high side fitting, so get the correct regulator the first time. It is not advisable to change high pressure fittings on a regulator without training. Regulators have a habit of sticking on full blast or exploding if tampered with. Thus you need to also buy the correct regulator, either new or used. Crack the main valve open for a fraction of a second before connecting the regulator, this cleans the fitting and keeps dust out of the regulator.

For the love of God (of your choice) chain the cylinder to a wall and leave the safety cap(s) on when not in use. This is mandatory world wide if the cylinder is not on a standard safety cart. Its not pretty if that much gas is suddenly released through a safety error. The cylinder can go airborne and through walls, but usually spins around its center of mass in a very violent way, if there is a accident.

Disposable tanks, (US Size DS1, DS2, D1, D2) are not worth it for more then a one off birthday party.

Beginners usually have to find out that at these high pressures, leaving the main valve open for any length of time more then a day or so results in a empty tank. This depends on the quality of the regulator fittings.

Vendors hate it when you return the tank fully empty, with air in it. Always leave at least two Bar of pressure in the tank.

Here in the US you either buy the tank outright, or get a five to seven year lease on the tank. This is jurisdictionally dependent, some regions never allow you to "own" the tank for liability reasons. You then swap tanks when empty, for a fee. Short term rentals are expensive compared to a lease.

Here in the US, vendors often get paranoid about allowing cylinders in private vehicles. I get away with it, but I had to convince them I know better then to roll the windows up. The car possibly expands like a balloon if the tank is damaged or the valve is opened. My local gas vendor has the photos to prove it. Thus you need to check if take-out is allowed or if it must be delivered.