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Propane Cylinder Size - Choosing

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Steven Vine21/05/2010 17:50:54
340 forum posts
30 photos
I need some help deciding on the right size propane cylinder to use for general silver soldering jobs in the home workshop.

I will be using the Sievert PMPX kit. I envisage having to use the 4 bar 12kw, 25kw, and 43kw burners at 4 bar on occasion. The first job will be a simple 5 inch copper cornish type boiler. Other jobs are likely to be silvering solder parts, to fist size lumps of mild steel.

I already have a 15kg Butane cylinder. I was hoping to do a direct exchange (without having to buy another agreement) for another Group A Calor cylinder, either the 3.9kg propane or the 13kg propane.I fancy the 3.9kg because it is portable, but was wondering if it is too small and would suffer the inconvenience of quickly running out of gas?.
The 6kg propane cylinder looks ideal, but it is in Group B and requires another one off £30 agreeement charge, so I am discounting that one at the moment. (unless this is THE one to get?)
 
What cyclinder size are you using in your home workshop? What cyclinder size can you recommend? Is the 3.9kg cyclinder too small? Should I get the 6kg size? Is the 13kg overkill?. Have you experienced freezing with the small size cylinder, or the bigger cylinders come to that?
 
Many thanks in anticipation of your reply.
 
Steve
Les Jones 121/05/2010 19:05:41
2241 forum posts
153 photos
Hi Steve,
                  I wave just done a search on the web for maximum take off rates. I found that a 13 kg propane cylinder has a maximum recommended take of rate of 15  KW Even a 47 KG cylinder is only recommended for 34 KW I have used a 3.9 KG cylinder with a blow torch for many years but I think the largest burner would be about 10 KW. You could try to find a 6 kg cylinder on Ebay to save on the deposit.. It might be worth considering using insulating fire brick or ceramic fibre blanket  to insulate the boiler rather than use 43 KW of heat. There has been on ongoing topic on silver soldering boilers but I can not remember the thread title. There is some useful information there if you can find it.
Les.
Les Jones 121/05/2010 20:15:48
2241 forum posts
153 photos
Hi Steve,
                 The title of the thread I mentioned in my last reply  is "Boiler making hearth"
Les.
dixie21/05/2010 20:32:48
31 forum posts
Hi Steve Dont know if it is just with the local supplier here but the last time I needed a refill  was told 8.2kgs is now the smallest produced. Still quite portable. 
Ian S C22/05/2010 11:27:31
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7468 forum posts
230 photos
It is possible to feed say two or three or more bottles via a manifold, there by getting a high rate of feed from smaller bottles. Ian S C
KWIL22/05/2010 13:19:09
3477 forum posts
66 photos
If you put the empty one on the manifold and invert the large one that is full above the manifold, the lower one refills miraculously so it would  appear.
Steven Vine22/05/2010 13:40:01
340 forum posts
30 photos
Thanks Dixie. Prompted by that I rang a local supplier and they do the Calor 3.9kg/6kg/13kg etc. These sizes are listed on the Calor site. Looks like that supplier near you may have chosen not to stock the sizes, or maybe it is not Calor?
Ian S C22/05/2010 14:09:02
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7468 forum posts
230 photos
KWIL, thats how I fill my small cylinders, the local filling station charges $NZ7 min for small cylinders, even if you only get$5 worth of gas.Ian S C
Steven Vine22/05/2010 15:06:43
340 forum posts
30 photos
Hi Les
 
Thanks, I looked at those take off rates as well, and that was when I started to get confused about this. If a 47kg cylinder will only do 34kw, then what the hell do you need for a 43kw burner? I think I am missing something here. Although not recommended by Calor, maybe the 3.9kg cylinder will deliver enough for a 43kw burner, but will go cold and lose pressure, or run out quickly.
 
I'm now thinking, maybe I will get a 3.9kg cylinder to start with and see if that 10kw burner will do me. If I have to I can then try bigger burners on it and see what happens . If the cylinder proves too small then I can always exchange it for a 13kg.
 
That link was interesting, and lead to some backyard hearth photos with 13kg bottles on a big burner, and what looked like a 3.9kg cyclinder on a 12kw burner. Thanks.
 
Any other comments will be welcomed.
 
Steve
 
 
 
Les Jones 122/05/2010 18:08:25
2241 forum posts
153 photos
Hi Steve,
                  To get more than the maximum output of one cylinder you need to connect a number of cylinders to a manifold. Even if you can get the 43 KW output from a 3.9 kg cylinder (Possibly by putting it in a tank of warm water.) then it will not last very long. look on the web to convert 43 KW to KG per hour of propane. It would not be very good to run out of gas part way through the work on your boiler.
Les.

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