Oxy-Propane Brazing Update 3

Oxy-Propane Brazing Update 3

I use oxygen and propane for my brazing. I did not want the expense and extra safety concerns of storing and using acetylene, and in particular did not want to get involved in contracts given the small number of frames I am likely to build as a hobbyist. Though contract free acetylene cylinders have become available, personally I see no advantage in using acetylene for building lugged frames, but it does have advantages for fillet brazing. Propane is relatively cheap and long lasting and widely available for a small cylinder deposit. I use a 11kg cylinder. Smaller ones are OK but I have found the larger cylinder more stable, especially when using a gas fluxer, I don’t know why. Storing the smallest size cylinders of practical use of any flammable gas is common sense.
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Cylinders should be secured from falling, preferably with chains, which don’t burn! Trolleys are available to store and move the cylinders if you have the space or need to shift station, indeed health and safety experts would suggest outside storage in a secure cage is preferable, though will add a great burden to setting up each time. Oxygen is now easier to obtain contract free. It is more expensive than the propane and you use a lot more of it and you need more compared with acetylene. I would recommend using 20L cylinders which last considerably longer than the smaller 10L size which tends to run out during the second frame. I used to obtain my cylinders from Gas UK, my nearest branch being in St Helens. I have now changed my supplier to Hobbyweld UK who are also a national organisation using agents throughout the country. I now have an agent local to me and use their 20L cylinder (below). This is filled to a higher pressure than the Gas UK cylinders were and has a slightly greater capacity and contains nearly 4 times as much gas as a 10L cylinder. Gas UK however now supply larger cylinders.  Also with the Hobbyweld  20L cylinders the Regulator gauges are included so there is no need to worry about buying and maintaining your own.
Additionally they have a shroud protecting the regulator assembly which would hopefully eliminate the risk of a falling bottle shearing off the regulator assembly and creating a extremely dangerous high velocity missile. All rental cylinders need a refundable deposit, which for Oxygen is substantial but you do get your money back if you ultimately do not exchange for further cylinders.
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You will need a handset (also called a torch or blowpipe). I use standard lightweight welding handsets which I find adequate, heavier duty handsets are available. I find the heavy duty sets too heavy to use for long periods. There is an excellent short video on the Welders Warehouse website on the choosing a handset:  ( https://www.thewelderswarehouse.com/Welding-Supplies/Lightweight-v-Heavy-Duty-Gas-Torches.html).They were initially designed for use with acetylene (see later).

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The system also requires check valves and flashback arrestors between the torch and both cylinders. check valves are usually provided in the torch end of the hoses and the hoses are marked to indicate which end to attach them

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You are required to insert flashback arrestors usually adjacent to the regulators on the cylinders and a further one adjacent to the gas fluxer if you are using one. Acetylene and Propane arrestors appear to be the same (coloured red and often labelled Fuel Gas), Oxygen has it’s own arrestor (coloured blue). Hoses are available in minimum 5 metre lengths. Propane and acetylene hoses are NOT the same, though I understand a lot of welders use acetylene hoses for propane as they are easier to obtain but will not last as long. Propane hoses are orange as opposed to red. Hose connectors are nearly always 3/8 size to connect to cylinders, flashback arrestors, economisers, gas fluxers and heavy duty torch handsets. The exception is lightweight torch handles which use 1/4, so in this case the run of hose to the handset will have 3/8 at one end and 1/4 at the handset end, these hoses also tend to be narrower. Single stage only regulators seem to be all that is required. Oxygen regulators usually come with two gauges for cylinder pressure and outlet pressure. Standard propane regulators come without gauges but you can obtain them with two gauges which is worth the extra expense, especially if using a gas fluxer which has limits on input pressure making accuracy more important
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A Standard propane regulator is difficult to set accurately.

I also use a gas economiser, difficult to obtain for propane, but possible. It has a different nozzle size and most suppliers don’t supply propane nozzles. I am not convinced the use of an economiser saves much gas but as a novice you tend to have to interrupt your work more often and it is very convenient to be able to put down the torch and pick it up without any readjustment but it does mean extra lengths of hose to incorporate it, the same for the gas fluxer.
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Sundry equipment will be: sparklighter (cup style for propane as it is heavier than air, but other types work), nozzle cleaners and selection of swaged welding nozzles. Again these were designed for use with acetylene. I have used everything from size 2 through to size 18 at some time. As a general guide when brazing with brass you need a size larger or more when using propane over acetylene, though with silver soldering this is not always the case. As a general rule a No 3 to No5 tip may be adequate for most lugs and dropouts and No3 for silver soldering. For most fillet brazing again a No3 tip is likely to be adequate but on larger parts such as bottom brackets a 5 or 7 tip may be used. You can use much larger tips on these parts with lugs because it is possible to withdraw the flame to avoid overheating whereas with fillet brazing the proximity of the tip to the work makes tip selection more critical, at least using the method I was taught. I know of builders using much larger nozzle sizes than I have been using for lug work and I cannot argue with their validity. In order to get the heat from a propane flame you will need to pump more gas through the torch and you end up with a much longer neutral cone. As the maximum heat is at the tip of the cone it also means with fillet brazing you are further away from the work which reduces control of the melting brass I would say. In order to combat this I found it helpful to countersink the tip of the nozzle using the tip of a drill bit (usually 110 deg) or a 90 deg screw countersink. Unfortunately this only reduces the cone a little, in fact with a No 3 nozzle I could only reliably shorten the cone by less than 1mm. I had previously only seen countersunk brazing tips for sale in the USA but now new specialist brazing tips are available in the UK.
Clarification over the types of welding torches
I have encountered some confusion over the use of torches, and I include my own in that. All the equipment I use is specifically for Propane, with the exception of the torch, which is of the same design as used for oxy-acetylene welding. As far as I am aware these torches are and have been widely used for oxy-propane with the standard swaged welding tips. Propane specific torches available in the UK seem only to be sold for heating (these have large multi jet nozzles, which may be suitable for lugs) and for cutting applications. They cannot be used with standard swaged welding tips and therefore that leaves the only option of using a standard welding torch and tips originally designed for oxy-acetylene. I have also heard that some people will tell you that you cannot maintain a flame using this set up and would concede it can be difficult to establish a stable flame but overall I have had no real difficulty. Some retailers are now stating that their standard handsets are suitable for both acetylene and propane.

Newer Propane Brazing Nozzles from the Welders Warehouse
I have tried these new nozzles specially developed for brazing and they only seem to be available from the Welders Warehouse. I had to purchase a second handset to use them at the time because I thought it may be propane specific, though this subsequently proved not to be the case.
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They are described as multi-jet and seem to be a cross between a heating and single jet nozzle with a larger central port giving a slightly larger central flame surrounded by smaller ones. They are supplied as No’s 1,3,5 and 7 sizes, but they use more gas and are hotter than the similarly numbered swaged nozzles. Initially I found I was not able to fillet braze properly using them as they seemed to have too wide a heat spread for the technique I was using. However, as there are other methods of fillet brazing than the one I was taught and it may be possible to use these nozzles for fillet brazing using a different technique. I have now revisited them and had another go at trying them for fillet brazing and am willing to believe it is possible. However my practice results were not that good and it is unlikely I will be using them in preference to the swaged nozzles myself.
For brazing lugs I have to say I like them. The wider heat distribution seemed to be a benefit rather than handicap and the central larger flame still sufficient to manipulate the solder along the joint edges. I have not tried the No1 size but found the No3 likely to be adequate for most lug brazing and even perhaps a little too hot for silver soldering. I have since spoken to someone who has used similar ones in the past but abandoned them due to repeated blockage of the fine nozzles. I have not found this a significant problem myself.
I had assumed the torch handles were specific to propane but I have had it confirmed that the torch handles for these and acetylene are the same so you can simply purchase the nozzles if you already have a torch handle from the welders warehouse. I think it is likely handles from other suppliers will also be suitable for these nozzles.

New Propane Brazing nozzles from noz-alls
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I was quite excited when I saw these new swaged tips from noz-alls (https://www.weldingdirect.co.uk/Lt-Wt-Oxy-Propane-Brazing-Nozzles). as I hoped they may be a big improvement on the standard swaged tips for fillet brazing. They look like a standard nozzle that has been countersunk with a vertical hole, however when I tried to reproduce the design (see later) I discovered they are different in bore to standard nozzles. Noz-Alls claim the flow rate is the same as the standard tips so you should be able to directly substitute the same size for the one you are used to. I disagree! They also state the advantage is a more stable flame, less likely to blow out, which may well be true. They are available for both light and heavy duty torches and are more than twice the price of standard acetylene nozzles. I initially purchased a No 3 to try, followed by a No 2.
I compared the specification with my existing tips and this came out as follows:
Standard No 2 Tip hole diameter 0.8 mm, Standard No 3  0.9 – 1 mm, Standard No 5  1.1 mm,   Standard No 7 1.26 mm.
Noz-Alls No 2 Tip hole diameter. 1.1 mm, Noz-Alls No 3  1.23 mm.  These are all the nearest approximation I could manage.
The Noz-Alls No 2 tip was countersunk to a depth of 1 mm and a diameter of 1.4mm. The No 3 Tip was countersunk to a depth of 1.2 mm and dia. of 1.7 mm.
For me the main advantage of the countersinking of the tips is to produce a shorter neutral cone to enable one to get the hottest part of the flame (just above the tip) close to the braze line. These new modified nozzles do achieve that to a greater degree than simply countersinking the tips with a drill tip or standard countersink bit. The pictures below are an attempt to show the shortening of the cones compared.

Standard No 3, Cone 6.5mm

Standard No 3, Cone 6.5mm

Countersunk No 3, Cone 5.5mm

Countersunk No 3, Cone 5.5mm

Noz-Alls No 3, Cone 4.5mm

Noz-Alls No 3, Cone 4.5mm

Standard No 2, Cone 5.5mm

Standard No 2, Cone 5.5mm

Noz-Alls No2, Cone 4mm

Noz-Alls No2, Cone 4mm

These new tips do spit and hiss a bit initially when focussing down the flame but when the tips heat up after a little while they remain stable. Although the length of the cone is diminished the bulk of the flame is splayed out wider. After trying out the two new tips I came to the conclusion that the No 3 nozzle I usually use for fillet brazing thin tubes with propane now can be done with a No 2 nozzle and I did an acceptable test piece despite having not done any brass brazing for quite some time so don’t be too critical! I shall likely use these tips for fillet brazing in the future, though I have yet to try them with silver.fullsizeoutput_8f7

I also tried to make my own for comparison. I used a 1/16 in (1.58mm) bull nose slot mill, the smallest I could get. I imagine a plain drill would work. It need to be set up very carefully to give an accurate result but I bored out a 1.58 mm countersink to a depth of 1.5mm in a No 3 standard nozzle to see how it compared. The hole diameter after boring was still 0.99mm suggesting the noz-alls tips are made to a different standard. Using this tip I achieved a stable flame after heating up and even a slightly shorter cone as small as 3.5mm if necessary and the fillet brazing performance , again on thin tubing, seemed the same as the
noz-alls No 2 and better than the unmodified tip. The upshot of this is this seems to be a design improvement over standard propane tips for fillet brazing.

Gas Fluxers:

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I find a gas fluxer a great boon, mainly for fillet brazing where it enables you to see the braze line clearly. Only the fuel gas passes through the fluxer. I use the same flux as used for oxy-acetylene brazing, indeed there only seems to be one type. They should be filled outdoors. The flux is liquid, toxic and highly flammable, but once loaded (at least 5 litres at a time), lasts a long time. However there is the increased risk of using, storing and monitoring even more flammable substances. You can obtain fluxers from both Sif and Plasmatech who also supply fluxes, I obtained mine from Plasmatech as a reconditioned model which they often sell through Ebay. The difference between some models of fluxer is the ability to switch the fluxer out of the circuit to enable you to change to using paste flux which you would have to do if using silver solder. My type W fluxer has this ability. With lugged frames you have to use flux in the mated joints but I have used the fluxer as well to minimise the amount of external flux to give a better view of the capillary joint. There is no liquid flux for silver yet available so it is only of use for brass brazing. The liquid flux dries to a white residue and this can clog up the hole in the gas economiser and the mesh filter in the flashback arrestor adjacent to the fluxer causing the propane pressure to drop off, so they require occasional cleaning. I think it is probably true that Propane does not pick up the flux quite as efficiently as acetylene, and I have noticed this with smaller tip sizes especially. To mitigate this I tend to use small amounts of paste flux on the joints even for fillet brazing, just not enough not to get in the way of a good view of the braze line.

Gas settings for brazing: My gas fluxer is designed to be used at a max pressure of 9psi (0.62 bar). Whilst to some extent you will have to use trial and error to achieve the desired flame with the chosen nozzle I as a rule use 5-6 psi (0.5 bar) Propane and 5 psi (0.5 bar) Oxygen. These are a bit higher than I have seen in some published recommendations but have worked very reliably for me. Oxygen cylinder instructions refer to opening the valve by one full turn only, though this guidance is omitted on the instructions for Hobbyweld cylinders, whilst propane cylinders can be opened fully. Make sure the regulators are closed when turning on the cylinders (screwed fully out) then turn on by screwing in until desired pressure is reached as shown on the gauges. Shutting down is as for acetylene, turn off at the cylinders first, vent the gas safely at the handset then close the regulators by winding out and shut off he handset. SAFETY NOTE: Please do not forget to leak test all the joints on your gas brazing set up regularly as well as a visual inspection of the whole system. Proprietary leak test sprays are widely available. Every time you use the system would be good.

 

Cobalt Blue Welding glasses from Plasmatech

I have given some information on eyewear for brazing elsewhere, but I have recently tried the Cobalt Blue glasses supposedly developed for brazing using gas flux. I cannot find any other supplier than Plasmatech in the UK though similar blue glasses are sold in the USA. Their principal attraction is they look cool, and also seem to be of considerably better quality than other welding spectacles I have seen, though this is reflected in their price.
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The idea is they eliminate the orange glare given off by the heated zone and therefore enable you to see the brazing area much more clearly due to the fact the flame with a gas fluxer is green. You can see below the effect compared with standard shade 3 safety glasses. The Cobalt blue lenses are shade 5 but I could still see more clearly than through the standard shade 3 lenses.

Unshaded flame

Unshaded flame

Standard No3 shade

Standard No3 shade

Cobalt blue No5 shade

Cobalt blue No5 shade

Hopefully you can see how much clearer the flame is through the blue lense. For Fillet brazing I found the blue glasses much better than standard shades. The braze line is much clearer due to the absence of orange glow. For Lug brazing I did not find them particularly helpful, largely because you cannot see the orange glow and therefore can miss the lugs getting overheated, whereas with fillet brazing you do not need to pay much attention to overheating as you are concentrating on the molten brass pool.
I have been asked a question as to whether these glasses are true safety spectacles and I cannot confirm this. They are CE, but not EN marked. They have side pieces which probably would be required to make them safety compliant and seem robust. I, personally, would not expect to be hit by a high speed object whilst brazing so am happy to use them but cannot say what there level of protection is. My reading of their use in industry is that blue lenses are only recommended for short periods of flame inspection, notably for viewing through the windows into furnaces. This is related to their inability to shield from infra-red, which I have mentioned elsewhere.

Propylene
Propylene is a newer addition to the brazing market. It is closely related to propane and I understand can be used with all the same apparatus. It burns hotter than propane to the extent it is claimed it can be used for fusion welding, though maybe not if your life may depend on the results. It is more expensive than propane and less widely available, but is still less expensive than acetylene and safer. I imagine it may have advantages for fillet brazing due to it’s increased heat but I do not know any framebuilders using it. I would love to hear of anyones experience of using it.

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