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I Forge Iron

Amal Burner


Casapa

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They are fairly rare here in the USA but I bought 3 out of a NOS lot of 50 off ebay 5 years ago on speculation.  Wish I'd bought all 50!  I've been using gas forges for over 20 years and these burners are hands down the best burners I've ever seen.  Can forge weld with 1 burner running at 10 psi. 

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The Amal injectors are not complete burners: just the clever bit that is really hard to do in the average home shop.

I've used them at work for nearly 30 years, mainly 2" injectors for pilot burners on waste gas plant, though I've also used some smaller ones. They are very good indeed. I've been using the 1/2", 3/4" and 1" for forges for a good few years and used a 1 1/2" in a forge for the first time this year. 

They were designed way back by the Amal Carburettor Company, who knew a bit about mixing fuel and air in a controlled manner. After Amal stopped making carburettors, etc, the injectors were made by an outfit called Grosvenor Works for many years. More recently, all the Amal IP seems to have passed to Burlen Fuel Systems, who were already making Solex and SU carburettors for old British cars. The Amal carbs (for motorcycles) are the core business, but some of the more unusual things they made still have niche markets: the atmospheric injectors are used by the sort off odd folk who mess with things like forges. They also have a range of big low-pressure gas valves that are used by the even odder folk who fly hot-air balloons.

I get the impression that they'll make and sell you whatever you ask for by part number, or similar precise identifier, but probably do not have the (expensive) technical staff to advise you on suitable products for new applications. That suits me fine, as I already know what I want and it keeps the prices reasonable.

There is one caveat for the guys across the pond, which is that the threads are BSP, not NPT. The gas jet threads are either British Standard Pipe or British Association (1BA for the small jets). If you need a selection of jets, it is best to order them with the injector. 

I think the factory jetting was worked out years ago and was probably for more "normal" industrial applications with secondary air. For Propane forges, I have found the factory Butane jetting gives a slightly more useful range of mixtures than does the slightly larger Propane jetting. For non-forge applications where screaming-hot temperatures are needed, even smaller jets will get the flame temperature up higher still. Using them in a forge just causes a ridiculous amount of scale, so the Butane jetting seems about optimum.

My experience has been that a straight pipe is fine as a burner in a forge. If the burner needs to work outside a forge, a flame retention cup is a good idea; one like that in the video. Note that the tapered expansion "flare" is part of the Amal assembly, so no extra flare is needed.

 

 

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  • 1 year later...
On 12/28/2018 at 7:39 AM, Judson Yaggy said:

They are fairly rare here in the USA but I bought 3 out of a NOS lot of 50 off ebay 5 years ago on speculation.  Wish I'd bought all 50!  I've been using gas forges for over 20 years and these burners are hands down the best burners I've ever seen.  Can forge weld with 1 burner running at 10 psi. 

How did you fit your fuel line to the gas inlet since it's a  BSPF threaded port?  Also, what did you use to for the pipe nipple since the outlet is probably also BSPF threads?

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To get from your hose to the BSP inlet (presumably 3/8" BSP), it is best to buy suitable fittings. Over here, NPT is the PITA and NPT-BSP adaptor fittings are available at decent pneumatic/hydraulic suppliers.

In a pinch, I have been known to run a tap down the existing threads (BSP tap and NPT thread in my case) and fit a "local" fitting with plenty of anaerobic pipe seal, though not, as yet, with gas pipework.

I think that the pipe nipple will probably screw in relatively easily, at least in the 3/4" size (1/2" and 3/4" have the same thread pitch in both NP and BSP). I always use an excessive amount of PTFE tape here anyway (BSP into BSP) to protect the female thread in the injector, and hand-tighten only. The PTFE tape is for padding only, not for sealing in this case, so there's no need to get too concerned about whether it's rated for gas. The clever bit about the Amal injector is the super-fine adjustment provided by the screwed choke and you really don't want to louse up the threads that provide this. I also dry-lube the thread further down to ensure it will adjust freely: Dry Molybdenum Disulfide, Dry PTFE, Graphite or some combination thereof. Grease tends to pick up dust and grit, making things worse, so I don't use it.

 

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