Compressed air for coal fired forges

[yesteryearforge]

Here is one to debate / discuss / ponder etc.
Has anyone here ever had any experience using compressed air as a source for the air supply of a coal fired forge and if so has there been any experience feeding multiple forges from one common air line.
What size air line ?
Does it require some sort of manifold to expand the air volume just before entering the tuyere ?
Will a common airgate when shut off restrict enough air so as not to consume an inordinate amount of coal ?
What psi should the air be restricted to and at what point ?
Any other ?s that you may feel compelled to answer that I havent mentioned.

Mike Tanner

[FieryFurnace]

I haven't ever tried that, and I don't know if it would be a good idea. I would think that the air is to concentrated. I use a Champion blower, and it will shoot little pieces of red hot coal out of the fire and onto my hand, at a high rate of speed. A compressor would be even worse, I think. You could try it but I would suggest turning it on from a safe distance so if it turns into a volcano you want be what the lava lands on! :mad: That's my thoughts on the matter!

The kidsmith,
Dave Custer

[Frosty]

It was pretty common in some industrial furnaces but they ran it through inducers rather than directly.

An inducer is the same basic thing as a naturally aspirated gas burner.

A small amount of high PSI air, gas, steam, liquid, etc. fired from a jet to induce a large volume of low pressure air, water, etc.

Running multiple forges from one compressor, even small one is no trick. The investment in machinery is much smaller and an induction device will take considerably more hostile conditions than an electric motor and blower will.

Frosty

[HWooldridge]

This subject has been discussed a bit so you may want to do a search.

A compressor is an inefficient and costly way to run a forge. Instead of a simple fan/blower, you are compressing the air and then regulating it down to a lower pressure. It can be done but would only be worthwhile to consider if the facility has a more important need for compressed air. It's a similar analogy to using air on a steam hammer - in the old steel plants, steam was readily available so was used on the big hammers but an air compressors makes more sense to run one in a small shop. Not many people will install a 150hp boiler just to run a hammer - same analogy for a compressor on a forge.

If you want to do it, each forge will need 250-400 cfm at a pound or two static pressure. That's about what a typical electric Buffalo blower used to produce and most of those would run two forges without much trouble (blower opened up and a damper on each fire).

[yesteryearforge]

These would be supplied by a 75 hp screw compressor that runs in the plant continously anyway.
Looking to run 7 forges at one time

Mike Tanner

[Valentin]

I have to agree with HWooldridge .... plust think of the noise :)

[Frosty]

These would be supplied by a 75 hp screw compressor that runs in the plant continously anyway.
Looking to run 7 forges at one time

Mike Tanner

Sounds like a good option in that situation. Build the inexpensive Reil EZ burner, scaled up to around 2-2 1/2" tube dia. (I'll send you the ratios if you need them) and use compressed air instead of propane. No need for a choke of course.

Use a needle valve for fine adjustment of the blast at each forge and a 1/4 turn ball valve for the on/off. Put one regulator in the line to the forges and set it to around 25psi. as a departure point. You'll need to experiment for the right setting in use.

It won't be any noisier than a blower, a naturally aspirated burner's jet engine roar is a product of combustion. Try turning the gas on without lighting it and give a listen. Just a gentle hiss, it'll be a little louder moving 300-400 cfm but not much.

This certainly isn't the way to go in many if not most cases but in a situation with several forges and shop air it'll be much cheaper and just as reliable.

Frosty

[yesteryearforge]

Frosty these will be side draft coal fired forges not gassers

Mike Tanner

[Frosty]

Frosty these will be side draft coal fired forges not gassers

Mike Tanner

I understand that, I'm not talking about building a gas burner, just the induction device.

What most everybody calls a naturally aspirated, venturii or atmospheric burner is actually an inducer or induction device.

These can be adapted to do all kinds of things from pumping bilges using steam pressure to milling grain by slamming it into a steel plate at a specific velocity.

If you think about what a naturally aspirated burner does you'll see it'll also work perfectly well to provide air to a fire.

An inducer uses a high velocity jet aimed down a constrained tube to create a low pressure zone that induces something else to follow it down the tube.

In the case of a burner it's a jet of high velocity gas, (Primary) propane usually but methane works just fine inducing a fixed ratio of combustion air (secondary) to follow it down the tube where it mixes and then burns.

What you want to do is supply a volume 200-400 cfm. of low pressure, 1-2 psi. air to a coal fire.

The ONLY difference in the devices is the primary and the end use. One mixes gas and air to make a combustible mixture and burn it, the other is using a small amount of high pressure air to induce MORE air to supply a coal fire.

Same device with tweeks of course, different kind of fire but the same end use. forged iron/steel.

This'll be substantially easier too seeing as you don't need to hit a specific induction ratio like a gas burner needs. All this will need to do is move air reasonably efficiently.

Put a 2"x4" bell reducer on a foot of 2" pipe. Put a 1/4" pipe nipple across the center of the bell reducer with a small jet hole, say 1/16", centered on the bore and aimed down the tube. one of the tweeks would be finding the right dia jet hole if you were building a gas burner, here it isn't nearly as important.

Attach the air line with shut off and needle valve to the 1/4" pipe nipple and attach the whole thing to your tuyere.

done deal.

Frosty Edited May 30, 2008 by Frosty

[HWooldridge]

One of the old ABANA Anvil's Ring magazines had an article on a shop in Germany that was using a compressor to drive several coke fired forges. I'll look through some back copies but I recall it was written 10-15 years ago.

I think Frosty's idea is a very good one. A venturi will pull in plenty of fresh air while allowing the pressure to be kept low. I haven't done the math but you could run a 2 inch line along the wall behind the forges and have the branch pipes come out from there. Put a regulator on each circuit and build the venturi like Frosty described.

[yesteryearforge]

Slight typo
It is actually 25 hp not 75 hp
Still should have plenty of air though

Mike Tanner

[Frosty]

No problem, even a 5hp might do the trick. At 20psi, a linear inducer like a Reil EZ will push up to 19:1.

So, even a lowly 5cfm@100psi compressor should easily produce 1,000 or more cfm of 1-2 psi air.

Piece of cake for 25hp.

Frosty

[Smokeman]

I like the idea of compressed air. I actually tried out my forge with an air nozzle. With my 60 gal tank, I used very little air for quite a while. How about just putting a gate valve in the line and have it fastened to the forge for easy operation. Open it for whatever air flow is needed.

[Frosty]

You can do it that way but the problem is volume. You need 200-300 cfm at low psi. Getting that directly off a high pressure air line is a pain unless you run it through a reduction device.

Think of the inducer I described like a transformer on a power line. It's taking low volume, high pressure air and transforming it into high volume low pressure air. An electrical transformer takes high voltage, low amperage current and turns it into low voltage, high amperage current.

Not a perfect analogy but close enough.

You can do it directly but for maybe $15-20 worth of plumbing parts you can save a few years of wear and tear on your compressor and provide a more useful air blast.

Frosty

[ThomasPowers]

I really see this as like wanting to drill all your holes with a CNC mill; sure it can be done that way but a cheap drillpress will work for almost all of them and not require expensive maintenance over time.

[Frosty]

Agreed, I'd find a blow drier, two if necessary first myself.

Unless I wanted to make several forges work and already had a good supply of compressed air and then I'd make air inducers that were as efficient as I could.

I'd put the word out at the local recyclers, Craig's list, eBay, etc. I was looking for a BIG blower too.

There are so many different approaches to most problems it's hard to say what's best, especially for someone else. I must say I do enjoy a pursuit where it's expected most problems are to be solved with a hammer.

Hammers. . . Mmmmmm. :cool:

Frosty

[Lysdexik]

Mike and Frosty
This type of device was used at Brown Lennox Chain and Anchor, to heat long stuff like anchor shanks. They called them plenums, and its basicaly a way of creating a velocity induced vacuum to pull a lot of ambient air through a tube and into the forge duck nest, although in this case the thing was close to 7' long, more like an aligator than a duck!
Paul.
don't confuse activity with accomplishment.
It's not over... Untill we Win!!!

[Lysdexik]

I called a guy who was in charge of looking after "the trough" it ran only coke, had 7 plenums one side and 9 the other, "rear tuyere" British style. running into the "nest" through refractory brick nozzles. It was finaly being run with a sulair vane comressor, he doesn't know the size. But it had 100mm (4"ish) feed lines down both sides, but he said that was overkill. according to him you could turn a 300mm shank into a sparkler, if you weren't watching. Believe I'da like to have seen that once, the worlds most expensive firework!!
Paul
It's not over...etc!

[Lysdexik]

I forgot to tell you, he said your ears would pop, if you ran that thing full bore, like altitude decompresion!
Paul

[Fruityloops31]

I use an air compressor on my coal forge and it works great. A simple plumbing valve allows me to control pressure. I don’t know how it would work with several forges thou.

[ThomasPowers]

Well as mentioned earlier in this thread I believe, sure it works; but why put wear and tear on expensive to replace and maintain equipment when simple cheap equipment can be used?

Now if the compressor has to run all day for other reasons then drawing off a little excess capacity could make sense

[Paul B]

Compressed air is very expensive, between the electric and maintenance and the initial cost.

[Fruityloops31]

i had the compressor already, i am looking into an electric blower, or maybe going realy rustic and making a huge belows!

[bruce wilcock]

has enyone made a pumping engine, i did some tongmaking for a small foundry and they had a old pumping engine out of use ,it was two cylinders worked with a dip crank, run of line shaft ,it pumped direct no air recever,i thought of making one with wood cylinders made up of staves as a cooper would.

[Lysdexik]

Hello Bruce.
I dont know whether they have a website but the museum in Chepstow, Monmouthshire was talking to a guy who had a pumping engine that had been used for forced air ventilation during the digging of the Severn tunnel. I believe that it was one of the GWR/Isambard Kingdom Brunell gizmos. I will call the guy who runs the county museum system for Monmouthshire and see if I can get a measured drawing. I dont know if it's still there but IKB put a beam engine halfway through the tunnel, they hit a spring in the excavation. The forced air system had over stroke pistons, made of a stack of enormous washers, four metal and three leather stacked alternately, the stroke/cycle was prety slow by all acounts. There was also a heavy oil engine with a slide shutter, that exposed a flame from a spirit wick to start combustion. The log book with it, said that they had run the engine on all kinds of stuff, coal dust, coal oil (which I assume is parafin), and a list of stuff that sounded like "if it will flow and burn". The HO engine was used to pump water out of the river Wye to the top of the cliffs above town, gravity gave the pressure in town. We think we have advanced, I'm not so sure!
Paul.
Don't confuse activity with accomplishment!
P.S. Have you seen the picture of IKB stood in front of the chains for the SS Great Britain, they were made at Brown Lennox in Pontypridd, They also made the chain for the Clifton suspension bridge, I worked at BL for a while, one of our engineers talked about retiring to the Shetlands, he's a six foot eight, milk fed boy from Banff, he'd make a bloody good striker. Keep warm!!