Image Capture for a Wood-Fired Boiler

A long time ago the company I worked for at the time built a CCTV for Pilkinton Glass in Scarborough. The camera was permanently mounted inside the glass furnace to monitor the molten glass pour and our automatic controls adjusted the ladle pour to maintain a constant width of molted glass over the zinc bed. This camera was housed in a water cooled case and high quality quartz glass was usd for the front viewport.

With modern CCD products you should be able to do something similar and you could take advantage of modern technology to get a radiant IR filter coating on the front glass. Blocking the IR will reduce heat gain inside the camera case.

How big a diameter are the tubes you plan to use for visual acess?

Elnav,

The tubes are 4". I was hoping to be able to use something about an inch in diameter so as not to make a big difference in airflow.

Jon.

If you look at some of the latest CCD cameras they are only 1/4" diameter. Even with a 1" diameter water jacket pipe or hose you would still have plenty of room for air flow.

I have only seen plastic used for camera housing etc. Even some of the optical grade fibes seem to be plastic or at least optical glass with a plastic jacket around them. I remember we had a special quatz glass front cover to reflect radiant heat. Otherwise the amount of heat entering the front would quickly melt delicate components.

If you have a $50,000 or greater budget, the IR video imaging companies probably have something already on the shelf. Steel mills as well as glass mills would be using the camera technology we first developed back in the seventies. Otherwise you must make it yourself.

I recently saw a fiber-optic bore scope with a flexible tube. It was about 1" diameter. And it was plastic. But the good part was the price of $265.00 Now it becomes affordable to spend some money to provide it with cooling water jacket and heat blocking transparent front lens cover.

your description suuggest you would only be using it intermittently for part of a hour at a time. Possibly even less time. Begin by measuring the temperature inside the air tube in which you plan to take the observations. You might also test to see how fast a black body ( disk or ball) picks up heat when placed at the observation point. That will give you a good idea of how much heat you have to cope with in your cooling system.

I was wondering about the possiblity of using a long glass rod, say, 48" long, with one end ground into a lens arrangement. It would be made of borosilicate or some other glass that can take the heat. A thermocouple could be attached to the side of the glass close to the front for a overheating warning.

The back end of the glass rod would be either polished flat or optically arranged so that a camera could be attached.

The idea would be to slide the arrangement into the firebox, quickly take a few photos and immediately withdraw. This would be through one of the existing air ducts, so we would have the advantage of the flow of cooling air.

My knowlege of optics is not so good, so thats what is causing my head scratching over what is possible and what is not.

Your comment about a commercially available borescope is a good one--I was just looking at a Milwaukee version at the local Home Depot. They seem to be a little short on the length of the snout (for our particular use--we'd need about another 2 feet) but the basic tool is there. Maybe it could be enclosed in a jacket with some forced air cooling to get our job done.

Jon.

If you have access to borosilicate glass rods and the required grinding machinery - try it. I think the bore scope I saw was also the Milwaukee - but not a home Depot. Check and see what result you get with a short glass rod with the ends polished flat.

Incidentally, most companies that use fiber optics for communications have the required polishing equipment. I once had to install a fiber link from our office to the shop building. Not knowing the procedure I hired at considerable cost a "specialist" to come and prepare the optic cable ends .

Afterwards I realized they used the same materials and procedures as is used to polish telescope mirrors or removal of scratches from aircraft windshields.

Fiber optics rely on a perfectly flat face perpendicular to the long axis of the cable.

My buddy at Bell was trained to repair splice fiber optics but they used a nematic fluid to effect the efficient coupling of light beams into the broken ends of a fiber cable. Maybe you can use a similar technique between the glass rod and the bore scope.

The Bore scope I saw also had fish eye lens arrangement. If that is preferred, maybe you could detach the fisheye lens and place it at the forward end of the glass rod and the camera at the back end.

Use the nematic fluid to give you a reflection free optical coupling.

You could use a hard fibre optic rod, if a lens at the 'hot' end produced an image on one end of the fibre optic that image would be reproduced at the other end. We use these types of optics in vacuum tubes & seal them to metal components using pyroceramic, these are fired at 450°C without harming the optics.

Talk to either Schott or Incom in the USA.

Fiber optic is the way to go. Just get a boroscope or endoscope - can probably find either on the surplus medical market. Get an adapter for a digital camera, hook it up to a LAN and you are all set.

Every industry has most likely today done something on video and I suspect something in fire has been done too. I was at one time in the Pest control business and at a convention a salesman showed me a fiberoptic camera and the optic cable was what was inserted to view back at the suit case reader. Seems like, back 10 years ago ,they were too much for me perhaps, $25,000. He told me if the fiber optic was damaged it was cheap to replace so you might could keep sticking new ones, in the hole to view with inexpensively.

Why not check with a fire departments, head investigator. They have access to all sorts of fire investigation equipment and the time to read about what they don't have yet. Also, other boiler makers may have explored this. Perhaps, a trade publications editor, would have a line on the equipment and or a reference.

Hope That Helps Some.

Best Regards,

Joe Woodall, Managing Partner

Georgia Adobe Rammed Earth & Renewable Energy

Dewy Rose, GA 30634

http://www.georgiaadobe.com

Join Our Yahoo Forums To Learn More At :

http://finance.groups.yahoo.com/group/georgiaadobeforums/

You could also contact a IR camera manufacturer and explain your application. They will certainly have solutions to propose you.

Flir Systems : http://www.flir.com/thermography/eurasia/en/

I've seen cameras inside cylinders of diesel engines for research of flame front, so I know super special cameras exist. I have no clue where to buy them. I've put in a question to head of a laboratory for a major diesel engine supplier to find out for you.

Good luck

Like this video? Click on the R.H. image, 2nd row down.

We supply the detectors for their cameras but you would need to save up for a long time to buy one.

You could do as Sam McGee and just crawl right in and have a look.

I am very interested in what you are working on. I worked designing and developing wood burning furnaces some years ago and still tinker at a hobby level. I built my own furnace a few years ago and I am considering buiding a new one to try out a few ideas.

Email me if your interested in corresponding on this topic.

ref: The Cremation of Sam McGee by Robert W. Service

Come to think of it can you recommend me something good on this issue?

Hello, all:

I have emailed Schott and Incom, although the guys that specialize in the defense and medical fields never seem to know the meaning of "low cost"...

Since I posted this question, I have also sent questions to several outfits who fell out of Google searches for "high temperature borescopes". I have found I can rent video equipment made for imaging in boilers for costs on the order of a couple of thousand $ per week. So far that's my only option, but the search isn't over yet.

The suggestion to chase down used medical endoscopes or borescopes is the best one yet for "low cost". Might have to steam clean the lumps off if the endoscope was last used for the wrong "end-o". (Sorry, couldn't resist)

gdevine, I am interested in talking to anyone with woodwaste combustion experience. The boiler in question is an old Dutch Oven and it is costing us tons of money per year in firebox refractory repairs plus pretty high particulate levels. It is 38 years old and certainly needs a dose of modern technology. We have lots of bells and whistles on it now- O2 analyser, PLC control, FD and ID fans with variable speeds, firebox pressure sensing and control loops to keep a negative pressure in the firebox. But the airflow and firebox shape are still yet to be massaged with some decent knowlege, thus the foray into trying to get an idea of what is happening in the firebox. By the way, I don't think I mentioned it is burning dry planer shavings--real good, hot fuel.

Thanks,

Jon.

Think outside the box.. :) pinhole camera. so that the components won't be melted, and the cost is much lower.

chris

Trouble with pinhole camera is the distance from pinhole to focal plane. In this case a 4" diameter tube approximately 24" long will mean the visible area is much too small.

The tube diameter wil act as a blinker. Try it and see what I mean. To get a good view inside the fire box requires a fish eye type wide angle and for that you need a lens, not a pinhole.

Chris,

Yes, thats how the big boys make the commercial units, so it is doable. I think it's pressurized with air as well, so there is a jet of air coming out of the pinhole keeping the opening clear and the whole thing cooled.

As elnav points out, the focal plane needs to be fairly close to the pinhole, to achieve the wide angle viewing desired, so the CCD will have to be closer to the action than one might hope for.

Jon.

Sawmilleng how much air pressure or air flow do you think you would get. I assume you are talking about inflow of fresh air to the combustion chamber.

Elnav,

I'm just talking about cooling the pinhole camera--the big guys use both air and water cooling. Nothing to do with the combustion air, although the tiny amount coming thru the pinhole ultimately adds to the combustion.

It would be my guess that they would use compressed air, so the pressures could be high enough to get enough air mass through the viewing device to balance the BTU's coming in through heating. Might be quite a bit, unless they used water cooling as well.

Just guessing here, as I have no detailed knowlege of how the commercial ones work, other than some brief looks at web pages over the last couple of days. Didn't look very long 'cause I couldn't afford them.

Jon.

For a very inexpensive method, you could use a series of small mirrors.

I recall a documentary about the pyramids. It suggested they used a series of mirrors to light the work inside the tunnels.

Perhaps you could simulate the turbulence and expanding gas flow using cooler mediums like water and injecting gas bubbles under pressure into a water filled and flowing chamber... ?

chris

or a water cooled hollow window?

Chris,

Boy, you really specialize in thinking outside of the box! Good on you! I'll bet your employer has to run after you some times with a butterfly net to get you back into a more boring reality that mere mortals can understand!

I expect modelling a of firebox has been done, but I'm guessing that it is in the realm of the big boys and in a computer modelling environment. It would be darned interesting, tho, to see how close to reality it could get.

I have located a low temperature borescope, 38" long x 8 mm diameter, good for about 200F, for $3,000. It has a screwed adapter that will adapt to a 37mm camera filter lens threads.

I can get it custom made with a wide angle lens on the end to do 90 degrees or better at a slightly higher price. Doesn't sound too bad but will have to give it some thought about a gas cooling shroud and a temperature sensor to warn that it is getting too hot.

It's still a lot more than I would be comfortable to pay. Still hoping to find someone who can explain the optics necessary to see if I could build my own for a tenth of what I would have to buy a commercial one for.

Jon.

thanks for the compliment... I remember our wood stove with the layers of mica for looking through.. about 2" square, as a boy.. and being fascinated watching the fire.

you know a Mig welder has a outward flow of gas (nitrogen, argon?) surrounding an inner core. I wonder if such an arrangement wouldn't also keep your borescope cool enough if it was contained within a heat resistant material(s).. with ceramic insulators.. I know there are sleeves you can get for fire-guarding hydraulic hose..

chris