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Eric Covington
04-21-2012, 08:16 PM
After much engineering, design and some bugs we finally went live and it is better than expected.

Even though we don't have much data yet it looks as if the 80lb melter is better than the design forecast. On the first melt, when idled the power consumption was around 1200 watts. During our first blowing session we had the power at 2100 watts.

I am logging all the consumption and will post a more detailed analysis in a month or so.

I kept a photo blog of the build details at: http://glengarry-glass-blowing.com/Melter

More after we get more experience.

Eric

David Patchen
04-21-2012, 09:15 PM
Interesting set of build photos. Nicely done. That's a ton of insulation!

Eric Covington
04-21-2012, 09:45 PM
When I did the thermal loss vs capital cost calculation it worked out at $0.14 /KWh that the break even for the extra insulation it ~15 months.

Best part is the surface of the melter is just warm to the touch and when gathering the exposure of the body to the heat is minimal.

The rolling lid makes half-post gathering a snap.

Hugh Jenkins
04-21-2012, 10:49 PM
The unintended payoffs can be just as important as the electric bill. Cooler work space, less fatigue, safer, peace of mind,..., maybe longer lasting elements?

Nice looking job!!

Eric Covington
04-22-2012, 09:20 AM
Yes we all want longer element life.

We are hoping for the best since we are controlling the power with a variable power source and not using the typical on/off mercury relay type control.

The folks at Kanthal stated that power cycling was probably one of the biggest strains on element life.

Thanks for all the good thoughts

Steve Stadelman
04-22-2012, 11:49 AM
When you say " variable power source" are you using a variac?

Eric Covington
04-23-2012, 09:45 AM
Yes a Powerstat variable transformer for now.

The downside of this device is that it requires that we learn the set points for various temperatures.

The upside was it cost nothing since we have a few on hand.

Later I am hoping to design a proportional, programmable control system using switching SCRs to "chop" the power at fairly high frequency. This would have the same constant power effect but would not require the attention of the variable transformer.

I suppose I could use the same control algorithm and a synchronous motor to adjust the Powerstat

All that will wait until I build the next one. Now to blow glass

Cecil McKenzie
04-23-2012, 10:15 PM
Is there a place for the glass to go if your crucible breaks? I noticed a leak detector . Do the elements get turned off if the detector detects a leak?

Eric Covington
04-24-2012, 10:35 AM
There is a small area for leakage (not 80lbs.) since the crucible is standing up off the IFB floor on a piece of kiln shelf. The floor and partway up the bottom row of bricks is lined with a layer of inswool to prevent glass sticking when the crucible breaks.

Right now the leak detector is not hooked up. I first need to measure the open circuit impedance and the conductivity of the hot glass. With those figures I will design the alarm system.

I say alarm system (maybe running David's pager :-) ) since I figure that when there is a leak we will want to empty the remaining glass before going cold.

Full diagrams and specs will be available (much) later

Pete VanderLaan
04-24-2012, 10:37 AM
If people just replaced their pots regularly as a cost of doing business, they would never have leaking pots.

Really.

Tom Clifton
04-24-2012, 10:28 PM
Refer to prior threads (http://talk.craftweb.com/showthread.php?t=8925&highlight=conductivity) about electrical conductivity of molten glass. Your sensor leads in the bottom of the furnace will act as a simple on/off switch that can control a lamp or relay. Not difficult or complicated.

Dave Bross
04-25-2012, 06:24 AM
Nice build!

Thanks for all the pics.
Got some good ideas for future planned projects there.

Ben David
04-25-2012, 07:04 AM
This project gives a good view of the furnace floor - I am curious what materials are generally recommended for this?

Will castable sustain the weight - or must it be something sintered?

Ben David

Pete VanderLaan
04-25-2012, 07:52 AM
Any castable or brick with a 70% alumina content will do very well. In your world, castables for cement kilns will do well. Look for those guys. They're everywhere in the world and they chew up the stuff.

Ben David
04-27-2012, 06:06 AM
Yes - we have a local manufacturer.
Thanks.
Ben David

Eric Covington
05-06-2012, 10:21 AM
Yes we did use a variac but on the next one I am considering a chopping type SCR proportional controller for unattended, programmed control

Franklin Sankar
05-06-2012, 06:59 PM
There is a space between the ends of your coils. Is that ok? cool spot???
Franklin

Eric Covington
05-07-2012, 10:20 AM
The ends cannot touch or that would cause a short. Too close and there might be a path for the plasma (hot gas) to conduct and make a path for an arc.

I suppose they could be closer but the real reason for that size is that we were using salvaged bricks from our old melter and that was the spacing we used then.

Since that spacing didn't cause a problem in the old one (many years) we just used it.

Food for thought though.

Franklin Sankar
05-08-2012, 12:48 PM
Thanks Eric. Glad to hear that news. I used a long coil that went around and around just in case the space I am talking about was somehow going to create uneven heating.
Thanks for the pictures, I love to see the construction. Wish I could make it so neat.
Franklin

Hugh Jenkins
05-08-2012, 01:06 PM
I think you can get too obsessive about perfectly even heating in any furnace. We certainly don't have perfectly even heating in most fuel furnaces. One electric furnace I know of purposely loaded the elements on one side more than the other to cause convection. Hard to say if it actually helped since the glass out of that shop was always so good anyway. No one hangs moly elements on the door wall that I know of. If the heat is contained with good insulation, it will even out inside.

Franklin Sankar
05-08-2012, 06:48 PM
Thanks Hugh. The next time it will make changing the elements much easier.
Franklin

Pete VanderLaan
05-15-2012, 08:20 AM
I often recall a comment made bu John Bingham years ago about new furnaces. He said people would build them and congratulate themselves on the efficiency of the design when in reality what they were really seeing was the benefit of new materials that had not had time to loosen up and become less efficient. I think he was right.

Travis Frink
05-15-2012, 09:41 AM
It seems a reasonable point for consideration- at what point do the savings expected from a rebuilt or even new model furnace outweigh the cost of new materials and rebuild time (read here also the motivation factor) needed to overhaul an older, less efficient furnace. Also, What materials can be reused without worry about reduced performance (insulation, durability, etc.)?

Eric Covington
05-16-2012, 10:06 AM
I will be posting a full cost/benifit analsys soon. I am very busy with our gallery opening at http://glass-blowing-place.com/ and launching our e-commerce web site (shopping cart). Once that is over I will put together all the details of our experience.

The short story is with creative cutting most of the materials that were not totally used up in the old melter were re-usable. On initial blush it looks as if out ROC (Return On Capital) is less than 1 year but more on that later.

FYI: It looks as is the our construction exceeded design specs in that we are idling (over night) at less than 1400 watts (designed for around 1500) and in production at around 2200 watts (designed for 3000).

But as I said more on the facts and details later

Franklin Sankar
05-17-2012, 08:07 AM
Eric, how long does it take you to recover when you charge?
Your power is very low, that is amazing.
When you open the door to gather how far down does the temp drop.
Franklin

Pete VanderLaan
05-17-2012, 09:07 AM
time has a way of making old men out of young men.

Tom Fuhrman
05-18-2012, 08:48 AM
time has a way of making old men out of young men.

Amen brother!

Pete VanderLaan
05-18-2012, 08:59 AM
So does glass by the way....

Eric Covington
05-18-2012, 09:56 AM
We charge at 18:00 after a day of work and the glass is crystal grade by noon the next day. We do separate out the fine bits of cullet (for later) and so far the biggest charge has been 20kg.

Generally the temperature doesn't drop noticeably except on long/big gathers on monster pieces. When we notice the glass getting a bit gooey we just turn up the watts for an hour or until it is more to our liking.

I am gathering detailed data and will publish it after we have done with our Grand Opening

Eric Covington
05-19-2012, 06:34 PM
Eric, how long does it take you to recover when you charge?
Your power is very low, that is amazing.
When you open the door to gather how far down does the temp drop.
Franklin

Overnight to recover

Temp doesn't seem to drop even during big gathers. Of course we don't leave the door open for long. Soon I am installing pyrometers in the lid (just above the glass) and I will have real munbers for all.

Franklin Sankar
05-20-2012, 07:28 PM
Thanks and i look forward to hearing more about its performance in time.
Franklin

Eric Covington
01-24-2013, 11:10 PM
Today we turned down the melter today for refurb/rebuild

After 9 months of operation it is time to replace the element set and re-design the rolling top.

I spoke to Sandvik today and the recommendation was that we probably would get greater life from our set of 5 elements if we powered them all instead of 4 with one spare. We would turn up the voltage to compensate for the lost elements as they failed.

An interesting note: We were able to still continue blowing with only three elements by just turning up the voltage.

The theory is that lowering the wire temperature increases life and even the "spare" was un-powered it would still oxidize and be more prone to fail when powered.

Sandvik has asked for photos of the failed elements in situ to work on engineering better elements. I will share their comments as they are made.

The other reason for the rebuild was that since the beginning the were elevating the rolling lid to compensate for sagging insulating board. In hindsight we should have used 2" ship-lap board to prevent this. Nonetheless we are going to try a 2" Kastolite bottom.

To follow our progress please look here:

http://glengarry-glass-blowing.com/Melter%20rebuild-refurbish/

On a different subject: I am going to be helping another glass blower to build a melter similar to mine and we are thinking of using 7 elements to further lower the wire temp.

Comments?

Jordan Kube
01-25-2013, 02:00 AM
Sounds good. I've never understood the spare element thing.

Rollin Karg
01-25-2013, 05:30 AM
There is a small area for leakage (not 80lbs.) since the crucible is standing up off the IFB floor on a piece of kiln shelf. The floor and partway up the bottom row of bricks is lined with a layer of inswool to prevent glass sticking when the crucible breaks.

Inswool is not going to be much protection if the pot leaks or breaks.

Mark Wilson
01-25-2013, 07:47 AM
Sounds good. I've never understood the spare element thing.

i have a spare element, that i use when i get week or broken elements...the spare element has been in place for several years, and in place while i have changed out the other elements several times....the spare element still measures out at 5 ohms even though it has been in there for years...that is the same resistance as a new one....the other elements that are normally on, typically measure out at 7,5 to 8 ohms by the time i replace them....to get a little more lifetime out of them, i pick the weakest element and swap it out with the spare.....the spare element does not look burnt at all...

Eric Covington
01-25-2013, 12:27 PM
Do you replace elements before they go open circuit?

What gauge elements are you using?

APM or A1?

I gather you determine the "weakest" by measuring the resistance?

How long is your melter up at any one time or do you run 7/24?

Mark Wilson
01-25-2013, 02:10 PM
Do you replace elements before they go open circuit?

What gauge elements are you using?

APM or A1?

I gather you determine the "weakest" by measuring the resistance?

How long is your melter up at any one time or do you run 7/24?

i normally replace them before they burn out, but i have had some burn out 1st.
i am using 13 gauge a1....used to use APM, but did not want to pay the extra cost.

yes the weakest has the largest resistance

normally, i fill the crucible with cullet at room temperature, turn on the heat, and then i can blow 24 hours later...that gives me 12 hours at 2150 before i blow so the glass fines out.....blow for a day or 2 then ramp down to room temperature and shut everything off.....its not a 24/7 studio.....this works for a 40 pound crucible, not sure if it would work well for a larger one!!!!

Eric Covington
01-31-2013, 09:56 AM
Yes powerstat 1156

Eric Covington
01-11-2015, 05:30 PM
So that I only have to monitor one page and it is all together,

Please make all new comments in here:

http://talk.craftweb.com/showthread.php?t=10152

Eric Covington
01-11-2015, 05:31 PM
Please use this thread for future comments.

http://talk.craftweb.com/showthread.php?t=10152