CraftWEB Hot Glass Talk  

Go Back   CraftWEB Hot Glass Talk > Hot Glass > General Hot Glass Discussion

Reply
 
Thread Tools Display Modes
  #1  
Old 01-23-2019, 11:14 AM
Danny Polk Danny Polk is offline
Registered User
 
Join Date: Sep 2010
Location: Eldersburg, MD
Posts: 4
Danny Polk is on a distinguished road
Calculating 9/18 Molly element size for rebuild

I am going to be doing a rebuild and would like to use 9/18 molly elements...I currently have single phase 200 amp 240 volt service and will be using a 300# freestanding pot. I need some advice on determining which size element i need as well as which size transformer to accomidate.

any advice would be great,
Danny
Reply With Quote
  #2  
Old 01-23-2019, 11:27 AM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 20,667
Pete VanderLaan is on a distinguished road
calculate the cubic footage of the furnace interior. Nominally a 300lb pot dictates a KW usage around 22-23 KW if one assumes about 2000-2200 watts per cubic ft dead air space. Insulation also matters. If those numbers were reasonably correct, you would need six 9/18 312/500 60A elements, straps and clamps. That in turn would dictate a transformer with 240V input and KVA of at least 23-25 and would need a secondary output of 36 volt accommodating two banks of three elements which draw 12 volts each, wired in series. You would likely need 350 MCM cable for the wiring. That will be a custom transformer and expect it to cost around $2500 dollars.

I believe Cheyenne Malcolm at Canned heat will have those elements. I no longer sell elements as the tariff wars and Chinese Customs have made it too much of a pain to do. I would happily sell the pot you need.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #3  
Old 01-24-2019, 06:40 PM
Danny Polk Danny Polk is offline
Registered User
 
Join Date: Sep 2010
Location: Eldersburg, MD
Posts: 4
Danny Polk is on a distinguished road
Thanks Pete! I am dealing with an ID of 32" and depth of 50" giving me 23.25 cubic feet. This comes out to 46500-51150 watts? Will this still be suitable for the recommended elements?


What kind of lead time if any do you need for the 300# pot?

Thanks again
Danny
Reply With Quote
  #4  
Old 01-24-2019, 06:47 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 20,667
Pete VanderLaan is on a distinguished road
Quote:
Originally Posted by Danny Polk View Post
Thanks Pete! I am dealing with an ID of 32" and depth of 50" giving me 23.25 cubic feet. This comes out to 46500-51150 watts? Will this still be suitable for the recommended elements?


What kind of lead time if any do you need for the 300# pot?

Thanks again
Danny
******
The pot is not an issue. We make them all the time. Your calc for Cu ft seems high as I casually read it. That becomes a lot of watts and is outside conventional calculations. I'm not doing the calcs for you. Out side my pay grade. I would think about 12 cu ft.
What is of concern is the original furnace sizing. Steve initially used a long 6/12 element, a 450 450. That required a long set of castings and the 312 shortened it. That in turn made for different castings including the front doghouse door.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #5  
Old 01-25-2019, 10:15 AM
James Burts James Burts is online now
Registered User
 
Join Date: Jul 2014
Location: Raleigh, NC
Posts: 36
James Burts is on a distinguished road
Danny-
Is the furnace already electric? That seems like an awful large chamber. When I designed and built my moly furnace for a 300# crucible, my heating chamber is roughly 27" radius and 31.5" high, for something around 12.2 cubic feet. The huge difference is the 18.5" of extra height you have in your heating chamber. From the floor of my heating chamber, I have:
  • 2" riser to keep crucible off the furnace floor
  • 15" for height of the crucible
  • 2" gap between the top of the crucible and the moly elements
  • 12.5" hot zone of the moly elements

How is it that you are using the space so that your furnace needs 50" of interior height?

--James--

Quote:
Originally Posted by Danny Polk View Post
Thanks Pete! I am dealing with an ID of 32" and depth of 50" giving me 23.25 cubic feet. This comes out to 46500-51150 watts? Will this still be suitable for the recommended elements?


What kind of lead time if any do you need for the 300# pot?

Thanks again
Danny
Reply With Quote
  #6  
Old 01-25-2019, 12:59 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 20,667
Pete VanderLaan is on a distinguished road
If it was an existing earlier Stadelman, the element likely was a 450/450 and that required a taller chamber. Retrofit on that to a 312 element can indeed be done but it means you need to use a shorter casting and doghouse door casting, which indeed we do supply. Economy of space is critical in these installations. Don't have dead air space for no reason.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #7  
Old 01-28-2019, 12:16 PM
Danny Polk Danny Polk is offline
Registered User
 
Join Date: Sep 2010
Location: Eldersburg, MD
Posts: 4
Danny Polk is on a distinguished road
Furnace was built originally for a 400# pot. I will be rebuilding with a 300# pot and moving it slightly closer to the gathering port.Therefore i believe i will have to redesign the crown to have less dead air space with the new elements. The original 6/12 elements were 36" total length with 5" out the top of the brick, 7.5" brick, and 23.5" out the bottom of the brick. (crown/lid 5.75" thick)

2" riser to keep the pot off the floor
15" pot (originally 17" pot)
2" spacing between pot and element
Reply With Quote
  #8  
Old 01-28-2019, 05:36 PM
Pete VanderLaan's Avatar
Pete VanderLaan Pete VanderLaan is offline
The Old Gaffer
 
Join Date: Apr 2002
Location: Chocorua New Hampshire
Posts: 20,667
Pete VanderLaan is on a distinguished road
The configuration you cite doesn't fit my old calcs. I'm not aware of Steve building a furnace that held a 28 inch pot prior to the introduction of the 9/18 elements. They were initially a 9/18/ 312/500 and the larger unit used a 9/18 450 /500 . The 300# furnace started off in a tall version with the 6/12 450/450 but was altered down the road to take the 9/18 / 312 /500. That took a different transformer at 36 volt with a big ass KWV.

Help me out, anyone who can tell me I'm wrong about that.
__________________
Where are we going and why am I in this basket?
Reply With Quote
  #9  
Old 01-29-2019, 10:21 PM
Jordan Kube Jordan Kube is offline
?
 
Join Date: Aug 2003
Location: Seattle, WA
Posts: 1,650
Jordan Kube is on a distinguished road
There might a have a few. Steve would have to confirm.
__________________
WWUD? Think for yourself.
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off
Forum Jump


All times are GMT -5. The time now is 11:49 AM.


All published comments within these message boards are the opinions of its contributor and does not represent
the opinion(s) of the owner(s) of this website. Please see the Terms of Use file for more details.

Books to Help Artists Avoid Online Scams: Top 10 Email Scams | Social Media Scams

Powered by vBulletin® Version 3.7.2
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
CraftWEB.com. Opportunity Network. 2008. All Rights Reserved.