Muffle Furnaces

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Overview

Muffel furnaces are heat treating furnaces having high temperature alloy removable chambers which operate under protective atmosphere. Commonly available in box type, the high quality heat treating furnaces having the capability to operate at high temperatures of up to 1800 oC proving to be a sophisticated instrument for laboratories. Muffle furnaces can be used for variety of applications including hardening, drawing, annealing, brazing, sintering and stress relief in both air and controlled atmosphere.[1] Wide range of Muffel furnaces are available depending on the experimental requirements. More details on available muffle furnaces manufactured by Lucifer Furnaces Inc. can be found here.

Muffle Furnaces at CAVS

CAVS carries three single chamber atmosphere muffle furnaces manufactured by Lucifer Furnaces Inc located in Oven room (1100). The furnaces are equipped with alloy muffle for operation with a positive flow of protective atmosphere and belong to the series of 7000 AM with maximum temperature of 2050 oF.[1] The alloy muffle is designed to separates the chamber refractory and heating elements from the workload and atmosphere.[1] This design minimizes scales and oxidation while also lowering dew points, reducing atmosphere consumption and purge time.[1] The ruggedly constructed furnaces are ideal for cyclical or production type applications and are rated for work loads up to 25 lbs per square foot of hearth area.[1]. Operated under inert atmosphere they can also be operated with flammable atmosphere with addition of Atmosphere Safety System as per NFPA Code 86 C. [1]

Muffle furnace of type 7AM - C12 located at CAVS


Standard Features [1]

  • Welded sheet metal shell construction with structural reinforcement.
  • Heavy gauge coil wound low watt density heating elements for longer life.
  • High grade alloy muffle with inlet pipe and front flange.
  • Multi-layered energy efficient lightweight firebrick and mineral block insulation for maximum heat storage and minimum heat loss.
  • Elements mounted in easy-to-replace holders located on side walls, and below the hearth for uniform temperature.
  • Silicon carbide hearth plate for full muffle support and thermal transfer from floor element.
  • Double-pivot horizontal swing plug door with high temperature ceramic fiber gasket, swing bolts and handles for sealing against muffle flange.
  • Honeywell digital temperature controller with type K thermocouple and contactor.
  • Controls mounted in separate side mounted NEMA 1 panel and operate on 115 volts.


Specifications [1]

Model Quantity (at CAVS) Chamber Overall Max Temperature (oF) kW Voltage Amps Weight (lbs)
H" W" L" H" W" L"
7AM - C12 2 (S/N - 7230 & 7233) 5 5 12 32 25 38 2050 4 230/1/60 19 500
7AM - F18 1 (S/N - 7507) 7 7 18 34 37 43 2050 8 230/1/60 36 650

Operating Instructions

Honeywell UDC 2500 Series Temperature Controller
Omega Data Logger Thermometer [2]

Normal Operating Instructions

  1. Turn on the main power supply.
  2. Turn on the Honeywell instrument control switch.
  3. Set the temperature to desired operating temperature.(Instructions below)
  4. The furnace is in operation and the chamber temperature should begin to rise (be patient as it might take few hours for the chamber to reach the set temperature).
  5. A defective thermocouple will cause the instrument connected to it to go to full scale reading which will effectively shutdown the furnace heating elements to safeguard the unit.
  6. While the furnace is heating up, the chamber should be purged with an inert atmosphere at least an hour ago to ensure the the gas has purged the air out.
  7. Once the chamber reaches the set temperature, open the furnace and insert the specimen. Make sure to use appropriate insulating gloves and tongs to hold the specimen.
  8. After the specimen has been heat treated for the required time, remove using gloves and tongs.
    • Multistage heat treatment - If the experiment requires multistage heat treatment, prepare the second furnace by following steps 1-6 (prepare the second furnace ahead of time so it is ready for use). Transfer the specimen from first furnace to second furnace.
    • Quenching - Specimen can be quenched in the required media. Take precautions when using oil as quenchant as it can be flammable.
    • Normalizing - Place the hot specimen on ceramic and allow it to cool in air.
  9. Leave the specimen in the oven and turn off the furnace if experiment requires annealing (oven cooling).
  10. To turn off the furnace, place the control switch in "OFF" position. For long term shutdown, turn off main power switch.


Honeywell UDC 2500 Series Setpoint Instructions

  1. Make sure a large "SP" is displayed in the lower display next to a number indicating the current setpoint. If not, press the LOWER DISPLAY button until "SP" appears in the display.
  2. Press the UP ARROW to increase the setpoint value, or the DOWN ARROW to decrease the setpoint value. As you hold the button, the changing number will increase in speed.
  3. The furnace temperature will now rise to and hold at current setpoint. After about 30 seconds, the controller's display will change back to displaying the chamber temperature.


Note - The controller provided with the furnace have been programmed with proper control parameters for the furnace operations and no further adjustments are required. If the controller is not functioning properly and setup procedure is required then please refer to the furnace manual. You would normally not go through this procedure

Collect real-time data

Real-time temperatures can be recorded by using a thermocouple attached to the specimen. The thermocouple is connected to a Data Logger Thermometer manufactured by Omega which transfers the data to SE309 interface software. Data from SE309 can be saved in excel or text format for easy access.

  1. Connect the thermocouple to the data logger thermometer by inserting it into one of the slots (T1/T2/T3/T4). Note you can have four thermocouple inputs at the same time by inserting a thermocouple in each of the four slots.(Image: Thermocouple input)
  2. Connect the other end of the thermocouple to the specimen.
  3. Connect the data logger thermometer to the computer using the USB wire provided. Turn on the data logger thermometer by pressing the power button.
  4. Open the SE309 interface software available on the desktop in Oven room.(Image: SE309)
  5. The software displays a empty plot and a virtual data logger thermometer on the screen. If the data logger thermometer is not connected it should display "Not Connected" in red. (Image: SE309 Display)
  6. If only one thermocouple is connected, select "Graph Options" on top of the plot to display a customization window (Image: Customization window). Further select "Subsets" and choose the the input that the thermocouple is using (T1/T2/T3/T4). Select "Apply" and save the changes. The plot should now only display the input that has been selected.([[Media:T1 input.PNG|Image: Selected input)
  7. Insert the sample in the furnace and select "Real Time", "Run" on the software.(Image:Run) (Use help from colleagues to start collecting the data and add sample to the furnace simultaneously)
  8. You should be able to see the software plot real-time temperatures.
  9. On completion of the experiment, select "Real Time", "Stop" to stop collecting the data. (Image: Stop)
  10. The data can be saved in form of excel or text file.(Image: Save file)

Safety Precautions

  1. Please equip yourself with required safety gears while using the furnaces. Always wear safety glasses and protective clothing when working in oven room. Use gloves and tongs while handling the specimen.
  2. Keep flammable materials away from the furnace, including things like paper, flammable liquid, old rags, etc.
  3. Cover the quench tanks when not in use. Do not let quenching oil be contaminated by water.[3]
  4. Be cautious when using oil as quenchant as it might catch fire. Quench oil is hot, splashes or skin contact may cause burns.[3]
  5. Turn on the ventilation in the oven room when working with the furnaces.
  6. Do not operate the furnace when vibrating.
  7. Be aware of your surroundings. Locate fire extinguisher, first-aid kit, eye-wash and shower station before lighting the furnace.
  8. Shut off the valves supplying gas to the furnace after use.
  9. Make sure to turn off the furnace and put all the equipment away after use. Clean up oil, water or other quenchant spills if any.
  10. Call 911 in case of emergency.

References

  1. 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Lucifer Furnaces Inc., Series 7000 AM - Alloy Muffle Box Furnaces, http://luciferfurnaces.com/products/all-products/series-7000-am-alloy-muffle-box-furnaces/
  2. Omega, User Guide HH309 Data Logger Thermometer, http://www.omega.com/manuals/manualpdf/M4147.pdf
  3. 3.0 3.1 Canada Center of Occupational Health and Safety, Metalworking Machines - Heat-treating, http://www.ccohs.ca/oshanswers/safety_haz/metalworking/heat_treating.html
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