Vacuum furnace

Introduction:

A vacuum furnace is a type of furnace that can heat materials, typically metals, to very high temperatures and carry out processes such as brazing, sintering and heat treatment with high consistency and low contamination. In a vacuum furnace the product in the furnace is surrounded by a vacuum. The absence of air or other gases prevents heat transfer with the product through convection and removes a source of contamination

Application:


1 Maximum occupational safety with one-of-a-kind safety concept
2 Fast, condensation-free drying processes
3 Homogeneous specimen drying

Some of the benefits of a vacuum furnace are:

1. Uniform temperatures in the range 11001500°C (20002800°F).
2. Temperature can be controlled within a small area
3. Low contamination of the product by carbon, oxygen and other gases.
4. Quick cooling (quenching) of product. .
5. The process can be computer controlled to ensure metallurgical repeatability.

TECHNICAL SPECIFICATION

1

 

Furnace Shell Material  :

Fully Metallic – Stainless Steel 3041 inside and outside

2

Chamber Construction
Design and fabrication as per ASME unfired pressure vessel code section V111 Division 11

Cylindrical, double walled, water cooled, with ports for vacuum pumping, vacuum gauges, control and survey thermocouples, view ports of 100 mm, 90 degree apart at top ( at two locations so that the job could be viewed from outside). Etc. Bottom door with hearth with molybdenum rails and pins for job support.
Inside will be electro polished and outside buffed. Platform and one ladder provided for reaching all the top area of the furnace

3

Orientation Optional

Vertical/ Horizontal

4

Chamber Door With Hearth

Bottom Door opening ( electrically operated) on Ball screws, Once opened the bottom door will be rolled out on an electrically powered trolley, So that job can be accessed from 360 degree. Separate control for opening the door and rolling out the trolley.
Electro pneumatic lock will be provided for the door

5

Support Structure

MS painted structure with provision for grounding on ground and electrical grounding

6

Hot zone and Heating Elements
( All Metal hot Zone)

Heating Elements (PLANSEE Mke) wide band dual V Grooved Lanthanum Doped molybdenum . Heat shielcs designed with optimum numbers of metallic layers of molybdenum/  lanthenated Moly/ Stainless steel

7

Max job size ( optional )

As per Customer Specification

8

Work Load (max)

As per customer Specification

9

Furnace Cooling

Furnace cooling by natural/ controlled cooling only.

10

Opening Temperature (Max)

1450 deg C 15 deg C.
(continuous operation for 2 hrs)

11

Max Temp

1500 Deg C (short duration (around 15min) for clean up cycle)

12

Temperature uniformity

±5 deg C.(550 to 1450 deg C)

13

Vacuum at 1450 deg C

Better than 5x 10-5 mbar

14

Leak rate (max permissible)

2 Microns/ hr

15

Pump down time

<10 min (once the diffusion pump is hot to pump) to achieve ultimate vacuum at amb temp and clean degassed furnace

16

Heating rate

0.1 deg C/min to ≥50 deg. C/min(fully variable at the rate of 0.1 deg/min)

17

Cooling Rate

Controlled cooling 1 deg.C/min to natural cooling (fully variable)

18

Vacuum Pumping System
(pumping cham with automatic switching control at appropriate vacuum levels)
Optional as per customer specification

  1. Roughing pump( rotary piston type)

(with oil mist filter)
Pumping Speed= Depends on chamber size

  1. Booster pump

Pumping speed= Depends on chamber size

  1. Diffusion pump

Pumping speed= Depends on chamber size

  1. Holding pump

Pumping speed= Depends on chamber size

19

Vacuum Valves

All valves including roughing, fore- line,
Hi vacuum, Holding, back fill etc.
Will be electro- pneumatic and stainless steel 304

20

Vacuum plumbing’s and bellows

All plumbing’s and bellows will be made of stainless steel and designed for appropriate size

21

Chiller plant

Mini chiller plant (stand alone system) with water circulating system for diffusion pump with appropriate capacity will be provided to bypass the chiller plant with water from over head tank for diffusion pump’s safety. In case of power failure

22

Baffles for Diffusion pump

Chevron baffles with appropriate stand alone cooling system

23

Hearth up/down/move out control and backfill

Manual control mounted on the support structure of the furnace- independent control with safety interlocks

24

Controls Cabinets
(2 separate cabinets- industrial standard and powder coated)

  1. For instruments, control panel and mimic
  2. For power supply system and contractors phase amplifiers etc

25

Control System ( Optional as per customer specification)

PLC from SIEMENS/ ALLENBRADELY/ ABB/ HONEY WELL
PID Controllers from HONEY WELL/ EUROTHERM/ YOKOGAWA/ SIEMENS

26

Temperature programmer
PID controller

Three separate zone control with one master and three slaves

27

Over temperature Controller
PID Controller

Three separate controllers for three zones

28

Control Console

  1. Touch control switches for controls
  2. All process parameters will be displayed. Real time process display in graphical and digital format.
  3. Separate voltmeters and ammeters for each zone will be provided

29

Process Data Recording

Data logging of process parameters and survey temps, DP temp, pump temp, events etc will be stored on hard disk and real time display on screen. It will be retrievable at any time and printable in trend and digital format

30

Measurement accuracy

±0.1% (400 deg.C to 1450 deg. C)

31

Thermocouples for temp control and over temp control
( all thermocouples from Omega/TL/ Tudor)

Molybdenum sheathed S type thermocouples with 3 zone control.
(Total nine thermocouples)
S type T/C- Calibration upto 1500 deg. C
Length-400mm
Sheath dia – 4.5mm
Three thermocouples in each zone. Viz one each per zone for temp, control redundancy and over temp., control
NB one additional port in each zone will provided for inserting one standard TC for calibration purpose

32

Manual over ride for

-Interlocks
- Heating rate auto mode, Manual mode

33

Vacuum Instrumentation
(controller and sensors from LEYBOLD/ PFEIFFER/TELEVAC/MKS

Vacuum controller with one cold cathode and two pirani inputs with alarms/switching at high and low settings (cross over) for all channels. One pirani for holding vacuum, second pirani for rough vacuum and cold cathode for high vacuum in furnace)
One additional port will be provided for one vacuum sensor for furnace vacuum system calibration.
One mechanical gauge will be provided on the chamber to see the rough vacuum

34

Additional Vacuum sensor ports will be provided

One port each of 25mm for vacuum monitoring in between roughing pump and booster pump, Booster pump and DP and DP pump and High vacuum valve

35

Health monitoring of furnace (optional)

Additional sensors for monitoring cooling water temp, Roughing Pump Oil temp., Diffusion Pump temp… etc with alarms and logging is optional

36

Power System for heating elements

Variable Reactance transformer separate with windings for each zones.
Power: 415 V3 phase 50 Hz

37

Work          load Thermocouples and port inside the chamber

9 Nos. of S type survey thermocouples each two meter long, flexible with connectors on separate flange

38

Safety Interlocks

  1. Electrical power fail/ restart on resuming power ( manually selectable)
  2. Vacuum level controls for heating and switching operations,
  3. Water pressure/ flow reduction/temp., rise etc
  4.  Pneumatic pressure failure
  5. Furnace opening minimum temperature (pre-settable)
  6. Ensure amb. Pressure to open the furnace
  7. Any vacuum pump failure
  8. Ground fault ( job touching on the heating element) Alarm/ switch off heating
  9. Over temperature Alarm/switch off heating
  10. Program end control not to restart any system automatically
  11. Ensure holding pump & valve operational to heat diffusion pump
  12. Door closing confirmation
  13. All other necessary interlocks for the health of the furnace and job

39

Alarms

All Alarms will have audio visual display/ indication with logging of values (if applicable)
Alarms will be provided for:

  1. Low water pressure/flow for pumps and furnace chamber
  2. Diffusion pump temperature high/low
  3. Roughing pump temperature high
  4. VRT temperature high
  5. Ground faul:- job touching the heating element etc
  6. Pneumatic pressure low/high
  7. Cycle complete indication
  8. And for all necessary safety interlocks