Chamber and Hot Zone
The chamber will accept a variety of our hot zones for different atmospheres, temperatures and different sample sizes (3″ x 2″ hot zone shown). An extensometer can be rear-mounted through the second access door on the side. A viewport is supplied for a pyrometer. Multiple spare ports are supplied for other instrumentation. An external temperature below 50 °C is maintained at all times. Access to the sample is by means of a hinged front cover.
The hot zone is sized* to accommodate customer samples and provides excellent temperature uniformity. The power supply for the heater is sized for the maximum temperature and has extra power for fast ramp rates and for less efficient aging hot zones.
A unique feature about this furnace chamber is that the depth of the chamber is so that the extensometer can be rear-mounted, not side-mounted. This prevents the chamber from being mounted in the test frame at an angle. The rear section of this chamber has an access port on the right side. This allows full access to the extensometer. A port is provided in the rear for a manipulator to preset the extensometer after the unit has been evacuated and backfilled with the desired inert gas and brought up to temperature.
The front door has a viewport. The rear of the chamber has provisions for mounting a 6.00″ High Vacuum Pumping System.
The Hot Zone shown is a 180 degree split design with Ceramic Refractory Shields. The heating elements are Moly- Disilicide and are capable of temperatures up to 1650°C. The usable, uniform, hot zone is 3.0″ ID x 2.0″ long. Power to the heating element is supplied by means of water-cooled water cables and feed throughs.
The chamber is designed to accept a higher temperature hot zone with different heating element and shield materials.*
* Many hot zone sizes available, consult MRF for details.
MRF works with the customer and test frame supplier to ensure full compatibility of the furnace chamber with the test frame. We provide ample ports and access lids to accommodate accessories such as grips, extensometers, test rods, samples, etc and to provide access to all hot zone areas. The chamber size is chosen according to the sample dimensions and the test sample mounting accessories.
The physical test rods will be sealed with metal bellows top and bottom. The bellows have adequate stroke to compensate for test actuator motion, to relieve strain on the load cell and for any misalignment of the rods.
A set of two mounting brackets is supplied to mount to a large variety of test frames.
Power Supply & Controls
The Power Supply is designed to match heating element resistance and accommodate a high ramp rate up to the maximum operating temperature of 1650°C.
The power console contains all electrical devices such as circuit breakers, contactors, over temperature controller, volt and amp meters, an SCR, step-down transformer, etc. The main step-down transformer is matched to meet the heating element resistance and provides high-current, low-voltage outputs.
Temperature control is accomplished either with discrete controllers or with an HMI Interface and Programmable Logic Controller (PLC). The HMI application, with an easy-to-use computer touch panel, replaces the individual controllers and switch panels. The HMI allows the user to control, view and record all furnace functions, allowing for data acquisition, recipe storage, trending, alarms and networking and capability for integration with the test equipment.
A type “C” sheathed and coated thermocouple is used to measure the furnace temperature up to the maximum furnace temperature. For hot zones with a maximum temperature above 2000 °C, control is automatically switched over to a Pyrometer.
Vacuum and Gas System
This furnace system was designed to operate in air, an inert gas environment or vacuum. A hydrogen kit is available as an option. Maximum operating pressure is 5 P.S.I.G. A relief valve and a compound gauge (30 P.S.I.G. x 30 in. Hg.) are located on the top of the furnace body. The relief valve has been factory preset at 2 P.S.I.G..
A solenoid valve with adjustable flow valve controls the gas flow. Gas flow is monitored and manually adjusted on the flow meter, and MFC is available for controlling and monitoring flow electronically.
The basic pumping system evacuates the furnace into the 10-3 Torr vacuum range. The purpose of this pumping system is to quickly remove most of the oxygen from the inside of the furnace and back fill with your desired gas, or to run tests in a vacuum atmosphere. Optional high vacuum systems are available for lower vacuum levels, and use the 6″ rear chamber port.
The vacuum system consists of the following components:
- A Rotary Vane Pump with an inlet and exhaust filter.
- A electro-pneumatic vacuum valve is provided to isolate the chamber from the pump for operation in process gas.
- Controls to monitor and operate the pumping system.
- A vacuum gauge controller or optional HMI indicates the furnace pressure through the use of a vacuum gauge. A high vacuum gauge is added in the event a diffusion pump or turbo pumping system is installed.
- Power to the heating elements is interlocked with the vacuum system through the use of process control relays on the vacuum gauge controller or PLC. A 6.00″ vacuum port is located on the rear of the chamber to accept a larger vacuum system.
Water Cooling System
The water manifold provided with this system is designed to cool the furnace and keep all external surfaces under 50 °C (120 °F). To insure proper flow, a water flow switch is installed with visual indication. In the event water flow is disrupted for more than 5 seconds, power will be disconnected to the heating elements.
The water manifold has several circuits supplying water to the various parts of the furnace. Each one of these can be manually adjusted to allow each circuit just the proper amount of flow to save water and allow a drain temperature of approximately 40 °C (100 °F).
The Furnace Water Cooling Manifold consists of multiple circuits to adequately cool all the furnace parts and includes a strainer, pressure regulator, pressure gauge, water inlet and outlet manifold, a water flow switch as a visual water flow indicator with a flow interlock to protect the furnace in the event of a water flow failure. This switch turns off power to the hot zone contactor if water flow is below recommended minimum for a certain amount of time. Each part of the furnace is supplied with a separate cooling circuit that can be regulated by independent manual ball valves.
||15 kVA, 208-240V/1-3/50-60 Hz (other voltages available).
||4GPM (15 lpm) @70F (20 °C) and 50 P.S.I.G. (3.4 bar), required flow dependent on kVA rating.
||Argon or Nitrogen 30 L.P.M., Hydrogen for optional H2 kit, @ 50 P.S.I.G.
||60 – 90 P.S.I.G. (4.1 – 6.2 bar) filtered.