1650C Air Furnace for physical testing

This furnace chamber can easily be mounted in test frames to combine our high temperature, controlled atmosphere zones with other manufacturers' physical testing units. 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.

Major parts

• Chamber and hot zone
• Power supply & controls
• Gas & vacuum system
• Water cooling
• Physical testing
• Utilities

Chamber and hot zone

The furnace chamber is a front loading rectangular chamber, double walled, manufactured with stainless steel and water-cooled. Chamber is equipped with top and bottom stainless steel welded bellows to allow operation of physical test grips while maintaining a protected environment. The chamber is polished after all welding and machining for an ergonomic appearance and good vacuum practice. Access to the furnace chamber is through the full opening hinged front door.

The 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 as others do. 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 pre-set the extensometer after the unit has been evacuated and back-filled 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 is a 180 degree split design with Ceramic Refractory Shields. The heating elements are Moly- Disilicide and are capable of temperatures up to 1650^oC. 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. An optional protective folding shroud can be installed to protect the door insulation assembly while the door is in the open position.

The chamber and power supply have been designed to accept a higher temperature hot zone. The chamber will have additional power feed ports for the power leads.

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Power supply & controls

The Power Supply is designed to accommodate a high ramp rate up to the maximum operating temperature of 1650C. The power supply is designed to accommodate different hot zones allowing higher furnace temperatures. Power is supplied to the elements with an SCR controlled Power supply.

A single power console contains all electrical devices such as: circuit breakers, contactors, over temperature controller, Volt and Amp meters, an SCR which provides an economical and efficient means of modulating power to the main stepdown transformer, etc. The Main Stepdown Transformer is matched to meet the heating element resistance. The transformer has two (2) secondary voltage taps, provided to match the element resistance for the different hot zones.

A set of water cooled power cables supplies the power to the heating elements from the main step down transformer. This reduces the conductor size as well as allowing for greater distances between the hot zone chamber and the control console.

The furnace temperature will be controlled through a Honeywell Digital Controller with setpoint programming. This controller has several segments of programming available for ramp
and soak, to be used to create a temperature profile as required. These segments are used to ramp the furnace up to operating temperature, then hold the temperature for as long as necessary.

This controller will read and display the furnace temperature up to 1650C from a type "C" thermocouple. This loop sends a controlling signal to the SCR which will modulate the power to
the furnace.

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Gas & vacuum system

This furnace system was designed to operate in air, an inert gas environment or vacuum. The normal positive pressure to be used in this furnace is 2 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 pre-set at 2 P.S.I.G.. A solenoid valve will serve as the gas valve. The inlet gas flow is regulated by means of a manual valve mounted on a flow meter.

This pumping system will evacuate 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 inert gas, or to run test in a vacuum atmosphere.

The vacuum system consists of the following components:

• A Rotary Vane pump with an inlet and exhaust filter.
• A electropneumatic vacuum valve is provided to isolate the chamber from the pump for operation in process gas.
• A vacuum relief valve (back to atmosphere) is provided for the purpose of releasing the pressure or to conveniently leak check the system.
• Switches and status lights are provided to monitor and operate the pumping system.
• A vacuum gauge controller will indicate the furnace pressure through the use of a vacuum thermocouple gauge tube. This controller will accept high vacuum gauges in the event the diffusion pump or turbo pumping system is installed.
• The power to the heating elements is interlocked with the vacuum system through the use of the process control relays on the vacuum gauge controller. A 6.00" vacuum port is located on the rear of the chamber to accept a larger vacuum system.

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Water Cooling system

The water manifold provided with this system is designed to adequately cool the furnace and power cables. The water temperature should be less than 68F. To insure proper flow, a water flow switch will be installed with a light for visual indication. In the event water flow is disrupted for more than 5 seconds when the furnace is at operating temperature the 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 100 F.

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Physical testing & mounting

The physical test rods will be sealed with metal bellows top and bottom. The bottom bellows will have adequate stroke to compensate for the bottom actuator and the top bellows will have approximately 1 inch of stroke to relieve strain on the load cell and for miss-alignment of the rods.
A set of two steel mounting brackets is supplied to mount to a large variety of test frames.

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Utilities

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