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Vacuum Furnace Systems, controls and Manufacturing
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Vacuum Furnace Technology column by Dan Herring, Metallography column by George Vander Voort, Vacuum Brazing column by Dan Kay, Vacuum Pump column by Howard Tring and other Educational Resources

Compact horizontal vacuum furnace designs provide great flexibility, excellent performance and ease of operation for general heat treating and brazing applications to deliver value to commercial and in-house heat treaters alike.

CLICK HERE for Standard Furnace Sizes

vacuum-furnace-35The standard VAH Series Horizontal, Front-loading, Vacuum Heat Treating and Brazing Furnace can be customized to suit unique applications such as high pressure gas quenching, high temperature heat treating, ultra-clean processing and more.

The furnace is designed to have fast heating rates to very uniform temperatures at high vacuum levels. Standard units are equipped with a gas quench system capable of cooling the load rapidly from processing temperatures at quench pressures up to two bar.

Advanced microprocessor controls are used exclusively to ensure precise control and repeatability. VAC AERO control systems can be integrated with internal networks and offer extensive data collection capabilities. VAC AERO also manufactures auxiliary equipment for quench gas storage and furnace cooling requirements.

CLICK HERE TO VIEW ACTUAL VACUUM FURNACE PRODUCTION SPECIFICATIONS

VAC AERO Vacuum Gas Quench Furnace features and capabilities include:

  • Operating temperatures up to 2400°F (1315°C).
  • Ultimate vacuum levels in the 10-6 torr range.
  • Modular hot zone design for easy maintenance.
  • All-metal hot zones are available for ultra-high vacuum processing.
  • Alternatively, economical graphite-based insulation provides extended durability.
  • Heating elements available in lightweight curved graphite or molybdenum strip.
  • Selectable gas quench pressures from 2 bar to 10 bar.
  • Fully automated control systems including PC-based controls with remote access.
  • Optional convection heating capability.

STANDARD OPERATING TEMPERATURE RANGE: 1000°F - 2400°F (538°C - 1315°C)

TEMPERATURE UNIFORMITY: Meets or Exceeds AMS 2750 Requirements.


HOT ZONE:

VAC AERO hot zones have unitized construction for easy removal and maintenance. Lightweight design with low thermal mass and inertia for faster quenching and long life.

  • Work Load Size: Standard sizes from small laboratory units up to 54” wide x 54” high x 72” deep. Larger models available.
  • Heating Elements: Customer’s choice of lightweight curved graphite, pure or lanthanated molybdenum strip.
  • Hearth: Constructed with quickly removable hearth rails of pure molybdenum designed to support uniformly distributed loads of up to 4000 lbs at 2400°F.

carbon_hot_zone.gifRadiation Shields: (Graphite-based Construction):

The standard graphite-based insulation package consists of three layers of carbon felt with an inner facing of graphite foil bonded carbon composite for added protection and enhanced reflectivity. The heat shield package is supported by a stainless steel assembly that also acts as a manifold to distribute the quenching gas uniformly throughout the workload.

Radiation Shields (All-Metal Construction):

For ultra-clean processing applications, VAC AERO also offers an all-metal hot zone construction. The standard all-metal insulation package consists of two layers of pure molybdenum sheet backed by three layers of stainless steel sheet. The heat shield package is supported by a stainless steel assembly that also acts as a manifold to distribute the quenching gas uniformly throughout the workload.

FURNACE CHAMBER:

The chamber and heads are a double-wall water-cooled design, primed and painted the customer's choice of colour. The chamber is equipped with all necessary thermocouple jacks, gauge ports, pumping ports and gas quench entries conveniently located for easy access. A powered rotary clamping system is used to secure the bottom head during processing. All VAC AERO VAH Series furnaces come with a manually operated load dolly as standard equipment.

VACUUM PUMPING SYSTEM:

The vacuum pumpdown is automatic and interlocked. The VAC AERO design uses a holding pump to maintain a low pressure on the diffusion pump foreline at all times. This feature, combined with proper timed sequencing of vacuum valves, virtually eliminates backstreaming of pump oils.

  • Mechanical Pump: Roughing Pump and Booster combination appropriately sized for furnace volume.
  • Diffusion Pump: Varian series complete with charge of Dow Corning fluid.
  • Holding Pump: Rotary vane pump.
  • Main, Roughing and Foreline Valves: Right angle poppet valve with electro-pneumatic operation.
  • Partial Pressure Capabilities: The furnace can be operated at partial pressures up to 1 torr (1000 microns) of inert gas (argon or nitrogen, whichever is used for quenching). Failsafe hydrogen partial pressure systems are also available.

GAS QUENCH SYSTEM:

VAC AERO’s IG Series Quench Gas Storage Systems are available as an option.

External recirculating inert gas quenching system distributes quench gas through circumferentially located internal nozzles for rapid, uniform cooling of the work load. The system includes:

  • Quench blower powered by electric motor with soft start.
  • Special high efficiency tube/fin heat exchanger.
  • Complete quench piping.
  • Selectable operating pressure.

hardwarealarms_vah.gifPROCESS CONTROLS with SCADA:

The VAC AERO control system is programmable and logic based. The design philosophy of VAC AERO is to simplify control by using the program capabilities to perform as many functions as possible, thereby reducing operator dependence. VAC AERO has also chosen proven hardware components, suitably hardened for an "industrial shop" environment. The system uses a state-of-the-art Hybrid controller to control the machine functions and furnace temperature. The controller integrates with software running on a personal computer to provide Supervisory Control and Data Acquisition (SCADA). Operator interface is provided though an LCD touch-screen mounted in a control panel. An extensive range of standard displays is available.

The key benefits of this system are:

  • Compatible with plant wide SCADA and network integration.
  • Process cycle validation.
  • Extensive alarm and event management and reporting.
  • Temperature control using advanced algorithms, auto tuning, and multiple PID loops.
  • Operator sign-on/sign-off security provides up to 255 control levels to limit operator control of individual items of plant and equipment.
  • Enhanced maintenance and troubleshooting management and trending.

Vacuum Instrumentation: A Vacuum Gauge Controller with 2 station, thermocouple gauge and 1 station Penning (cold cathode) gauge is used to monitor the chamber and the pumping system. This instrument is integrated with the process controller to provide dedicated setpoints that control all critical vacuum-related process functions.

Overtemperature Safety Controller: Digital manual set 0°F - 3100°F, Type S.

Power Supply: The heating element power is supplied by an A.C. water cooled power supply containing single phase VRT assemblies. Each VRT has a 0 – 100% trim control for optimum temperature uniformity in the hot zone.

FURNACE COOLING SYSTEM:

Furnace water system consists of a compact manifold containing all necessary pressure regulators, valves, pressure switches and flow regulators with supply and drain hoses and fittings. As an option, VAC AERO can provide a Dual Loop Cooling System to supply coolant to the furnace.

INSTALLATION AND START UP ASSISTANCE

The system is shipped complete, tested and ready for installation. VAC AERO offers installation supervision or complete installation services. After installation, a qualified VAC AERO technician will visit the site to commission the equipment and provide instruction in furnace operation. As part of every furnace contract, VAC AERO also provides pre-delivery training in heat treating processes furnace operation and maintenance.

pdf_fileicon.gifDowload VAH series Furnace Specifications

pdf_fileicon.gifDowload VAH series Auxiliary System Product Sheet

 
 

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VAC AERO News, Education & Training

vacuum-furnace-manufacturersVAC AERO Sells Vacuum Furnace to a Major Airline

Burlington, Ontario, July 20, 2015 - VAC AERO has sold a VAV6648 HV-2 vertical vacuum furnace to an international airline company. The furnace is designed to have rapid heating rates while maintaining tight uniformity at high vacuum levels. The furnace features a 66” diameter x 48” high hot zone using metal elements in a graphite hot zone and a heavy duty hearth designed to support a uniformly distributed load of 4400 lbs. The furnace, which is capable of meeting applicable AMS 2750E requirements, is also equipped with VAC AERO’s advanced Honeywell HC900 interactive hybrid control package with SCADA and complete network integration capabilities and remote monitoring and control. VAC AERO’s 50-plus years of experience operating its own heat treating facilities allows them to provide turnkey solutions to customers such as technology transfers as well as training, hands-on instruction and collaboration.

Vacuum Technology with "The Heat Treat Doctor"

vacuum-furnace-nlThe Use of Tungsten in Vacuum Furnace Applications

Tungsten is used in vacuum furnaces when there is a need for structural integrity at elevated temperature and/or in situations where other materials may degrade, such as when lower melting point eutectics are a concern. One example of its use in is roller rail assemblies in which graphite wheels are positioned between molybdenum rails using tungsten axles. Tungsten (chemical symbol W) is a member of the family of refractory metal (Mo, Nb, Re, Ta, W) and has the highest melting point and vapor pressure of this group. Due to this unique property, it is commonly used as a material of construction in specific areas of vacuum furnace hot zones operating above 1315ºC (2400ºF). Tungsten can also be used for heating elements given that it has the highest duty temperature, typically 2800°C (5075°F). In practice, this rating is often downgraded as it is for all heating element material choices. Tungsten will become brittle, however, if exposed to oxygen or water vapor and is sensitive to changes in emissivity. In general, tungsten is resistant to corrosion below 60% relative humidity.

Vacuum Brazing with Dan Kay

Fig-1 nlConcerns re Furnace Brazing of Carbon and Alloy Steels When Using Copper Brazing Filler Metal

All metals expand when they are heated, and contract when they cooled. This fact has been thoroughly explored over the years, and data-tables have been published showing the coefficients of thermal expansion (CTE’s) for each of the many metals available for use in product design and construction. But carbon-steels present a unique situation to designers and brazing companies, because when being heated all the way up to copper-brazing temperature, the metals will actually go through a temperature-range where the steel will actually be contracting (shrinking) while being heated, and then do just the opposite when cooling, thus potentially causing distortion and/or fracturing of brazements during a high-temp brazing cycle. Such a scenario is illustrated in Fig. 1 where an automotive fuel rail brazement failed to braze properly, because some unique CTE problems associated with carbon-steels was not properly taken into account during the furnace brazing cycle.

Metallography with George Vander Voort

intro nlMeasurement of the Volume Fraction of Beta Phase in Naval Brass

Measurement of the amount of phases or constituents in metals and alloys is probably the most commonly performed quantitative microstructural test. The amount present is usually referred to as the volume fraction, although it is rarely expressed as a fraction but usually as a percentage. The volume fraction, or VV, in stereological terms, is the volume per unit volume of the phase or constituent. However, there is no simple direct way to measure the volume fraction. Instead we measure the area fraction, AA, a lineal fraction, LL, or a point fraction, PP, which can be measured and correlate with the volume fraction: VV = AA = LL = PP. Areal analysis was first described by Delesse, a French geologist, in 1848. As the minerals were rather coarse in size, he could measure the area fraction of the grains of interest compared to the total two-dimensional area. As microstructures are rather fine in size, this is not a simple method to perform manually. Delesse suggested that a linear ratio of dimensions could also be used, but he thought that the accuracy would not be as good and did not try to develop a lineal analysis method.

Vacuum Pump Practice with Howard Tring

howard tring-6Shaft Seals for Rotating Shafts

On any machine that has a rotating shaft there will be a shaft seal of one type or another. If the machine is a simple electric motor, for example, the seal may be used just to retain the lubricant in the bearings and to prevent dust and dirt from entering the bearing. This type of seal generally needs little or no maintenance for small motors from ¼ to perhaps 10 HP. The shaft seals in any pump that the electric motor drives are ones that do need maintenance and replacement, whatever type of pump it is. If the pump moves liquids, such as a centrifugal water pump, it is important that the seal doesn’t leak although in some applications a small amount of leakage can be tolerated. If the liquid being pumped is hydraulic fluid, it may be at high pressure and the seal would be designed to withstand that pressure without failing.

Front and Bottom Loading Vacuum Furnaces

vacuum furnace-0115Constructed of the finest materials and craftsmanship, VAC AERO’s high performance vacuum furnaces are operator friendly and designed to minimize maintenance and downtime to deliver outstanding quality and  value to commercial and in-house heat treaters alike. VAC AERO’s vacuum furnaces are designed for rapid heating rates to very uniform temperatures at high vacuum levels and can be customized to suit unique applications such as high pressure gas quenching, high temperature heat treating, ultra-clean processing and more. VAC AERO’s high efficiency hot zones are designed for easy maintenance and reduced energy consumption. Our external quench system allows for easy maintenance of the heat exchanger and quench motor. A high efficiency blower and motor combine fast cycle times and quenching speeds to provide uniform gas distribution and superior cooling performance from processing temperatures at pressures of up to 10 bar.

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