Many companies that outsource vacuum heat treating must eventually decide if they would be better served by setting up this capability in-house. Establishing a new vacuum heat treating capability requires a significant capital investment in furnace equipment.  However, there are also other factors that should be considered when assessing the business case.  VAC AERO offers some guidelines to assist in this process.

Furnace Selection

There are a number of factors to consider in selecting the best furnace equipment for a new vacuum heat treating operation.

Size:  Vacuum furnaces are available in many sizes.  The initial capital outlay and operating costs are roughly in proportion to size.  The furnace manufacturer can review the customer’s heat treating requirements and advise on the most appropriate furnace size and design. 

Budget:  The basic equipment price for most popular smaller and medium sized vacuum furnaces will range from $300,000 to $500,000.  Additional costs will likely be incurred for site preparation and installation, auxiliary systems, tooling and other incidentals. 

Throughput:  The amount of work that can be processed in a single furnace load is proportional to the size of the furnace.  Typical vacuum heat treating cycles range in duration from a minimum of about five hours to much longer cycles, many in excess of twelve hours.  With allowances for loading and unloading time, only three or four heat treating cycles are typically completed in a 24 hour period.

Site Preparation & Utilities

Vacuum furnaces usually do not require special foundations.  Floor space requirements vary widely with furnace size, but an area of at least 400 ft2 (approximately 20 feet square) would normally be required for a medium-size furnace.

Vacuum furnaces are connected to supplies of electricity, water (for cooling), quench gas and compressed air.  Electricity costs during service will vary depending on the size of the furnace and type of heat treating.  The furnace manufacturer can assist in estimating these costs.

If a central cooling water recirculation system is not already in place, it is recommended that an auxiliary cooling system be purchased for the furnace.    Water consumption in these cooling systems occurs only through evaporation and is relatively low. 

The amount of quench gas used in each heat treating cycle is directly proportional to the size of the furnace chamber and the quenching pressure required.  For all but very small furnaces, it is recommended that a permanent liquid bulk supply of quench gas be installed. 

Compressed air is required to operate valves and other pneumatic devices on the furnace.  The air supply pressure is regulated to between 80 and 100 psig.  While this supply should be continuous (even when the furnace is not operating), consumption is very low.

Noise & Environmental Issues

Modern, well-maintained vacuum furnaces do not radiate excessive heat to the surrounding environment or release harmful emissions.  However, many mechanical vacuum pumps operate with a continuous noise level approaching 82 dbA and there may be occasional noise spikes slightly above this level when the furnace backfills or the quench blower activates. 

Staffing

Due to the length of typical heat treating cycles and in order to generate the best return on the investment in the equipment, heat treating operations are usually run 24 hours per day, often 7 days per week.  Fortunately, once loaded, modern vacuum furnaces can be operated in a fully automated mode without an attending technician.  Control systems can also include a remote access capability that allows for monitoring or regulating the furnace via secure connections.  These systems can also be used to activate pagers or dial phone numbers if an alarm condition develops. 

While a single, properly-trained technician can effectively operate and maintain one or two furnaces, safety regulations may require at least two persons per shift.  A quality control inspector is usually required at some point in the operation, but may not be needed 24 hours per day. 

Fixtures & Tooling

Parts for heat treating must be properly loaded into baskets or onto trays.  The initial capital outlay for sufficient tooling to support a medium size furnace can easily reach the range of $10,000 to $20,000. 

Maintenance and Miscellaneous Operating Expenses

With a reasonable preventive maintenance program and good operating practices, a vacuum furnace can be depended upon to operate reliably for twenty years or more.  The cost for consumables associated with preventive maintenance is relatively low.  For every furnace customer, VAC AERO provides comprehensive training in preventive maintenance and good operating practices.  This training should allow the customer to use in-house resources for many maintenance and repair activities.

More major maintenance expenses should be anticipated within every five to seven years of operation.  The mechanical vacuum pumps may require an overhaul and hot zone repairs may also be necessary. 

Summary

There is an array of decisions to be made when a business assesses the viability of establishing a new vacuum heat treating capability.  Innovations in furnace design such as hot zone materials, control packages and quenching systems can offer many operating and performance improvements, but will also affect the capital investment.  There can be significant costs beyond the price of the furnace equipment that also need to be understood.  From years of experience as both a heat treater and furnace manufacturer, VAC AERO can provide informed answers to cost/value questions affecting these complex business decisions.