We at G-M feel that this question is best answered using real testimonials from our customers around the world:

G-M Enterprises build “Furnaces that Really Work”, we believe that “Anything Is Possible” you just need some ingenuity and imagination. Our team is built with the understanding that we must “Simply Be Outstanding.”” Hey don’t believe us just yet, want to make a bet, then ask American Brazing President Richard Penrose. We are simply outstanding and our furnaces Really work. See some customer testimonials below. G-M Enterprises, because we care and we want to get you up and running with less hassle and maintenance on your part. “Thinking ROI, Thinking Quality, Then Think G-M Enterprises”.


External vs. Internal Cooling Comparison


It is a perception that an internal quench would take less floor space for internal quench vs. external quench. However, over-all floor space is a push. Internal quench would take more length for the following reasons:

Internal – The vacuum vessel is longer due to the rear mounted heat exchanger, fan and motor assembly. Additionally behind the furnace about additional 36” is required for the removal and/or maintenance of the fan and motor assembly.

External – As compared external quench assemblies would take up more width. The furnace will be able to be place up against the back wall. Additionally external quench assemblies can be configured to take up even less width by installing the blower can in the air at 10:30 or 1:30 on the clock.


Internal – In internal quench the heat exchanger is located in the rear of the furnace between the hot zone and the fan assembly. It is difficult to service the heat exchanger in the event there are leaks.

External – In the external quench the heat exchanger is located outside of the main furnace for easier maintenance and service. In external quench assemblies the large heat exchanger is utilized to handle the heat load effectively, whereas, smaller heat exchangers are used in internal quenches due to limited space.


Rear mounted fan and motor assemblies for internal quench units generally see higher gas temperatures resulting in frequent motor problems as well as the fan going out of balance. This requires higher maintenance whereas in external quench the fan and motor assembly are remotely mounted hence they are exposed to much lower gas temperatures.


Under external Cooling Blower arrangement, a Post Cooler is installed prior to gas entry into the plenum. Due to Post Cooler arrangement the returned cold gas is below 100oF. Whereas without the Post Cooler the return Gas will be over 120oF. This provides a benefit in cooling towards the lower range for External Blower as compared to Internal Cooling Blower.


The volume for External Cooling Blower is about 12% to 15% more than Internal Cooling Blower arrangement. Therefore; initial backfill would require about 12% to 15% more cooling gas; however, more molecules of the gas would help in removing additional BTUs faster than in Internal Cooling Blower Arrangement. Therefore, higher cooling gas volume and post cooler accounts for faster cooling time for External Cooling Blower arrangement.


External quench systems will produce 10 to 15% faster quenches as compared to the internal quench due to effective gas flow, larger heat exchanger and post cooler. External quench is easy to service and maintain as compared to the internal.


G-M has the full expertise in providing either design – External Cooling Blower or Internal Cooling Blower. Internal Cooling Blower arrangement may require more maintenance than External Cooling Blower and motor may require frequent maintenance as it will be exposed to higher temperature in Internal Cooling Blower vs. External Cooling Blower.


G-M has a complete checklist for possible considerations to ensure furnace effectiveness and efficiency. This results in limiting future operational halts, any maintenance issues, designing of the right furnace, and get the best ROI.

Request a copy of our Guide to the Selection of Vacuum Furnaces by clicking on the link below.