Heat treaters know that the heart of a vacuum furnace system is the pumping system. As broad as the variety of furnaces is, so is the selection of pump types.
A roots blower, which also goes by the name “booster pump” and “intermediate stage vacuum pump,” is a dry, gas transfer pump that boosts the performance of the primary pump, providing an increase in pumping speed and pressure. This article from VAC AERO International’s Vacuum Pump Technology: Education and Training page provides an exhaustive analysis of the heart of a vacuum furnace system: the pump.
“Roots blowers have the reputation of being virtually indestructible and run for years seemingly unattended while the primary (mechanical) and high vacuum (diffusion pumps seem to receive all the attention. While they need little day-to-day maintenance, monitoring of the oil level in the pump is required. The main function of these booster pumps is to improve pump-down rates and ultimate vacuum levels.” ~ VAC AERO International
Vacuum furnace heat treaters know that one of the most critical parts of their system is the pump oil, but it may be a bit overwhelming trying to determine which is the right kind of oil is needed. Selecting the correct vacuum pump oil starts with knowing your pump.
“‘Oil’ is a bit of a misnomer because modern pump oil technology has evolved well beyond the original distilled petroleum products. There are now double- and triple-distilled oils available, as well as hydro-treated oils, low sulfur oils, silicone-based synthetic oils, and flushing oils used to clean the pump. Due to the wide variety of formulations available, these are often now referred to as pump ‘fluids’ rather than pump ‘oils’.” — VAC AERO International
“Different pump oil formulations are specifically designed for different pumps and different vacuum applications,” notes VAC AERO, and a key factor in learning how to select the correct pump oil is the understanding of vapor pressure, viscosity, and distillation methods, as well as solvent refining, hydrotreating, synthetic oil (Perfluoropolyether), flushing oil for vacuum pumps, and diffusion pump oils.
Relative Gas Supply Cost Notes: [a] Based on a minimum usage of 2830 cubic meters (100,000 cubic feet) per month. [b] All gases compared to nitrogen whose relative cost is unity. [c] Based on liquid supply.Heat treaters use a variety of gases with vacuum furnaces during the processing cycle in partial pressure operation, for backfilling to atmospheric pressure at the end of the processing cycle, and for cooling/quenching. In this article, VAC AERO describes the most common of these gases — (in order of frequency of use) nitrogen, argon, hydrogen and helium — as well as other common gases such as various hydrocarbons and ammonia (for vacuum carburizing/carbonitriding) and specialty gases such as neon (for certain electronics applications), and analyzes their uses and value in various vacuum heat treating processes. In addition, their relative cost per 100,000 cubic feet, the liquid properties and physical properties of common backfill gases, and the conversion between common pressure and vacuum units are explored.
Mr. William Jones, CEO of the Solar Atmosphere Group of Companies, listened with interest to the recent Heat Treat Radio podcast featuring Phoenix Heat Treating president, Peter Hushek. Peter introduced a new 3D TUS tool, Virtual Visual Surveys.
Below, Mr. Jones offers his comments about this new tool and TUS practices in general.
If you’d like to listen to the Heat Treat Radio episode that sparked these comments, click here.
Please note that immediately following Mr. Jones’ comments is a response from Peter Hushek.
Unedited comments from Mr. Bill Jones, CEO, Solar Atmospheres & Solar Manufacturing…
Like Peter Hushek we have been in this TUS business for more time than we like to remember. So, most up to date HT companies track our TUS data on paperless video recorders and down load onto an Excel spread sheet and plot out the data a minimum of every 30 seconds. This is done with a preprogrammed digital temperature controller thru the necessary ramps, soaks, and set points. The Excel spread sheets also contains all the survey and controller TC correction factors. Prior to the survey each data point contains the preset temperature controller PID parameters. All survey TC’s are set into their preset locations per AMS 2750E with careful notation to position and correct TC length and care for equal hot / cold lengths. Prior to survey each electronic instrument is checked with a calibrated thermocouple millivolt run-up box and each instrument calibrated. Normally midafternoon each furnace under test is set up thus and the survey to run preprogrammed overnight. Our QC department downloads the data, reviews and makes the pass fail decision, within a few hours, the next day. If the TUS failed back to maintenance to look into the issues, make corrections and rerun the TUS. Problems are not always furnace related but thermocouple, TC position, jack panel, jack panel wiring, instrumentation, and numerous other issues. I view the VVS 3D presentation as an aide but only part of the story”.
William R. Jones, CEO, FASM Solar Atmospheres Inc. Souderton, Pa.
And Peter Hushek’s unedited response to Mr. Jones’ comments…
In regards to the response from the listener I can say he makes some valid points. There are many issues that can affect the outcome of a TUS. We realize that the evaluation of the furnace uniformity involves many aspects and we are only addressing the data generated by the process. We believe that when companies begin the process of actual data analytics they will become more aware of the process and improve the quality of their processing as a result. VVS is only beginning to scratch the surface of the data flow that occurs daily in processing companies. We look to greater innovation through customer supplier interface as well and technological improvements that can be used as feed stock to improve future generations of this software. We are only starting the process and I hope the market realizes that this is not a static process or company.
If you haven’t done so already, clicking here to listen to the Heat Treat Radio episode being discussed above.
