B08 - Questions and Answers for Vacuum Furnace - AMD 0001.pdf

Vendor Questions for Vacuum Furnace – Sol. W519TC26QA184

Q1. 4.3.1 Why the metal hot zone and molybdenum heaters requirement? We’ve produced furnaces with metal hot zones in the past but we’re generally more specialized in graphite hot zones.

We do 17-4SS, 316SS, Ti64, IN718 routinely and expect to do critical components. So, we are leaning towards cleanliness and qualification risk if use graphite hot zones.

Q2. 4.3.2 Are we allowed to use graphite heating elements? Section 4.3.1 specifies “system shall include … molybdenum heating elements” but 4.3.2 immediately contradicts this and allows graphite as well. We’d prefer to use graphite but want to ensure that’s allowed.

We will change to “All metal hot zone”. No Graphite

Q3. 4.1.2 Work zone dimensions (18” x 24” x 18”) sounds reasonable. Is the “internal hearth” a retort contained within the work zone or does the inside of the hearth need to be 18”x24”x18” and thus the hot zone needs to be larger than that?

The 18” x 24” x 18” requirement is the usable internal work-zone size; the hearth is within that work zone.

Q4. 4.5.2 High-Vacuum system “a dedicated holding pump system capable of attaining an ultimate vacuum of less than 1.0 x 10^-5 Torr (0.01 microns) for high vacuum brazing and specialized processing” – 1.0 x 10^-5 Torr will be difficult to maintain at temperature. Is this requirement purely for a measurement at the start of a process (rate of rise check) or do we need to maintain 1.0 x 10^-5 Torr throughout?

The requirement is for demonstrated ultimate vacuum capability of less than 1.0 × 10⁻⁵ Torr with the furnace empty, clean, dry, and at ambient temperature. Continuous maintenance of this pressure at process temperature is not required.

Q5. 4.6.1 Gas quenching with nitrogen or argon seems reasonable. When it says, “injection nozzles distributed 360° around the perimeter of the hot zone”, how many nozzles do you need to meet that spec? Do two nozzles on opposite sides count or do you need a specific amount? Do the nozzles need to blow directly on the hearth, or can they add gas outside the insulation and allow it to diffuse in?

Basically, we are looking at uniform, high-severity cooling throughout the usable work zone.

The contractor may determine the number, location, size, and orientation of injection nozzles keeping these in mind.

Q6. For high cooling rates, we specifically have an accelerated cooling fan that can be mounted on the chamber to circulate gas around the water-cooled shell. Would this be of interest?

Yes

Q7. 4.6.3 Closed-Loop pumping station, What’s in the sealed tank of 500 gal capacity? We typically cool our chambers with a water-glycol mixture.

A water-glycol mixture is acceptable. The contractor shall provide the recommended coolant type and glycol concentration necessary to protect the system from freezing, corrosion, and biological growth while maintaining required cooling performance.

Q8. 4.6.5 External Evaporative Tower – do you have any on-site cooling already present? We prefer to give you the heat rejection capacity of the system and allow you to size the cooling plant accordingly. We can quote one, but it’s not our area of expertise. If there’s cooling capacity on site already, it may be possible to utilize existing capacity with our furnace.

No

Q9. 4.7.3 Power Output Optimization mentions individual heating zones (front, center, rear) to maintain temperature uniformity. Would a single zone be acceptable if temperature uniformity can be maintained? Do you anticipate running the zones at different temperatures or are they purely for adjustments to increase temperature uniformity?

A single heating zone may be acceptable if the contractor demonstrates, through temperature-uniformity testing, that the furnace meets the specified temperature-uniformity requirement across the full qualified temperature range and usable work zone.

Q10. 4.8.3 Temperature Uniformity Survey – We can include a TUS fixture rated for up to max operating temp (2400°F) conforming AMS 2750H specifications. What do the results of the TUS need to be in terms of uniformity and/or furnace class?

Class 2. +/-10F

Q11. 8.1.4 Maintenance Parts – We can create a list of critical spare parts, what stocking level do you need? 100% replacement or expected replacement needs per preventative maintenance cycle? What does “periodic replacement” mean in this context? If a part (such as a heating element) only needs to be replaced infrequently (ex: less than once per year), should that be included?

A list of critical spare parts would be great, replacement needs per preventative maintenance will suffice. If the part needs to be replaced infrequently, but is a specialized part or has a long lead-time please include it.

Q12. 3.2.11 Service access says “Components subject to periodic adjustment, replacement, or servicing shall be readily accessible. Meaning that experienced personnel can access the part after no more than 30-min of labor.” – We generally design our systems with maintenance in mind and try to make them convenient to adjust and fix. With that said, some components (say the heater or insulation package) take more than 30 minutes to replace but are replaced infrequently. How should we interpret “periodic” in this context?

Components that are replaced or adjusted for preventative maintenance or daily from normal wear and tear shall be readily accessible within 30-min.

Q13. 3.2.8.2 says “approximately 80psi compressed air … does not include filters, dryers”, how much flexibility do you have with that pressure? Our systems typically require 90 psig of clean compressed air. We can investigate using lower pressure for air actuated equipment, but 90 psi is preferred.

Yes, we can provide 90 psi

Q14. What are the inside working area dimensions?

18” wide * 24” deep * 18” deep

Q15. Max Vacuum you would like to achieve?

Maximum vacuum capability is an ultimate vacuum of less than 1.0 × 10⁻⁵ Torr (0.01 microns), demonstrated with the furnace empty, clean, dry, and at ambient temperature using the high-vacuum system. Continuous maintenance of this pressure at process temperature is not required.

Q16. Max Temperature you would like to achieve?

2400F

Q17. Would a VRT be acceptable in lieu of SCR? SCR is not standard for vacuum furnaces.

SCR power supply is what is required per the scope.

Q18. Do you require a condenser trap to capture any wax or solvents for the parts? If so, what is the material, density, and amount per load?

No condenser traps are required.