Responses to questions.pdf

Answers to Questions Solicitation 1333ND25QNB680246

1. Chamber Dimensions Q. The CAD drawing indicates an internal chamber height of 51 mm. Could you please confirm this dimension?

Answer. There is a typo in the drawing. All dimensions are in inches. (I can provide an updated drawing, but not by Friday). The height of the keep-out region is 51”.

2. Material Specification Q. The CSS refers to stainless steel construction but does not fill in the “MATERIAL:” field on the drawing. Can you confirm that all metal components must be fabricated from 304 stainless steel, 18 ga?

Answer. There is not a material specification in the requirements document. The contractor can choose many materials for the oven enclosure (and will need to, since insulation and heaters are typically not fabricated from stainless steel)

3. Temperature Ramp Control Q. What level of PID control does NIST expect for the temperature ramp profile up to 135 °C? Is a local user interface required to program and adjust ramp rates and set-points in the field?

Answer. Yes, we expect a local user interface. Ramp rates should be 0.1 C per minute to 1 C per minute as specified in the requirements document.

4. Valve Port Sizes and Locations Q. Please provide the exact diameters and coordinates (relative to the chamber datum) for the pneumatic valve ports.

Answer. The dimensions and locations of the valves can be measured in the supplied .step file (let me know if this did not go out with the solicitation and I can send it, it should be provided to all vendors). The part of the actuator that must be outside the enclosure is the cylindrical drum (gray cylinders in figures and drawings, circled in red in Figure 2). I can also supply the CAD in other formats if that is preferable, but that will have to wait until Monday. Similarly, I can provide a drawing with more dimensions, but not before Monday.

5. Actuator Mounting Holes Q. Where should the actuator mounting holes be located? We need center-to-center distances and any positional tolerances.

Answer. The dimensions and locations of the holes can be found using the supplied .step file (see comments in 4. above). The holes must be large enough to allow the pneumatics to be installed and removed with the heater enclosure installed as specified in the requirements document, but thermal leaks need to be minimized. One way this could be accomplished is with a large diameter hole that is filled in with flexible, removable insulation. 0.05” clearance on each side of the pneumatic valve cross section should be sufficient for installation and removal.

6. Scope of Pneumatic Valves & Temperature Sensing Q. Please confirm that procurement of the pneumatic valves themselves is outside the scope of this RFP.

Answer. Yes, pneumatic valve procurement is outside scope. (Note: the chamber and table have already been constructed and installed, this procurement is only for the heater enclosure) Q. At which point on the exterior of the UHV chamber should the 135 °C temperature be measured? What measurement tolerance will NIST accept for this reading?

Answer. resolution of 0.1 C or better is sufficient, accuracy better than 2 C (thermocouple accuracy) is needed. An RTD or K-type thermocouple could be used for temperature control. The K-type overtemperature protection thermocouple will be attached to the large flange that roughly divides the chamber in half vertically (the DN350CF flange). The thermocouple or RTD controlling the temperature PID controller should measure the air temperature within the enclosure (that is to say, the temperature sensitive point of the RTD should not be in direct thermal contact with the chamber or enclosure).