RESPONSE_TO_BIDDER_QUESTIONS_6-14-18.docx

80KSC018R0016

QUESTION & ANSWERS 6/14/19

RESPONSE TO BIDDER QUESTIONS:

1. REFERENCE: Section 43 42 41.99 par. 2.1.3.7 QUESTION: Please confirm that unit “microns” in spec section 43 42 41.99 par. 2.1.3.7 refers to micronHg (mercury). The thermal conductivity of insulation material depends on the level of vacuum in the evacuated state and the mean temperature of the service. Is it permissible to use a thermal conductivity of 1.1 mW/m-K for the 3M K1 glass bubbles (microspheres) at 50 millitorr evacuated condition for liquid hydrogen? (Note that similar thermal conductivity was observed at 50 millitorr for liquid nitrogen service which has a higher mean temperature than liquid hydrogen service. Thermal conductivity reduces as the mean temperature of the service reduces).

ANSWER: Micron in Subpart 2.1.3.7 refers to micrometer of Hg. A thermal conductivity for the 3M K1 Glass Bubbles is not specified at the evacuated condition and operational temperature. It would be expected to be calculated, or assumed with the basis technically substantiated, by the contractor as part of the delegated engineering, then submitted to NASA for review and approval as required by the specification. 3M indicates thermal conductivity of 0.047 W/m-K at standard atmospheric pressure and 70 deg F, which corresponds to 47 mW/m-K at those conditions, approximately equal to the 0.3467 BTU inch/(hr*square foot*deg.F) noted in Specification 79K40362 Section 43 42 41.99 Subpart 2.2.5.1.

1. REFERENCE: RESPONSE_TO_BIDDER_QUESTIONS_5-30-18.docx, Question 3 Response, Specification 79K40362 Section 43 42 41.99 Para 2.1.3.1a.

QUESTION: In response to Item 3 from customer document 80KSC018R0016, we are including a 1/16” corrosion allowance on the outside of the outer sphere. No corrosion allowance is included for the inside of the outer sphere, and no additional corrosion allowance is included for the outer sphere plates that have attachments to the inside surface. No additional corrosion allowance is being included for the attachments made to the outside of the outer sphere plates. Reinforcement for attachments will be provided as required by the ASME VIII Code. Please advise if the above assumptions are accurate.

ANSWER: NASA's response to Question 3 in "RESPONSE_TO_BIDDER_QUESTIONS_5-30-18.docx" clarified that the 1/16" corrosion allowance is for metal thickness comprising the outer sphere shell plates. A corrosion allowance applies to the overall wall thickness of the applicable metal regardless of where the corrosion would occur (interior or exterior). That said, no corrosion is expected on the interior side of outer shell plate in the evacuated space, and by extension, no corrosion is expected for attachments on the interior side of the outer shell plate in the evacuated space. Question 3 in "RESPONSE_TO_BIDDER_QUESTIONS_5-30-18.docx" did not ask for clarification of corrosion allowance for attachments on the exterior of the outer sphere. Specification 79K40362 Section 43 42 41.99 Para 2.1.3.1a requires 1/8" corrosion allowance at locations of attachments. To clarify, that 1/8” corrosion allowance is applied to the materials used to make the attachment (reinforcement plate, thermal barrier, etc.) on the exterior of the outer sphere where the corrosion would be expected to occur, and not the shell plate. Reinforcement areas and thickness shall be per ASME BPVC Section VIII, except where specified as larger, such as the area of the reinforcement for the non-vacuum-jacketed pipe penetrations.

1. REFERENCE: Spec 43 99 99, Section 3.1.5 QUESTION: Please confirm:

A - Due to the source strength a (130 curie) will be used for the Sphere X-Ray on site.

B - The contractor will be allowed to shoot all x rays on second shift.

ANSWER: During construction, a Request for Extended Work Hours can be submitted to the Contracting Officer and Contracting Officer's Representative for approval for each period of work (for example, a week of dates) to be performed outside the work period contractually defined as needed by the contractor. A form will be provided to the contractor to complete and submit. It is requested the form is submitted at least five (5) working days ahead of the first date cited in the request for coordination with other activities at LC 39B as the need date for extended work hours approaches. Late requests can be accommodated in some instances, but are more likely to be rejected.