Questions and Responses.docx

Questions Submitted by Industry:

1. What is the design intent of the PLC? My understanding is the heating system works on a feedback loop of tank shell temperature. Does the government intend to control/monitor the system remotely?

The system is spread out over a large distance and PLC indications are necessary to quickly identify failures and automate protective actions for sensitive equipment. It is essential to provide some indication of the operating condition, whether a discrete digital signal from the controller or a current measurement from the breaker or other. It is essential that the PLC receives a status signal from the controller. It is preferred but not essential to be able to control the heaters directly from the system PLC.

A terminal box that routes to the system PLC is being installed just inside the building for another project. Ten spare 4-20 mA transmission cables have been reserved for the thermal blanket.

1. Can the government provide details/locations/distances to existing power sources in the NCNR and available panel spaces?

Several 1ϕ and 3ϕ power sources are available in the adjacent laboratory room, which is comparable to an industrial work area. The tank is located 6 ft outside wall and the room is about 100 ft x 100 ft. Depending on the type and load, a rough estimate for the length of conduit needed is approximately 50 ft.

1. Can the government clarify the basis for selection of an R30 insulation? Depending on insulation material, this can be 10” of typical fiberglass (not standard) and may impeded future rework. With 3” of fiberglass (R=9), we expect a maximum heat demand of 1.8KW on the coldest days to maintain 100F.

NCNR will remove the R30 requirement. NIST expect that R9, 1.8 kW would be a competitive design. Note that 100 F is a maximum temperature selected in anticipation of 100 F summer days with no cooling and minimal solar absorption. The constraining parameter is actually ΔT < 30 F.

1. Are there any requirements for labor wages when on NIST property such as Davis-Bacon/ prevailing wages?

No

1. Is solar reflective foam sufficient for a solar reflector?

The solar emissivity in SOW section B is intended to mitigate radiative heating of stainless steel in full sunlight. There are no specific material requirements.

1. What is the total warranty period you're looking for?

1 year from completion.

This amendment changes the Statement of Work, section III, Scope, from two years to one year to be consistent with Statement of Work, section, XI, Warranty.

1. "The heating system must incorporate three parallel elements that can be controlled independently for efficiency and redundancy." Is this correct?

NIST will accept any system in which one element can fail in winter and the system continues to operate within the specified 30 F band without operator intervention. Independent automation of each heating element via the existing system PLC is not essential.

1. Supply an equation, pseudo-code, or PID settings that describe a control scheme for the elements based on measured outdoor temperature."

I'm not sure what you're asking for here. Can it be explained?

The measured outdoor temperature in Gaithersburg, MD varies both with daily weather and seasonal effects. The controller for the heaters must be able to turn them off and on automatically without operator intervention and continue to control within the established band during a loss of a single heater. It is acceptable for the contractor to supply their own controller that meets these requirements, or to use the existing PLC system.

In either case, it is anticipated that the control system will utilize variable settings based on outdoor temperature and the delay time of the heaters that could conceivably break or be lost. After the 1-year warranty period, NCNR will be responsible for any repairs. Contractor must provide sufficient detail for a future technician to be able to troubleshoot failed components and restore or replace the system quickly.

1. What does "a 4-week live demonstration" look like? Do we need someone on site for four weeks?

The “4-week live demonstration” requirement is hereby removed from the Statement of Work and replaced with the following:

Contractor shall perform and document a live test of the system to verify the R-rating and that the system will meet the design requirements using the installed heaters and temperature sensors. This shall take place at the Gaithersburg, MD campus on a mutually agreed upon date and time, in accordance with the COVID guidelines in effect at NIST.

1. Can we take exception to the following: 1) Conceptual design documents and drawings, 2) Preliminary design documents and drawings and 3) A thermal analysis report?

NCNR staff must be able to review the design and coordinate changes based on the specific needs of the experiment, monitoring signals for the PLC, etc, prior to installation.

Because the blanket is expected to be installed in spring or summer time, a thermal analysis report that proves by extrapolation that the system will be capable of operating in band, 365 days per year, is essential.

Therefore, the exceptions are not granted. The exceptions would prohibit the technical evaluator from being able to adequately analyze the product(s) being offered.

1. What is the scope of thermal blanket insulation? Does it include the piped manifold at right of pictures (inside metal housing)?

Modest insulation shall cover the outside of the metal box while ensuring it remains accessible to workers for non-routine maintenance. See SOW item A.vi. A heater is not required for the box. Exposed piping is beyond the scope of this work.

1. The solicitation specifies: “The heating system must incorporate three parallel elements that can be controlled independently for efficiency and redundancy.” Can NIST clarify the intent of this statement, specifically is NIST requesting 3ea. 100% redundant heating elements or 3 heating circuits with 33% capacity, arranged in a lead/lag/lag configuration. Given current control systems, installation size, warranties, and limited power draw industry-best practices is to provide two circuits each capable of providing 100% of the required capacity

RESPONSE: Any system that enables the tank to stay in the operating band in winter during a failure of a single element is acceptable.