Answers to Questions.pdf

1. The SOW refers to photographs of the existing APPS and fill station, including “Photo 1” and “Photo 2,” but the provided PDF does not contain the photographs. Please provide the missing images. – This has been added.

2. Will NIST conduct a pre-quote site visit, or may offerors request one? – no site visit will be available.

3. Please provide the existing equipment manufacturer/model, dimensions, connection sizes, pipe specifications, valve types, inlet/outlet orientation, working pressures, relief settings, and available electrical service.

(a) APPS Unit: The current APPS unit is an Adjustable Pressure Phase Separator made by Chart Industries. Per the manufacturer, the connecting supply piping at the inlet is 1/2” male 45 degrees flare fitting. Per the manufacturer, the outlet fitting is a 1” MVE female bayonet that should be connected to a vacuum insulated pipe system. The working pressure at the inlet is typically between 120 psi and 135 psi. The outlet pressure is typically between 20 psi and 30 psi. There is a 150 psi relief valve on the outlet plumbing and a 235 psi relief valve on the inlet. The electrical connection is 120 VAC / 60 Hz and is hard-wired to a supply box about 1.5 meters from the APPS unit.

(b) Fill Station: The current fill station is a Lo-Loss Liquid Cylinder Filling System made by Chart Industries. The part number on the system label is 11203508. The standard inlet/outlet piping configuration provided by the vendor is shown below (This is NOT a photograph of our installation). The inlet connection (labeled C-1 in the figure) on our unit has been fitted with a threaded connector that is supplied by an insulated, semi-flexible line (Chart P/N 20570303). The working pressure at both the inlet and outlet is generally set by the output of the APPS unit and is typically between 20 psi and 30 psi. There is a 350 psi relief valve on the curved stem near outlet C-3. (The dewars that we fill at this station generally have their own 22 psi relief valves.) There are two 120 VAC/60 Hz outlets located less than 0.5 m from the station at a height of about 2 m. This part is designed to work with an optional scale (see answer 4 below).

4. What method of full-dewar detection is currently used or preferred—temperature sensing in the vent stream, conductivity, weight, differential pressure, or another method?

When the current fill station was originally installed circa 2011, it was configured to detect a full dewar based on weight. However, that system failed within one year after it was commissioned, which was attributed to fragility of the weight monitoring system after exposure to year-round outdoor operation.

The statement of work does not prescribe a specific implementation (see CLIN 0002, requirement 10: “The Fill Station shall include a mechanism for sensing when the dewar is full and automatically terminating the fill.”) Based on NIST’s past experience described above with the original weight detection scheme, the government’s evaluation of the contractor’s Technical Approach may consider the durability and reliability of the solution in an outdoor environment (see CLIN 0002, requirement 4: “The Fill Station be compatible with yearlong outdoor operation at NIST’s site in Boulder, Colorado”). As stated in the statement of work, one of the goals of this procurement is to reduce the need for “frequent maintenance and repair by staff,” so technical approaches that require less maintenance and repair may provide additional value to the government.

5. Must the automatic fill system include emergency-stop controls, alarms, timeout protection, data logging, remote monitoring, or oxygen-deficiency-monitor integration?

Per CLIN 0002, requirement 12: “The new, installed Fill Station shall meet all relevant OSHA safety standards for liquid nitrogen transfer, including standards related to pressure relief, ventilation, interlocks, and labeling.” To the best of our understanding and knowledge, OSHA standards do not explicitly require any of the features listed in this question. (Though some of these features may be interpreted to support compliance with the OSHA general duty clause.) That said, additional safety features like emergency stop controls, alarms, timeout protection, remote monitoring, and data logging may provide additional value to the government. Given the outdoor, highly-ventilated environment, oxygen-deficiency-monitoring is not required.

6. Who is responsible for electrical modifications, wall penetrations, mounting reinforcement, concrete work, permits, inspections, and isolation/draining of the existing LN2 system?

The government will isolate and drain the LN2 system per its established safe operating procedure. Minor electrical and other minor utility work (e.g. re-locating an outlet, running conduit, clean up of debris in the vicinity of the system) can be performed by the government in preparation for the installation. Also, in preparation for installation NIST can lock out the breaker for the relevant circuits, as well as disconnect and re-connect those circuits as needed. The contractor is responsible for the other activities listed in this question.

As a note, the government has envisioned only minor mechanical modifications (e.g. drilling new bolt holes, augmenting mounting systems, etc) as part of this work. In particular, for the APPS unit (CLIN 0001), we envisioned that the new unit might have a different bolt arrangement, which would then require minor concrete work, but no other major modifications. If, based on the contractor’s expertise and experience, more substantial modifications may be required, then it would be beneficial for the contractor to explain in their bid why such modifications are necessary. This will help in our evaluation of how the contractor’s proposed approach may benefit the government.

7. Can installation require a full system shutdown, and what shutdown duration is permissible?

The liquid delivery system can be fully shutdown for installation, provided that the duration of each shutdown does not exceed 48 hours. Ideally, no more than two shutdowns (one for APPS, one for fill station) will be required. Note that the time required for isolation and draining (2 to 3 hours) will count toward those 48 hours. Also note that a different, isolatable branch of the system delivers nitrogen gas (boiled off from the main liquid tank) and that gas delivery system should remain operational during installation.