Low Frost-Point Generator (LFPG) External Temperature-Control System (ETCS)

The National Institute of Standards & Technology (NIST) seeks information on commercial vendors that are capable of providing a Low Frost-Point Generator (LFPG) External Temperature-Control System (ETCS). The NIST LFPG is our nation's primary humidity generation standard for trace humidity. The humidity generator currently produces humid nitrogen streams by flowing dry nitrogen over ice maintained at a constant temperature between -100 - C and 0 - C. This humidification process occurs within a cylindrical copper saturator, maintained in vacuum in order that heat from the laboratory environment does not unduly impose temperature gradients on the ice. The temperature of the saturator, and the ice contained within, is adjusted and maintained by pumping heat between the saturator and adjacent disc-shaped copper heat reservoirs (one each located at the flat top and bottom surfaces of the saturator) using Peltier heat pumps. The temperature of the heat reservoirs is currently adjusted by expanding a mixture of liquefied ethylene and propane within the reservoirs. The refrigeration system supplying this mixture has reached the end of its service life and must be replaced. In addition, industrial need for enhanced trace humidity standards compels NIST to decrease the lowest operating temperature to -120 - C. Because of the increased temperature range and difficulty of expanding refrigerants inside the heat reservoirs over a wide temperature range, NIST anticipates that the new system will contain more than one refrigeration subsystem, and will transfer heat to the LFPG heat reservoirs through recirculation of cryogenic heat transfer fluids. After results of this market research are obtained and analyzed and specifications are developed for a LFPG ETCS that can meet NIST's minimum requirements, NIST may conduct a competitive procurement and subsequently award a Purchase Order. If at least two qualified small businesses are identified during this market research stage, then any competitive procurement that resulted would be conducted as a small business set-aside. The following outline the performance requirements for the LFPG ETCS: 1. Operating temperature range - The ETCS shall be capable of operating continuously at any setpoint temperature between 0 - C and -120 - C. The ETCS shall also be capable of repeatedly operating between + 25 - C and 0 - C on startup, without damage to the ETCS. The LFPG does not normally operate at temperatures above the ice point, but must operate in the startup range for several hours when each time LFPG operation commences. 2. Temperature Stability - The temperature stability of the ETCS shall be less than - 0.1 - C, as measured in the heat transfer fluid at the inlet to the LFPG vacuum chamber. 3. Heat transfer fluid - The ETCS shall transfer heat to / from the LFPG using a cryogenic heat transfer fluid (HTF), with an appropriate specific heat and volumetric flow rate to meet the slewing rate specification in 4. 4. Slewing Rate - The ETCS shall change the temperature setpoint at a minimum slew rate of 1 - C per minute, in both cooling and heating directions, as measured within the copper saturator of the LFPG. The minimum slew rate applies throughout the entire temperature range specified in 1 and 2. For the purposes of calculating slew rate and determining relevant component sizes, the ETCS will be cooling / heating approximately 68 kg of OFHC copper (the LFPG saturator), housed within a vacuum chamber. Two parallel passageways, approximately 150 inches in length, with square cross-section (3/8 inch per side) are located at the top and bottom of the cylindrical copper mass, for the purpose of effecting heat exchange between the HTF and the copper. The estimated heat leakage from the lab environment to the copper through the chamber wall is approximately 20W at -100 - C. The estimated heat loading on the saturator from a secondary control system consisting of peltier heat pumps is 50W. Proper component sizing shall include sufficient factor of safety to insure successful attainment of item 11. 5. Heat transfer loop plumbing scheme - The following specifications for the HTF flow loop shall be met: a) The HTF flow loop shall be constructed from double-walled, stainless-steel, evacuated tubing designed for pumping cryogenic fluids. b) The HTF shall include connection fittings compatible with the existing bulkhead fittings on the LFPG vacuum chamber. These are metal face-sealed fittings, such as Swagelok VCR. c) No in-line shutoff or throttling valves are permissible within the HTF loop. d) The circulation pump shall be designed for cryogenic service. e) The pump motor shall be replaceable without removing the pump from the HTF flow loop. f) The HTF flow loop shall be closed and under sufficient pressure to prevent pump cavitation at high temperatures. g) The HTF flow loop shall include a header tank designed to accommodate thermal expansion of the cryogenic fluid over the temperature range specified in 1 and 2. h) The HTF flow loop will contain provisions for safe and complete recovery of the cryogenic fluid in the event that the flow loop must be opened for service. 6. Refrigeration scheme- Electro-mechanical refrigeration systems for cooling the HTF are envisioned within the ETCS. Multiple refrigeration systems optimized for different subsets of the operating temperature range are permissible. Cryogenic assist is permissible at low temperatures. In the event that multiple systems are employed, any cascading or switching between systems shall be performed automatically, without the need for human intervention. Chilled water is available for removing heat from refrigerants after compression. 7. Working voltage - Available line voltage is 120V, 208 V single phase, and 208 V 3-phase. 8. Heating scheme - electric heaters are envisioned for raising the temperature of the HTF. These heaters may be used for fine-temperature tuning / control of the HTF. The use of heaters within the ETCS shall be fully automatic, requiring no human intervention. 9. System configuration and layout - The ECTS is intended for use in a laboratory environment. While parts of the ECTS may be shielded or closed for various reasons, enclosure from an aesthetics point of view is not necessary. It is more important that items be located in optimal positions for proper heat transfer, drainage of liquids, separation of oil from refrigerants, serviceability, etc. System layout and configuration shall be compatible with existing laboratory space. 10. Human Machine Interface and system control - The ECTS shall be controlled via LabView-driven FPGA. There shall be an included touch-screen display for input of necessary operational commands and display of salient data, such as setpoint and process temperature. The control system shall include connections for an external computer, such that changes to the control system may be easily accomplished. LabView drivers must be furnished by the contractor. 11. Installation and testing - Manufacturer shall install and test the ETCS, with assistance from NIST personnel. 12. Training - Manufacturer shall train NIST personnel in use of the ETCS. 13. Documentation - The ETCS shall be sufficiently documented such that NIST personnel are capable of changing control parameters as needed to fine-tune the system, and so that NIST personnel may service the system, where possible. 14. Alternative Technical Approaches - While we envision the use of more than one refrigeration system acting on a single recirculation system, we are open to other approaches, provided that they can be sufficiently justified on a technical basis. NIST is seeking responses from all responsible sources, including large, foreign, and small businesses. Small businesses are defined under the associated NAICS code for this effort, 334516, as those domestic sources having 500 employees or less. Please include your company's size classification in any response to this notice. Companies that manufacture such equipment are requested to email a detailed report describing their abilities to judy.pace@nist.gov no later than the response date for this sources sought notice. The report should include achievable specifications and any other information relevant to your product or capabilities. Also, the following information is requested to be provided as part of the response to this sources sought notice: 1. Name of the company that manufactures the system components for which specifications are provided. 2. Name of company(ies) that are authorized to sell the system components, their addresses, and a point of contact for the company (name, phone number, fax number and email address). 3. Indication of number of days, after receipt of order that is typical for delivery of such systems. 4. Indication of whether each instrument for which specifications are sent to judy.pace@nist.gov are currently on one or more GSA Federal Supply Schedule contracts and, if so, the GSA FSS contract number(s). 5. Any other relevant information that is not listed above which the Government should consider in developing its minimum specifications and finalizing its market research.