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TOC Search:
, 2024
- ASHRAE Online Bookstore
- Addenda
- Errata
- Return to Previous Page
- ANSI/ASHRAE Standard 172-2024 [Go to Page]
- Contents
- Foreword
- 1. Purpose
- 2. Scope
- 3. Definitions
- 4. Safety [Go to Page]
- 4.1 Introduction. There are inherent hazards when handling sealed glass or metal vessels and the materials being tested. At times, the absolute pressure inside the tube is in excess of 6000 kPa (870 psia). It is not unusual for a sealed glass tube to...
- 4.2 Safety Shield. The operator shall stand behind a large safety shield made of safety glass or plastic whenever examining a vessel that may be under pressure. This safety shield shall protect the operator’s head, face, and body.
- 4.3 Personal Protective Equipment. Personal protective equipment (PPE) shall include a face shield, heavy cloth lab coat, and heavy gloves (see Figure 1). A neck protector is optionally added to the mandatory PPE. The face shield shall extend down to...
- 4.4 Handling Flammable Solvents. Solvents used in this method are highly flammable. Provide adequate ventilation; wear proper gloves (e.g., neoprene, nitrile); and avoid sparks, flame, or heat. Know the location of the nearest fire extinguisher and t...
- 4.5 Charging Manifold. Safeguards must be taken to avoid excessive pressure on the glass system that could cause a rupture while using the charging manifold. Even with these safeguards in the design and use of the equipment, the operator shall wear a...
- 4.6 Eye Protection from High-Temperature Flame. While sealing a glass tube with an oxygen-gas torch, protect the eyes from the yellow flare in the gas flame by using dark glasses (e.g., didymium).
- 4.7 Refrigerant Handling. Several safety considerations are required for handling refrigerants under pressure. The operator shall be thoroughly familiar with the information about the environmental impact of refrigerants 5 and RSES Service Applicatio...
- 4.8 Handling Liquid Nitrogen or Other Nonflammable Low-Temperature Cooling Solutions. Nonflammable low-temperature cooling solutions in a Dewar flask are used for cooling the sealed glass tube to load it with refrigerant and for a subsequent analysis...
- 4.9 Compatibility of Materials. All materials of construction used in the test apparatus that come in contact with the test materials must exhibit sufficient compatibility to prevent rupture or general failure of the equipment.
- 5. Apparatus [Go to Page]
- 5.1 Sealed Glass Tubes or Metal Test Cells
- 5.2 Charging Manifold. The charging manifold is illustrated in Figure 3. This apparatus consists of a manifold (metal or glass), vacuum pump, pressure gage, high-vacuum gage, refrigerant cylinder, valves, and filling ports. The function of this appar...
- 5.3 Temperature Controlled Bath. A cooling bath is required to achieve the necessary temperature control and must be large enough for testing three sample tubes at one time. The bath is constructed of a reservoir filled with alcohol, glycol, or aceto...
- 5.4 Temperature Measuring Devices. The temperature is measured with a calibrated temperature device with accuracy ±1°C (±1°F). Suitable devices are type K, type T, type J, platinum resistance thermometers, or alcohol thermometers. Digital thermoc...
- 5.5 Graph Paper. Graph paper is used with a glass plate as a background to judge the cloudiness of the test sample. The graph shall have a minimum of 20 lines per 1.0 in. (25.4 mm).
- 5.6 Mechanical Vacuum Pump. A mechanical vacuum pump that provides an absolute pressure of 13 Pa (100 mTorr) shall be used.
- 6. Test Material Specification and Their Preparation for Use [Go to Page]
- 6.1 Glass Tube Cleanliness and Inspection. The tubes must be scrupulously clean. The tubes shall be stored in a sealed container so that they do not collect contaminants. Prior to use, the tubes shall be cleaned to remove all contaminants. After form...
- 6.2 Alternate—Metal Test Cell Cleanliness and Inspection. The metal test cell must be scrupulously clean and dry. The test cell should be free of any residues and the windows clean. The cell shall be dried by placing on the charging manifold and pu...
- 6.3 Refrigerant Purity and Supply Cylinder Requirements. The refrigerant used shall be of known purity, meeting specifications of AHRI Standard 700 9. Refrigerant transfer cylinders shall be fitted with a pressure relief device and an adjustable need...
- 6.4 Lubricant. The refrigeration lubricant shall be isolated from atmospheric moisture and light. The moisture content shall be measured by ASTM D 1533 10 or ASTM D 6304 11, and the value shall be noted in the final report.
- 7. Procedure [Go to Page]
- 7.1 Charging Lubricant to Glass Tubes. Load a syringe possessing a needle narrow enough to fit into the top of the glass tube with lubricant to be used in the test. Insert the needle into the top of the glass tube and inject the desired amount of lub...
- 7.2 Forming Capillary in Glass Tube. Remove the sample tubes from the desiccator, remove the stopper or cap, and place a 30 mm (1.2 in.) length of rubber or PVC tubing over the open end of the tube so that 15 mm (0.6 in.) of the sample tube is covere...
- 7.3 Charging Lubricant to a Metal Test Cell. The procedure is very similar to that used for charging lubricant to a glass sample tube.
- 7.4 Preparing the Manifold and the Refrigerant Tube Loading Apparatus for Use. The interior of this apparatus shall be clean, dry, and thoroughly leak tested. A proper leak-free system shall be capable of being evacuated to a pressure of 2.0 Pa (15 m...
- 7.5 Charging Refrigerant to the Glass Tubes
- 7.6 Charging Refrigerant to the Metal Test Cell
- 7.7 Flame Sealing the Glass Tubes
- 7.8 Alternative Glass Tube Flame Sealing Method
- 7.9 Unused Refrigerant Recovery and Securing the Charging Manifold
- 7.10 Inspection of Tubes. After the sealed tubes have been stored in the protective pipes or heating block overnight at ambient temperature, carefully remove each tube for inspection (see Section 4, “Safety”). Wipe each tube with a tissue and ins...
- 7.11 Measurement of the Precipitation Temperature
- 7.12 Disposal of Sealed Glass Tubes. For disposal of sealed glass tubes, place the tube in a Dewar containing liquid nitrogen until frozen. Tubes are removed one at a time and scored with a file, and the tops are then snapped off. The tubes without a...
- 8. Significance of Results
- 9. References
- Informative Appendix A [Go to Page]
- A1. Example: Calculation of Refrigerant Pressure in Sealed Tubes Containing Oil and 1 Gram Refrigerant
- A2. Calibration of Manifold Volume [Go to Page]
- A2.1 Measure and record the weight of a prenecked glass tube as M1 and connect to the manifold at port valve 6.
- A2.2 Evacuate the manifold, including the ballast and tube, to 13 Pa (100 mTorr) or less. Close isolation valve 3 between the refrigerant trap and the manifold.
- A2.3 Open three-way valve 7 to the refrigerant supply cylinder and allow a refrigerant to expand into the manifold (do not exceed atmospheric pressure). Close three-way valve 7, disconnecting the refrigerant supply. Measure and record the pressure in...
- A2.4 Cool the bottom of the prenecked glass tube in liquid nitrogen. Open port valve 6 and allow a portion of refrigerant to condense and freeze inside of a tube to a designated pressure, P2, (typically around 30 kPa [228 torr]). Close port valve 6 a...
- A2.5 Seal the tube and remove the stub end from the manifold.
- A2.6 Measure and record the weight of the sealed glass tube, including the stub end, as M2.
- A2.7 The mass of refrigerant, Mrefrigerant, is the difference between M2 and M1.
- A2.8 Determine the density of the vapor refrigerant at P1 and P2 and record as r1 and r2 (Ideal Gas Law, equation of state, etc., where T and P are known). Estimate the internal volume of the manifold, Vmanifold, and calculate the initial and final m...
- A2.9 Additional tube sealing iterations may be required to improve the confidence level.
- A3. Calculation for Refrigerant Charging by Change in Manifold Pressure [Go to Page]
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