ASHRAE Standard Project Committee 97—1999
`Sealed Glass Tube Method to Test the Chemical Stability of Materials
`for Use Within Refrigerant Systems
`SPLS Liaison: Thomas E. Watson
`
`Robert G. Doerr*, Chairman
`Jay Field, Secretary
`Warren R. Clough*
`Lois L. Lin*
`Thomas R. Rajewski*
`Shelvin Rosen*
`
`Andrew Swallow*
`Henry Balduzzi
`Tom Leck
`Cheri Wellman
`Robert W. Yost
`
`* Denotes members of voting status when the document was approved for publication
`TC—3.2 Refrigerant System Chemistry
`
`ASHRAE STANDARDS COMMITTEE January 1999
`
`Michael R. Bilderbeck, Chair
`Arthur E. McIvor, Vice-Chair
`George F. Carscallen
`Waller S. Clements
`Piotr A. Domanski
`Richard A. Evans
`Mark C. Hegberg
`Martha J. Hewett
`Douglas C. Hittle
`Frederick H. Kohloss
`William J. Landman
`Rodney H. Lewis
`
`Nance C. Lovvorn
`Amanda K. Meitz
`Davor Novosel
`Joseph A. Pietsch
`James A. Ranfone
`Gaylon Richardson
`Ganesan Sundaresan
`Thomas E. Watson
`Bruce A. Wilcox
`J. Richard Wright
`James E. Woods, BOD ExO
`Ronald P. Vallort, CO
`
`Claire Ramspeck, Manager of Standards
`
`SPECIAL NOTE
`
`This American National Standard (ANS) is a national voluntary consensus standard developed under the auspices of the American
`Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). Consensus is defined by the American National Standards
`Institute (ANSI), of which ASHRAE is a member and which has approved this standard as an ANS, as “substantial agreement reached
`by directly and materially affected interest categories. This signifies the concurrence of more than a simple majority, but not necessarily
`unanimity. Consensus requires that all views and objections be considered, and that an effort be made toward their resolution.”
`Compliance with this standard is voluntary until and unless a legal jurisdiction makes compliance mandatory through legislation.
`ASHRAE obtains consensus through participation of its national and international members, associated societies, and public
`review.
`ASHRAE Standards are prepared by a Project Committee appointed specifically for the purpose of writing the Standard. The
`Project Committee Chair and Vice-Chair must be members of ASHRAE; while other committee members may or may not be ASHRAE
`members, all must be technically qualified in the subject area of the Standard. Every effort is made to balance the concerned interests
`on all Project Committees.
`The Manager of Standards of ASHRAE should be contacted for:
`a. interpretation of the contents of this Standard,
`b. participation in the next review of the Standard,
`c. offering constructive criticism for improving the Standard,
`d. permission to reprint portions of the Standard.
`
`ASHRAE uses its best efforts to promulgate Standards and Guidelines for the benefit of the public in light of available information
`and accepted industry practices. However, ASHRAE does not guarantee, certify, or assure the safety or performance of any
`products, components, or systems tested, installed, or operated in accordance with ASHRAE’s Standards or Guidelines or that
`any tests conducted under its Standards or Guidelines will be nonhazardous or free from risk.
`
`DISCLAIMER
`
`ASHRAE INDUSTRIAL ADVERTISING POLICY ON STANDARDS
`
`ASHRAE Standards and Guidelines are established to assist industry and the public by offering a uniform method of
`testing for rating purposes, by suggesting safe practices in designing and installing equipment, by providing proper definitions
`of this equipment, and by providing other information that may serve to guide the industry. The creation of ASHRAE Standards
`and Guidelines is determined by the need for them, and conformance to them is completely voluntary.
`In referring to this Standard or Guideline and in marking of equipment and in advertising, no claim shall be made, either
`stated or implied, that the product has been approved by ASHRAE.
`
`p
`
`
`
`
`
`
`
`
`
`
`
`6
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
` N
`
` p
`
`
`
`b
`
` p
`
` D
`
`b
`
`
`
`
`
` b
`
`
`
`
`
`
`
`
`
`Arkema Exhibit 1108
`
`Page 1 of 12
`
`

`
`CONTENTS
`
`ANSI/ASHRAE 97-1999
`Sealed Glass Tube Method to Test the Chemical Stability of
`Materials for Use Within Refrigerant Systems
`
`SECTION
`
`PAGE
`
`Foreword
`1 Purpose ............................................................................................................................................................ 1
`2 Scope................................................................................................................................................................ 1
`3 Apparatus ......................................................................................................................................................... 1
`4 Procedure for Preparing the Sealed Glass Tubes............................................................................................ 2
`5 Aging the Sealed Glass Tubes ......................................................................................................................... 5
`6 Analysis of the Tubes ....................................................................................................................................... 5
`7 Significance of Results ..................................................................................................................................... 6
`8 Safety Requirements ........................................................................................................................................ 6
`9 References ....................................................................................................................................................... 7
`Appendix A: Calculation of Refrigerant Pressure in Sealed Tubes Containing 0.7 mL of Refrigerant ............... 7
`
`p
`
`
`
`
`
`
`
`
`
`
`
`6
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
` N
`
` p
`
`
`
`b
`
` p
`
` D
`
`b
`
`
`
`
`
` b
`
`
`
`
`
`
`
`
`
`Page 2 of 12
`
`

`
`(This foreword is not part of this standard and is
`included for information only.)
`
`FOREWORD
`
`This standard, developed under the sponsorship of
`ASHRAE Technical Committee 3.2, Refrigerant System Chem-
`istry, describes a uniform means for testing the various mate-
`rials used within hermetic and nonhermetic refrigerant
`systems. It is primarily intended as an accelerated screening
`tool and can provide valuable information on the chemical
`stability of system materials. It is an ASHRAE Standard Prac-
`tice test procedure and is a revision of the standard published
`in 1983 and reaffirmed in 1989.
`
`1. PURPOSE
`
`The purpose of this standard is to establish a test proce-
`dure utilizing sealed glass tubes for the evaluation of materials
`for use in refrigerant systems.
`
`2. SCOPE
`
`2.1 This standard describes the preparation of sealed glass
`tubes and the procedure for charging them with refrigerant,
`lubricant, other materials to be tested, or combinations of
`these
`
`2.2 A procedure for aging the tubes, usually at elevated tem-
`peratures, is described. The tubes are evaluated by quantita-
`tive or qualitative analysis, or both, of the tube contents to
`yield information for determining the compatibility or chem-
`ical stability of materials in refrigerant systems.
`
`2.3 The technique described may be used for evaluating
`many different types of materials. Therefore, the standard
`does not describe in detail the preparation of the materials to
`be tested prior to placing them in the glass tubes, the condi-
`tions of exposure, nor the methods of analysis.
`
`2.4 Detailed safety precautions are included in Section 8,
`Safety.
`
`3. APPARATUS
`
`3.1 A sealed glass tube generally consists of a borosilicate
`glass tube 9 mm (0.35 in.) OD × 7 mm (0.27 in.) ID × approx-
`imately 180 mm (7.1 in.) long with one end formed into a
`round bottom. The above are the finished dimensions. The
`tube is charged with the refrigerant and materials to be tested
`and then sealed in a rounded tip at the other end.
`
`3.2 The tube charging apparatus is illustrated in Figure 1.
`This apparatus consists of a manifold (metal or glass), vac-
`uum pump, pressure gauge, high vacuum gauge, refrigerant
`cylinder, valves, and filling ports. The function of this appa-
`ratus is to evacuate the tube, add refrigerant, and seal it along
`with the test materials. It is calibrated so that the refrigerant
`may be added very accurately by following the change in
`
` Figure 1 Manifold for filling glass tubes.
`
`pressure on the vacuum gauge as refrigerant is added to the
`tube.
`
`3.3 An aluminum block is used for aging the sealed glass
`tubes at elevated temperatures. The aluminum block has
`cylindrical holes in it to support the sealed glass tubes being
`tested. The purpose of the aluminum block is to protect the
`tubes from each other in the event of breakage. A further func-
`tion is to maintain temperature uniformity. A typical alumi-
`num block is illustrated in Figure 2. The holes in the block
`should be drilled completely through, and the block should
`have a separate removable bottom to simplify cleaning. A
`vent may be included to release pressure should a tube burst.
`The overall dimensions shall be sized to accommodate the
`desired number of sealed glass tubes while maintaining ade-
`quate wall thickness. A small wad of glass wool should be
`
` Figure 2 Aluminum block for aging sealed tubes.
`
`ANSI/ASHRAE STANDARD 97-1999
`
`1
`
`p
`
`
`
`
`
`
`
`
`
`
`
`6
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
` N
`
` p
`
`
`
`b
`
` p
`
` D
`
`b
`
`
`
`
`
` b
`
`
`
`
`
`
`
`
`
`Page 3 of 12
`
`

`
`a. proper storage of the glass tubing,
`b. proper cleanliness of the tubing,
`c. cutting to obtain square ends,
`d. the use of a small, sharply pointed oxygen-gas flame
`and proper glass blower’s torch,
`e. obtaining a uniform wall thickness throughout,
`f. proper safety precautions (see Section 8).
`4.1.2 Typically the tubes are made from 9 mm (0.35 in.)
`OD standard wall borosilicate glass tubing. This tubing has an
`ID approximately 7 mm (0.27 in.), and the tube should be cut
`into 240 mm (9.45 in.) lengths. One end is sealed to form a
`rounded bottom. The other end is fire polished.
`4.1.3 The tubes must be scrupulously clean. The tubing
`should be stored in a sealed container so that it does not col-
`lect any contaminants. After forming the rounded bottom, the
`tubes should be flushed with distilled or deionized water, fol-
`lowed by a rinse with acetone or other suitable solvent. The
`tubes should be dried at 125°C (257°F) and cooled in a desic-
`cator. If desired, further cleaning can be accomplished by
`annealing the glass tube one hour at 580°C (1076°F). After
`drying, the tubes should be stored in a desiccator.
`4.1.4 Before use inspect all tubes for cleanliness and for
`any cracks, severe scratches, or other faults in the glass. Dis-
`card any defective tubes.
`
`4.2 Preparation of Materials
`
`4.2.1 The refrigerant used should be of known purity, suit-
`able for the tests being performed. If refrigerant is being used
`from a transfer cylinder, it shall be fitted with a pressure relief
`
` Figure 4 Alternate tube opening apparatus.
`
` Figure 3 Tube opening apparatus.
`
`placed in the bottom of the drilled hole to cushion and support
`the tubes during aging.
`
`3.4
`Individual pipe chambers may be more convenient for
`testing a small number of samples, instead of the aluminum
`block described above. These individual chambers may be
`constructed of metal pipe and closed at both ends with
`threaded caps.
`
`3.5 The electrically heated aging oven shall have mechani-
`cal convection capable of maintaining a uniform temperature
`with ±1.0°C (1.8°F) throughout the test chamber. The oven
`chamber shall be large enough to accommodate the aluminum
`block and allow for adequate air circulation and venting. The
`oven shall be equipped with an indicating controller with a
`control sensitivity of ±0.5°C (0.9°F).
`
`3.6 The tube opening apparatus is illustrated in Figure 3.
`This apparatus is suitable for safely and conveniently opening
`a sealed tube for subsequent analysis of the contents. An alter-
`native apparatus is illustrated in Figure 4.
`
`3.7 Flexible tubing (PVC or rubber) is often used in prepa-
`ration of sealed glass tubes. It is important to clean the tubing
`prior to use. It must be free of excess plasticizer, lubricants,
`powders, and other contaminants.
`
`4. PROCEDURE FOR PREPARING THE SEALED
`GLASS TUBES
`
`4.1 Preparation of the Glass Tube
`4.1.1 The preparation of these tubes shall be performed by
`someone skilled in the art of glass blowing. A skilled glass
`blower will take into consideration such factors as
`
`2
`
`ANSI/ASHRAE STANDARD 97-1999
`
`p
`
`
`
`
`
`
`
`
`
`
`
`6
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
` N
`
` p
`
`
`
`b
`
` p
`
` D
`
`b
`
`
`
`
`
` b
`
`
`
`
`
`
`
`
`
`Page 4 of 12
`
`

`
`device. The refrigerant cylinder should be fitted with an
`adjustable needle valve.
`4.2.2 A refrigeration lubricant to be used as a reference
`should be kept dry and away from light.
`4.2.3 One or more metal coupons are generally added to
`the tube to act as a catalyst. The metals should be chosen to
`represent those used in actual refrigerant systems. The sur-
`face finish of the metal should be specified and reported with
`results. Metal specimens should be cut into the desired size,
`degreased, and stored in a noncorroding environment. A typ-
`ical metal sample is 3 mm (1/8 in.) wide × 50 mm (2 in.) long
`× 0.15 mm (0.006 in.) thick with uniform surface finish.
`4.2.3.1 Steel strip made of highly polished flapper-
`valve stock15 is often used as a convenient and reproducible
`catalytic iron surface.
`4.2.3.2 Copper, such as CDA110 or CDA120, may be
`used to represent the copper used in hermetic motors or
`refrigerant tubing.
`4.2.3.3 Aluminum, such as AA1100 or AA1200, is
`often included to represent the aluminum tubing used in
`refrigerant systems. Also AA380 or AA390 may be included
`if aluminum castings are used in the systems.
`4.2.3.4 The catalytic action of metals depends both on
`the chemical nature of the surface and on the area of the sur-
`face exposed to the reactants. The surface area of the metal in
`contact with the lubricant and refrigerant will vary greatly
`with the surface finish. For example, a surface that has been
`etched or abraded to remove stains or other foreign matter
`may have a much greater effect on the reaction than a surface
`that is more highly polished.
`4.2.3.5 Before cutting and degreasing, inspect the
`metal and make certain it is free of corrosion. Discard cor-
`roded metal. Degrease the metal and cutting shears with a
`suitable solvent. During cutting and thereafter handle the
`metal with clean forceps. Transfer metal specimens to a
`small, clean vacuum desiccator. Vacuum dry the strips in the
`desiccator at room temperature. Break the vacuum with dry
`nitrogen and store in the desiccator until use.
`4.2.4 Materials, such as motor insulation, wire enamel,
`elastomers, plastics, lubricants, or materials of construction,
`may be added to the sealed glass tube for evaluation. These
`materials should be carefully prepared so that they are free of
`contaminants and are representative of the refrigerating sys-
`tem. Failure to properly prepare test materials may result in
`erroneous and misleading conclusions.
`4.2.5 Sufficient tubes with identical contents should be
`prepared such that one can be stored unaged for later refer-
`ence and the others can be used in the necessary tests after
`aging.
`
`4.3 Adding Materials to Tubes
`4.3.1
`Insertion. The order of insertion of materials in the
`tubes varies, depending on the physical size, shape, and com-
`
`position (gas, liquid, or solid) of the material to be tested.
`Generally, solid materials are placed in the tube first, followed
`by the lubricant and nonvolatile liquids and then refrigerants
`and other gases.
`4.3.2 Adding Solid Materials. Do not handle the clean
`sample or metals with bare or gloved hands—use clean for-
`ceps. Purge the tube with a gentle flow of dry nitrogen, then
`cover it with a stopper or plastic cap, and store in a suitable
`desiccator.
`4.3.3 Adding Liquid Materials. Load a 5 mL syringe
`with lubricant to be used in the test, and, using a syringe with
`a locking needle, attach a 150 mm (5.9 in.) long #18 needle.
`Insert a 2 mm (0.08 in.) diameter × 140 mm (5.5 in.) long
`glass tube into the tube to be loaded. The tube should have a
`handle or clamp at one end to prevent its falling into the
`larger glass tube. Insert the #18 needle through the 2 mm
`(0.08 in.) glass tube. The syringe needle should extend
`through the entire length of the 2 mm (0.08 in.) glass tube.
`Inject 0.7 mL of lubricant, withdraw the syringe, and then
`withdraw the 2 mm (0.08 in.) glass tube. The glass tube pre-
`vents the last drop of lubricant on the syringe from contacting
`the upper surface of the glass tube. Purge the tube with a gen-
`tle flow of dry nitrogen, replace stopper or cap, and store in a
`desiccator.
`4.3.4 Forming Capillary in 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 about 15 mm (0.6 in.) of sample
`tube is covered. About 60 mm (2.4 in.) from the unsealed end,
`reduce the tube to a capillary size large enough to pass a #18
`needle. This operation must be done by an individual ade-
`quately skilled in glass blowing. Other connection means may
`be used, such as commercially available ferrule fittings or
`compression O-ring seals.
`4.3.5 Preparing Manifold for Use. Prepare the refriger-
`ant tube loading apparatus for use (Figure 1). The interior of
`this apparatus shall be clean, dry, and thoroughly leak-tested.
`A proper leak-free system should be capable of being evacu-
`ated to a pressure of 2.0 Pa (15 millitorr) and having a rise of
`no more than 27 Pa (200 millitorr) in an hour. The cold trap
`between the manifold and the vacuum pump (see Section 8,
`Safety) will condense any refrigerant and thus avoid condens-
`able gases entering the vacuum pump.
`4.3.5.1 Hold the tube carefully by the flexible tubing
`covered section and slide it over the filling port on the mani-
`fold.
`4.3.5.2 Open the port valve slowly to gradually evacuate
`the tube. Initially the lubricant may foam vigorously. Avoid
`letting this foam rise to the capillary area. Warm air from a hot
`air gun may be used to collapse the foam. Tap the tube gently
`with a pencil covered with a piece of flexible tubing to accel-
`erate the out-gassing. When bubbling no longer occurs when
`the tube is tapped, or the pressure is below 6.7 Pa (50 milli-
`torr), close the filling port valve.
`
`ANSI/ASHRAE STANDARD 97-1999
`
`3
`
`p
`
`
`
`
`
`
`
`
`
`
`
`6
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
` N
`
` p
`
`
`
`b
`
` p
`
` D
`
`b
`
`
`
`
`
` b
`
`
`
`
`
`
`
`
`
`Page 5 of 12
`
`

`
`4.3.5.3
`If the manifold accommodates more than one
`tube, repeat 4.3.5.1 and 4.3.5.2 until all the manifold ports
`have tubes attached to them. The tubes are now ready for
`addition of refrigerant.
`
`4.4 Adding Refrigerant to the Tubes
`4.4.1 Evacuate the manifold and the line between the
`manifold and the refrigerant supply cylinder to 6.7 Pa (50 mil-
`litorr) or lower.
`4.4.2 Fill the Dewar flask(s) with liquid nitrogen and
`place under each tube so that the liquid nitrogen level is about
`20 mm (0.8 in.) below the capillary.
`4.4.3 Support the Dewar flask(s) on lab jacks. Close the
`valve between the refrigerant trap and the rest of the manifold.
`4.4.4 Add refrigerant to the manifold until the absolute
`pressure is at least 6.7 kPa (50 torr) higher than that necessary
`to fill the tubes. However, never exceed a pressure of 100 kPa
`(750 torr) in the manifold. Single-component refrigerants can
`be drawn from the liquid phase or vapor phase in the refriger-
`ant supply cylinder. All refrigerant blends (azeotropic or non-
`azeotropic) must be drawn from the liquid phase in the
`refrigerant supply cylinder to ensure proper blend component
`ratios.
`4.4.5 Slowly open the valve on the filling port and meter
`in the desired quantity of refrigerant by monitoring the change
`in pressure on the gauge. Close the filling port valve when the
`desired pressure is reached. A method for calculating the
`desired pressure is given in the Appendix. Repeat 4.4.4 and
`4.4.5 until refrigerant has been added to all tubes.
`4.4.6 Allow a few minutes to ensure that the tube contents
`are completely frozen.
`4.4.7 Slowly open the valve to the refrigerant trap and
`evacuate the manifold until the pressure is less than 6.7 Pa
`(50 millitorr).
`4.4.8 Open the valve to the filling port.
`
`4.5 Sealing the Tubes
`4.5.1 Lower the lab jack sufficiently to allow space to seal
`the tube at the capillary above the Dewar flask. Hold the tube
`with gloved hand about 30 mm (1.2 in.) below the capillary
`(use either cotton or leather gloves). Seal and detach the tube
`with a glass blowing torch. The tube should be sealed imme-
`diately (20-30 seconds) after the Dewar flask is removed to
`prevent the refrigerant from vaporizing and building up pres-
`sure. After sealing, the tip of the tube shall be annealed. This
`is done by gradually reducing the oxygen supply to the torch
`until the oxygen is shut off and carbon is deposited on the
`tube. Place the tube in the individual pipe chamber or in the
`heating block, whichever is being used.
`4.5.2 Alternative Tube Sealing Method. Attach two
`test tube clamps—one on either side of the tube—just below
`the capillary. Lower the lab jack so that the clamps are about
`30 mm (1.2 in.) above the top of the Dewar. Heat the capil-
`lary area with a glass blowing torch to seal the tube. As the
`glass becomes molten, the tube gently falls until the clamps
`rest on top of the Dewar flask. Complete the seal and anneal
`as in 4.5.1.
`
`4.5.3 Repeat 4.5.1or 4.5.2 until all of the tubes have been
`filled and sealed.
`4.5.4 After all the tubes have been filled and sealed, close
`the valves to the refrigerant trap. Recover the refrigerant from
`the trap with suitable refrigerant recovery equipment.
`4.5.5 Close the refrigerant supply cylinder valve and dis-
`connect the cylinder from the manifold.
`
`4.6 Alternative Filling Methods
`
`4.6.1 Filling with Uncalibrated Manifold. If the mani-
`fold is not calibrated and the refrigerant is to be added by
`visual estimation, only the bottom 40 mm (1.6 in.) of the
`tube is immersed in the liquid nitrogen, and the refrigerant is
`slowly condensed into the tube to a level, previously
`marked, about 20 mm (0.8 in.) above the level of the lubri-
`cant in the tube. After the refrigerant has been added, the
`tube is immersed in the liquid nitrogen to a level about 20
`mm (0.8 in.) below the capillary. All of the refrigerant must
`be frozen solid before the tube can be sealed.
`4.6.2 Filling Tubes by Mass. Refrigerant may be added
`to tubes by mass difference. The open end of the tube is con-
`nected to a stainless steel valve using compression fittings
`with polytetrafluoroethylene (PTFE) front and back ferrules.
`Prior to adding refrigerant, the tube/valve assembly contain-
`ing all nonvolatile components is weighed. The tube is then
`connected to the vacuum manifold, evacuated, and placed in
`liquid nitrogen to a level slightly above that expected for the
`desired mass of refrigerant. Refrigerant is slowly metered
`through the vacuum manifold and allowed to freeze in the bot-
`tom of the tube up to the level of the liquid nitrogen. The valve
`is closed, and the tube and contents are allowed to return to
`room temperature. Re-weigh the tube and record the refriger-
`ant mass as the difference between this and the previous mass.
`The amount of refrigerant is adjusted by adding or removing
`refrigerant through the valve. Reconnect the tube/valve
`assembly to the vacuum manifold. Freeze the tube contents,
`open the valve to the manifold, and seal the tube as described
`in 4.5.1 or 4.5.2. Care must be taken to tighten the fittings suf-
`ficiently to hold the tube securely while under pressure. In
`addition, a physical restraint may be added between the valve
`and the tube bottom to eliminate the possibility of the tube
`being ejected from the valve while under pressure.
`
`4.7
`
`Inspection of Tubes
`
`After the sealed tubes have been stored in the protective
`pipes or heating block overnight at room temperature, care-
`fully remove each tube for inspection (see Section 8, Safety).
`Wipe each tube with a tissue and inspect the tube for the
`following:
`
`a. metal and liquid appearance,
`
`b. proper volume of liquid,
`
`c. appearance of glass, especially in the vicinity of the
`tube seal, and
`
`d. the absence of extraneous materials, such as metal
`fines.
`
`4
`
`ANSI/ASHRAE STANDARD 97-1999
`
`p
`
`
`
`
`
`
`
`
`
`
`
`6
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
` N
`
` p
`
`
`
`b
`
` p
`
` D
`
`b
`
`
`
`
`
` b
`
`
`
`
`
`
`
`
`
`Page 6 of 12
`
`

`
`If any tube does not pass the visual inspection, dispose of
`it using the technique illustrated in Figure 4 and described in
`6.3.2.
`CAUTION: Whenever inspecting tubes, use protective
`gloves, a safety shield to protect the entire body, a face shield,
`and a lab coat. Be sure that people in the vicinity are not
`directly exposed to the tubes.
`
`4.8 Testing in Metal Vessels
`Frequently, it is necessary to test materials that cannot be
`inserted in glass tubes because of size, shape, or pressure
`considerations. In these instances, metal containers of various
`sizes, shapes, and composition may be used. Examples are
`pressure vessels, stainless steel cylinders, standard steel cylin-
`ders, resealable drier shells—all with valves attached. The
`same criteria (cleanliness, safety, accuracy) used for prepara-
`tion of glass tubes shall be used in testing with metal contain-
`ers.
`
`5. AGING THE SEALED GLASS TUBES
`
`5.1 Aging Times and Temperatures
`The temperature and time chosen for aging shall be
`selected by the experimenter according to the requirements of
`the test being conducted. Various temperatures from 100°C
`(212°F) to 200°C (392°F) have been used in the past. Typical
`testing of insulation has been conducted at 150°C (302°F).
`Lubricant stability is typically evaluated in the range of 175°C
`to 200°C (347°F to 392°F). As the temperature rises, the pres-
`sure in the tube rises, and the frequency of tube failures rises
`considerably. Therefore, testing at temperatures above 200°C
`(392°F) is not recommended. Exposure temperatures above
`the critical temperature of the refrigerant can result in
`extremely high pressures because the refrigerant exists only
`as vapor. Various time periods from a few days to a year or
`longer have been used in the past. When lubricant stability is
`evaluated, the time period typically used is 14 days.
`CAUTION: Tubes in which extensive reaction has
`occurred are extremely dangerous, even at liquid nitrogen
`temperatures. Fluorine-containing acids can weaken the tube
`by attacking the glass, and noncondensables such as hydrogen
`can exert significant pressure even at the temperature of the
`liquid nitrogen.12, 13
`
`5.2
`
`Inspection During Aging
`It may be desirable to inspect the tubes visually and record
`observations at several time intervals before opening the tubes
`for analysis. In that case, the aluminum block shall be removed
`from the oven and allowed to cool thoroughly before inspec-
`tion or analysis.
`
`5.3 Aging Tubes with Equalized Pressure
`In some circumstances, the pressure achieved in the
`sealed tubes at aging temperature exceeds the capability of the
`glass and seals. In these cases, the tubes may be aged in metal
`pressure vessels that are charged with refrigerant to increase
`the pressure outside the tubes, thus reducing the pressure
`
`differential maintained by the glass. Sealed tubes are placed in
`a pressure vessel. The pressure vessel is evacuated and subse-
`quently charged with refrigerant or inert gas. The type and
`amount of gas charged shall be carefully chosen so that the
`pressure achieved in the pressure vessel is no greater than that
`achieved in the tubes. The pressure vessel shall be equipped
`with a safety relief valve rated below the pressure rating of the
`vessel. This technique should be considered for high-pressure
`refrigerants such as R-32. It shall not be used in lieu of reliable
`glass sealing capability or in cases where high pressure is
`expected due to excessive reactivity in the sealed tubes. Unre-
`liable sealing capability or excessive reactivity during aging
`may result in unsafe conditions even at room temperature.
`
`6. ANALYSIS OF THE TUBES
`
`6.1 The exact method of analysis shall be chosen by the
`experimenter according to the intended purpose. Analytical
`methods that are recommended and have been used in the past
`include: visual analysis, halide analysis, gas chromatography,
`infrared spectroscopy, mass spectroscopy, and lubricant anal-
`ysis such as total acid number and ion chromatography. Other
`methods may also be suitable.
`
`6.2 A visual inspection has been used in the past. Both the
`liquid phase and the metal test pieces in the tubes are exam-
`ined, and the appearance of the tubes is compared with
`controls containing materials of known stability.
`
`6.3 Opening Tubes for Gas Analysis
`
`6.3.1
` The method for opening the glass tube is shown in
`Figure 3. In this procedure, immerse the lower half of the tube
`in liquid nitrogen until the tube contents are frozen. Momen-
`tarily remove the tube and make a file scratch near the tip. Use
`extreme caution (see Section 8, Safety). Refreeze the tube.
`Remove the tube from the liquid nitrogen and insert in the
`opening fixture, shown in Figure 3, until the tip hits the stop.
`Connect the fixture with inserted tube to the gas sampling sys-
`tem. Open the valve to the gas sampling system. Break off the
`tip by turning the handle until a gentle snap is felt and heard.
`Allow the tube contents to warm to room temperature. The
`more rapid the warming, the more turbulent the mixing in the
`tube. In several minutes all the gases will have expanded out
`of the tube. The gas sample is collected in a pre-evacuated gas
`sampling system and then fed to the gas analysis instrument
`described in “A Sealed Tube Gas Chromatograph Method for
`Measuring Reaction of Refrigerant 12 with Oil.” 7
`
` Another method of opening the glass tube is illus-
`6.3.2
`trated in Figure 4. To use this procedure, rinse the tube with
`acetone and dry carefully with a clean paper towel. Place the
`tube in the apparatus and evacuate to 6.7 Pa (50 millitorr).
`Close the valve, disconnect from vacuum pump, and break the
`tube by squeezing the center of the copper tubing with pliers
`or a vise. The tube contents are then ready for gas analysis.
`Note: The tube must be made long enough to allow for com-
`plete evaporation of the liquid refrigerant.
`
`ANSI/ASHRAE STANDARD 97-1999
`
`5
`
`p
`
`
`
`
`
`
`
`
`
`
`
`6
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
` N
`
` p
`
`
`
`b
`
` p
`
` D
`
`b
`
`
`
`
`
` b
`
`
`
`
`
`
`
`
`
`Page 7 of 12
`
`

`
`6.3.3
` Tubes that are not going to be opened for analysis
`may be disposed of as described in 6.3.1 (Figure 3).
`CAUTION: Tubes with blackened contents indicate
`gross decomposition has occurred. The pressure achieved
`upon breaking the tube may exceed the capability of the gas
`sampling system. If considerable reaction has occurred in the
`tube, a safety hazard exists (see Section 8). In this case the tube
`shall first be frozen in liquid nitrogen and placed in the appa-
`ratus shown in Figure 4. Then the copper tube shall be
`squeezed to break the tube.
`
` Reference Analysis Methods
`6.4
`6.4.1
` “Chloride Analyses as a Measure for the Evaluation
`of Sealed Tube Tests6” gives a detailed description of the
`method of collecting the contents of a tube in preparation for
`halide analysis.
`6.4.2
` “A Sealed Tube Gas Chromatograph Method for
`Measuring Reaction of Refrigerant 12 with Oil”7 and Appen-
`dix C to ARI 700-958 describe procedures for gas chromato-
`graphic analysis of the gases from a sealed tube and the
`method for calculating the percent refrigerant decomposed.
`Appendix C to ARI 700-958 also describes many other proce-
`dures for refrigerant analysis.
`
`7. SIGNIFICANCE OF RESULTS
`
`7.1 The sealed tube test procedure has long been used to
`evaluate and select materials for use in refrigeration systems.
`1-5, 10, 14 Data obtained from these tests have been invaluable,
`but their use as a final definitive test requires considerable
`experience in refrigeration chemistry and system operation.
`The sealed tube procedure is primarily a screening test. Where
`possible, these tests should be supplemented with component
`or system tests.
`
`7.2 It is recommended that the following information be
`included when reporting results: aging time and temperature,
`identification and quantities of materials included in the tubes,
`preparation of the materials, and information concerning
`other variables that might impact the results.
`
`7.3 This method is not a specification with pass/fail criteria.
`It is used for preparing, aging, and analyzing sealed tubes to
`obtain test results for such specifications. It is left to the inter-
`ested parties to establish pass/fail criteria of results.
`
`8. SAFETY REQUIREMENTS
`
`8.1 There are hazards in handling sealed glass tubes and the
`materials being tested. At times the absolute pressure inside
`t