1、Designation: F 2523 07Standard Practice forBlowout Resistance of Room-Temperature VulcanizedElastomers1This standard is issued under the fixed designation F 2523; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last rev
2、ision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice provides a means to determine the blowoutresistance of a room-temperature vulcanized elastomer system(RTV) usin
3、g a standard fixture.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this stand
4、ard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 907 Terminology of AdhesivesD 1566 Terminology Relating to RubberF 2468 Classification for Specifying SiliconeAdhesives andSe
5、alants for Transportation Applications2.2 SAE Standard:SAE J1199 Mechanical and Material Requirements forMetric Externally Threaded Steel Fasteners33. Terminology3.1 DefinitionsSome terms in this practice are defined inTerminologies D 907 and D 1566.3.2 Definitions of Terms Specific to This Standard
6、:3.2.1 blowout, ndisruption of the uncured RTV integrityin a joint from system pressurization resulting in sudden loss ofpressure.3.2.2 Tjoint, ninterface created in a sealing surfacewhere three structural components meet.3.2.2.1 DiscussionThis interface may exist as a small gaprequiring a material
7、such as room-temperature vulcanizedelastomer (RTV) to seal.3.3 Acronym:3.3.1 RTVroom-temperature vulcanized elastomer4. Summary of Practice4.1 Condensation cures RTVs as a one-component systemcure when exposed to moisture in the ambient air or astwo-component systems when those components are mixedt
8、ogether. RTVs are often used to seal joints where three flangesmeet (T joints) such as an automotive engines front cover,engine block, and oil pan. Because of machining and assemblytolerance variations, these T joints may have a slight misalign-ment or gap. We also find gaps in the half-round area o
9、f the oilpan to block and in the valley between the intake manifold andblock on certain V-engines as a result of manufacturingtolerances. The RTV is used to seal in fluids. In some assemblyline applications, soon after the RTV is applied and the flangesfastened together, the system is subjected to a
10、n air decay test ata designated pressure. This test is used to determine an RTVscapability to withstand loss of integrity at this designatedpressure.4.2 When using this practice, one must first determine themaximum gap based on stack tolerances of the system. Atwo-piece round fixture uses the top po
11、rtion to mirror thesystem gap (default gap is 1 mm), while the bottom halfprovides the mating flange and the connection for the pressureinput. The gap is machined into the top half of the fixture in a“pie slice” 60 angle. A continuous bead of RTV is applied tothe entire bottom portion of the fixture
12、, the top half is carefullyattached, and the fixture is pressurized to the prescribed limitsand held for a specified time period. If the RTV is not capableof sealing at the pressure applied, a sudden loss of pressure willoccur.5. Significance and Use5.1 This practice may be used to determine the via
13、bility ofan RTV sealant to withstand pressure leak testing before cure1This practice is under the jurisdiction ofASTM Committee F03 on Gaskets andis the direct responsibility of Subcommittee F03.70 on Formed in Place Gaskets.Current edition approved Oct. 1, 2007. Published November 2007. Originallya
14、pproved in 2005. Last previous edition approved in 2005 as F 2523 05.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM
15、website.3Available from Society of Automotive Engineers (SAE), 400 CommonwealthDr., Warrendale, PA 15096-0001.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.at maximum gap conditions of a system. This practice may beNOTETorque seque
16、nce shall be “crisscross” pattern.FIG. 1 Aluminum Blowout FixturesF2523072used to indicate an RTVs acceptability to undergo an assemblyline leak check without causing a leak path due to materialblow out.6. Apparatus46.1 FixtureAluminum, see Fig. 1.6.1.1 Aluminum casting, forging, or bar stock with 6
17、0Brinell hardness, minimum.6.1.2 Surface finish shall be in the range of 0.7 to 3.2 m Ra.6.1.3 Top half of fixture shall have a machined cutout to thedesired gap depth (1.0 6 0.025 mm default gap), per Fig. 1.The gap and flange width are critical dimensions and should becontrolled to a tight toleran
18、ce (62.5 % is recommended). Allother dimensions are allowed 610 %.6.1.4 Four nut, bolt, and washer sets per SAE J1199 (4.8hex head) or equivalent, M10 3 1.5 3 50.6.2 Air supply and regulator.6.3 Polyethylene tubing (or equivalent), polytetrafluoroeth-ylene (PTFE) pipe tape, plastic, or brass tube fi
19、ttings.6.4 Inline pressure gage or equivalent, 0 to 138 kPa,accurate to 60.7 kPa.6.5 Timing device with 1-s increments.6.6 Measuring device, capable of measuring an adhesivebead height of 2 mm.6.7 Environmentally controlled room (temperature, humid-ity monitoring, and control).7. Reagents and Materi
20、als7.1 Cleaning SolventAppropriate cleaning solvent asspecified by RTV manufacturer.7.2 Clean, lint-free cloth.8. Conditioning8.1 Sample containers shall be allowed to equilibrate to 21to 25C. Time required may vary depending on the size ofcontainer and previous storage conditions.9. Initial Step9.1
21、 Connect air supply to regulator and to pressure gageusing polyethylene tubing. Plastic or brass press fit fittings maybe used for the connection points, depending on the adaptorconnection on the three components. Fittings threads shall havepipe sealant applied before installing into fixtures.9.2 Co
22、nnect tube to bottom fixture with a brass fittingcontaining pipe sealant applied around threads.9.3 Block off open hole of fixture with a properly securedrubber stopper or compress a soft silicone plaque against thehole. Check for leaks at the various connection points byspraying a dilute liquid soa
23、p and water solution5while lookingfor air bubbles.9.4 Test environment shall be set at 21 to 25C and 40 610 % relative humidity.10. Procedure10.1 Use either the default gap of 1 mm or choose a fixturewith the desired machined gap.10.2 Make sure all traces of cured or uncured RTV fromprevious test ha
24、ve been removed.10.3 Following the initial setup instructions in Section 9,verify the system is free of leaks.10.4 Method ATime to Blowout at a Specified Pressure:10.4.1 Preset pressure regulator to the applicable test pres-sure.10.4.2 Open exhaust valve to prevent any pretest internalpressure and c
25、lose inlet ball valve.10.4.3 Apply a continuous 4-mm bead (based on defaultgap, user will have to determine proper bead size for alternategaps) on the flange of the bottom fixture.10.4.4 Apply the top half of the fixture, taking care not tomove the fixture horizontally.10.4.5 Tighten bolts to 1.0 kg
26、m 6 10 %.10.4.6 Close exhaust valve.10.4.7 Immediately after assembly (within 2 min of RTVapplication) open ball valve to pressurize the system quickly tothe preset pressure.10.4.8 Start the timer and record the time in seconds atwhich the sudden loss of pressure occurs. If no loss of pressureoccurs
27、 after 1 min, report it as “60 s.”10.4.9 Disassemble and clean the fixture thoroughly, remov-ing all traces of RTV.10.4.10 Repeat Steps 10.4.1 to 10.4.9 a second time.10.4.11 If the second result is within 610 % of the firstresult, report the average blowout time to the nearest second.10.4.12 If the
28、 second result is in excess of 610 % of thefirst, repeat until a consistent value is obtained.10.5 Method BMaximum Blowout Pressure Determina-tion:10.5.1 Method B shall be done at or near maximumapplication/flow rate of the sealant.10.5.2 Open exhaust valve to prevent any pretest internalpressure an
29、d close inlet ball valve.10.5.3 Apply a continuous 4-mm bead (based on defaultgap, user will have to determine proper bead size for alternategaps) on the flange of the bottom fixture.10.5.4 Apply the top half of the fixture taking care not tomove the fixture horizontally.10.5.5 Tighten bolts to 1.0
30、kgm 6 10 %.10.5.6 Close exhaust valve.10.5.7 Screen for approximate blow out pressure by open-ing the ball valve immediately after assembly (within 2 min ofRTV application), so as to increase the pressure by 6.9 kPaevery 10 s until blow out occurs. Subsequent iterations todetermine blow out pressure
31、 may start 6.9 kPa below thisscreening pressure. If this screen pressure is at or below 20.7kPa, the iterations shall use 3.45 kPa increments in thismethod; otherwise the increments shall be 6.9 kPa.10.5.8 Immediately after assembly (within 2 min of RTVapplication), open the ball valve and start inc
32、rementally in-creasing the pressure every 5 s until the initial pressure of thescreening pressure minus 6.89 kPa is reached.4The sole source of supply of the blowout fixtures in both materials known to thecommittee at this time is Kovil Manufacturing, 925 Sherman Ave., Hamden, CT06514. If you are aw
33、are of alternative suppliers, please provide this information toASTM International Headquarters. Your comments will receive careful consider-ation at a meeting of the responsible technical committee,1which you may attend.5Commercially available products exist from a wide variety of distributors.F252
34、307310.5.9 Start the timer. If no loss of pressure occurs after 1min, incrementally increase the pressure and start the timer.Repeat this process until failure occurs and record this value.10.5.10 Disassemble and clean the fixture thoroughly, re-moving all traces of RTV.10.5.11 Repeat the steps in 1
35、0.5.1 through 10.5.10, using thevalue obtained in 10.5.9. If this again results in a failure, cleanthe fixture and repeat the process using the value obtained in10.5.9 minus 6.9 kPa.10.5.12 If failure occurs, repeat the process of cleaning andapplying fresh RTV and testing, each time reducing thepre
36、ssure until a “pass” occurs, then record this pressure.10.5.13 Repeat the test a second time at this pressure toverify a “pass.” Report this value as the maximum blowoutpressure.11. Potential Failure Modes of Test Procedure11.1 Inconsistent results in the procedure may be due toseveral reasons and s
37、hall be reviewed. Some of these may be:11.1.1 Inconsistent RTV bead applied. RTV should beapplied in an amount sufficient to fill the gap when the fixtureis assembled and bolts torqued. Insufficient RTV will result invoids within the fixture gap. These voids will result inpremature failure when runn
38、ing Method A, and possible lowerpressure values when running Method B. Excessive RTVapplied in the fixture gap will result in an internal and externaldam of RTV that will resist movement of air by the appliedpressure. This can result in artificially high time to blow out(Method A) and resistance to
39、blow out pressure (Method B).11.1.2 Misplacement of bead. RTV bead biased toward theinside or outside can result in non-fill of the fixture gap,resulting in lower time to blow out (Method A) and resis-tistance to blow out pressure (Method B). Addition of RTV tocompensate for this offset of the bead
40、placement can result inan excessive amount of RTV, and is further discussed in 11.1.1.11.1.3 Air entrapment in RTV bead. Entrapment of air orother contaminants that create voids in the RTV can createresults similar to insufficient RTV application, and is furtherdiscussed in 11.1.1.11.1.4 Improper ga
41、p. The induced gap should be machinedprecisely to the agreed dimension within the tolerance limitstated in 6.1.3 (1 mm is the default gap). Failure to properly setgap will result in correlation issues between laboratories. Useof fixtures with improperly low gaps can result in artificiallyhigh result
42、s. Use of fixtures with improperly high gaps canresult in artificially low results.11.1.5 Improper torque sequence or setting. Improper se-quence can result in inconsistent gap fill or shifting of RTVbead, or both, thus providing inconsistent and impreciseresults. Low bolt torque can result in shimm
43、ing of fixturecreating a slightly larger than desired gap, and artificially lowdata.11.1.6 Contamination by improperly cleaned fixture. Im-properly cleaned flanges in the non-gap areas can causeshimming of the fixture which may result in artificially lowdata. Improperly cleaned flanges in the gap ar
44、ea can result ineither artificially high or low data, depending on how thecontaminant acts on the fresh RTV bead during fixture assem-bly. Contaminants such as partially cured RTV encapsulated bythe bead can cause air entrapment and voids which may resultin artificially low data. Partially cured RTV
45、 carried on theinside edge of the fresh bead can act as a barrier to airmovement through the bead resulting in artificially high data.11.1.7 Faulty pressure regulator or pressure measurementdevice, or both. Faulty equipment will provide unreliable andun-correlatable data with other laboratories.11.1
46、.8 Air leaks within the system, some of which can varyvia fixture handling and movement. Air leaks prior to thepressure regulator system may cause variations of availablepressure between the source and the regulator. This could causeerratic data if the source setting is close to the pressure beingap
47、plied by the regulator to the fixture. Air leaks between theregulator and the fixture will result in artificially high data.11.1.9 Low-viscosity RTVs evaluated with large gaps mayresult in lower between lab correlation.12. Report12.1 Report shall consist of:12.1.1 Material classification per Classif
48、ication F 2468,12.1.2 Fixture type used in the evaluation,12.1.3 Fixture gap used in the evaluation,12.1.4 Laboratory test environment (temperature and rela-tive humidity) and location,12.1.5 Material supplier and product code,12.1.6 Application rate(s) evaluated,12.1.7 Method used, and12.1.8 Averag
49、e blowout time in seconds for MethodAalongwith test pressure and maximum blowout resistance pressurefor Method B.13. Precision and Accuracy13.1 Statements are included for Method B, Blow OutPressure Determination only.13.1.1 RepeatabilityTwo test results obtained within onelaboratory shall be judged not equivalent if they differ by morethan the “r” value for that material; “r” is the intervalrepresenting the critical difference between two test results forthe same material, obtained by the same operator using thesame equipment on the same day in the same laborato
