1、SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirelyvoluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefro
2、m, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions.Copyright 2001 Society of Automotive Engineers, Inc.All rights reserved. Printed in U.S.
3、A.TO PLACE A DOCUMENT ORDER: (724) 776-4970 FAX: (724) 776-0790 SAE WEB ADDRESS: http:/www.sae.org400 Commonwealth Drive, Warrendale, PA 15096-0001AEROSPACE RECOMMENDED PRACTICEARP901 REV.AIssued 1968-03Revised 2001-05Superseding ARP901Bubble-Point Test Method1. SCOPE:This test method describes a pr
4、ocedure for measuring the largest pore or hole in a filter or similar fluid-permeable porous structure. A standard referee test method for precise determination or resolution of disputes is specified. A simpler inspection test procedure for quality assurance “go-no-go” measurement is also given. Bub
5、ble-point testing physics, analysis of bubble-point test data, and correlation with other methods of pore size determination are separately discussed in the appendix.2. APPLICABLE DOCUMENTS:The following publications form a part of this document to the extent specified herein. The latest issue of SA
6、E publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however
7、, supersedes applicable laws and regulations unless a specific exemption has been obtained.2.1 U.S. Government Publications:Available from DODSSP, Subscription Services Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094.MIL-H-5606 Hydraulic Fluid, Petroleum Base; Aircraft; Missile an
8、d OrdnanceMIL-PRF-5624 Turbine Fuel, Aviation, Grades JP-4, JP-5, JP5/JP-8 STMIL-E-51454 Ethyl Alcohol, (Ethanol)Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE ARP901 Revision A- 2 -3. METHOD OUTL
9、INE:The filter is immersed in a test liquid which wets and saturates the filter pore structure. Gas pressure is applied to one side of the porous wall so that the liquid phase which wets the pores is displaced by the gas. The gas pressure is slowly increased until the first steady stream of gas bubb
10、les is observed to emit from a point on the porous surface. The measured gas pressure required to form the “first bubble” is essentially equal to the pressure force which is in equilibrium with the surface tension force at the largest pore. This bubble-point pressure is a relative measure of the por
11、e size after appropriate corrections for immersion depth and test liquid surface tension have been made.4. REFEREE TEST:Capillary pressure or “bubble-point” tests have long been used to measure the largest pore and characterize the pore size distribution of various porous materials. Many different m
12、ethods of testing and analysis have been developed. No bubble-point test measures actual pore size, but only allows correlation of the measured capillary pressure with some dimensional characteristic of the pore structure. Rationalization of bubble-point test data depends on detailed definition of t
13、he test method, analysis and correlation employed. Therefore, a standard referee test is necessary to assure common interpretation of data and understanding of specifications.4.1 Test Equipment:Suitable bubble-point test equipment includes a source of clean compressed air or nitrogen with provisions
14、 for regulating and measuring the gas pressure. A test liquid container and appropriate fixtures for sealing and holding the test element are also required. Further provisions for maintaining system cleanliness may be desirable, especially for Clean Room operations, but they are not generally requir
15、ed for ordinary testing. A suitable apparatus for typical filter elements is shown schematically in Figure 1 and requires the following components or their functional equivalent.4.1.1 Shut-off valve (optional) to allow disconnecting and servicing other components (1).4.1.2 Water-oil separator/filter
16、 or other provision to insure clean compressed air or nitrogen gas (2).4.1.3 Primary pressure regulator to reduce gas pressure below the maximum inlet pressure of the low pressure regulator (3).4.1.4 Secondary precision low pressure regulator to (0 to 50 in of water pressure or similar range) for fi
17、nal gas pressure control (4).4.1.5 Three-way PTFE plug valve (optional) to facilitate venting of test elements (5).4.1.6 Manometer, preferably well-type, or calibrated pressure gage to read gas pressure with a precision of at least 0.1 in of water pressure (2.54 mm) (6).4.1.7 Tank or similar contain
18、er for holding test liquid and allowing observation of bubbles from test element.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE ARP901 Revision A- 3 -FIGURE 1 - Bubble-Point Test ApparatusCopyrigh
19、t SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE ARP901 Revision A- 4 -4.1.8 Means for maintaining and measuring test liquid temperature in the range of 79 F 5 F.4.2 Test Liquid:The standard referee test li
20、quid is specified to be American Chemical Society reagent grade isopropanol (isopropyl alcohol) having a surface tension of 21.15 dynes/cm 0.10 dynes/cm at 77 F (25 C). Substitutions are not permitted. Other test liquids may be used for routine, non-referee bubble-point testing provided that test re
21、sults must be shown to correlate with, standard referee test results. Typical alternative test liquids include commercial grades of isopropanol, Ethanol 3-190 or other brands of denatured ethanol, and MIL-H-5606 hydraulic oil, JP-5 fuel and other hydrocarbon solvents have also been used but they are
22、 generally less suitable, because of larger variations in surface tension and wetting characteristics.4.3 Test Procedure:The test element is wetted, attached to the gas source, and tested to locate the approximate area containing the largest pores or holes. The element is turned to bring the bubblin
23、g area to the top and additional tests are performed to confirm the largest pore location and to measure the net capillary pressure causing the first bubbles. Bubble-point tests are to be conducted at a measured temperature in the range of 75 F 5 F.4.3.1 Inspect the test element to assure that it is
24、 clean and dry, free from oil, grease, or other visual contamination or defects which may affect test results.4.3.2 Immerse the element in the tank to thoroughly wet and saturate the pore structure. Remove and drain excess liquid.4.3.3 Insert stopper or other sealing device attached to the gas tubin
25、g for pressurizing and plug other orifices if necessary.4.3.4 Immerse the test element just below the liquid surface, gradually increase the gas pressure from zero until the first bubble is observed, and note the location on the element.NOTE: Air bubbles may be trapped on or within the outer structu
26、re resulting in a few spurious bubbles. These bubbles are ignored. The “first bubble” appears in a continuous stream as long as internal gas pressure is maintained. Adequate lighting is necessary for reliable observation. Gas pressure must be increased slowly to allow continuous establishment of equ
27、ilibrium and prevent overshooting. Mechanical vibration or jarring of the test element must be avoided to prevent upsetting bubble equilibrium which causes erroneous low pressure readings.Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking pe
28、rmitted without license from IHS-,-SAE ARP901 Revision A- 5 -4.3.5 Turn the element, if necessary, so that the area emitting the first bubble is nearest the liquid surface.4.3.6 Release the gas pressure in the filter to allow the pores to be flooded with liquid and repeat the procedure of 3.3.4.NOTE
29、: Internal gas pressure must be completely released between each bubble determination either by venting to atmosphere or by removing the stopper seal. If complete pore flooding is blocked by gas pressure, spurious low pressure readings may result.4.3.7 Rotate the test element while maintaining this
30、bubble pressure and note any other areas which may also bubble.4.3.8 Repeat the procedures of 3.3.4 through 3.3.7 until the area which bubbles at the lowest pressure is located nearest the liquid surface.4.3.9 Read the lowest pressure on the manometer at which the first bubble is released and record
31、 to the nearest 0.1 in of water.4.3.10 Measure the vertical distance from the point at which the first bubble is emitted to the liquid surface and record to the nearest one-sixteenth of an inch.4.3.11 Measure the liquid temperature with a thermometer and record to the nearest degree F.4.4 Calculatio
32、ns:All bubble-point test results are to be reported as the net standard bubble-point pressure measured in inches of water head. Corrections for depth of immersion and surface tension variation due to temperature may be required. For non-referee tests using liquids other than isopropanol, larger corr
33、ections for surface tension are necessary. Standard bubble-point pressure is defined by the following equation.(Eq. 1)P is standard bubble-point pressure based on isopropanol at 77 F (25 C) having a surface tension of 21.15 dynes/cm. Actual liquid surface tension, either directly measured or determi
34、ned from the temperature measurement of the known liquid, is denoted by S. Measured capillary pressure, P, is corrected by the measured depth of immersion, h, times test liquid density (specific gravity), d. Surface tension and density are shown as a function of liquid temperature for isopropanol an
35、d Ethanol 3-190 brand denatured ethanol in Figures 2 and 3 respectively.P 21.15S-P-dh()=Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE ARP901 Revision A- 6 -FIGURE 2 - Test Liquid Surface TensionC
36、opyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE ARP901 Revision A- 7 -FIGURE 3 - Test Liquid DensityCopyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or
37、 networking permitted without license from IHS-,-SAE ARP901 Revision A- 8 -4.4.1 Calculation Examples:1. A referee bubble-point test using standard isopropanol test liquid is performed on a filter element and the following measurements are determined.Bubble-point pressure, P 14.6 in WATER COLUMNImme
38、rsion depth, h 0.5 inLiquid temperature, t. 70 FSurface tension and density for isopropanol at 70 F are found from the curves of Figures 2 and 3.Surface tension, S 21.65 dynes/cmDensity, d 0.785 gm/ccThis data is substituted in the equation for standard bubble-point pressure:(Eq. 2)The standard bubb
39、le-point pressure for this test is determined to be P = 13.9 in of water based on isoproanol at 77 F.2. A routine bubble-point test is conducted according to the referee method on the same filter element described in Example 1, except that Ethanol 3-190 is used as the test liquid. The following meas
40、urements are obtained:Bubble-point pressure, P 16.0 in WATER COLUMNImmersion depth, h 0.5 inLiquid temperature, t 70 FSurface tension and density for Ethanol 3-190 at 70 F are read from the curves of Figures 2 and 3.Surface tension, S 23.80 dynes/cmDensity, d 0.810 gm/ccP 21.1521.65-14.60.785()0.5()
41、=21.1521.65-(14.2)13.8713.9 (to nearest 0.1)=Copyright SAE International Provided by IHS under license with SAENot for ResaleNo reproduction or networking permitted without license from IHS-,-SAE ARP901 Revision A- 9 -4.4.1 (Continued):This data is used, as in Example 1, in the equation for standard
42、 bubble-point pressure.(Eq. 3)The standard bubble-point pressure for this test if also found to be P = 13.9 in of water. The apparent bubble-point difference between Examples 1 and 2 of 1.4 in of water is resolved by proper correction for surface tension difference.4.4.2 Nomograph Calculations: The
43、numerical calculations specified in 4.4.1 should be used for disputes or other work requiring good accuracy. Routine test calculations may be conveniently solved for surface tension correction only by using the nomograph of Figure 4. The net measured bubble-point pressure (total observed bubble-poin
44、t less the head due to immersion depth, hxd) is found on the left vertical axis. The appropriate reference mark describing the test liquid and its temperature is located on the diagonal axis. A straight-edge or ruler connecting these two points intersects the right vertical axis at the corresponding
45、 standard bubble-point pressure.Example: A filter element is tested in Ethanol 3-190 at 75 F and has a bubble-point of 16.8 in with an immersion depth of 1.0 in. Immersion head is approximately 0.8 in (0.81 x 1.0 = 0.8) and net bubble-point Is 16.0 in (16.8 0.8 = 16.0). Find 16.0 on the left axis, r
46、eading upwards. Find the Ethanol 3-190, 75 F reference mark on the diagonal axis. Connect both points to intersect the right axis as shown by the dashed line. Read downwards on right axis to find standard bubble-point of 14.3 in at intersection.5. INSPECTION TEST:Ordinary bubble-point testing may no
47、t require the accuracy nor warrant the cost of the specified referee test. Alternative test liquids such as commercial grade isopropanol, denatured ethanol, or may be used for non-referee tests employing the referee procedure or a functional equivalent modification of the procedure, providing that t
48、he user must show proper correlation with the referee test and must report data in terms of “standard bubble-point” as specified for the referee test. For tests which only require assurance that a specified minimum bubble-point is met by a filter element, a simpler “go-no-go” procedure may be used.5
49、.1 Test Equipment:Apparatus similar to that specified in 3.1 and shown in Figure 1 is satisfactory. Modifications to meet special auxiliary requirements for cleanliness, higher production rate, etc., are allowable, providing that referee test correlation can be shown for test results.P 21.1523.80-16.00.8100.5()=21.1523.80-
