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 entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
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4、SA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/ARP6255 AEROSPACE RECOMMENDED PRACTICE ARP6255 Issued 2013-03 Aviation Lubricant Tribology Ev
5、aluator (ALTE) Method to Determine the Lubricating Capability of Gas Turbine Lubricants RATIONALE The Aviation Lubricant Tribology Evaluator (ALTE) is a device designed to assess the relative lubricating performance of aviation turbine oils. The aim of the ALTE is to produce test conditions which al
6、low lubricants to be evaluated on a laboratory scale, in a timely manner without deviating greatly from representative wear mechanisms. 1. SCOPE Employing ball-on-cylinder philosophy, a non-rotating steel ball is held in a vertically mounted chuck and using an applied load is forced against an axial
7、ly mounted steel cylinder. The test cylinder is rotated at a fixed speed while being partially immersed in a lubricant reservoir. This maintains the cylinder in a wet condition and continuously transports a lubricating film of test fluid to the ball and cylinder interface. The diameter of the wear s
8、car generated on the test ball is used as a measure of the fluids lubricating properties. The apparatus can be used, by adjusting the operating conditions, to reproduce two different wear mechanisms; mild and severe wear, the ALTE therefore has the ability to assess a lubricants performance in that
9、regard. These mechanisms are described below. 1.1 Mild Wear As the test cylinder rotates, the lubricant is continuously transported to the ball and cylinder interface. At this interface under abrasive wear conditions, there is an elastohydrodynamic/boundary layer of lubricant which only allows conta
10、ct of the surface asperities of the ball and cylinder. Due to the difference in hardness of these asperities and motion of one surface relative to the other, abrasion and hence mild wear occurs (two body abrasive wear). Hard wear debris carried from the cylinder to the wear scar area can result in t
11、hree body abrasive wear of the softer surface. Abrasive wear gives a characteristic surface topography consisting of long parallel grooves in the sliding direction. 1.2 Severe Wear At a specific load, a transition from mild to severe wear can be observed, at this transition, a reduction and subseque
12、nt breakdown of boundary lubrication and film thickness occurs. This results in full metal-to-metal contact of the sliding surfaces, leading to adhesive wear and a large wear scar. If loading is increased beyond this transition point then localized welding and eventual seizure will occur. It should
13、be noted that the mild and severe wear mechanisms described above are entirely different tribological phenomena where a transition of lubricating film thickness gives a change in the amount of metal surface contact. SAE ARP6255 Page 2 of 9 2. APPLICABLE DOCUMENTS The following publications form a pa
14、rt of this document to the extent specified herein. The latest issue of SAE 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
15、 text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been obtained. 2.1 AIR4978, Temporary Methods for Assessing the Load Carrying Capacity of Aircraft Propulsion System Lubricating Oils. 2.2 Aviation L
16、ubricant Tribology Evaluator (MkII), Operating Manual 2.3 Aviation Lubricant Tribology Evaluator (MkIII), Installation the load arm and support are arranged with a moment such that the ball load is four times that applied to the arm. The test ring is rotated and the ball is lowered to contact the ri
17、ng surface throughout the test period. SAE ARP6255 Page 3 of 9 4.3 Assessment The diameter of the wear scar generated at a given ball load is measured. Testing can be carried out to determine the load at which a specific wear scar diameter is obtained or conversely the wear scar diameter formed at a
18、 specific load. 5. APPARATUS 5.1 Aviation Lubricant Tribology Evaluator MkII or Validata MkIII to the specifications tabulated below, these values represent the required upper limit of the equipment, the ALTE however will also be required to operate below these values depending on the specific test
19、requirements. The tabulated values have been found to enable the user to determine the load required to generate a 1.5 mm wear scar diameter for the majority of current gas turbine lubricants. TABLE 2 Requirement Test Ring Rotation Speed (rpm) g149 220 Oil Temperature (C) g149 150 Oil Heater Power (
20、Watts) g149 400 Arm Load Capacity (kg) g149 25 Ball Load Capacity (kg) g149 100 Timer Range (s) 0 to g149 3600 5.2 A set of calibrated test weights (1 to 20 kg). 5.3 Desiccator, dedicated solely for this test, filled with a suitable desiccant. 5.4 A travelling microscope or an optical microscope in
21、conjunction with suitable measurement software. The microscope used should be capable of 100 times magnification (minimum) and calibrated to ensure measurement to the nearest 0.01 mm can be achieved. 5.5 Ultrasonic bath suitable for cleaning components. 6. CONSUMABLES 6.1 Test balls to the following
22、 specification: TABLE 3 Material Chrome Alloy AISI 52100 Steel Hardness 64-66 HRC Surface finish Grade 5-10 EP (extra polish) Dimensions 12.7 mm diameter The balls are described in ISO 3290-1:2008. The HRC shall be 64 to 66, a closer limit than is found in the ISO requirement. SAE ARP6255 Page 4 of
23、9 6.2 Test rings to the following specification: TABLE 4 Material SAE 8270 Steel Hardness 58-62 HRC Surface finish 0.56-0.71 m rms Metallurgical Treatment Carburized Steel Dimensions 49.25 +0.00/-0.15 mm diameter The ball and test ring specifications described above are identical to those listed in
24、ASTM D5001, Measurement of Lubricity of Aviation Turbine Fuels by Ball-On-Cylinder Lubricity Evaluator (BOCLE). The sole source of supply of test rings known to the committee at this time is: Falex Timken Test Ring, Part Number 002-560-001, Falex Corp., 1020 Airpark Drive, Sugar Grove, IL, 60554 USA
25、. Test balls are available from multiple suppliers including Falex Corp. and PCS Instruments, 78 Stanley Gardens, London, W3 7SZ, United Kingdom. A diagram showing the test ring design is shown in Figure 2. 6.3 Propan-2-ol (common name, isopropyl alcohol), reagent grade or better. 6.4 Propanone (com
26、mon name, acetone), reagent grade or better. 6.5 A segregated supply of Mobil Jet Oil II is to be used for calibration purposes. Where possible this should be from sealed quart cans, where this is not possible a bulk supply may be used however lubricant properties including acidity and water content
27、 should be checked before each batch of tests. Total Acid Number (ARP5088) should not be allowed to deviate more than 0.10 mg KOH g-1from its original value (on the Certificate of Analysis) and the water content (ASTM D6304) should not be greater than 1000 ppm. 6.6 Polymer/cotton gloves. 6.7 Lint-fr
28、ee cloths or lint-free paper towel. 7. APPARATUS PREPARATION Care should be taken to adhere to strict cleanliness requirements and to the specified cleaning procedures. During handling and installation procedures, protect cleaned test components (cylinder, balls and reservoir) from contamination by
29、wearing polymer or cotton gloves and by handling the specimens using lint-free paper or cloth. Handling with paper/cloth removes the possibility of the transfer of plasticizers or oil contaminants from the gloves to the specimen surface as this could influence the test result. 7.1 Test Rings (as rec
30、eived) 7.1.1 Strip the wax protective coating from the test ring by vigorously manually wiping it with a lint-free cloth or paper soaked in propanone. Repeat this process. 7.1.2 Clean the test rings in propanone using an ultrasonic bath for a period of 15 minutes. Drain off the propanone and refill
31、before returning to ultrasonic bath for a further 15 minutes. 7.1.3 Drain off propanone and rinse thoroughly with fresh propanone. Dry with a lint-free cloth/paper. 7.1.4 Visually inspect components, discard any that exhibit pits, corrosion or surface abnormalities. Store the acceptable specimens in
32、 a desiccator. SAE ARP6255 Page 5 of 9 7.2 Used Test Rings (between tests) 7.2.1 Remove the test ring from the mandrel. 7.2.2 Using a propanone soaked lint-free cloth/paper remove test lubricant from the test ring surface. 7.2.3 Follow steps 7.1.2 to 7.1.4. 7.3 Test Balls (as received) 7.3.1 Remove
33、the oil coating from each ball by wiping with a propanone soaked lint-free cloth/paper. 7.3.2 Follow steps 7.1.2 to 7.1.4. 7.4 Test Ball Retainer Housing and Ring Mandrel 7.4.1 Wipe all components with a dry lint-free cloth/paper to remove excess lubricant. 7.4.2 Vigorously wipe all components with
34、a propan-2-ol soaked lint-free cloth/paper. Repeat this process. 7.5 Oil Tank, Ball Retainer Nut, Ring Retaining Plate and Screws 7.5.1 Wipe all components with a dry lint-free cloth/paper to remove excess lubricant. 7.5.2 Clean all components in propan-2-ol using an ultrasonic bath for 15 minutes.
35、7.5.3 Drain and rinse thoroughly with fresh propan-2-ol. 7.5.4 Dry with a lint-free cloth/paper and store in a desiccator. 8. CALIBRATION AND STANDARDIZATION 8.1 The following parameters should be calibrated as detailed in the manufacturers operating instructions: lubricant temperature, ring rotatio
36、nal speed, test duration, ball descent rate, and test weights. 8.2 A standardization test should be run to check each new batch of test rings. This check should also be carried out after periods of rig inactivity. The test should be carried out in accordance with the standard test procedure however
37、using the conditions tabulated below. If the ALTE is only to be used for severe or mild wear then only the specific standardization test is required, if both test regimes are to be used, both standardization tests are required. TABLE 5 Mild Wear Severe Wear Rotational Speed: 220 rpm 5 rpm Rotational
38、 Speed: 220 rpm 5 rpm Oil Type: Mobil Jet Oil II Oil Type: Mobil Jet Oil II Oil temperature: 150 C 2 C Oil temperature: 150 C 2 C Ball Load: 8 kg (i.e., 2 kg arm load) Ball Load: 36 kg (i.e., 9 kg arm load) Test duration: 30 minutes 0.10 minutes Test duration: 1 minutes 0.05 minutes 8.3 Test data sh
39、ould be generated and recorded until sufficient data is available to define the standard wear scar diameter. Until data is available, operators should ensure that each ALTE produces repeatable standard test results 0.05 mm of the mean result. If the first standardization test falls outside these lim
40、its then a second repeat should be conducted. If this second repeat also falls outside these limits the test ring should be discarded and the test repeated with a new ring. SAE ARP6255 Page 6 of 9 9. ASSEMBLY 9.1 Using a spirit level, ensure that the ALTE test unit is level, where necessary adjust t
41、he unit feet to level the unit. 9.2 A test ball, ring and all oil wetted components should be cleaned in accordance with the procedures defined in Section 7. 9.3 All test weights for the previous test should be removed from the weight hanger. 9.4 Switch on the unit and datum the pivot arm position i
42、n accordance to the manufacturers instructions, this will ensure the pivot arm is in the start position. 9.5 Install the test ball by using the retaining nut to securely locate the ball such that it cannot rotate. 9.6 Install the ring and securely fasten the retaining plate/nuts. Ensure that the tes
43、t ball and ring do not become contaminated by using cotton gloves when installing test specimens. 9.7 Assemble the oil tank and add 40 ml 1 ml of test lubricant. This should give an approximate immersion depth of 5 mm measured radially from base of the test ring. Install the oil tank ensuring that t
44、he thermocouple tip is submerged within the oil. 9.8 If a new test ring is being used then set the datum axial position in accordance with the manufacturers instructions. 9.9 Set the axial position of the ball on the test ring in accordance with the manufacturers instructions, this should be at leas
45、t 2 mm from the edge of the previous wear scar. 9.10 Place the required test weight on the weight hanger. Note that the weight generated at the ball and cylinder interface will be four times that applied at the weight hanger. Fully close the safety door (MkIII only). 10. TEST SEQUENCE 10.1 Adjust th
46、e test parameters (test rotation speed and test time) to those required, this should be done in accordance with the manufacturers instructions. 10.2 Switch on the test ring rotation. 10.3 Set the oil bath heater temperature to 150 C and turn on the heater. Allow the rotating test ring to act as a st
47、irrer whilst the oil temperature rises. 10.4 Once the oil bath temperature has stabilized at the set point temperature (this should take approximately 15 minutes), run the test. 10.5 At the end of the test period the pivot arm will automatically return to the start position and rotation of the test
48、ring will cease. 10.6 Turn heater off and allow cooling to ambient temperature. 11. DISASSEMBLY OF TEST APPARATUS Only once the apparatus has returned to ambient temperature should disassembly be attempted. 11.1 Remove the oil bath and allow the test ring to drip dry in to suitable waste tray. 11.2
49、Loosen the test ball retaining nut and remove the test ball. Rinse the ball with propan-2-ol and transfer to a labeled plastic bag. SAE ARP6255 Page 7 of 9 11.3 Remove the test ring retaining plate/nut, this will allow the test ring to be removed. A slide hammer may need to be used to release the test ring from the mandrel; however care should be taken to ensure the ring is not damaged. 11.4 Clean all components as
