SAE ARP 5996C-2015 Evaluation of Coking Propensity of Aviation Lubricants Using the Single Phase Flow Technique.pdf

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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 theref

2、rom, is the sole responsibility of the user.”SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions.Copyright 2015 SAE InternationalAll rights reserved. No part of this publi

3、cation may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE.TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada)Tel: +1 724-776-4970 (out

4、side USA)Fax: 724-776-0790Email: CustomerServicesae.orgSAE WEB ADDRESS: http:/www.sae.orgSAE values your input. To provide feedbackon this Technical Report, please visithttp:/www.sae.org/technical/standards/ARP5996CAEROSPACERECOMMENDED PRACTICEARP5996 REV. CIssued 2003-01Revised 2015-12Superseding A

5、RP5996BEvaluation of Coking Propensity of Aviation Lubricants Usingthe Single Phase Flow TechniqueRATIONALEThe tendency of a lubricant to form deposits in an engine oil system is a critical factor that can influence engine design, performance and maintenance intervals. Therefore it is important to h

6、ave an understanding of the coking propensity of the lubricant. The ARP has been revised to make the method more applicable to the use of more modern instruments and to introduce a procedure for extending the test for a further 20 hour period.1. SCOPEThis method is designed to evaluate the coking pr

7、opensity of synthetic ester-based aviation lubricants under single phase flow conditions found in certain parts of gas turbine engines, for instance in bearing feed tubes. This method is applicable to lubricants with a coking propensity, as determined by this method, falling in the range 0.01 to 5.0

8、0 mg.2. APPLICABLE DOCUMENTSThe following publications form a part 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 be

9、tween the text of this document and references cited herein, the 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 Alcor, Hot Liquid Process Simulator (HLPS), or Falex Thermal Foulin

10、g Tester (FT2), users Manual appropriate to the type and series of instrument being used.3. WARNINGThis document may involve hazardous materials, operations, and equipment. This document does not purport to address all of the safety problems associated with its use. It is the responsibility of the u

11、ser of this document to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.SAE INTERNATIONAL ARP5996C Page 2 of 234. OUTLINE OF METHOD4.1 A measured volume of sample is placed in the apparatus. The apparatus is pressurized with ai

12、r and the sample is then pumped through the system over a resistance-heated, tube-in-shell, heat exchanger for a specified period (normally 20 or 40 hours). The weight of deposit formed on the tube is then determined.4.2 This method assumes a degree of familiarity with the test equipment. Users must

13、, therefore, familiarize themselves with the apparatus, and the users manual, before attempting to use this method.5. APPARATUS5.1 Any of the instruments listed below are considered suitable for this method. It is recommended that the instrument be operated in a temperature-controlled environment to

14、 reduce the impact that room temperature fluctuations may have on method precision.5.1.1 Alcor, Hot Liquid Process Simulator (HLPS) 300 series.5.1.2 Alcor, Hot Liquid Process Simulator (HLPS) 400 Series.5.1.3 Falex Thermal Fouling Tester (FT2).5.2 Data recording/storage device suitable for recording

15、 the output from the various instrument thermocouples.5.3 Oven capable of maintaining a temperature of 100 C 5 C.5.4 Desiccator, dedicated solely for this test, filled with a suitable desiccant. It is recommended that the desiccator is operated in a temperature controlled environment to reduce the i

16、mpact that room temperature fluctuations may have on method precision.5.5 Laboratory balance capable of weighing heater tubes to 0.01 mg. It is recommended that the balance is operated in a temperature controlled environment to reduce the impact that room temperature fluctuations may have on method

17、precision.5.6 Measuring cylinders, 100 ml and 250 ml capacity.5.7 Boiling tube, of dimensions such that the top of the center section of the heater tube is at least 30 mm below the top of the boiling tube, or other suitable receptacle, in which to soak the heater tubes in petroleum spirit.6. REAGENT

18、S AND/OR MATERIALS6.1 Stainless steel (grade 316) short heater tubes. A diagram showing the tube dimensions is shown in Appendix G. The following heater tubes have been found to be satisfactory:PAC/Alcor part number 91747Falex part number 400-560-0036.2 Acetone GPR/LG.NOTE: GPR/LG = general purpose

19、reagent grade / laboratory grade.6.3 Petroleum spirit (any type between BP 40 to 60 C and BP 80 to 100 C) GPR/LG. Heptane may be used as an alternative.6.4 Trisolvent (equal quantities of acetone, propan-2-ol and toluene; all GPR/LG grade).SAE INTERNATIONAL ARP5996C Page 3 of 236.5 Lead, 99% minimum

20、 purity, for thermocouple performance verification.6.6 Tin, 99% minimum purity, for thermocouple performance verification.6.7 Pre-weighed filter papers, Teflon 5 m (suggest Millipore Cat no LSWP04700) (see Appendix C).6.8 Reference Heater TubeA heater tube complying with the requirements of 6.1 of k

21、nown mass. This tube is used solely as a control for detecting inconsistencies in the method weighing process and is not to be used as a sample analysis tube.6.9 Compressed air supply, clean, dry and oil free, capable of pressurizing the sample reservoir to 1380 kPa 140 kPa (200 psi 20 psi).7. SYSTE

22、M VERIFICATIONNOTE: Apart from the daily tube thermocouple calibration (7.1.1), it is not necessary to perform all of the system verification tests indicated below before every test. They should be conducted as often as is necessary to provide the user with confidence that the system is functioning

23、correctly and consistently. It is recommended, however, that the temperature profile obtained during the test procedure (9.10) be compared with that obtained during the last system verification check to detect any inconsistencies.7.1 Heater Tube Temperature Control Thermocouple7.1.1 The thermocouple

24、s should be checked in accordance with the method stated in the instrument users manual. If the manual states to use the eutectic temperature of tin (232 C), the performance should also be evaluated using a lead standard which has a eutectic point of 327.5 C. The temperature and power levels quoted

25、in the manual have to be adjusted to accommodate the eutectic temperature of the lead. Some users may find it more convenient to use a central or external calibration service in lieu of the above. This is permissible provided the service results are in a degree of calibration equivalent to that prov

26、ided by the above method. In cases of dispute, the tin and lead eutectic method shall be the referee method. Calibration should be carried out every 6 months as a minimum.7.1.2 The values obtained for the eutectic temperatures of lead and tin should be within 3 C of the quoted eutectic temperature.

27、If this is not the case then the thermocouple in question should be replaced and the verification step (7.1.1) repeated.7.1.3 Whichever calibration scheme is used, any deviation from the true melting point temperature values of more than 1 C shall be compensated for when setting control temperatures

28、, and when taking temperature measurements, by applying an appropriate correction to the setting or measurement. The degree of correction required may not be constant across the temperature range being used. Therefore, the extent of the calibration should be sufficient to determine the corrections n

29、ecessary for the critical temperature settings.7.1.4 Check the heater tube thermocouple for proper position. Raise the thermocouple so that the tip is flush with the top of the heater tube and upper bus bar end cap. The corresponding position on the thermocouple height scale must be 51 mm above the

30、zero point on the scale.7.2 Pump Flow Rate7.2.1 Set the pump to obtain a flow rate of 1 ml min-1. It has been determined that a flow rate of 1 ml min-1will yield 20 drops (including a count of drop zero) in 30 seconds from the reservoir return tube. For instruments with a window at the top of the re

31、servoir the appropriate flow controller setting can be determined by this method. The flow should be set to obtain 20 drops in 30 seconds 1 second.SAE INTERNATIONAL ARP5996C Page 4 of 237.3 Power Setting7.3.1 The temperature of the tube is measured via a height adjustable thermocouple positioned wit

32、hin the heater tube. The test requires that the specified maximum tube temperature be achieved at the hottest pre-determined position “A“ as measured on the thermocouple (right hand) height scale. If position A is not known see 7.4.1 and Appendix A.7.3.2 The power level on more modern instruments is

33、 internally controlled on a feedback control loop to keep the temperature at the required set point. However, on older instruments the power level must be set manually to achieve the required temperature and the power level required will depend on the type of power controller employed. Reference sho

34、uld be made to the user instructions for the controller employed. 7.3.3 For manually controlled systems, to ascertain the power level required, set up the test as defined in the procedure section. Align the top of the thermocouple slide with the hottest pre-determined point A (start with the 10 posi

35、tion on the thermocouple height scale if point A is not known). Run the test and monitor the temperature. Adjust the power level until the required temperature is achieved.7.4 Tube Temperature Profile7.4.1 One of the most important stages in setting up the apparatus for this test is to determine the

36、 position of the hottest point on the tube, and the tube temperature profile. Appendix A explains how to do this, shows a typical profile and discusses the factors that can affect both the hottest point and the general profile. Users who are unfamiliar with these critical issues should refer to Appe

37、ndix A before proceeding any further.7.4.2 The procedure in Appendix A should also be performed following any significant changes to the system such as replacement of heating system parts, or after thermocouple calibration. In such cases it is acceptable to start the verification process using the p

38、reviously known position A.7.4.3 Determination of the tube temperature profile is also part of the test procedure. Profiles obtained at the beginning of test runs should be compared with those obtained at 7.4.1 and 7.4.2. Such comparisons can be used to ensure that the system has remained stable. If

39、 the comparison shows a deviation then the causes should be investigated (see Appendix A). If the hottest point on the tube has moved and it is not possible to return it to the previous position A following the investigation, then this must become the new position A.8. PREPARATION OF APPARATUS8.1 Cl

40、ean the pump by passing through a minimum of 150 mls of acetone followed by 150 mls of the lubricant to be examined. It is recommended that this be done by first attaching specially designed cleaning tubes (see Appendix B). Discard the lubricant used to clean the pump.NOTE: If the equipment manufact

41、urer recommends the use of solvents other than acetone then alternative solvents are permissible provided they completely remove the previous sample from the pump.8.2 Once the last of the 150 mls test lubricant has passed through the pump, continue to allow the pump to run until the majority of lubr

42、icant has been removed from the pump.8.3 Any remaining oil pipes and oil-wetted parts that were not cleaned at 8.1 should be flushed with the acetone and blow dried with a clean, oil-free air supply. All O-rings related to the thermocouples and pipework should be changed for each test. The large sea

43、l(s) in the reservoir may be reused and should be cleaned with the petroleum spirit and not be exposed to the acetone, which will cause them to swell.8.4 To clean out the reservoir remove the top and (if removable) the bottom of the vessel.8.5 Clean the heater test section with a nylon brush and ace

44、tone. Blow dry with a clean, oil-free air supply. If deposits remain following this procedure then the use of Trisolvent is recommended (see Appendix B).SAE INTERNATIONAL ARP5996C Page 5 of 238.6 Take a new heater tube. Inspect the thermocouple hole and ensure there is no debris present. If in doubt

45、, pass a probe through the hole to ensure any debris is removed. Rinse the outside and inside of the tube with pet spirit and then with the acetone. If there is any concern that rinsing alone will not remove all contaminants (such as a temporary protective coating) then it is recommended that the tu

46、be be wiped with lens tissue soaked in pet spirit and then in acetone before finally rinsing the tube with the solvents. Dry the tube in the oven at 100 C 5 C for 30 minutes and cool in a desiccator filled with a suitable desiccant for at least 30 minutes. Perform the same process with the reference

47、 heater tube. Following cleaning, these tubes must be handled with clean gloved hands (powder free latex, PVC or other impervious materials, not cotton) or PTFE coated or silicone tipped forceps. Touching the narrow center section of the tube must be avoided.8.7 Weigh and record the masses of the cl

48、eaned tubes to an accuracy of 0.01 mg. Because of the high degree of accuracy required it is recommended that the tubes are weighed several times and the average of these weighings taken as the initial tube weight. Return the reference heater tube to the dedicated desiccator until required for the p

49、ost test weighing. The other heater tube is to be used for the oil sample test.8.8 Mount the test heater tube within the test section such that the groove on PAC tubes, or the company logo on Falex tubes, is at the top and the shoulders may be seen centrally positioned through the side arms.8.9 Assemble the pipes and fittings as specified in the instrument manual for the standard test without filters or diff