1、July 2009 English price group 8No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 21.100.20!$XC instead, it describes inf
2、ormatively, using examples, how, in the modified rating life calculation for rolling bearings according to DIN ISO 281, the level of contamination of the lubrication or, in the modified reference life calculation according to ISO/TS 16281, the purity class of the oil can each be estimated as a funct
3、ion of measures to keep the gear units clean. The degree of contamination should be applied in connection with the procedure for the calculation of the modified rating life Lnmspecified in DIN ISO 281 according to Table 13. The oil purity class should be used in connection with the procedure for the
4、 calculation of the modified reference working life Lnmspecified in ISO/TS 16281 in accordance with DIN ISO 281, Figures A.1 to A.9. The following aspects are to be taken into consideration: Cleanliness of the interior of the gear unit and the internal components after gear assembly; Cleanliness of
5、the lubricant circulation system; Cleanliness of the gear oil on initial filling and all later fillings; Screening of the interior of the gear unit, the bearings and the lubricant circulation system to prevent penetration by contaminants; Removal of friction particles from the oil during the gear ru
6、nning-in phase and later operation through oil filtering, particle separators and/or regular oil changes or oil cleaning. The more effort is made, from design through assembly, trial runs, installation, commissioning, running-in phase and operation to maintenance and repair, to keep the gear unit fr
7、ee from contaminants, the longer the life of the rolling bearings can be expected to be. In particular, it is recommended that, if the gear unit is used in surroundings with a highly contaminating effect, the bearing points of the connection shafts are protected by special design measures against th
8、e penetration of dirt particles. For further measures, see Clause 8. 2 Symbols and designations aISOlife modification factor Cufatigue load limit Dpwmean bearing diameter eCcontamination factor P dynamic equivalent load viscosity ratio f symbol for formulae (no parameter) x(c)filtration ratio (filte
9、r retention rate) NOTE The index (c) means that counting procedures for automatic particle counters shall be calibrated for the particle size x (in m) according to ISO 11171. DIN ISO 281 Suppl. 3:2009-07 5 3 Life modification factor aISOIn DIN ISO 281, the life modification factor aISOis estimated f
10、rom formulae and/or diagrams as a function of the parameters eC, CU, P and , in the form = ,uCISOPCefa (1) The contamination factor eCcovers the voltage overshoot in the rolling contact between the rolling element and the raceways as a result of contamination. 4 Cleanliness of the rolling bearing Th
11、e following procedure is recommended to keep the gear unit and thus the rolling bearings and the lubricant clean: The gear components (housing, gear wheels, shafts, bearings, oil pipes, etc.) are cleaned before being assembled and the gear, with clean oil, is subjected to a test run on a test stand.
12、 It undergoes an initial running-in phase with the formation of friction particles. Depending on the type of oil lubrication, the lubrication oil used for the trial run is cleaned with filters during the test run and/or afterwards for further use. The gear unit is then delivered to the place of use
13、in the assembled state, either with or without oil preserved inside and protected against penetration by foreign bodies where it is erected and started up with clean oil. It is also possible to carry out the test run with preservation oils that have been specially developed for this purpose. In such
14、 cases, there is no need for subsequent preservation. Start-up is generally followed by a second running-in phase. After this second running-in phase, the oil should be cleaned or changed. After this, the operator is required to follow the specifications laid down by the manufacturer for oil cleanin
15、g/oil changing intervals. The type of oil specified for the trial run and for later operation, the oil changing intervals and/or intervals for oil analyses and the contamination limit values before measures are introduced to clean or change the oil shall be logically related to the degree of contami
16、nation and should be documented in the relevant gear unit operating instructions. Tables 3 and 4 provide a guide, by way of example, to the degree of contamination of the lubricant. The filter grades listed in Table 3 are laid down in this supplement according to Table 1. Table 1 Filter classificati
17、on Filter finenessaUltrafine filter 2 m to 5 m (c) Fine filter 5 m to 10 m (c) Medium-fine filter 10 m to 25 m (c) Coarse filter 25 m to 100 m (mesh size) a Filter with filtration ratio x(c) 200 (except for coarse filters such as wire fabric filters, mesh size given for these) DIN ISO 281 Suppl. 3:2
18、009-07 6 5 Degree of contamination 5.1 Oil lubrication with filtering The lubrication oil is sucked out of the gear unit interior using a pump and, in an oil lubrication system, passed through a filter either in the main flow, in the main and secondary flow or just in the secondary flow. Depending o
19、n the fineness of the filter, it removes contamination particles above a particular size from the oil and returns the filtered oil back to the gear unit. Table 3 provides information on the degree of contamination. Using the degree of contamination, the factor eCcan then be established with the aid
20、of Table 13 in DIN ISO 281 as a function of the mean bearing diameter Dpw. 5.2 Oil lubrication without filtering With gear units with oil bath lubrication, the oil is generally unfiltered between individual oil changes or oil cleaning sessions. In such cases, Table 4 provides a guide to estimating t
21、he degree of contamination. This also applies for gear units with circulation lubrication without oil filtering in the main and secondary flow. Using the degree of contamination, the factor eCcan then be established with the aid of Table 13 in DIN ISO 281 as a function of the mean bearing diameter D
22、pw. 6 Oil purity class The measures listed in Tables 3 and 4 also affect the purity of the oil. It is suggested that the oil purity class should be assumed as being related to the degree of contamination according to Table 2. Using the oil purity class specified in ISO 4406 and with the aid of the d
23、iagrams in DIN ISO 281, Figure A.1 to Figure A.9, the factor eCcan be estimated as a function of the mean bearing diameter Dpwand the viscosity ratio . Table 2 Degree of contamination and oil purity class Degree of contamination according to Table 3 or 4 Oil purity class according to ISO 4406 Extrem
24、e cleanliness /13/10 High level of cleanliness /15/12 Normal cleanliness /17/14 Slight contamination /19/16 Moderate contamination /21/18 Severe contamination /21/18 DIN ISO 281 Suppl. 3:2009-07 7 7 Measures for keeping the gear unit clean 7.1 General The degree of cleanliness of the gear unit influ
25、ences the operating reliability and working life of the oil, the gear wheels and the rolling bearings. Care shall therefore be taken to ensure that the oil in the gear unit is clean. The following recommendations are measures which will help to ensure that less contamination occurs in or enters the
26、gear unit. NOTE Naturally, to achieve a long bearing life, only high-quality bearings should be used. The catalogues of the better known rolling bearing manufacturers also contain important instructions for the installation and removal of rolling bearings. It is important that these instructions are
27、 followed. 7.2 Design Low occurrence of wear and tear through the use of case-hardened gear wheels with smooth tooth flanks. If shot blasting of the gear wheels is carried out to increase the strength of the teeth bases, it may also be necessary to cover the tooth flanks if the blasting has a major
28、detrimental effect on the surface roughness. Recommendations for the choice of gear oil are based on the following points: CLP oil according to DIN 51517-3; synthetic oil if it has to be used due to special requirements regarding the oil life at high oil sump temperatures or specific load conditions
29、; the maximum oil viscosity that is still practical; high scuffing load according to the scuffing load test in DIN ISO 14635-1 determined if necessary for the temperature range of the later area of use; high micropitting resistance after the micropitting test in FVA 54/7 or DGMK Research Report 575
30、determined if necessary for the temperature range of the later area of use; low rolling bearing wear after test with rolling bearing lubricant test device as in FE8, DIN 51819-1 and DIN 51819-3; low foaming and good air separation capacity. Lubrication oil circulation systems with replaceable fine f
31、ilters with water absorption capacity. Oil coolers to keep down oil temperature. If necessary, additional attachment of a compensator vessel for expanding oil. Operation of fluid couplings and brakes with separate oil systems. Rolling bearings with oil-resistant cages. Housings painted inside with o
32、il-resistant paint. Use of oil-compatible housing and shaft seals. Design and layout of oil fill and outlet openings, inspection openings, openings for removal of oil samples, oil dipsticks and magnetic bungs so that simple maintenance is possible without contamination. Avoiding the penetration of c
33、ontamination such as brake rubbings or spray water in labyrinth and felt ring seals, vents and breathing filters by locating them in clean, pressure-free areas away from contamination wherever possible. Complete sealing of the gear housing in hostile environments. DIN ISO 281 Suppl. 3:2009-07 8 Vent
34、s and breathing filters should be provided in a sufficient size and with sufficiently fine filters to suit the choice of system filter, depending on conditions of use, with an additional water separator function (“ventilation dryer”). 7.3 Assembly Components shall be washed thoroughly before the sta
35、rt of assembly. Components which cannot be dismantled, such as rolling bearings, should not be washed. Only remove bearings from original packaging immediately before installation. If necessary, remove corrosion-protection. Assemble gear unit in a clean room. Use clean tools and assembly equipment.
36、Clean assembly procedures to be applied. If necessary, monitor cleanliness of assembly by analyzing the oil after the factory trial run. Improve assembly cleanliness if necessary. 7.4 Trial run Make sure that the test oil is properly clean for the trial run. If necessary, filter the test oil before
37、adding. With lubrication oil circulation systems, use an ultra-fine or fine filter during the trial run to remove contaminant residues caused by assembly and running in. After the trial run, the test is to be drained off if necessary, the gear unit rinsed and new filters installed.1)With gears that
38、are running in, increase the load and speed in stages; run in gear using special oil. If necessary, cool the oil during running-in. 7.5 Operation and maintenance Change the oil regularly and in plenty of time to avoid serious contamination from abraded matter and oil ageing. If replacing oil with th
39、e same type of oil, keep residues in the gear unit to a minimum. Do not mix gear oils of different types or produced by different manufacturers. Residues left after an oil change are to be tested for compatibility with the next oil to be used. If oils of very different types or oils containing very
40、different additives are changed especially if polyglycols are replaced with another type of oil, and vice versa rinse through the gear unit thoroughly with the new oil. Remove leftover old oil from the gear unit completely or check the compatibility of the new oil with the oil residues. Never rinse
41、the gear unit with petroleum or other cleaning products. 1) In a trial run with high-performance preservation oils, there is no need to rinse the gear unit after draining out the test oil. There is no need for later rinsing before start-up if it can be ensured that the gear oil to be used is compati
42、ble with preservation oil residues. DIN ISO 281 Suppl. 3:2009-07 9 Avoid mixing the oil with foreign matter in any way. Add oil that has been cleaned first with ultra-fine or fine filters from a filter trolley, connected to the gear unit with quick-release couplings. Check the used filter elements f
43、or residues and contamination. Use clean procedures when taking oil samples. If necessary, monitor lubrication oil for contamination and ageing with particle counters, spectrographic and ferrographic analyses, analyses of acid content, viscosity and water content. With high water contents, change oi
44、l or remove water using replacement filters which will absorb water. Make sure that the oil cooler is working and cooling the oil. Avoid external heating from secondary equipment. 8 Degree of contamination Table 3 applies for gear units with oil filtering and Table 4 for gear units without oil filte
45、ring. The measures given in the tables are examples and can be replaced by other measures that have the same effect. It is also possible to use other combinations for logically establishing the degree of contamination. DIN ISO 281 Suppl. 3:2009-07 10 Table 3 Examples of the classification of cleanli
46、ness for oil lubrication with filtering Measures for ensuring cleanliness Degree of contamination Laboratory conditions: Contamination in the oil to the height of the lubrication gap. Extreme cleanliness Components rinsed before assembly in a closed washing system. Cleaning liquid used cleaned with
47、ultra-fine filters. Concealed housing interiors carefully cleaned with vacuum air. Oil system pipes and fittings carefully rinsed before first trial run. Used rinsing product cleaned with fine filters. Gear unit trial run on test stand at manufacturers premises under high test load with ultra-fine f
48、ilters in main flow. Oil contamination from abraded particles checked continuously. Start-up at place of use with ultra-fine-filtered fresh oil. Ultra-fine filters in main flow. During operation at place of use, monitoring of oil purity and compliance with oil change regulations. Topped up with ultr
49、a-fine-filtered fresh oil. Measures to ensure cleanliness documented. High level of cleanliness Components rinsed before assembly in a closed washing system. Cleaning liquid used to be cleaned with fine filters. Oil system pipes and fittings carefully rinsed before first trial run. Used rinsing product cleaned with fine filters. Gear unit trial run on test stand at manufacturers premises under medium test load with fine filters in main flow. Oil contamination from abraded particles checked continuously. Start-up at place
