Hydraulics & Pneumatics March 2022

HYDRAULICS 42 HYDRAULICS & PNEUMATICS March 2022 www.hpmag.co.uk rarely agree and are therefore likely to confuse the user. The BFPA developed a method for determining the RCL based on a number of specific requirements for both the system and the user, and this has since been accepted as an ISO standard – ISO 12669 [2] . Comprehensive method for selecting the RCL – ISO 12669 The basis of the method is the careful consideration of the individual operational requirements of both the system and the user, namely: The sensitivity of the components to particulate contamination The system working pressure and duty cycle The cost of breakdown and also the cost of the replacing the component used, in conjunction with Figure 1, to obtain the RCL for the system. Figure 1 shows the relationship between the RCL and weighting and this was obtained using practical examples from operational systems that were known to be operating efficiently and reliably. The example given in ISO 12669 is a large excavator at a quarry operating at 350 bar with a pressure compensated pump and large cylinders. Duty is heavy and 4,000 hours’ life is required. The total weighting or score for this is 19 and this gives an RCL of ISO 4406 [3] 15/13/10 Conclusions The development of ISO 12669 provides the user with an unambiguous, consistent and repeatable method of determining the RCL for the individual requirements of the operator of that system and will overcome the potential confusion created when other methods are used. It will provide an RCL that is more relevant to requirements of both modern hydraulic equipment and the user’s requirements for reliability and lifetime. As earlier methods were usually based on history or hearsay, they cannot reflect individual and modern requirements. Finally, the use of lower RCLs will increase the life and reliability of the system, as well as giving earlier warning of adverse increases in contamination – and so allowing earlier corrective actions. It will also mean that current monitoring procedures will have to be reviewed as Figure 1 of ISO 12669 states that online measurement should be used for cleanliness levels better than ISO 4406. References 1. M.J. Day: ‘How to specify the cleanliness of the hydraulic fluid to suit your individual requirements’ – presented at the British Fluid Power Association (BFPA) Conference on ‘Managing Fluid and Lubricant Contamination’, University of Bath 10-11 September 2019. 2. ISO 12669: ‘Hydraulic fluid power – Method for determining the required cleanliness level (RCL) of a system’, International Standards Organisation (ISO), Geneva, Switzerland 2017. 3. ISO 4406: ‘Hydraulic fluid power – fluids – Method for coding the level of contamination by solid particles’, International Standards Organisation, Geneva, Switzerland 2021. www.reynoldscc.co.uk The life and reliability required by the user Any additional safety concerns Each of these are sub-divided into levels of ‘severity’ for which a score or weighting is given; one such category is given in Table 1. This is to account for the working pressure and severity of the operation. Both these factors will influence the dynamic clearance in the components and, hence, the wear rate of all components The user works through the list of parameters and selects the sub-division which closely defines the system concerned. The score or weighting is recorded, and the user then moves on to the next parameter. This is repeated for the other subjects shown above. The weightings are added up and this is