23rd International Colloquium Tribology - January 2022 449 Designing a REACH Conform Small Conrod Bearing of a Plunger Pump with the Help of EHD Simulation Vincent Hoffmann Tribo Technologies GmbH, Barleben, Germany Corresponding author: vincent.hoffmann@tribo-technologies.com Felix Hartmann Hammelmann GmbH, Oelde, Germany Christian Stelzer CADFEM GmbH, Grafing bei München, Germany 1. Introduction Plunger pumps from Hammelmann are often used in the chemical, oil and gas as well as the food industry. The pumps can reach a performance of 1100kW, generate a volume flow of 3000 l/ min and maximum pressure values of up to 3000 bar. The pressure build-up of the pump is generated by plungers which are set in motion by a crankshaft in combination with conrods. A typical plunger pump and conrod of Hammelmann are depicted in Figure 1. Figure 1: Hammelmann plunger pump and conrod Due to the regulation 1907/ 1906 concerning the registration, evaluation, authorization and restriction of chemicals (REACH) manufacturers are obligated to avoid the usage of any dangerous materials like lead in their products [1]. Motivated by this regulation a material change of the bearing shell of the small conrod bearing of a plunger pump is analysed. Here a bearing layer structure with a sliding surface made of a leaded bronze on a steel back is replaced by a REACH conform bronze without a steel back, see Figure 2. Previous Bearing Layer Structure REACH conform Bearing Layer Structure Figure 2: Analysed bearing shell layer structures The load carrying capacity is analysed with the help of elasto-hydrodynamic simulations of both conrod bearing designs. 2. EHD Simulation For this investigation the operating behaviour of the small conrod bearing is analysed with the help of the simulation tool Tribo-X inside Ansys. 450 23rd International Colloquium Tribology - January 2022 Designing a REACH Conform Small Conrod Bearing of a Plunger Pump with the Help of EHD Simulation Figure 3: Process for the determination of a reliable REACH conform bearing design Therefore, due to a load surge resulting from the operation of the plunger pump it is of great importance to consider transient load conditions including the panning motion of the small conrod bearing which results from the transformation of the rotational movement of the crankshaft into the translational movement of the plunger [4]. Furthermore the small conrod bearing has to carry loads up to 200 kN during a load cycle of the pump. This generates high hydrodynamic pressure values in the lubricating gap, which makes the consideration of elastic deformations necessary to generate reliable results [2] [3]. In case wear affected areas occur in the lubricating gap a mixed friction model is used to identify those areas. The input quantities for the mixed friction model are deduced with the help of measured surfaces of the conrod and pin of the previous bearing design [3]. Therefore, the new bearing layer structure is expected to have a similar surface topography. In order to introduce a REACH conform bearing design for the plunger pump the previous leaded bronze bearing is analysed as a reference. Based on the acquired results a material change and a design modification of the supply pockets of the small conrod bearing are investigated. The main goal here is to improve the operating behaviour compared to the previous bearing design. The process is depicted in Figure 3. 3. Results Due to the operating conditions of the pump, which consist of a low pressure phase at the beginning and a high pressure phase at the end, the minimum film thickness changes significantly during one load cycle, see Figure 4. Therefore, the minimum film thicknesses are about 3.5 µm at the first half of the operating cycle. And it reaches values below 1 µm for the second half of the load cycle. In consequence for both bearing designs the simulation shows a contact between bearing shell and pin. Minimum Film Thickness Figure 4: Calculated minimum film thicknesses for previous and REACH conform bearing layer structure In conclusion the material change from the leaded bronze to the REACH conform material resulted in a worsened bearing performance. The analysis of the hydrodynamic pressure distribution of the bearings showed that the positioning of the lubricant supply pockets has a significant influence on the pressure build up. Due to a centric positioning of the supply pockets the sliding surface for a hydrodynamic pressure build up is limited. This results in a narrow hydrodynamic pressure field including high absolute pressure values. In this investigation it could be shown that the bearing performance could be significantly improved when the supply pockets are positioned non-centrically, farther to the bearing top. In consequence wear can be completely avoided after this modification. Furthermore the evaluated hydrodynamic pressure values are significantly smaller. A comparison between the hydrodynamic pressure values in dependence from the supply pocket positioning is shown in Figure 5. 23rd International Colloquium Tribology - January 2022 451 Designing a REACH Conform Small Conrod Bearing of a Plunger Pump with the Help of EHD Simulation Centric Positioning of Supply Pockets Non-centric Positioning of Supply Pockets Figure 5: Influence of supply pocket positioning on the hydrodynamic pressure at 340 degree crankshaft 4. Conclusion A material change of a small conrod bearing is analysed with the help of EHD simulation. It could be shown that the bearing performance of a REACH conform bearing design is worse compared to the previous bearing design. By evaluating the pressure distribution of the bearing it was possible to identify a significant design improvement. Therefore, it could be shown that a new positioning of the supply pocket leads to a heavily improved bearing performance. References [1] “Regulation (EG) Nr. 1907/ 2006: Registration, Evaluation, Authorization and Restriction of chemicals (REACH)”, 2006. [2] “ISO 7902 - 1…3: Hydrodynamic plain journal bearings under steady-state conditions - Circular cylindrical bearings”, 2013. [3] Bartel, D., “Simulation von Tribosystemen - Grundlagen und Anwendungen“, Vieweg+Teubner, Wiesbaden, 2010.