Evaluation of Palm Stearin as Shaft Lubricant

Transcription

1 Evaluation of Palm Stearin as Shaft Lubricant N. Sapawe a*, S. Syahrullail b, M.F. Idris Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, UTM Skudai, Johor, Malaysia. a norzahirsapawe@gmail.com, b syahruls@fkm.utm.my Keywords: RBD Palm Stearin, Grease, Shaft, Frictional force Abstract. The shaft is very important which have been used to transmit the power. Over a longer period, shaft may be worn. Hence to reduce the worn effect, the shaft must be lubricated. Nowadays, Malaysia is being one of the biggest producers and exporters of palm oil product. Thus, by using this advantage, Palm Stearin which is solid fraction obtained by the fractionation of palm oil after crystallization is being used as a shaft lubricant. This research has been conducted to determine the frictional force of rotational shaft and to observe the wear and surface roughness. The experiment is conducted within 20 mins for each speed which are variance from 200 rpm to 1200 rpm with increment by 200 rpm by using modified pin on disc machine. Based on the result, Palm Stearin show the good performance which is has the lower frictional force compare with two others industrial lubricants. Besides that, surface roughness and wear of shaft did show any significance difference for before and after the experiments. It can be conclude that the Palm Stearin has the lower frictional force which is in the range from 2 N to 4.1 N. Introduction Energy that used in industrial countries to overcome friction is one third of all energy. More than 30% of the production goes to replace worn equipment which caused by high friction and lead to high wear [1-3]. Hence, by controlling and reducing friction and wear with low energy consumption is one major challenge [4]. Besides the mineral based and synthetic as a lubricant, vegetable oils are being investigated as a potential source of environmentally favorable lubricants [5]. However, vegetable oil has the limitation as industrial lubricants due to poor low temperature properties, low oxidation, thermal stability and the range of available viscosities is a narrow [1-3,5]. Oil and grease are not identical. When the oil is not practical or suitable, grease is used. By matching the machinery and operating conditions, the lubricant that can be used can be decided with desired lubricants characteristics [6]. Material and Method The experimental condition is the rotational speed varies and no load is applied. The speed of disc is rotating from 200 revolutions per minute (rpm) to 1200 rpm with incremental of 200 rpm. Next, the amount of lubricants applied is kept constant which is 0.2 g for Grease Koya, Grease BBG and RBD Palm Stearin. This amount is measured by using electronic weight balance. Then, lubricate the shaft and shaft casing with lubricants. After that, attach it on the disc. The disc has the square hole to allow the shaft attach to the disc. Before slot in the shaft casing, place the bearing below it. The bearing is use to prevent the friction occur between shaft casing and disc. On the shaft casing also has the rod that has been attach which is use to contact with the sensor to measure the frictional force. Figure 1 show the photograph of the equipment related to the rotating shaft equipment. After that, set the experiment duration to 20 mins. Each speed will be conduct in 20 min. This experiment will using WINDUCOM 2008 software to record the data related with the experiments which is frictional force and duration of experiments.

2 Results and Discussion Figure 1. Arrangement of rotational shaft equipment Frictional Force Analysis. Figure 2 show the relationship frictional force of Grease Koya with the speed. Generally, the value of frictional force is during the lowest speed which is at 200 rpm is high which is in the range of 22 N to 35 N Figure 2. Frictional force with related speed of Grease Koya Then, the frictional force during the highest speed rotational speed which is at 1200 rpm is within the range from 6.5 N to 22.8 N. Based on this data, it can be seen that the frictional force is decreasing as the rotational speed is decreasing. Figure 3 shows the frictional force of rotational shaft by using Grease BBG. Mostly, the frictional force for all speed is within the range of 2 N to 8 N. However, there might be some error occur which is at 800 rpm, the frictional force is slightly different from other which is 12.4 N. Figure 3. Frictional force with related speed of Grease BBG

3 Generally, RBD Palm Stearin shows in the Figure 4 which is the frictional force with related speed, as the speed is increases, the frictional force also increased. The range of frictional force for overall speed is within 2.5 N to 6 N. Figure 4. Frictional force with related speed of RBD Palm Stearin By comparing with three lubricants, Grease Koya has higher frictional force compare with other lubricants which is in the range between 27 N to 14 N. The pattern of frictional force with speed shows that frictional force linearly decreases as the speed increased. Meanwhile, for Grease BBG, it shows that the range of frictional force is within 3.9 N to 5.3 N. Figure 5 shows that the frictional force of overall lubricants. Figure 5. Overall frictional analysis related with speed Then for the RBD Palm Stearin frictional force analysis, the data shows the some similarity trend with the Grease BBG which is the data of frictional force is within the range of 2 N to 4.1 N. The reading of frictional force also shows that, it linearly increased as the speed of rotational shaft is increased. Viscosity of lubricants especially grease may influence the result of frictional force of rotational shaft. NLGI grade for Grease Koya is grade 2 and for Grease BBG is grade 1. Meanwhile, the experimental results conducted by Tiago showed that the grease formulation had very significance influence on friction torque and operating temperature. The friction torque depends on the viscosity of the grease, base oil and also the interaction between grease thickener and base oil, which affected contact replenishment and contact starvation, thus influence the friction torque. Wear and Surface Roughness Analysis. After done the experiment, the wear analysis has been done into three parts which is show in Figure 6. Wear that occurs on the upper shaft show in Figure 6 (a) are in the range from μm to μm. Meanwhile wear occurs in this location, Figure 6 (b) is a little bit high compare to first location which is in the range from μm to μm.

4 Then, the third location which is shows in the Figure 6 (c) which is from μm to μm. In this research the casing of shaft are slot together with shaft. So there possibility that hard particle is stick on the shaft surface or shaft casing when the experiment is running. (a) (b) (c) Figure 6. Wear scar of shaft after experiments (a) upper part of shaft (b) middle part of shaft (c) lower part of shaft Meanwhile for surface roughness analysis shows that there is no significance difference compare with before and after experiment for all lubricants that has been applied on rotational shaft. Figure 7 show that the average surface roughness (R a ) with related shaft and casing position. R a value of shaft for before the experiment is from to 0.687μm and after experiment, the R a value is from to 0.766μm. Meanwhile for casing, R a value before experiment is from to 1.489μm and after experiment, the R a value is from 0.934tp 1.895μm. (a) (b) Figure 7. Average surface roughness after experiments (a) Shaft position (b) Casing position Load Analysis. The normal applied load has been calculated by using standard static coefficient friction (μ s ) of lubricated and greasy surface for steel to steel contact which is Normal load can be calculated based on equation as shown where F is friction force, μ is coefficient friction and N is normal load applied. The expected normal applied based on lubricant is shown in Table 1. Table 1. Expected normal load with related lubricants RBD BBG KOYA Speed Friction Load Friction Load Friction Load (rpm) Force (N) (N) Force (N) (N) Force (N) (N)

5 By comparing with three lubricants, Grease Koya can have the highest normal load that can be applied. The maximum expected normal load that can be applied for Grease Koya is 168 N. Meanwhile, for Grease BBG and RBD Palm Stearin, there is no big significance different for expected normal load can be applied. Within the rotational speed from 200 rpm to 1200 rpm, the maximum expected load for Grease BBG and RBD Palm Stearin is 33.1 N and 25.6 N. Figure 8 show that the relationship of load with related speed and lubricants. Conclusions Figure 8. Expected normal load with related speed and lubricants Based on the result, it can be conclude that RBD Palm Stearin show the good performance which is has the lower frictional force, followed by Grease BBG and then Grease Koya. Performance of RBD Palm Stearin also shows the similar result with the industrial lubricants which is Grease BBG. Based on the result of frictional forces versus speed, RBD Palm Stearin and Grease BBG show that as the speed of rotational shaft increase the frictional force is also increase. Hence, RBD Palm Stearin might have some improvement in term of performance if there do some modification such as mix with additives. Acknowledgements The authors wish to thank the Faculty of Mechanical Engineering at the Universiti Teknologi Malaysia for their support and cooperation during this study. The authors also wish to thank Research Management Centre (RMC) for the Research University Grant (GUP-03H58) from the Universiti Teknologi Malaysia, Fundamental Research Grant Scheme (FRGS-4F229) and E-Science Grant from the Ministry of Education of Malaysia for their financial support. References [1] S. Syahrullail, N. Nuraliza, Friction and wear performance of double fractionate palm olein lubricant using pin-on-disk tribometer, Appl. Mech. Mater. 554 (2014) [2] S. Syahrullail, H.M. Norhakem, N. Sapawe, K. Amir, The influence of normal load in wear resistance characteristic of palm fatty acid distillate, Appl. Mech. Mater. 554 (2014) [3] S. Syahrullail, A.M. Azmi, N. Sapawe, K. Amir, Wear characterization of aluminum lubricated with palm olein at different normal load, Appl. Mech. Mater. 554 (2014) [4] K. Holmberg, Friction science saves energy, VTT Impulse 2 (2009) [5] P.L. Boey, M.I. Saleh, N. Sapawe, S. Ganesan, G.P. Maniam, D.M.H. Ali, Pyrolysis of residual palm oil in spent bleaching clay by modified tubular furnace and analysis of the products by GC-MS, J. Anal. Appl. Pyrol. 91 (2011) [6] C. Tiago, G. Beatriz, C. Armand, S. Jorge, Friction torque in grease lubricated trust ball bearing, Tribol. Int. 44 (2011)