1986 ◽  
Vol 108 (3) ◽  
pp. 221-227 ◽  
Author(s):  
M. G. Karfakis ◽  
R. W. Heins

One mechanism of bit failure in geothermal drilling is thought to be directly related to the overheating of the bearings. High temperatures alter the microstructure of the bearing material and reduce its wear resistance. This paper presents a laboratory study on bit bearing temperatures in rotary drilling using a two-roller cone micro-bit drill rig and a statistical approach referred as response surface methodology. The effects of the drilling variables on bearing temperatures were investigated. The range of bearing temperatures for the test conditions under study was determined. A second-order bearing temperature predicting equation is presented.


2011 ◽  
Vol 236-238 ◽  
pp. 2323-2326 ◽  
Author(s):  
Jun Liang Sun ◽  
Xin Hong Liang ◽  
Jie Zeng ◽  
Guang Lei Li ◽  
Jun Liang Sun

The aim of this work was to optimize the process parameters through the statistical approach for the production of alpha amylase by Bacillus subtilis ZJF-1A5 in submerged fermentation (SMF). The process parameters influencing the enzyme production were identified by using response surface methodology. Among the variables screened, the temperature and time were most significant and showed a positive interaction. The optimum levels were: temperature 35.8 °C, pH 5.03 and time 54h and under these conditions α-amylase yield was up to 191.15 U/mL.


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