Due to yield increase, some farmers in Iran plant sugarbeet in 50-cm row spacing instead of conventional 60-cm row spacing. Low row spacings force farmers to harvest three consecutive rows instead of two alternate rows. This would increase the amount of draft requirement to pull the Lifter through the soil. In order to use common medium tractors for pulling the three-unit sugarbeet Lifter and properly lifting the sugarbeet tubers out of the soil, applying vibration to the shanks of the Lifter was taken into considertion. In this study, the effects of vibration frequency and share rake angle of a vibratory Lifter on its performance were investigated. Draft, slippage, percentage of broken and non-harvested tubers were determined for four vibration frequencies (0, 9, 10 and 12 Hz) and three share approach angles (11, 24 and 36 deg.), using a factorial experiment arrangement in a randomized complete block design with three replications. The results showed that the variations in draft and slip with frequency and rake angle were similar. Although the minimum value of draft resistance was obtained at 24 deg. of share rake angle with non-vibrated shanks, 50 percent of tubers remained in the soil and were not harvested. However, the non-harvested tubers reduced to only 20 percent when vibration was applied to the Lifter. So using the vibrating shanks improved the removal of the tubers out of the soil. A ratio (K) of draft to the harvested tubers (whole and broken tubers) was defined for selecting the optimum combination of the rake angle and vibration frequency. The K ratio was calculated and analyzed for different combinations of the rake angle and vibration frequency. K ratio comparison showed that, for minimizing percentages of broken and nonharvested tubers, the sugarbeet Lifter should have share rake angle of 24 deg. and vibrate with frequency of 9 Hz.

Tumbling mill liners transfer the energy to the mill charge and have a significant effect on the load behavior. A plant audit at the Sarcheshmeh copper complex indicted that due to the inappropriate design of ball mills liners, the liners wear and tear increased and the grinding efficiency decreased. With the objective of investigating the design of initial, current and proposed liners, charge trajectory was simulated by the GMT and KMPCDEM software packages. It was observed that the charge impact point for the current liners design was above the toe and on the shell liners. By simulation it was found that increasing the liner Lifter face angle from 0 to 15° and the Lifter height from 18 to 21cm could decrease the difference between the impact point and the toe and direct ball impacts to liners. Given the promising results, the new liners were designed, constructed and installed in ball mill 4. The result of sampling for a period of one liner life indicated that the amount of particles smaller than 75 microns in ball mill 4 product (with proposed design) compared with ball mill 3 (with current design) increased by 2. 5% and the liners life of the first half and second half increased by 18% and 20%, respectively.

Due to certain advantages in (semi-)Autogenous-Ball mill circuits in most of the high throughput ore grinding units of mineral processing plants, much attention is paid to optimize mill performance. Despite the maturity of the grinding mill mechanical design, the efficiency of the grinding media has previously been ignored. Different liner materials and shapes are used in different situations (in a variety of ore types and operational conditions), but the best economically and operationally chosen for one operation is not the same for the other. In this research, the possibility of establishing a relationship between liner/Lifter wear rate and variations in the composition (SiO2% and FeO%) of an iron ore is investigated. The ore belongs to a magmatic high grade iron ore deposit located at Chadormalu mine in the province of Yazd, Iran. A significant change in the mineralogical composition of the ore was observed during the sampling days which resulted in the variation of the feed ore work index. Measurements and determination of liner/Lifter wear rates and patterns concluded that the critical liner segments posed too much abrasion during ore grinding. By performing the metallurgical analysis of liner materials and after correlation of wear rate with ore composition, it was concluded that the homogeneity in the metallurgical microstructure of the alloyed steel (such as the uniform distribution and amounts of the constituent phases) has a great influence on the response of the liner/Lifter to the variations of ore composition. Magnetite with a greater abrasion index than hematite, also in finer particles, is responsible for additional wear rate (abrasion) in liners, but hematite with greater toughness/grindability (work index) exists in the mill with larger particle sizes, thus it could produce wear on liner parts with less tolerance to impact as is the situation for martensitic steels.

To date, there has been limited research conducted comparing the effects of various grinding media shapes on milling kinetics, load behavior, and mill power draw. However, no research has been conducted on their effects on a Lifter. This study aims to fill the gap in knowledge. An investigation into the effect of grinding media shape on the lateral movement of the charge (grinding media and material), by analyzing specific breakage rate parameters in a laboratory dry rod mill, has shown how grinding media can act as a Lifter. Two grinding media (simple and grooved rods) were compared. The specific breakage rate parameters were determined using the Austin model. The values related to the μ parameter, whose increase means a decrease in the specific rate of breakage and an increase in the lifting of the grinding media, were equal to 3758.76 and 4144.63 for simple and grooved rods, respectively. Results proved that although the grooved rods have a lower specific breakage rate than simple rods, they can perform well as a Lifter. They had the highest cataracting effect of the charge.

Liners in tumbling mill transfer energy to the mill load and has a significant impact on the load behavior. In order to achieve a domestic technology of liner design, a knowledge-based package of liner design was developed by using of domestic equipment and software packages. At the first stage, a proposed liner that provides an appropriate load trajectory is obtained by simulation using GMT (grinding media trajectory) software and discrete component method (3D-DEM, KMPCDEM software). In the next stage, after validating by a model mill, the manufacturing drawings of the proposed design are prepared. After the construction and installation of the proposed liners, the liners wear is recorded using a special measuring device and after preparing a three-dimensional model of liners, a new design is proposed. Applying this domestic liner design technology for AG mill liners at the Gol-e-Gohar mining and industrial company and increasing the liner Lifter face angle from 7 to 30° while keeping the original Lifter height resulted in an overall increase of 17% in the mill throughput. By use of this design package in the Sarcheshmeh copper complex ball and increasing the liner Lifter face angle from 0 to 15° and the Lifter height from 18 to 21cm, the amount of particles smaller than 75 microns in ball mill 4 product (with proposed design) compared with ball mill 3 (with current design) increased by 2. 5% and the liners life of the first half and second half increased by 18% and 20%, respectively.

The equations governing the motion of steel balls and their impact onto shell liners in industrial Semi-Autogenous Grinding (SAG) mills are derived in full details by the authors and are used in order to determine the effective design variables for optimizing the working conditions of the mill and to avoid severe impacts which lead to the breakage of SAG mill shell liners. These design variables are the Lifter height H, the working coefficient of friction m, Lifter face inclination angle j, steel ball size rB, mill rotational velocity w, and mill size R. In order to optimize the operating conditions and avoid severe impacts to its shell liners, the effect of these parameters need to be studied. The effect of Lifter height (H) and the coefficient of friction (m) on some of the main impact characteristics are simultaneously investigated for a SAG mill in Sarcheshmeh Copper Complex. It was shown that as the Lifter height or the coefficient of friction increases, the impact position tends to move upward, but the maximum impact force and the absolute value of the maximum principal stress decreases, reducing the impact severity.

The number of Lifters in the liner of ball mills and the mill rotation speed are among the most significant factors affecting the behavior of grinding charge (balls) and their motion trajectory, and consequently, the comminution mechanism in these mills. In this research, in order to find a suitable range for the number of Lifters in the liner of ball mills, the DEM method is utilized. Initially, a pilot-scale ball mill with dimensions of 2. 0 m × 1. 11 m without any Lifter is simulated. Afterwards, by adding, respectively, 1, 2, 4, 8, 16, 20, 26, 30, and 32 cuboid Lifter(s) with dimensions of 2 m × 5 cm × 5 cm, nine other separate simulations are performed. The influences of the number of cuboid Lifters on the two new factors introduced here, namely ‘ head height’ (HH) and ‘ impact zone length’ (IZL) at various mill speeds, that is, 70% and 80% of its critical speed (CS) are investigated. The results indicate that in order to find a suitable range for the number of Lifters in the liner of ball mills, it is necessary to consider these two parameters simultaneously as the criteria for selecting the appropriate range, That is, liners that simultaneously produce both a higher HH and a greater IZL are more suitable for use in the industry. The results also demonstrate that the suitable range for the number of cuboid Lifters in the liner of ball mills is between 16 and 32, which field research on the ball mills of three different plants in the industry confirms the accuracy of the results obtained in this research. Unlike the previous research works, it has now been shown that the number of ball mill Lifters does not only depend on the diameter of the mill but also depends on the width, height, angle of the Lifter, and generally on the type of Lifter.

Purpose: To quantitatively analyze central corneal thickness (CCT) in patients with primary angle closure glaucoma (PACG) and primary open‑angle glaucoma (POAG), and to evaluate its correlation with severity of glaucoma.Methods: In this retrospective study, records of patients with previously diagnosed POAG or PACG at a tertiary glaucoma service were reviewed. CCT was measured by ultrasound pachymetry. Mean deviation (MD) on visual field (VF) testing was recorded for glaucoma severity determination. CCT and age‑ and sex‑adjusted CCT were compared among the study groups using Student’s t‑test and analysis of covariance (ANCOVA), respectively. Univariate and multivariate regression models were used for correlation of age, MD and CCT.Results: A total of 115 patients with PACG, 215 with POAG, and 100 normal controls were included with mean age of 64.1±10.4, 59.9±10.5, and 62.04±10.80 years, respectively. CCT was thicker in PACG eyes (545.5±46.1 mm) as compared to POAG eyes (531.7±37.3 mm) and controls (531.0±38.3 mm) even after age and gender adjustment (ANCOVA, P=0.05). CCT was found to decrease with increasing age only in the POAG group (b=-0.57, P=0.01). Disease severity (MD of VF) was significantly and inversely correlated with CCT in both POAG and PACG eyes (b=1.89, P=0.02; and b=1.38, P=0.04, respectively) after age and sex correction.Conclusion: PACG eyes had thicker CCT as compared to POAG and normal healthy eyes in Iranian subjects. Severity of the disease was inversely correlated with CCT in eyes with both POAG and PACG.