Thrust
Ball Bearings
Thrust
ball bearings are separable and their limit rotational speed is low.
Structures:
1.51000
type single-direction thrust ball bearings, this type of bearing can only
accommodate axial load on one direction and can control the axial movement on
one direction of the shaft and housing.
2.52000
type double-direction thrust ball bearings, this type of bearings can
accommodate axial load on double direction and can control the axial movement
on double direction of shaft and housing.
3.
560000 type thrust angular-contact Ball Bearing, as this structure can carry
axial load and radial simultaneously.
Cage materials
When
the outside diameter is equal or lesser than250mm, thrust ball bearings generally adopt pressed
steel sheet cages, when the outside diameter is more than250mm,it will adopt solid cages.
Minimum axial load
When
the Thrust Ball Bearing is operating, if the applied axial load is too small,
the axial direction is not tightly pressed, then acted by centrifugal force,
the steel ball will slip and displace and destroy the normal operation of the
bearings. To avoid the occurrence of such case, an axial load, Famin must be
applied when the thrust ball bearings is working. The calculating formula is:
In
the equation, Famin Minimum axial
load (kN)
A Minimum load constant
N Revolution (r/min)
Minimum
load constant A is showing in the bearings dimension table. If the applied
axial load is small, a spring must be used to preload the bearing.
Permissible tilt angle
The
double supporting surface of thrust ball bearings should be parallel. The axis
center line should be square with shell supporting surface, if this is not
assured, it can compensate by adopting spherical housing washer and
self-aligning washer.
Tolerance
The
tolerance value of thrust ball bearings is showing in the section [the
tolerance of rolling bearing".
Dynamic equivalent axial load
Whenα=90°,thrust
ball bearings can only carry axial load and its dynamic equivalent axial load
is: Pa=Fa
Whenα≠90, acted by constant and invariable radial and
axial loads, the dynamic equivalent axial load is: Pa=XFr+YFa
See
Annex Table 1 for the coefficients of X and Y.
Static equivalent axial load
Whenα=90°,
the static equivalent axial load is: P0a=Fa;
Whenα≠90°,
the static equivalent axial load is: P0a=2.3Frtanα+Fa.
Where:
For double-direction bearings, this equation is applicable to the status when
the ration of radial load and axial load is an arbitrary value; for
single-direction bearings, when Fr/Fa≤0.44ctgα, the
equation is reliable; when, the Fr/Fa＞0.67ctgα,
the equation can still give satisfactory P0avalue, but not very conservative.
Table 1 Value
of X and Y
α1)
Single-direction
Bearings2)
Double-direction
Bearings
e
X
Y
X
Y
X
Y
45º 3)
50º
55º
60º
65º
70º
75º
80º
85º
0.66
0.73
0.81
0.92
1.06
1.28
1.66
2.43
4.8
1
1.18
1.37
1.6
1.9
2.3
2.9
3.89
5.86
11.75
0.59
0.57
0.56
0.55
0.54
0.53
0.52
0.52
0.51
0.66
0.73
0.81
0.92
1.06
1.28
1.66
2.43
4.8
1
1.25
1.49
1.79
2.17
2.68
3.43
4.67
7.09
14.29
α≠90º
1.25tanα×
(1-
(1-
(1-
1.25tanα×
(1-
1.25tanα
Notes: 1)
For α`s medium value, use linear interpolation to calculate the values of X, Y
and e.
2) Fa/ Fr≤e is not
applicable to single-direction bearings.
3) For thrust bearings withα>45°, use interpolation method to calculate the
value of whenα=45°.
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sinα)
tanα×
sinα)
tanα×
sinα)
sinα)
Treatment and recovery of soot and arsenic trioxide
For some of the pyrite-type arsenic pyrite gold ore leaching difficult, in addition to the firing process flue gas SO 2 is generated, there are dust, arsenic, mercury, cadmium, lead and other harmful elements, so the addition of SO 2 while, These harmful elements should be treated.
1. Treatment and recycling of arsenic-containing soot
During any firing operation, a certain amount of soot will be produced depending on the fineness of the charge and the firing conditions. A cyclone is used to recover soot from the exhaust. However, the dust fineness cannot be recovered by a general cyclone. Unrecovered soot must comply with dust emission regulations. Formula for determining allowable dust emissions in Nevada, USA:
(1) When the dry material feeding speed is less than 30000kg/h, E=0.0193W 0.67
(2) Feeding speed of dry material above 30000kg/h E=11.78W .011 -18.14
Where E - the allowable dust emission, kg / h;
W—process feed rate, kg/h.
If lime is used to purify the exhaust gas to control SO 2 , this method can sufficiently remove the dust to meet the air discharge regulations; if the dust is not sufficiently removed, an electrostatic precipitator or a bag filter must be used to reduce the dust.
Further, as described above, the amount of gold contained in the extremely fine dust generated at the time of baking is usually higher than the average value of the thick ore concentrate, and the fine dust which cannot be recovered by the cyclone may have a large amount of gold loss. Therefore, the installation of an electrostatic precipitator or bag filter can achieve a dual purpose; reducing the amount of dust emitted into the air and increasing the recovery of gold.
2. Treatment and recycling of arsenic and mercury containing gases
Many of the hard-to-lead gold mines currently found contain very low concentrations of arsenic and mercury. The arsenic content of the Lancefield arsenic pyrite in western Australia is very high. For low arsenic, Nevada states that the maximum allowable arsenic concentration at the inlet to the roasting operation is 1/42 of the threshold (TLV), and the current threshold is 0.2 mg/m 3 . The arsenic concentration was 4.76 μg/m 3 . The allowable mercury concentration is 1/42 of the threshold value. The threshold value of mercury is 0.05 mg/m 3 , and the mercury concentration calculated therefrom is 1.19 μg/m 3 .
If lime, sodium hydroxide or sodium carbonate is used to remove SO 2 , some of the arsenic, possibly some mercury, can be removed from the exhaust. If further removal of arsenic and mercury is required to meet atmospheric requirements, wet electrostatic precipitators are effective for collecting arsenic, and the removal of mercury from the activated carbon bed impregnated with sulfur compounds in carbon can be used.
The Western Australian Mining Company is the gas cleaning system used after the two-stage fluidized bed calciner. The system consists of a two-stage hot cyclone and an air-to-air heat exchanger that cools the gas to 400 °C before entering the dual zone electrostatic precipitator (ESP). The inlet gas to the electrostatic precipitator has a soot loading of about 38 g/m 3 , and the typical outlet soot amount is below 100 mg/m 3 . After electrostatic precipitator, the purified gas was cooled to 105 °C with outside air and passed through four baghouses. Each dust room has 84 Goretex dust bags with a length of 5505mm and a diameter of 130mm. These dust bags are cleaned with reverse air pulses based on the measurement data of the differential pressure sensor. About 92% to 95% of As 2 O 3 is collected and can be sold as a commercial port. Exhaust gas from the flue behind the baghouse is lower than Australia's 10mg/m 3 arsenic, antimony , cadmium, lead, and mercury.
In solving the problem of cloth material, the polyacrylonitrile cloth bag was used initially, and then the polytetrafluoroethylene was changed. Finally, the polyphenylene sulfide (Rytou) was found to have satisfactory performance, and the physical dust removal was improved. The arsenic damage recovered As 2 O 3 .