Comparison of two methods for measuring the preload of the bearing bush

Source: China Bearing Network Time: 2017-12-26

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The bearing bush of the compressor needs a certain pre-tightening force (the back interference of the tile back) when the device is installed; the main effect is to ensure the matching force of the tile back and the tile seat; to avoid the spindle transition and constant oscillation when the unit is running. In the process, the relative displacement of the two affects the oil passage; then the bearing is damaged, the machine is unstable, the oscillation is increased, and even the serious equipment such as the broken rotor is formed. Some of the machine's bearing bush is made into a detachable bearing bush (only in repair and replacement) Need to change the core; can reduce the cost); for this type of bearing, there is still one interference, the second interference; the effect is the same. However, whether it is a one-time surplus or a second interference is the demand Within the scope; if the interference is too small, it will loosen; if it is too large, it will deform the bearing.
Jiangsu Sugang Group Co., Ltd. 4500m3/h air separation plant; depicted by Kaifeng Air Separation Group Co., Ltd.; China No. 3 Metallurgical Construction Equipment Company (hereinafter referred to as Kaifeng Plant and Xye); on April 5, 2002 Debug out the oxygen. Xye is in the process of measuring the preload of the bearing bush in the H500 6. 2/1. 0 twin-shaft air compressor in the process of the air separation plant; it is found that the secondary bearing and the open factory are installed at the factory. There is a big difference in the value of the test run. The analysis is as follows; for us to refer to; to prevent similar faults.
2 The original drawing device value of the open plant is the H500 6. 2/1. The original drawing device value of the 0 type air compressor is shown in Table 1.
Table 1 H500 air compressor original drawing device value item shaft diameter tile back crossover gap single side gap first and second bearing bush Ï†115 0.03~0.05 0.186~0.248 0.093~0.124 Three, four-stage bearing Ï†105 0. 03~0. 05 0.168~0.218 0.084~0.109
The value of the device (measured by the pressure lead method) was carried out; the test condition was outstanding. Then the package was sent to the user.
3 The method of measuring the back of the tile on both sides and the value of 3. 1 measure the back of the tile is shown in Figure 1; if in the free state, the top of the bearing pad A and the tile cover are closely attached; in the upper and lower mouth of the tile cover There are O at the contact faces B and C. The gap of 05mm, then; when the B and C are pressed, the tile cover and the bearing bush are tightly held; the tile cover and the bearing bush have an interference of 0. 05mm. The measurement of the back of the tile is usually carried out by pressing the lead method; The values â€‹â€‹a, b, c; can get the back of the tile:
Î´=(b+c)/2-a
3. 2 Ã— smelting measurement method and numerical value Ã— smelting in the process of the process using the pressure lead method to measure the secondary Wawa back interference when the upper and lower tile cover opposite the two contact faces B, C each pad thickness b = c = 0. 10mm copper skin; put a Ï†0. 5mm lead wire at the point A between the top of the bearing pad and the tile cover; after the tile cover is pressed, the thickness of the lead wire at A is measured as a = 0.11mm; The surplus is: Î´ = (b + c) / 2 - a = (0. 10 + 0. 10) / 2 - 0. 11 = - 0. Olmm; that is, the secondary tile has no over-profit; instead, there is 0. The gap of Olmm. This is obviously different from the value of the compressor before the factory is 0. 03~0. 05mm; and the repeated measurement results are basically the same; therefore, we need to contact the manufacturer to deal with it.
3.3 Measurement method of the open factory and the skill of the open-air factory. After the person arrives at the scene; put Ï†0. 5mm lead wire at each of A, B and C; evenly tighten the bolt after covering the tile cover Lightly tightened and then opened:; measured the thickness of the three lead wires a, b, c; then the back of the tile back Î´. After three measurements; the results of the interference value is not counted; see Table 2.
Table 2: The measurement value of the open factory personnel a (mm) b (mm) c (mm) Î´ (mm) The first measurement is 0. 285 0. 335 0. 330 0. 048 The second measurement is 0. 220 0. 265 0. 275 0. 050 The third measurement is 0. 295 0. 345 0. 340 0. 048
4 Two methods of measurement compare and analyze two seemingly similar methods; why are the results very different?
Conversely imagine that the secondary wattage's original interference value is indeed 0. 05mm; it is reasonable to say that the thickness of the lead wire at point A should be Î´ = (b + c) / 2 - a = 0.05 mm; Ã—Mechanical practice measured is 0. 11mm. And measuring the knot: the fruit is repetitive; the reason is the problem? The crux of the problem is to measure the diameter of the lead wire and its deformation and extension limit. Anatomy [1]; the lead wire diameter required when measuring the gap of the bearing pad by the lead method is usually It is a value of 1.5 to 2 times the gap; but the reason is not clarified; nor does it clarify the demand for the diameter of the lead wire when measuring the bearing bushing. The author thinks; the measured bushing interference is the same as the measuring bushing top clearance; the same demand wire diameter is 1 5 to 2 times the measured value; this is because the standard lead wire has its limit of deformation and extension.
(1) Ï†0. 5m of lead wire; its limit value of deformation Î» is about 0. 11mm; thus, the thickness of the lead wire of point A is 0. 11mm; instead of 0. 05mm; it is because when it is pressed to 0. 11mm or so after the limit is no longer deformed; therefore, the measured interference is an illusion of -0.11mm. Therefore, if the required interference Î´ is 0. 05mm; the lead wire diameter can be changed to 1. 5~2 times the measured value Such as Ï†0. 10mm can be accurately measured.
(2) If the copper piece is (Î»+Î´)=0.16mm (or above) at the two points B and C; then the gap between the top of the bearing pad and the tile cover after the height is 0.11mm (or more) When the lead is pressed, the thickness of the lead wire is above the ultimate deformation value; then accurate results can be obtained.
(3) When the lead wire is used for the three points A, B and C; the pressing force only needs to ensure that the lead wires of the three places are moderately crushed by the upper force; if the pressing force is too large; the B and C are both The lead wire is pressed to its (Î» + Î´) = 0.16 mm or less; a condition similar to the thickness of the pad of 0. 16 mm or less is generated; and the result of the fault is obtained.
Aligned with the above analysis; the author repeated the following tests; proved the above twist:
Test 1: Pressing the Ï†0. 5mm lead wire with two faces; the result shows that the deformation limit value Î» is about 0. 105~0. 110mm,
Test 2: Pads of 0. 25mm copper at two points B and C; Ï†0. 5mm lead wire is re-measured and over-performed; accurate results are obtained.
Test 3: Put Ï†0. 5mm lead wire at each of A, B and C; then tighten the fastening bolt with a large pressing force; the result is a fault.
5 Conclusion When using the pressure lead method to measure the preload of the bearing bush; it is necessary to pay attention to the diameter of the lead wire used is 1. 5~2 times, if only the wire with a relatively large diameter is used; attention should be paid to the deformation and extension limit; When the lead wire is not pressed to the limit of its deformation; otherwise it will lead to faulty results.

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