The flameproof joint surface of the rotating machine shaft should be designed in such a way that it will not wear out during normal operation. The structure of a flameproof joint surface can be of the following three types:
- Cylindrical joint surface (see Figure 1)
- Curved joint surface (see Fig. 2)
- Floating shaft seal joint surface (see Figure 3)
Fig. 1, the cylinder joint surface for the shaft of the rotating electric machine is shown
Figure 2 shows an example of a curved joint surface for a rotating machine shaft
The serial number in the figure is described: 1: clearance, 2: brake device to prevent the gland from rotating.
Fig. 3: An example of a floating bearing cover joint surface for a rotating motor shaft
Symbols in the diagram are described: k: the minimum allowable frictionless radial clearance, m: the maximum radial clearance when the k value is factored;
Fig. 4, the joint surface of the rotating motor shaft and the bearing cover
The requirements for each of these three types of mating surfaces are described below.
1. Cylindrical joint surface
If the cylindrical joint bread contains a groove to hold grease, the area containing the groove should neither be counted nor the width of the grooved partition in determining the width of the flameproof joint surface (see Figure 1).
The minimum radial clearance k of the rotating machine shaft (see Fig. 4) should not be less than 0.05mm.
2. Curved joints
Curved joints that do not meet the requirements of Table 2 and Table 3 (see the standard for details) in GB/T 3836.2-2021 can be considered to meet the requirements if they pass the relevant test assessment specified in Chapter 14~16 of GB/T 3836.2-2021.
The minimum radial clearance k of the rotating machine shaft (see Fig. 4) should not be less than 0.05mm.
3. Floating bearing cover joint surface
The maximum float of the bearing cover should be determined taking into account the bearing clearance and permissible bearing wear specified by the manufacturer. The bearing cover can move freely radially with the shaft and axially on the shaft, but should be concentric with the shaft. There should be a device to prevent the bearing cover from rotating relative to the shaft (see Fig. 3). Floating bearing covers are not permitted for use in Class II.C electrical equipment.