Prevent bearing failures due to electrical discharge currents
SKF Shaft Grounding Ring Kits TKGR series The SKF Shaft Grounding Ring Kits have been developed as a solution to help prevent bearing failures due to electrical discharge currents, which can occur when variable frequency drives are used to control AC motors.
Bearing micro cratering damage
They have been specifically designed for retrofitting on existing IEC frame size industrial electric motors, reducing the need to spend time, effort and cost in replacing the existing bearings. Other SKF solutions designed to overcome the effects of electrical discharge currents include SKF INSOCOAT and SKF Hybrid bearings. Bearing fluting damage
Prevent bearing failures due to electrical discharge currents TKGRs are primarily suitable for retrofit applications: • For small motors below 30kW, all SKF solutions are generally suitable to protect the bearings from current damage • For motors between 30kW and 75kW, the bearing protection depends on the overall electrical regime. TKGRs may need to be used in combination with SKF INSOCOAT or SKF Hybrid bearings • For motors over 75kW, the combination of a TKGR with an SKF INSOCOAT or SKF Hybrid bearing on the non-drive end is recommended • TKGRs can be used to help protect the entire application from electric current problems beyond pure bearing protection
NOTE: TKGRs are not suitable for use in explosive atmospheres.
Typical TKGR applications include fans, pumps and compressors controlled by variable frequency drives. • Helps prevent electrical discharge current damage in rolling bearings • Designed to be easily retrofitted to existing electric motors • Protects both motor bearings and the bearings in attached equipment • Designed to be maintenance free, they improve system reliability, helping reduce motor repair costs and unplanned downtime • A potential high return on investment (ROI) Is possible by fitting SKF TKGRs • Flexible 3 or 4 bracket mounting design fits virtually any IEC motor • Easy to order the SKF TKGR. Selection is based on the motor “D” dimension, clears slinger or shaft shoulder
Mounting details
3 hole bracket pattern
D2 max 120° D1 min
Shaft
D1
D2
D1
D2
mm
mm
mm
mm
mm
† 28
75
121
74
93
† 38
85
131
84
103
† 42
89
135
88
107
† 48
95
141
94
113
† 55
102
148
101
120
† 60
107
153
106
125
† 65
112
158
111
130
† 75
122
168
121
140
† 80
127
173
126
145
† 95
142
188
141
160
4 hole bracket pattern 11,3
D2 max
90°
17,7
(mm)
(mm)
9,5 3
4,8
D1 min
1
1: † Max shaft shoulder = † Shaft + 12,7 mm
1
1: † Max shaft shoulder = † Shaft + 12,7 mm 2: † Max slinger = † Shaft + 25,4 mm
2
2
The SKF Shaft Grounding Rings Kits (TKGR series) consist of the following items: • Shaft grounding ring with an aluminium brush holder which helps ensure that the conductive brushes are in contact with the surface of the motor shaft • Four different sets of mounting brackets (4 brackets per set) which virtually ensures that the SGR can be fitted to almost all IEC frame motors • Selection of mounting screws, washer and Allen keys
D1
D2
D1
D2
D1
D2
D1
D2
mm
mm
mm
mm
mm
mm
mm
mm
129
148
107
148
129
148
107
148
139
158
117
158
139
158
117
158
143
162
121
162
143
162
121
162
149
168
127
168
149
168
127
168
156
175
134
175
156
175
134
175
161
180
139
180
161
180
139
180
166
185
144
185
166
185
144
185
176
195
154
195
176
195
154
195
181
200
159
200
181
200
159
200
196
215
174
215
196
215
174
215
40,1
40,1
(mm)
32
32
28,8
28,8
1
2
27,4
(mm)
27,4
(mm)
19,3 16,1
1
2
(mm)
19,3 16,1
1
2
1
2
1: † Max shaft shoulder = † Shaft + 12,7 mm
1: † Max shaft shoulder = † Shaft + 12,7 mm
1: † Max shaft shoulder = † Shaft + 12,7 mm
1: † Max shaft shoulder = † Shaft + 12,7 mm
2: † Max slinger = † Shaft + 81,3 mm
2: † Max slinger = † Shaft + 59,1 mm
2: † Max slinger = † Shaft + 81,3 mm
2: † Max slinger = † Shaft + 59,1 mm
3
Box contents Items
Quantity
Shaft grounding ring
1
Universal bracket sets (4 brackets per set)
4 sets
5-40 ™ 3/8 in. flat head screws
4
M4 ™ 10 mm socket head cap screws
4
M4 split lock washers
4
M4 flat washers
4
5/64
in. Allen key
1
3 mm Allen key
1
Designation and suitability guide Designation
To suit motor shaft size diameter
IEC frame
TKGR 28
28 mm
IEC 100L, 112M (2, 4, 6, 8 pole)
TKGR 38
38 mm
IEC 132S, 132M (2, 4, 6, 8 pole)
TKGR 42
42 mm
IEC 160M, 160L (2, 4, 6, 8 pole)
TKGR 48
48 mm
IEC 180M, 180L (2, 4, 6, 8 pole)
TKGR 55
55 mm
IEC 200L (2, 4, 6, 8 pole); IEC 225S, 225M (2 pole)
TKGR 60
60 mm
IEC 225S, 225M (4, 6, 8 pole) ; IEC 250M (2 pole)
TKGR 65
65 mm
IEC 250M (4, 6, 8 pole); IEC 280M, 280S, 315S, 315M, 315L (2 pole)
TKGR 75
75 mm
IEC 280S, 280M (4, 6, 8 pole); IEC 355M, 355L (2 pole)
TKGR 80
80 mm
IEC 315S, 315M, 315L (4, 6, 8 pole)
TKGR 95
95 mm
IEC 335L, 335M, 355L, 355M (4, 6, 8, 10 pole)
Shaft sizing is a guide only and the shaft should be properly measured before ordering an SKF TKGR
® SKF is a registered trademark of the SKF Group. © SKF Group 2012 The contents of this publication are the copyright of the publisher and may not be reproduced (even extracts) unless prior written permission is granted. Every care has been taken to ensure the accuracy of the information contained in this publication but no liability can be accepted for any loss or damage whether direct, indirect or consequential arising out of the use of the information contained herein. SKF Shaft Grounding Ring Kits are manufactured in the USA by Electro Static Technology, an ITW Company. US Patent 7136271,7193836 PUB MP/P8 12765 EN · April 2012
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