the point where spring pressure is felt, before measuring solenoid air gap.) As friction disc wear occurs, the air gap will increase as well as stopping time. If solenoid air gap exceeds 11/16”, adjustment is necessary.
2.The solenoid air gap may be decreased by turning both wear adjustment screws (10) equal amounts clockwise, approximately 1/8 turn, until solenoid gap is attained. Counterclockwise rotation will increase gap.
3.Follow Step 1 and Step D of Installation Procedure, Section I, to replace housing.
4.Restore power source to brake.
B. Replacement of friction discs
Follow Steps
C. Inspection or replacement of solenoid and associated components
1.Refer to Figures 8 and 9. Insert screwdriver between support plate (126) and lever arm (17). Wedge apart and remove as an assembly bearing pin (26), bearing (6), pin (131), solenoid lever (8) connected to solenoid link (13) and plunger (29).
Figure 9
2.On coil type (12A) remove plunger guide screw and lock washer. Remove both plunger guides (82) by prying up on the flanges. Slide coil (12A) sideways from frame noting position of coil terminals or lead wires.
a)On coil type (12B), remove plunger guide (82A) by lifting out of top of solenoid frame. Coil (12B) has a lock tab, located at bottom of coil opposite lead wire side which is pressed against coil and coil is slid sideways from solenoid frame.
3.Inspect and clean all items. If coil, plunger guides, or solenoid replacement is required, refer to appropriate replacement parts list and select necessary replacement part, kit or assembly. Kits or assembly packets contain full retrofit instructions.
Copyright© 1997 by Rexnord Industries, Inc.
4.Reassemble brake in reverse order of Steps 1 and 2.
5.Replace housing.
6.Restore power source to brake.
D. Miscellaneous parts replacement (see Figures 1 and 8)
All parts shown in Figures 1 and 8 are available as kits, assemblies, or piece parts. Consult appropriate parts list for ordering information. Kits and assembly packets contain complete repair instructions.
V. Troubleshooting
A. If brake does not stop properly or overheats, check the following:
1.Are friction discs excessively worn, charred, or broken?
2.Hub may have become loose and shifted on shaft. Recheck Section I, appropriate Step.
3.Is hub clean, and do friction discs slide freely?
4.Do stationary discs slide freely in the endplate? Check slots of endplate for wear at the areas where stationary discs are in contact. Grooves in the slots can cause
5.On vertically mounted brakes, are springs in place in disc pack? See Sheet 301.4 for 55,000; 55,300; 55,400 and 57,500 or Sheet 301.5 for 55,300 and 55,500 if correct sequence is in doubt.
6.With brake
(7) removed, check compressed length of pressure springs (11). Compare to tabulated values and adjust to minimum height to obtain desired stop times. See Torque Adjustment, Section III, Table 1.
7.Is solenoid air gap adjusted correctly? See Section IV and refer to Air Gap Setting, Table 2.
8.Solenoid may not be energizing and releasing the brake. Check voltage at the coil and compare to the coil and/or nameplate voltage rating.
9.Whether brake is AC or DC a voltage drop may be occurring. If excessive drop in voltage is noted, check wire size of power source. Correct as needed.
Note: A method to check voltage at coil is to insert a block of wood of the approximate thickness of the solenoid air gap between the solenoid frame and plunger. (The block will prevent brake from releasing when coil is energized.) Connect voltmeter leads at the coil terminals or lead wires. Energize coil. Voltmeter needle will not fluctuate and reading can be taken. Reading should be taken immediately and the coil
10.If brake is DC solenoid style, check switch actuation and condition of coil. The switch should open with a 3/16” approximate air gap. (This is plunger
travel remaining before plunger seats to frame.)
11.Check linkage for binding. The approximate pressure applied to the top of the solenoid link to move plunger is:
#4 coil | |
|
|
#K4 coil | 5 lbs |
|
|
If excessive force is required, determine cause of binding and correct. Do not overlook bent, worn or broken plunger guides as a possible cause for binding.
12.Are controls which govern start of braking cycle operating properly?
13.Brake coil should be energized at same time or prior to energization of motor, and
14.If stopping time is more than 1 second (rule of thumb) and/or application is more than five stops per minute, check thermal requirements of load versus thermal rating of brake.
15.Check mounting face to which brake is attached per Installation Procedure, Note 2 after Item 1.
16.Replace friction disc(s) when worn area is one half of original thickness (3/16”).
17.Check to be sure wear adjust screws are of equal height. Measure from inboard side of support plate with depth micrometer. Turn one screw to obtain equal height, reassemble and see Adjustment for Friction Disc Wear.
B. If solenoid hums, pulls in slowly, or coil burns out, check the following:
1.Check
2.Check for broken shading coil.
3.Plunger guides may be excessively worn. Does solenoid plunger rub on solenoid frame laminations?
4.Solenoid frame and plunger may be excessively worn.
5.Is solenoid dirty?
6.Solenoid mounting screws may have become loose, causing frame to shift and plunger to seat improperly.
142 139W 139S 139 3 142S 4 16 161 16S 2
57,500 16A 16S 4A 16B 16S 4B
Rexnord Industries, Inc., Stearns Division, 5150 S. International Dr., Cudahy, Wisconsin 53110, (414)
