General Information on Track Circuits - RGS Online

Railway Group Approved Code of Practice
GK/RC0752
Issue Two
Date December 1998
Page E50 of 52
Withdrawn Document
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<strong>General</strong> <strong>Information</strong> on Track Circuits
All contact surfaces should be coated with a uniform layer of jointing paste
(Catalogue No. 7/26200) immediately after cleaning and any surplus cleaned
away after tightening. The paste prevents moisture filling the resultant air
spaces between the dissimilar metal surfaces, preventing corrosion which occurs
very rapidly, particularly when aluminium is exposed to air or moisture.
Where screw and nut connections are made to aluminium plate, eg. the
aluminium busbar or P3 impedance bond lug plate, it is essential that
mechanical connections are not over-tightened. This is because aluminium
displays the property known as ‘‘cold flow” under pressure and if a certain
pressure is exceeded, a flow away from the pressure area occurs and the
connection becomes loose, resulting in a high resistance connection.
Details of side lead/busbar connections and torque values are shown in the
tables in Figure E52 and Figure E53.
Where possible, the side lead connections should be tested, using a millivolt
meter in accordance with GK/RC0754 Part G.
Figure E52
Type
of Impedance Bond
Type Of Connection
Busbar(Item) Side lead (Item)
Type 3 D E
MR D E
B A C
M A A
P3 A C
DE A B
DD A A
S D E
Item Description Torque Setting Catalogue No.
A M12 x 50 Long Hex Hd Screw, Steel EZP 30Nm 35/101102
B M12 x 70 Long Hex Hd Screw, Steel EZP
35/101142
M12 Nut, Lock (Bent Beam) Steel EZP
30Nm
03/180167
M12 Washer, Steel EZP
03/190932
C M10 x 50 Long Hex Hd Screw, Steel EZP
35/100842
M10 Nut, Lock (Bent Beam) Steel EZP
16Nm
03/180166
M10 Washer, Steel EZP
03/190930
D M16 x 50 Long Hex Hd Screw, Steel EZP 60Nm 35/101272
E M16 x 70 Long Hex Hd Screw, Steel EZP
35/101312
M16 Nut, Lock (Bent Beam) Steel EZP
60Nm
03/180168
M16 Washer, Steel EZP
03/190936
Figure E53
E 50 R A I L T R A C K