General Information on Track Circuits - RGS Online

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<strong>General</strong> <strong>Information</strong> on Track Circuits
Railway Group Approved Code of Practice
GK/RC0752
Issue Two
Date December 1998
Page E13 of 52
8.5 Aluminio–thermic Welding
Thermic welding is a method of fixing threaded pins to the rail by means of a
thermo–chemical reaction. It can be used for traction bonding in both a.c. and
d.c. traction areas.
Two types of studs are available:
Description Catalogue No.
1
/2 ” x 7 / ” fully threaded stud, complete with
8
nut and washers.
5
/8 ” stud with nut, spring washer and
: Available from ERICO.
flat washer. : 46/19800.
Note (1): Aluminio–thermic welding is also referred to as Cadweld and
Thermoweld.
Note (2): Any person engaged in these operations must hold a Certificate of
Competency for the task to be undertaken.
8.6 Pin Drive
This method should be used only where pin braze or Cembre fittings cannot be
used.
A bimetal rail lug (Railway Catalogue No. 55/27614) provides an aluminium barrel
for crimping to aluminium cable and a copper lug for insertion into the rail.
Where pin–drive lugs are used to make connections to the running rails, the
22mm holes are drilled by Permanent Way Engineering staff. If the rail
connection is not made at the time of drilling, the hole is immediately given a
coating of jointing paste (Railway Catalogue No. 7/026200) to minimise the risk
of a high resistance connection due to corrosion.
The connection is made as follows:
Before the lug is inserted in the rail, it is cleaned of all existing jointing paste and
all contact surfaces should be clean, bright, brushed with a circular wire brush
(Railway Catalogue No. 5/4266) and re–coated with a uniform layer of jointing
paste (Railway Catalogue No. 7/026200).
The lug is secured to the rail by means of the rail lug bond pin, refer to Figure
E10. Pin size No.1 (Railway Catalogue No. 55/27860) , is driven in with a
hammer and is used for the first installation. Pin size No. 2 (Railway Catalogue
No. 55/27862) is used for subsequent installations of a lug. Pin size No.3
(Railway Catalogue No. 55/27863) should be used only when the rail hole is
oversize, eg. 7 / 8 ” rather than 22mm. After installation, surplus jointing paste
should be wiped off.
All rail lug connections should be inspected after installation to ensure that the
lug is tight and free from cracks. Any cracked or loose connections are to be
remade.
R A I L T R A C K E 13