SWITCHES & CROSSINGS

• Commonly known as S&C
• Defined as track components that exist to provide a means whereby trains may be directed from one track or route to another track or route.
• Consist of: one (or more) sets of switches

         common (or acute) crossing and (sometimes) obtuse crossings   

 TURNOUTS  

COMMON (or ACUTE) CROSSING – where ‘turnout’ rail and ‘through’ rail intersect.

SWITCHES (or points) – where divergence between alternative routes begin.

DIAMOND CROSSINGS

* 2 x COMMON CROSSINGS

* 2 x OBTUSE CROSSINGS

SLIP DIAMOND CROSSINGS

SETS OF SWITCHES WITHIN THE DIAMOND TO ALLOW TRAINS TO ACCESS ADDITIONAL PATHWAYS.

SLIP DIAMONDS CAN BE OF A SINGLE OR DOUBLE VARIETY.

DESCRIPTION

• Denoted by LETTER to indicate planing
• V after letter indicates a VERTICAL configuration
• Types: A … 2.9m PLANING LENGTH

                  B … 3.5m

                  C … 4.25m

                  D … 5.2m

                  E …  7.0m

                  F …  8.55m

                  G … 11.6m

                  H … 17.495m

GRAPHITE LUBRICANT INSERTS IN A COPPER-TIN ALLOY MATRIX (Hence the CuSn prefix)

Mandatory requirement at switch toe to tie the stock rails to the req’d gauge. Gauge stops are welded to locate the slide baseplate

NOTE : SHALLOW-DEPTH SWITCHES

COMMON CROSSINGS (BUILT-UP UNITS) COMPRISE:

DESCRIPTION:

DENOTED BY CROSSING ANGLE  i.e. 1 in xx

COMMON ANGLES IN USE :

                            1 in  8

                            1 in  91/4

                            1 in  10

                            1 in  103/4

                            1 in  131/4

                            1 in  15

                            1 in  18

                            1 in  21

                            1 in  24

                            1 in  28

                            1 in  32

DESIGN OF SWITCHES & CROSSINGS

NR60 S&C

• Flat bottom, inclined shallow depth designs of S&C

• Designed for use in tracks carrying high speeds or heavy tonnages

• Units are strengthened for use with C.W.R.

• NR60 C-8.25 turnout with concrete bearers

Note that TWO back-drives are fitted with the shallow depth switches

NR60 S&C with ‘TORSION’ type drive bar (down centre of fourfoot)

This system is a variation of the drive system shown on the preceding slide

NR60 transition rail

Provided at the back of the switches to allow transfer from E1 to 113A rail sections

Note the ‘piggy back’ fastening pad to provide connection for the shallower-depth rail.

BALL and CLAW

Fitted to any NR60 layout using switches SHARPER than an F design

Minimises longitudinal creep of the switch rails and provides a useful ‘tell-tail’ for monitoring the position of the switches.

Note : the ball and claw does NOT provide for any stress transference between switch and stock rails. 

33 C 1 CHECK RAILS

Continental style check rails

Are being increasingly used in S&C layouts

The design enabled the full width of the 113a rail foot to be retained for increased stability.

33 C 1 Check rail bracket baseplate

33 C 1 Check rail bracket baseplate

The design allows for the insertion of shims between the vertical face of the back of he check to compensate for wear on the rubbing face of the check.

NR60  1 in 13.5 SWING NOSE CROSSING

Comprises an electro-slag welded moveable nose within 60 E 1 wing rails

Note the use of hollow steel bearers at the nose and heel of the crossing.

NR60  1 in 13.5 SWING NOSE CROSSING   HEEL FLEXING JOINT

A mitred joint to allow for the movement of the crossing

Switching stations

1. Can be

2. Feeder stations – where electricity from Electricity Supply industry is brought and is supplied to OLE, or

3. Track Sectioning cabins or Track Sectioning Locations – which perform function of switching, sectioning, paralleling and electrical protection.

4. Are unattended, kept closed, locked and alarmed for security.

5. Switchgear is remotely controlled by supervisory control from Electrical Control Room concerned (SCADA system), and is contained within buildings or outdoor housings, or is structure mounted.

Feeder stations

1. 20 to 30 miles apart – distance between railway feeder stations determined by consideration of traffic to be handled, the performance required of electric traction units and electrical characteristics of overhead and supply systems. Not always possible to achieve optimum spacing in practice due to desirability of locating the feeder stations close to Grid substations in order to avoid long feeders and of locating feeder stations at railway junctions or intersections.

2. To keep the unbalance on the 3 phase grid system within specified limits, power for traction is tapped off the grid system across the different phases at adjacent feeder in cyclic order.

3. A Feeder station has normally two supply transformers, one will feed, say northwards and the other southwards.

4. Catenaries are connected together on a bus bar at the feeder station and again at track sectioning cabins via circuit breakers

5. Approximately midway between feeder stations the catenaries are connected together (i.e. paralleled) at a boundary t.s.c but again two feeds (from feeder stations adjacent) are kept separated

6. At each feeder station and boundary t.s.c.s, a short length of catenary is isolated from live centenary on either side and is earthed to form Neutral section

7. Intermediate t.s.c.s are provided midway between feeder stations and the boundary t.s.c.s. This is to reduce the length of section where power block is taken for maintenance work, etc. Here again the catenaries are paralleled via circuit breakers.

8. At intermediate t.s.c.s. the contact wire is made discontinuous by terminating the contact wire from each direction (e.g. north and south) in such a way that for a short distance they run parallel to each other

Feeder and Switches

Feeders

1. A transmission line or cable in the electrical power distribution system for:

2. Bringing a supply of electricity to a Feeder station

3. Connecting a Feeder station or Track Sectioning Cabin or Track Sectioning Location to overhead line equipment

4. Cable run from feeder stations are either underground or in troughing at ground level

Switches

1. Feeder switch – A switch mounted on a OLE supporting structure , provided to connect a section of OLE to its feeder at a switching station

2. Section switch – A switch mounted on a OLE supporting structure , provided to connect one section or subsection of OLE to another

Jumpers

1. Cables from Feeder Stations are generally terminated in sealing ends adjacent to overhead feeding switches

2. Short jumpers are usually installed between termination of bare feeders or sealing ends of cables and switches and also between switches and the OLE.