IRSE Sept 08.indd

THAILAND CONVENTION REPORT
IRSE
On the Tuesday morning a convoy of
coaches left the Shangrila Hotel for
Chiangrak and Huamak to look at the SRT
signalling installations. Leaving Bangkok
on one of the main arterial routes, passing
miles of stationary traffic going into the
city, the level of congestion could be
appreciated at first hand, emphasising the
need for an integrated city transport
network. The city was eventually left
behind with buildings reluctantly giving way
to rice and tapioca fields and palm trees of
various genres. The landscape was
punctuated by water courses, used to
transport goods in and out of the city and
take away the rainwater from the tropical
storms. After an hour or so, the intrepid
IRSE buses arrived at their destination.
Skimming under electric cables and
telephone wires with just about enough
ground clearance to the cross river
bridges, areas obviously not designed with
52 seat coaches in mind.
At Chiangrak members were taken to
the SRT training school and were able to
view and play with various examples of
signalling equipment which is still used to
control the real railway. At one end of the
spectrum was the modern Ebiloc 950
interlocking with its duplicated hot standby
facilities, each half of the interlocking
containing two processors, with two
channels of diverse software. At the other
end a token ball machine, where the
tokens consisted of coded steel balls. The
steel balls are inserted into the top of the
machine and are issued through a slot at
the bottom, rather like an old fashioned
penny one armed bandit, should you be
lucky enough to win.
An LG EIER-520 III interlocking was
observed, an example of the first type of
CBI installed in Thailand. This type of
interlocking uses a set of Q-type relays to
interface with line side equipment. The
interlocking is used in a one out of two
configuration, with the second channel
working in hot standby for availability only.
If one channel fails the system works as a
one out of one, without any diverse data or
checking. This is a very pragmatic cost
effective solution, which although not at
the level of integrity expected in the UK
and Europe, provides an improvement in
previous safety levels at minimal cost. A
considerable amount of ruminating and
close questioning took place as members
viewed the equipment, ensuring they had
understood the explanation correctly, not
quite believing what they had just heard.
A Westinghouse T84M 220v a.c. point machine at Chiangrak
After a short journey to Hua Mak
members were shown the new station
control room which stands in the shadow
of the viaduct for the new SRT line from
central Bangkok to Suvarnabhumi Airport,
opening in 2009. In one direction, it
controls three lines of way, interlocked by
the new Ebiloc 950 interlocking (one line is
currently out of use allowing the new
airport link to be built above it). In the
other direction, towards Bangkok, the
single line block is controlled by a token
instrument and a small relay interlocking.
At the lineside, new signals and point
machines have been provided, controlled
by standard OCS 950 lineside object
controllers installed in double skinned
location cases to protect the equipment
from the extreme temperatures and high
humidity.
A token ball machine at the SRT training school -
these are still in use on the Thai infrastructure
The centralised Ebiloc 950 CBI is
connected to the object controllers using a
fibre loop over distances of up to 40 km,
although copper can also be used for short
distances. Repeaters power onward
communication loops, enabling objects to
be controlled over greater distances.
Points and signals are driven from the
object controller cards, with relays on the
point cards allowing direct drive to the
machine. Standard BR 867 track feed
units are used along with BR966 QTA1
nine ohm track relays for the track circuits,
switching inputs on the object controllers.
10
Issue 137 September 2008
IRSE
NEWS