“Mind the gap” - travelling in Hong Kong
07 October 2016
In the megacity of Hong Kong, millions of people use railway, which is among the busiest and most modern in the world, every day.
For operator company MTR (Mass Transit Railway), passenger safety is the top priority. This is why the transport company charged the Schmersal Group with kitting out some of the platforms in the aboveground stations with safety systems.
Hong Kong is a city of superlatives: There are over 7 million people living in a hectic metropolis covering some 1000km2. Time is always short and efficiency is a must. Most of them prefer the railway as the quickest and safest form of transport in the densely populated city. MTR carries around 5 million passengers every day. At peak times, the trains run every two to four minutes. A total of ten running lines and a network covering over 200km are the arteries of the city of Hong Kong.
When it comes to safety, they leave nothing to chance in Hong Kong. A several page brochure from MTR informs passengers of all the safety aspects of travelling the network, from safe use of the escalators to what to do the event of a fire. “Mind the gap” rings out from a loud-speaker when you enter the train, and yellow markings on the edge of the platform also remind passengers to watch out for the gap between the train and the platform. But just in case some of them are not paying attention, MTR commissioned the Schmersal Group with the development of a safety solution. “The distances between the train and the edge of the platform vary considerably, as some lines curve as they enter the station.” explains Schmersal managing director Michael Mandel. This is the case at the “University” aboveground station, for example. This is a stop on the East Rail Line which leads north to the New Territories on the border to Shenzhen. As in some other stations, Schmersal has installed pressure-sensitive safety mats in the track bed.
A robust safety solution
A safety mat consists of two separate conductive metal plates. Insulating separator strips keep the plates apart. If someone steps on the safety mat, an electrical cross-circuit is established between the metal plates. The safety relay module (SRB) connected evaluates this signal and forwards it to the PROTECT PSC safety controller, which then sends it on to the control computer. In the control unit, signal lights are activated and the train is prevented from moving. “MTR opted for the pressure-sensitive mats as a safety solution, because it is a very robust, resistant safety solution,” explains Mandel. The Schmersal products of the series SMS 4/5 have IP65 degree of protection and are characterised by the fact they have resistance to acid, alkalis, oil and petrol. At the same time, they are resistant to the sparks triggered by the grinder car which is regularly used to maintain the tracks in the Hong Kong underground.
Reliable signal analysis - even at subtropical temperatures
The safety relay module used is the SRB 301HC/T produced in Schmersal’s factory in Wettenberg, Germany. The technical characteristics of the SRB 301HC/T include a STOP-0 function and a 2-channel controller. The 45mm casing has a pluggable connection terminal which means pre-assembled cable looms can be used and servicing is quicker. Thanks to the ventilation slots in the casings, the SRBs can also be used in warmer ambient temperatures, the service range is -25 to +60°C. This is a benefit in the subtropical climate of Hong Kong. During the day, the control cabinet can reach temperatures of up to +50°C.
Nights are the time for the safety experts
The programmable modular safety control system, Protect PSC, can be adapted and scaled to the task in question at low cost – from eight inputs and six outputs in the simplest version to more than 250 inputs and outputs at the maximum configuration level. A special feature of Protect PSC is its ability to integrate standard PLC functions. For this task, system modules with operating inputs and outputs are available, which can be freely assigned by programming. This ensures that sub-tasks can be realised directly on site or even in some cases a conventional PLC can be dispensed with entirely.
Overall, the safety solution has already proved its worth in the Hong Kong railway network. Some platforms were fitted with the Schmersal safety system in 2014 and 2015. In conjunction with system integrator Pilot Electronics & Engineering Limited from Hong Kong, Schmersal has this year fitted a total of six platforms with 3600 safety mats, 720 safety relay modules and 6 Protect PSC safety controllers.
As before, on-site servicing is largely carried out by Schmersal Industrial Switchgear Co. Ltd based in Shanghai. Because of the scale of the project, Schmersal has put together an extended project team so that the Application Engineering department at the headquarters in Wuppertal can be directly involved for support purposes.
However, the limited working hours represent a real challenge. Measurements and installation work can be carried out virtually exclusively at night between 01:00 and 04:30h. It is only then that the wheels on the railway network in Hong Kong are still - in the city that never sleeps.
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