Distributed Power, Locotrol, the why, how and its Future
Distributed power is the method of attaching several locos to freight/goods trains. The locos are attached not only heading the train but in the center and most certainly at the end for reasons I shall explain. This practice gained a major fillip during the major recession of 2008, when railroad companies in the US and Canada(esp. Canadian Pacific) resorted to longer and heavier trains to carry freight in a cost cutting move to remain competitive with freight carriers using roadways. There were several advantages and out of many I list three:
1. The locos except the leading one are not manned and so there is a saving of manpower and so the attendant cost of paying salaries, pension and so on goes down.
2. There is a lot of force on the drawbars and knuckles in the coupling system of heavy loaded freight. For example a DFC type of train on a 1:70 incline like between Maramjhiri-Ghoradongiri between Itarsi and Nagpur on the busy Chennai-Delhi mainline would experience a force of 200 tonnes on the lead coupling, something which would exceed the design of the couplers, leading to a break and a runaway train. This is the reason that a design requirement of the DFC is that the ruling gradient is capped at 1:200 whereby the lead coupler experiences a force of 70 tonnes. Having an engine at the rear enables that the force on the couplers is lower and within permissible limits.
3.
Charging of the brake system: Imagine a long DFC freight with 160 BOXN freightcars brought to a halt at Chamchamnagar outer by the loco pilot Kirori Mal Thirugnanasambandar. After bringing the rake to a halt, he now has to charge the brake system to between 5-6 kg/cm^2 that is 5-6 bar or 500-600 kilo pascal KPA, that is the same pressure as 70-90 psi on American railroads(passenger trains on American railroads work with brake pressures at 110 psi!). The charging of such a long rake will take forever for the pressure to build up all the way to the last freight car. Typically on IR, the duty of the guard is to monitor this pressure by means of a gauge in his last van and alert the loco pilot that the pressure has reached a permissible limit. But with the long rakes the time taken to charge will be forever and this means unnecessary occupation of the mainline. Having an engine in the rear will make the charging process go faster and several compressors can be used to make short shrift of the job. EOTT devices can then alert via telemetry the WILMA device in the engine heading this freight.
How is Distributive power achieved ?
In the US distributed power is achieved usually by
Locotrol devices. This is the proprietary system developed by GE for distributive power which sounds like some sort of laxative. However, it has become synonymous with distributive power just like Xerox just means copying and not the company anymore. In the US locotrol connections between locos involve 23 pin plugs to feed control signals between locos and also a system of pneumatic pipes between locos which ensure proper and synchronous braking, charging of brake lines and of course simultaneous acceleration. This is what a Locotrol device looks like
https://www.ge.com/digital/sites/defaul ... 160824.pdf
Yes you can read the PDF but here are some highlights which may not be or maybe in the document above. After all I am the original Illuminati and the info is indeed funneled through me hahahahha
1. Control messages are sent by the lead loco in a specific message format and protocol.
2. Communications occur in less than 1 second.
3. Messages are transmitted by the lead loco at the minimum of once every 20 seconds.
4. Locotrol does communication checks every 10 seconds between the lead loco and the remotes. When the check is unsuccessful, the backup radios intervene. If this fails, a communication interruption is declared. If continuous communication is not restored, a penalty brake application is automatically propagated throughout the train.
5. The possibility of wayside interference frequencies, operation in tunnels, or momentary malfunction of radios means there could be occasional instances where communication between the lead and the remotes is lost. If communication is lost for more than 45 seconds, a communication interruption condition is signaled, whereby the head end unit displays show the last status of the remotes. During this time the lead cannot communicate commands to the remotes, which continue to operate the last function commanded prior to the communication loss.
When there is a loss of radio communication, a significant propagation of the brakes is one method of isolating the remotes. When this occurs, the remotes cut out their feed valve and begin what is known in Locotrol as the Communication Loss Idle Down (CLID) procedure. This means that when the remotes sense a brake pipe reduction while in a state of communication loss, they automatically step down traction and cut out the brake valve. If in Dynamic Braking (DB), the DB force will be maintained.
When communication is re-established, the operator in the lead unit follows a special sequence of key functions to cut the feed valves back in and recharge the train from the head end. Each remote needs to sense a rise of 4 psi per minute in its brake pipe to automatically cut in the feed valve.
Studies have shown that Locotrol enabled trains have many advantages apart from the ones listed at the beginning:
(a) Brake application and release commands are transmitted by the same radio communication protocol, significantly shortening all brake command propagation times.
(b) Stopping distances are reduced through faster brake application, and more rapid acceleration and deceleration is possible.
Did IR try Locotrol ?
Yes IR tried Locotrol in the late 1980s. In 1989 on the Metre Gauge section in Assam, Lumding-Guwahati-Badarpur YDM4 locos were fitted with Locotrol with inclines of 1:50 and 1:37 and tonnage of 1500 tonnes. These trials were not successful. The remote loco had to be placed 2/3rds of the way down the train and this required unnecessary shunting and other issues.
Locotrol was also tried on Broad gauge on rakes with 113 wagons on the Hatia-Kiruburu line on part of the DBK railway. If you do not know what DBK railway is look up my post on the Deterrence thread, you will know. These trials were conducted in August-November 1989 when this was part of SER, the old BNR(Bengal Nagpore Railway). 49 trials were conducted and the trials were not encouraging. WDM2 diesels were used and there was frequent breakdown of equipment. The lessons learned by IR for the future were:
(a) Seamless control of pneumatic brakes is essential.
(b) Interchangeability of Lead and Remote units i.e. any locomotive can be configured as lead or remote is vital for operational flexibility.
(c) Indigenous service and spares support base for equipment is must for equipment upkeep.
(d) Training of maintenance and operations staff a must for sustainable operations.
(e) Distributed power can be successfully used for long trains on difficult grades and technology overcomes many conventional restrictions of rail operations.
Having said this it was not the end of Locotrol in India. AJNI shed in Ajni, Nagpur which is an electric loco shed and where part of the fleet of the new Alstoms will be homed and has a large holding of WAG-9s is experimenting with Locotrol with several locos. With so many types of locos both diesel and electric there is always the issue of compatibility between different models for the Locotrol system to work. This is reminiscent of the issues that the IAF faces in integrating radar between different models of aircraft.
Locotrol is successfully employed on the Sishen-Saldanha line in South Africa with very heavy freight running on surprisingly 3ft 6inch gauge but with rail having density 68 kg/m. This is far smaller than the gauge used in India 5ft 6 inches on BG. Another feature of the Sishen-Saldanha line is the use of 50KV for traction that allows TSS, traction sub-stations to be placed further apart. Distributed power is used in Australia a lot on ore carrying lines.