Pakistan Railway Loco Pilots go on strike, demand Dynamic Braking in Locomotives

[Ankit Kumar]

QUETTA: The provincial capital remained cut off from northern parts of Balochistan and Sindh for the second consecutive day on Monday as railway authorities cancelled two passenger trains.

However, Jaffar Express and Akbar Bugti Express left for Rawalpindi and Lahore respectively several hours late.

The passengers who had purchased tickets for Bolan Mail to travel to Karachi and Chaman by another train faced difficulties because the railway authorities did not inform them about cancellation of the trains.

Take a look: Train drivers go on strike in Quetta

The railway officials said four trains, including Jaffar Express and Akbar Bugti Express, were on track.

Quetta division’s Chief Controller Mohammad Kashif Khan told Dawn that efforts were being made to meet the demands of locomotive drivers who were on strike.

He said the protesting drivers had been demanding locomotives which had the dynamic brake control system.

Dynamic brakes had been installed in four engines carrying trains to and from Quetta, Rawalpindi and Lahore. The demands of the Quetta division had been sent to the Railway headquarters, the chief controller added.

“It is the job of the mechanical engineering section to send equipment for installing in locomotives.”

Kashif Khan said it would take time to install dynamic brakes in all locomotives running between Quetta and other cities.

Meanwhile, the protesting drivers said they were ready to operate trains which were in good condition and had locomotives fitted with the dynamic brake control system. “It is not a matter of saving lives of railway employees only but also of thousands of passengers,” they said.

Mohammad Hussain, the leader of the striking drivers, said they were running locomotives with air brakes, while drivers had been demanding locomotives with dynamic brake control.

“Locomotives running trains in other parts of the country have both systems of brake control.”

Out of 15 locomotives at the Quetta division, only four had dynamic brake control system.

A senior railway officer said the situation would normalise in three to four days because the dynamic brake control system was being installed in other locomotives too.

Published in Dawn, November 24th, 2015

 

[Ankit Kumar]

Train drivers press for engines with dynamic brake control system - Pakistan - DAWN.COM

@anant_s
Sir do all our locomotives have dynamic braking?
I know that most of the electric locomotives do have. Do all our Alcos have this?
And what are the safety concerns in its absence?

 

[Nilgiri]

Good move by the pilots .

Somewhat related was the PTC issue that almost brought many US railroad to a halt.

Not specifically dynamic braking but a more comprehensive safety legislation nonetheless that has now been extended because US railroad companies have been slow to adopt it (for various reasons)

House introduces legislation to extend rail safety deadline to 2018| Reuters

Thanks for bringing in anant saab @Ankit Kumar . I am also curious to know about the situation w.r.t Indian railways. I would also like to know his opinions on PTC and its potential relevance to India. Other informed members comments are much appreciated as well.

 

[indianBong]

Train drivers press for engines with dynamic brake control system - Pakistan - DAWN.COM

@anant_s
Sir do all our locomotives have dynamic braking?
I know that most of the electric locomotives do have. Do all our Alcos have this?
And what are the safety concerns in its absence?

Dynamic systems are used on diesel locomotives (not all though) and on electric locos with DC traction motors like WAP4, WAG7 etc... .
Primary braking system involves Air Brakes...
Another system of brakes called Regenerative brakes system is used in electric locomotives with Induction motors like WAP5, WAP7, etc

 

[Nilgiri]

Dynamic systems are used on diesel locomotives (not all though)

Do you know the % of diesel locos that have it?

 

[The-king]

Dynamic braking (locomotive)

Dynamic braking is the use of the electric traction motors of a railroad vehicle as generators when slowing the locomotive. It is termed rheostatic if the generated electrical power is dissipated as heat in brake grid resistors, and regenerative if the power is returned to the supply line. Dynamic braking lowers the wear of friction-based braking components, and additionally regeneration can also lower energy consumption. Dynamic braking can also be used on railcarsmultiple units, light rail vehicles, trams and PCC streetcars.
Principle of operation[edit]
During braking, the motor fields are connected across either the main traction generator (diesel-electric loco) or the supply (electric locomotive) and the motor armatures are connected across either the brake grids or supply line. The rolling locomotive wheels turn the motor armatures, and if the motor fields are now excited, the motors will act as generators.

During dynamic braking, the traction motors, which are now acting as generators, are connected to the braking grids (large resistors), which put a large load on the electrical circuit. When a generator circuit is loaded down with resistance, it causes the generators to slow their rotation. By varying the amount of excitation in the traction motor fields and the amount of resistance imposed on the circuit by the resistor grids, the traction motors can be slowed down to a virtual stop (approximately 3-5 MPH).

For permanent magnet motors, dynamic braking is easily achieved by shorting the motor terminals, thus bringing the motor to a fast abrupt stop. This method, however, dissipates all the energy as heat in the motor itself, and so cannot be used in anything other than low-power intermittent applications due to cooling limitations. It is not suitable for traction applications.

Rheostatic braking[edit]
The electrical energy produced by the motors is dissipated as heat by a bank of onboard resistors. Large cooling fans are necessary to protect the resistors from damage. Modern systems have thermal monitoring, so, if the temperature of the bank becomes excessive, it will be switched off, and the braking will revert to friction only.

Regenerative braking[edit]
Main article: Regenerative braking
In electrified systems the similar process of regenerative braking is employed whereby the current produced during braking is fed back into the power supply system for use by other traction units, instead of being wasted as heat. It is normal practice to incorporate both regenerative and rheostatic braking in electrified systems. If the power supply system is not "receptive", i.e. incapable of absorbing the current, the system will default to rheostatic mode in order to provide the braking effect.

Yard locomotives with onboard energy storage systems which allow the recovery of some of this energy which would otherwise be wasted as heat are now available. The Green Goat model, for example, is being used by Canadian Pacific Railway, BNSF Railway, Kansas City Southern Railway and Union Pacific Railroad.

On modern passenger locomotives equipped with AC inverters pulling trains with sufficient Head End Power loads braking energy can be used to power the train's on board systems as a form of regenerative braking if the electrification system is not receptive or even if the track is not electrified to begin with. The HEP load on modern passenger trains is so great that some new electric locomotives such as the ALP-46 were designed without the traditional resistance grids.

Blended braking[edit]

A picture of an ex-ConnexClass 466 EMU at Blackfriars station in the year 2006. The popular Class 466 EMUs use Dynamic blended braking.
Dynamic braking alone is insufficient to stop a locomotive, as its braking effect rapidly diminishes below about 10 to 12 miles per hour (16 to 19 km/h). Therefore it is always used in conjunction with the regular air brake. This combined system is called blended braking.Li-ion batteries have also been used to store energy for use in bringing trains to a complete halt.[1]

Although blended braking combines both dynamic and air braking, the resulting braking force is designed to be the same as what the air brakes on their own provide. This is achieved by maximizing the dynamic brake portion, and automatically regulating the air brake portion, as the main purpose of dynamic braking is to reduce the amount of air braking required. This conserves air, and minimizes the risks of over-heated wheels. One locomotive manufacturer, Electro-Motive Diesel (EMD), estimates that dynamic braking provides between 50% to 70% of the braking force during blended braking.

Self-load test[edit]
It is possible to use the brake grids as a form of dynamometer or load bank to perform a "self load" test of locomotive enginehorsepower. With the locomotive stationary, the main generator (MG) output is connected to the grids instead of the traction motors. The grids are normally large enough to absorb the full engine output power, which is calculated from MG voltage and current output.

Hydrodynamic braking[edit]
Diesel engined locomotives with hydraulic transmission may be equipped for hydrodynamic braking. In this case, the torque converter or fluid coupling acts as a retarder in the same way as a water brake. Braking energy heats the hydraulic fluid, and the heat is dissipated (via a heat exchanger) by the engine cooling radiator. The engine will be idling (and producing little heat) during braking, so the radiator is not overloaded.

Dynamic braking (locomotive) - Wikipedia, the free encyclopedia

 

[MastanKhan]

Hi,

As far as I can rember---the locomotives purchased till the 70's all had dynamic braking available. I think a lot has changed in the last 15 years---a lots of corruption has destroyed the railways.

 

[indianBong]

Do you know the % of diesel locos that have it?

No bro... waiting for @anant_s to reply.....

@MastanKhan corruption in south asia has destroyed many things...

 

[anant_s]

Train drivers press for engines with dynamic brake control system - Pakistan - DAWN.COM

@anant_s
Sir do all our locomotives have dynamic braking?
I know that most of the electric locomotives do have. Do all our Alcos have this?
And what are the safety concerns in its absence?

Dear Ankit,
First of all we must understand what dynamic braking is.
All types of locomotives that make use of motors for driving locomotives (be in Diesel Electric or Pure electric), use motors to drive wheel mounted on bogies. these motors are fed through a supply circuit which consists of a transformer and conditioning circuit (like IGBT drive etc) in electric locomotives and through locomotive mounted Diesel Generator set in case of diesels.

Now when you want to brake a locomotive, the idea is to stop motors from feeding torque to wheels and bring down train to stop. If you compare this with an automobile, we have friction brakes that is a drum and liner or shoe and liner arrangement which, first disconnects prime mover (by clutch) and then dissipates the energy in form of heat through frictional interaction bringing vehicle to stop.

How are Trains different?
in case of trains, the prime mover is locomotive with a trailing load of rake (coaches or wagons). Since mass of train is very large a train has two types of brake.
First is called train brakes and second is Locomotive braking.

Train Braking
Train braking is similar to any automobile where friction is used to slow down and bring train to stop. only thing this is done through air pressure (also called pneumatic braking, where air pressure pushes friction surface to brake drum). In olden days vacuum braking was done (Similar principle but vacuum forced liner away from drum).

Locomotive Braking

For a locomotive to brake, two stages are used:
1. Dynamic Braking
2. Pneumatic braking.

Dynamic Braking

As i told above, motors feed the wheel power to move. As train starts moving, the resistance reduces and trains gains momentum. Now when you want to brake, you can use these motors to your advantage.
The motors are taken into Generating mode. What is means is that initially motors were feeding power to wheels driven by power coming from Diesel generator or Transformer. During braking, momentum of trains allow motors to become generator that start generating power (or current). This current if can be used, can bring down train to loose momentum (as it is now powering the motor).
The current generated can be used (or dissipated) in two ways:
1. If the current is fed to a set of resistors and the energy is dissipated as heat (by ohmic heating Q=i*i*R), the method is called Rheostatic braking.
2. If the current generated is fed back to catenary for use by grid or OHE, the method is called Regenerative Braking.

Shown here is Rheostatic braking, where the current generated by motors during braking is dissipated by resistors and cooling is achieved by a cooling fan.

Finally when speed becomes very low, pneumatic brakes are applied to bring locomotive and train to stop.

As on today all ALCO series (WDM 2, WDM 3A, WDM 3D, WDG 3A) and DC motored (or TAP Chnager locomotive) like WAM 4, WAG 5, 6, 7 and WAP 1 and 4 are fitted with Rheostatic braking.
3 Phase electrics
WAP 5, 7 and WAG 9 are fitted with regenerative braking.

Diesel Locomotive Brakes | Engineering Expert Witness Blog

With reference to Pakistan Railways, i'm not sure what the problem is?
I can't believe that fast Diesel locomotives in PR are not using Dynamic braking (& essentially relying on pneumatic train braking). this simply is too dangerous an operating procedure and don't think technical and safety authorities in PR would allow it.
@Donatello Sir, you are probably the best person to respond on what exactly the technical problem with locos is. To my knowledge, newer locos used by PR (supplied by GE and Chinese locomotive companies) have latest train safety systems. So are we talking of older locomotives or there is more to strike by loco pilots.

As far as I can rember---the locomotives purchased till the 70's all had dynamic braking available.

Thats absolutely true.
@Rain Man @gslv mk3 Would u like to add something here?

 

[The-king]

Dear Ankit,
First of all we must understand what dynamic braking is.
All types of locomotives that make use of motors for driving locomotives (be in Diesel Electric or Pure electric), use motors to drive wheel mounted on bogies. these motors are fed through a supply circuit which consists of a transformer and conditioning circuit (like IGBT drive etc) in electric locomotives and through locomotive mounted Diesel Generator set in case of diesels.
View attachment 274325

View attachment 274326

Now when you want to brake a locomotive, the idea is to stop motors from feeding torque to wheels and bring down train to stop. If you compare this with an automobile, we have friction brakes that is a drum and liner or shoe and liner arrangement which, first disconnects prime mover (by clutch) and then dissipates the energy in form of heat through frictional interaction bringing vehicle to stop.

How are Trains different?
in case of trains, the prime mover is locomotive with a trailing load of rake (coaches or wagons). Since mass of train is very large a train has two types of brake.
First is called train brakes and second is Locomotive braking.

Train Braking
Train braking is similar to any automobile where friction is used to slow down and bring train to stop. only thing this is done through air pressure (also called pneumatic braking, where air pressure pushes friction surface to brake drum). In olden days vacuum braking was done (Similar principle but vacuum forced liner away from drum).
View attachment 274327


Locomotive Braking

For a locomotive to brake, two stages are used:
1. Dynamic Braking
2. Pneumatic braking.

Dynamic Braking

As i told above, motors feed the wheel power to move. As train starts moving, the resistance reduces and trains gains momentum. Now when you want to brake, you can use these motors to your advantage.
The motors are taken into Generating mode. What is means is that initially motors were feeding power to wheels driven by power coming from Diesel generator or Transformer. During braking, momentum of trains allow motors to become generator that start generating power (or current). This current if can be used, can bring down train to loose momentum (as it is now powering the motor).
The current generated can be used (or dissipated) in two ways:
1. If the current is fed to a set of resistors and the energy is dissipated as heat (by ohmic heating Q=i*i*R), the method is called Rheostatic braking.
2. If the current generated is fed back to catenary for use by grid or OHE, the method is called Regenerative Braking.
View attachment 274330 View attachment 274331
Shown here is Rheostatic braking, where the current generated by motors during braking is dissipated by resistors and cooling is achieved by a cooling fan.

Finally when speed becomes very low, pneumatic brakes are applied to bring locomotive and train to stop.
View attachment 274332
As on today all ALCO series (WDM 2, WDM 3A, WDM 3D, WDG 3A) and DC motored (or TAP Chnager locomotive) like WAM 4, WAG 5, 6, 7 and WAP 1 and 4 are fitted with Rheostatic braking.
3 Phase electrics
WAP 5, 7 and WAG 9 are fitted with regenerative braking.

Diesel Locomotive Brakes | Engineering Expert Witness Blog

With reference to Pakistan Railways, i'm not sure what the problem is?
I can't believe that fast Diesel locomotives in PR are not using Dynamic braking (& essentially relying on pneumatic train braking). this simply is too dangerous an operating procedure and don't think technical and safety authorities in PR would allow it.
@Donatello Sir, you are probably the best person to respond on what exactly the technical problem with locos is. To my knowledge, newer locos used by PR (supplied by GE and Chinese locomotive companies) have latest train safety systems. So are we talking of older locomotives or there is more to strike by loco pilots.


Thats absolutely true.

I read somewhere that these types of brakes used only in emergency and a big cause behind derailments. is this true.

 

[MastanKhan]

Hi,

Basically what it is like you are driving in your manual transmission car----you are going down the hill---you leave it in gear and take your foot off the gas pedal---then you can further slow it down by down shifting down gears----.

I read somewhere that these types of brakes used only in emergency and a big cause behind derailments. is this true.

Hi,

They are for everyday use---you have derailment because of the lack of it.

 

[anant_s]

I read somewhere that these types of brakes used only in emergency and a big cause behind derailments. is this true.

Can you share some information on what is the maximum allowed speed for diesel locomotives in PR?
Theoretically speaking, if there are no contingencies (such as bringing train to sudden stop), pneumatic baking can be used to run a train, but the speed limitations of 10-15 kph come in force. & i'm sure trains are running at much higher speeds than that on PR.
Safety authorities (that oversee all rolling stock healthiness) cannot allow trains to run without dynamic brakes.
I therefore doubt that there is something fishy with how drivers are behaving.

 

[The-king]

Can you share some information on what is the maximum allowed speed for diesel locomotives in PR?
Theoretically speaking, if there are no contingencies (such as bringing train to sudden stop), pneumatic baking can be used to run a train, but the speed limitations of 10-15 kph come in force. & i'm sure trains are running at much higher speeds than that on PR.
Safety authorities (that oversee all rolling stock healthiness) cannot allow trains to run without dynamic brakes.
I therefore doubt that there is something fishy with how drivers are behaving.

Bro some diesel locomotive in PR attain 120 KMS speed even back in 1990
In the early 1990s, diesel locomotives in China could attain a maximum speed of 120 km/h (75 mph) on passenger trains. Here a N595 diesel locomotive is shown hauling passenger coaches on theGuangzhou–Sanshui Railway at Foshan in 2008.

 

[anant_s]

Bro some diesel locomotive in PR attain 120 KMS speed even back in 1990
In the early 1990s, diesel locomotives in China could attain a maximum speed of 120 km/h (75 mph) on passenger trains. Here a N595 diesel locomotive is shown hauling passenger coaches on theGuangzhou–Sanshui Railway at Foshan in 2008.

Yes thats exactly the point, locomotives are running at 100+ speed cannot do so without dynamic braking. So the premise that locomotive pilots are running trains at such high speeds only depending on air or vacuum braking doesn't look correct. & thats exactly why i couldnot understand why LPs are demanding Dynamic braking now? These would already be present on locomotives on PR.

 

[The-king]

Yes thats exactly the point, locomotives are running at 100+ speed cannot do so without dynamic braking. So the premise that locomotive pilots are running trains at such high speeds only depending on air or vacuum braking doesn't look correct. & thats exactly why i couldnot understand why LPs are demanding Dynamic braking now? These would already be present on locomotives on PR.

But i believe they upgraded to some superior tech which pilots find difficult or not sufficient enough in use.