Vacuum Trains Being Fixed for the Long Haul
Even the most powerful vacuum cleaner in New York City has to go in for a tune-up once in a while. So, after years of sucking up tons of track debris from the underground portions of the subway system, one of MTA New York City Transit’s two vacuum trains is receiving an extensive late-life overhaul and upgrade aimed at improving efficiency, increasing reliability and easing maintenance tasks.
The vacuum train or VakTrak is a five-car, self-propelled work train equipped with a high-powered vacuum cleaning system designed to remove trash and steel dust from type-two (concrete-ballasted) subway track. The trains roll through the system overnight between 11 p.m. and 5 a.m., making their rounds between passenger trains and out of the sight and earshot of most subway customers. Aside from the aesthetics involved, keeping the road bed clear of trash is a key element in the ongoing effort to reduce track fires, and the deployment of the vacuum trains is the most efficient way to perform the task.
The first train, VT #1 was delivered in 1997 and the size of the fleet was doubled with the arrival of VT #2 three years later. Both of the French-built, diesel-propelled trains were specially-designed and manufactured for the New York City subway’s unique operating environment and perform cleaning work previously done by hand.
Purchased for about $15 million dollars apiece, the trains consist of five cars (two Propulsion cars, two Filter cars and one Vacuum car). Each train generates 20,000 pounds of air pressure, is equipped with 252 filters (156 in each filter car alone) and four diesel engines (two in each propulsion car). The vacuum system of each 225-foot long train draws in 70,000 cubic feet of air a minute.
In vacuum operation, the train travels at speeds of about 1.5 to 4 mph to ensure thorough cleaning. When headed to and from work locations it is also capable of speeds up to 40 mph but, as per work train rules, is limited to a speed of 25 mph through the system. Both trains are the same 8’-9” width as the cars on the numbered lines (the smallest cars in the system), so they can work and travel throughout the system.
Unlike subway cars, which are purchased in multiples of 100, the VakTraks are the only two vacuum trains built to NYC Transit specifications. Though not exact copies, as every rail system has unique characteristics which must be accommodated during design, ten other vacuum trains of different designs were built for other railroads throughout the world. The other trains of similar vintage have since been retired from service.
Spare parts for NYC Transit’s two trains have long been exhausted and there are no more replacement parts to be had. However, what at first would appear to be a problem has been turned into an opportunity. The Division of Car Equipment has a long history of creating specialized equipment to meet the needs of our subway system. The division’s personnel also have an enviable reputation for making improvements to existing rolling stock.
“We are replacing the old components with new, more reliable ones,” said Joseph Ragusa, General Superintendent, Division of Car Equipment-Work Equipment. “These trains were not what we would call maintenance-friendly equipment. We are taking this opportunity to make changes and improvements, and we will take what we have learned as we design the next generation of vacuum trains.”
VT #2 is currently going through several system upgrades, and several shortcomings in the train’s original design are being addressed. These changes will increase the train’s reliability and improve performance. One of the items being improved is the air brake compressor, which is being changed over from belt to hydraulic drive to keep the RPMs constant at 1800, which provides for more dependable build-up of air. It will also solve the problem of broken belts, which had to be swapped out often.
Another area in need of improvement was the actual cleaning performance. The vacuum operation was being adversely affected by damage to the upper suction hood assembly, which is a sheet of metal below the roof that connects the ducts to the bins. “We noticed that with everything else working properly, we weren’t getting the suction we should have been getting,” said Maintenance Supervisor Wendel Charlton. “An examination showed several holes in the upper hood assembly, which compromised the unit’s effectiveness.”
A new upper hood is currently being fabricated of stainless steel, a material far more resistant to corrosion. A similar change to the earlier vacuum train has been successful and increased use of stainless steel will be specified for the next vacuum trains, particularly for areas within the train affected by the build-up of debris and moisture.
The control cabin is being upgraded with modern equipment, including a new “Slip/Slide Feature.” The exhaust system on the diesel propulsion units is being upgraded to a cleaner system that will employ a catalyst to help lower emissions. The vacuum trains are incredibly complex and one of the goals is to simplify that operation.
Even if the vacuum system is operating perfectly, there are times when the train is out of service due to problems with the propulsion system. The next trains will be ordered without the propulsion units. The train will instead be powered by units from NYCT’s diesel fleet, which can easily be swapped if the need arises.
The vacuum trains are a major part of NYC Transit’s to keep the system free of trash. The current work allows us to make upgrades to existing equipment and even more importantly, utilize many of the lessons learned to further improve the operation of new equipment.