Monday, December 30, 2013

NYCT VakTrak due for overhaul

Written by  Mischa Wanek-Libman, Engineering Editor
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 (NYCT) two vacuum trains is receiving an extensive late-life overhaul and upgrade aimed at improving efficiency, increasing reliability, and easing maintenance tasks.

The five-car, self-propelled work train, known as VakTrak, is equipped with a high-powered vacuum cleaning system designed to remove trash and steel dust from type-two (concrete-ballasted) subway track.

NYCT received the first of its custom built VakTraks, VT #1, in 1997 and added a second to the system in 2000, VT #2. The trains were purchased for close to $15 million each and automated work previously done by hand. Both trains are 8-feet, 9-inches wide, the same as the numbered lines (A Division), which have the narrower cars (in terms of loading gauge) on the system, so the trains can work and travel throughout NYCT’s entire system.

Spare parts for NYCT’s two VakTraks have long been exhausted and there are no more replacement parts to be had. However, the Division of Car Equipment has a long history of creating specialized equipment to meet the needs of New York’s subway system. “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 NYCT says 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 1,800, 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.

The vacuum trains are a major part of NYCT’s efforts to keep the system free of trash. The current work allows NYCT to make upgrades to existing equipment, and even more important, utilize many of the lessons learned to improve the operation of new equipment.