Wednesday, October 02, 2013

NYAB DB-60 II control valve maintains brake pressure on grades

Written by  William C. Vantuono, Editor-in-Chief
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Heavy-haul freight trains require fully charged brakes. When operating a train on a downgrade, brake usage levels on individual cars climb, equipment heats up, and braking power levels can drop drastically, sometimes forcing the engineer to stop the train. New York Air Brake has developed a new control valve, the DB60 II, to address these issues.

“All air brakes leak—the allowable standard is one psi per minute—and they leak more when cold or worn,” says New York Air Brake Senior Vice President Jason Connell. “This leakage is not normally a problem on flat terrain, when brakes are applied for short periods of time. But when brakes are applied on a long grade for an hour or more, they need recharging. When a train reaches a long downhill grade, the engineer applies some dynamic brake and, depending on the brake force required, also reduces the pressure in the brake pipe to trigger the brake valves and apply the air brakes. With standard control valves, the brake cylinders don’t get charged continuously. And over a period of time even small leakage can cause brakes to fail.”

The brake cylinders on some railcars in a given consist will leak more than others, and those cars have less braking power. “This puts more of the burden of slowing the train on to those cars that leak less and therefore can apply more braking force,” Connell points out. “The brake shoes on the ‘good cars’ heat up faster and wear down more quickly. Heat damages wheels. The train brakes unevenly, making the entire train less stable, increasing in-train forces, leading to broken knuckles and drawbars and damaged lading.”

“Reduced braking force due to leakage requires more dynamic brake, which can become overheated, or more air brake, which may require the engineer to reduce brake pipe pressure below allowable limits and in turn force him to stop the train,” Connell stresses. “The engineer must release all the pressure in the brake pipe to trigger a risky full stop, bringing the train to a halt for as long as an hour while the brake system recharges. This costs railroads money: It makes the train late, and the delay ripples out across the network as other trains must be slowed, stopped, or re-routed around the stopped train.”

New York Air Brake’s “brake cylinder maintaining” feature on its new DB-60 II brake valve solves this problem by enabling a constant recharge of the brake cylinder during braking. “This improves safety and ensures a more even brake cylinder pressure along the entire train, enabling the cars in the train to brake evenly,” says DB60 II Product Manager Deepak Kumar. “It dramatically reduces the risk of bringing the train to a halt on a steep grade. Maintenance costs decrease, fuel use lessens, and ontime performance improves.”

The DB60 II was introduced at Railway Interchange 2013 in Indianapolis. A Quicktime video on this product is available on the NYAB website.

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