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Braking System

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LMSDUCHESS

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8 Jun 2014
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4
Hi Everyone,
I'm slightly confused about the idea of a two piped brake. I've been on the Scotrail thread that ran away recently, and wouldn't mind if somebody could explain what is a two piped braking system. I apologise if this is the wrong thread.
 
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RailUK Forums

Dunfanaghy Rd

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16 Sep 2019
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Alton, Hants
If you are OK with Single Pipe Air Brake, the Two Pipe is simply the addition of a Reservoir Pipe feeding the Auxiliary Reservoirs on each vehicle directly from the locomotive / control cab. The advantage is that the Auxiliary Reservoirs are always replenished by the supply irrespective of whether or not there is a brake application. The reservoir pressure is also higher (85 - 105 psi) than Brake Pipe Pressure (72.5 psi), giving an extra reserve. Another aspect is that the Brake Pipe only has to transmit a signal to the distributor, not feed the Auxiliary Reservoir as well, which can speed up release times. I was once told that Foster Yeoman, who had twin-pipe on all their wagons, reckoned on a saving of 80 gallons of fuel between Westbury and Acton due to not powering against brakes that were not fully released. How they knew that I don't know, unless they compared with the Hanson trains when they linked up as Mendip Rail.
Pat
 

hexagon789

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Joined
2 Sep 2016
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15,715
Location
Glasgow
Compared to the single pipe system the main advantages are greatly reduced chances of being able to use up all the air with successive heavy applications and releases of the brakes and a faster release of the brakes. It is also graduable in application and release while the single pipe was generally graduable in application only, but modern distributors no longer mean that's an issue.
 
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