Post by Nortube on Mar 15, 2013 1:47:40 GMT
The EP brake circuit (diagram at the end of this post)
Lap
Service Westinghouse
Both positions are exactly the same from an EP brake point of view.
The slider connects the Supply, Holding and Audible warning fingers together
When the brake handle is moved to Lap, the slider moves away from the application finger and makes contact with the Audible warning finger
There is no longer 50v on the Application wire and so the application valve is de-energised and closed, preventing any more air entering the brake cylinders. The application magnet valve interlock is open but, as the slider is now connecting the supply finger with the audible warning finger, the audible warning magnet valve will still remain energised.
The holding magnet valves are energised and closed, preventing any air escaping from the brake cylinders.
The blowdown magnet valves are also energised, so the brake cylinders are able to retain up to the maximum brake pressure.
When the brake handle is moved to Service Westinghouse, nothing changes. The Service Westinghouse position is for when the Westinghouse brake is being used.
Emergency
Emergency is the same as Full EP - where the brake handle is moved to the furthest part of the Application range. In Emergency and the full EP end of the Application range, the self lapper is by-passed, meaning that as long as the brake handle is left in that position, main line air will continually be going through the open application magnet valve into the brake cylinders. A safety valve, set at 55 psi, is fitted to the brake pipe. Any pressure greater than that will be vented to atmosphere.
In Emergency, as well as a full EP application, an emergency Westinghouse application will be made
As I don't show the self-lapper on the diagrams, the diagram for Application (stage 1) is exactly the same diagram as that for Emergency.
Lap and Service Westinghouse
Lap
Service Westinghouse
Both positions are exactly the same from an EP brake point of view.
The slider connects the Supply, Holding and Audible warning fingers together
When the brake handle is moved to Lap, the slider moves away from the application finger and makes contact with the Audible warning finger
There is no longer 50v on the Application wire and so the application valve is de-energised and closed, preventing any more air entering the brake cylinders. The application magnet valve interlock is open but, as the slider is now connecting the supply finger with the audible warning finger, the audible warning magnet valve will still remain energised.
The holding magnet valves are energised and closed, preventing any air escaping from the brake cylinders.
The blowdown magnet valves are also energised, so the brake cylinders are able to retain up to the maximum brake pressure.
When the brake handle is moved to Service Westinghouse, nothing changes. The Service Westinghouse position is for when the Westinghouse brake is being used.
Emergency
Emergency is the same as Full EP - where the brake handle is moved to the furthest part of the Application range. In Emergency and the full EP end of the Application range, the self lapper is by-passed, meaning that as long as the brake handle is left in that position, main line air will continually be going through the open application magnet valve into the brake cylinders. A safety valve, set at 55 psi, is fitted to the brake pipe. Any pressure greater than that will be vented to atmosphere.
In Emergency, as well as a full EP application, an emergency Westinghouse application will be made
As I don't show the self-lapper on the diagrams, the diagram for Application (stage 1) is exactly the same diagram as that for Emergency.
Lap and Service Westinghouse