Lapping/en: Difference between revisions

Revision as of 20:41, 9 March 2025

There are two types of compressed air brake system control valves : self-lapping and non-self-lapping.

Self-Lapping

Self-lapping control valves are newer. With them, the control lever corresponds to the brake cylinder pressure, and is more beginner friendly. The further the lever is set in the “apply” direction, the stronger the braking application, and vice versa. The valve automatically handles the dumping and charging of the brake pipe , to get to the desired cylinder pressure.

Non-Self-Lapping

Non-self-lapping control valves are older. With them, the control lever manipulates the brake pipe pressure directly, and the process is more hands-on. The lever has a few fixed positions. Two of the positions, called “release” and “service” can be thought of as adding and releasing the brake pipe pressure, respectively. The position in-between them, called “lap”, is used to maintain whatever pressure is in the brake pipe. The furthest position, called “emergency”, releases pressure at the fastest possible rate.

By control the brake pipe pressure, you indirectly set the cylinder pressure to the required amount.

Auxiliary reservoirs are partially drained whenever brakes are applied. When brakes are then released, it takes some time for the reservoirs to be recharged. The lap position, however, functions only if the auxiliary reservoirs are full. So, to stay in full control over the brakes it is recommended to not release non-self-lapping brakes when knowing that moments later braking may be needed again. Calculated, infrequent moves are preferable when operating non-self-lapping brakes.

Monitoring

With both control valve types it is crucial to monitor the brake pipe and cylinder gauges to fully understand the current brake state.

Conflicts

In case a train contains multiple motorized vehicles their control valves will conflict each other. The conflicts will be even more severe if there are mixed self-lapping and non-self-lapping types. To ensure safe operation it is necessary to cutout all excess control valves, other than the one intended to be used.

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-Depending on the motorized vehicle type, there are two ways to control the brake pipe pressure: self-lapping and the older, non-self-lapping.
+There are two types of {{pll|Air Brake System Overview|compressed air brake system control valves}}: self-lapping and non-self-lapping.
-On the self-lapping systems, the brake pipe pressure is handled automatically. The driver can set the train brake lever to any position in a range. The further it is set in the “apply” direction, the stronger the braking force, and vice versa. The valve automatically handles the dumping or pressurizing of the brake pipe depending on the position of the lever.
+==== Self-Lapping ====
-On non-self-lapping systems, the process is more hands-on. The lever has a few fixed positions. Two of the positions, called “release” and “service” can be thought of as adding and releasing the brake pipe pressure, respectively. The position in between them, called “lap”, is used to maintain whatever pressure is in the brake pipe. The furthest position, called “emergency”, will release pressure at the fastest possible rate.
+Self-lapping control valves are newer. With them, the control lever corresponds to the {{pll|Air Brake System Overview|brake cylinder}} pressure, and is more beginner friendly. The further the lever is set in the “apply” direction, the stronger the braking application, and vice versa. The valve automatically handles the dumping and charging of the {{pll|Air Brake System Overview|brake pipe}}, to get to the desired cylinder pressure.
-Auxiliary reservoirs are being drained when braking. When the brakes are released, it takes some time for auxiliary reservoirs to fill up again. The lap position, however, functions only if the auxiliary reservoirs are full. To stay in full control over braking it is recommended to not release non-self-lapping brakes when knowing that moments later braking may be needed again. Calculated, slow moves are preferable when releasing the non-self-lapping brakes.
+==== Non-Self-Lapping ====
-With both brake types, the driver can see exactly how much braking force they are applying by looking at the brake pipe and brake cylinder gauge needles.
+Non-self-lapping control valves are older. With them, the control lever manipulates the brake pipe pressure directly, and the process is more hands-on. The lever has a few fixed positions. Two of the positions, called “release” and “service” can be thought of as adding and releasing the brake pipe pressure, respectively. The position in-between them, called “lap”, is used to maintain whatever pressure is in the brake pipe. The furthest position, called “emergency”, releases pressure at the fastest possible rate.
-Both systems are fairly simple to use, although self-lapping may be more intuitive to beginners. In simple terms, with self-lapping the control device sets the desired braking force, leaving it to the automatic valve to do the work, whereas with non-self-lapping the control device directly sets the braking force.
+By control the brake pipe pressure, you indirectly set the cylinder pressure to the required amount.
-In case a train contains motorized vehicles with both self-lapping and non-self-lapping brake valve types, only the self-lapping ones will be functional when operating the brake. For that purpose, vehicles are also equipped with brake cutout valves, which can be used to isolate certain vehicles from the brake system and resolve this conflict.
+Auxiliary reservoirs are partially drained whenever brakes are applied. When brakes are then released, it takes some time for the reservoirs to be recharged. The lap position, however, functions only if the auxiliary reservoirs are full. So, to stay in full control over the brakes it is recommended to not release non-self-lapping brakes when knowing that moments later braking may be needed again. Calculated, infrequent moves are preferable when operating non-self-lapping brakes.
+==== Monitoring ====
+With both control valve types it is crucial to {{pll|Monitoring|monitor the brake pipe and cylinder gauges}} to fully understand the current brake state.
+==== Conflicts ====
+In case a train contains multiple motorized vehicles their control valves will conflict each other. The conflicts will be even more severe if there are mixed self-lapping and non-self-lapping types. To ensure safe operation it is necessary to {{pll|Brake Cutout|cutout}} all excess control valves, other than the one intended to be used.
-{{See also|Air Brake System Overview|Brake Cutout|Monitoring|Train Brake|Independent Brake|Brake Shoes}}
 [[Category:Air Brake System|2]]