Lapping/zh-hant

貫通司軔閥 分為兩種：「自動保壓」和「非自動保壓」。

自動保壓

較新型的司軔閥能夠「自動保壓」，也就是根據手柄的位置自動地完成三個動作：釋放、增加並維持軔管 中的壓力。它們對於初學者較易上手，因其手柄的位置也直接對應著軔缸 壓力。愈向「緊軔」方向推動手柄，施加的軔力愈強；愈向「鬆軔」方向推動推動手柄，施加的軔力愈弱。

非自動保壓

The 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 controlling the brake pipe pressure, you indirectly control the cylinder pressure, and thus, brake application.

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 non-self-lapping brakes it is recommended to not release when knowing that moments later braking may be needed again. Calculated, infrequent moves are advised instead.

監控

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

衝突

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