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In hydraulic systems, a 'fuse' is a component which prevents the sudden loss of hydraulic fluid pressure. It is a safety feature, designed to allow systems to continue operating, or at least to not fail catastrophically, in the event of a system breach.
The term "fuse" is used here in analogy with electrical fuses which perform a similar function.
Hydraulic systems rely on high pressures (usually over 7000 kPa) to work properly. If a hydraulic system loses fluid pressure, it will become inoperative and components such as actuators may collapse. This is an undesirable condition in life-critical systems such as aircraft or heavy machinery. Hydraulic fuses help guard against catastrophic failure of a hydraulic system (for instance, by line breakage or component failure) by automatically isolating the defective branch.
When a hydraulic system is damaged, there is generally a rapid flow of hydraulic fluid towards the breach. Most hydraulic fuses detect this flow and seal themselves if the flow exceeds a predetermined limit. There are many different fuse designs but most involve a passive spring-controlled mechanism which closes when the pressure differential across the fuse becomes excessive.

Contents

Types

In dam spillways

See also

Types

There are two types of hydraulic fuses. The first one acts like a pressure relief valve, venting in case of a pressure surge. The second is more or less like a check valve. The only difference is a check valve is in place to prevent upstream fluid from coming back and venting out. A fuse is in place before the venting area and stops fluid from venting forward of it.
Hydraulic fuses are not a perfect solution to fluid loss. They will probably be ineffective against slow, seeping loss of hydraulic fluid, and they may be unable to prevent fluid loss in the event of a catastrophic system failure involving multiple breaches to hydraulic lines. Also, when a fuse activates it is likely that the system will no longer function as designed.
Depending on the system, hydraulic fuses may reset automatically after a delay, or may require manual re-opening.

In dam spillways

In the design of a spillway for a dam, a fuse plug is a water retaining structure designed to wash out in a controlled fashion if the main dam is in danger of overtopping due to flood, and if the normal spillway channel is insufficient to control the over topping.

See also

★ Relief valve

★ Safety valve

★ Fuse for the other meanings of the word.