Velocity Fuse

Alcaro supplies velocity fuses throughout Australia!

A Velocity Fuse, (Hose Burst Valve), is a safety device that senses the flow rate of hydraulic fluid out of a cylinder and ‘locks’ if the flow rate exceeds the allowable rate.

A velocity fuse requires a flow potential large enough to meet the differential pressure setting. The flow normally required to trip the fuse is 30% above the rated flow. This usually accommodates flow surges without tripping the fuse.

Flow surges can be caused by sudden starts and stops, valve actuations, motor reversals, etc. The fuse allows reverse free flow. Depending on the system requirements, velocity fuses can reset automatically when the pressure is removed or with reverse flow.

An adjustable velocity fuse can optimise the fuse trip setting and can be externally adjusted to provide a flow trip setting without having to disconnect the hydraulic lines. Once the fusing flow is set, the housing can be locked for repetitive operation.

A hydraulic fuse serves the same function as a fuse or circuit breaker in electrical circuits. When an electrical circuit is overloaded, the excessive current either burns the fuse element or trips the circuit breaker. This feature saves lives and prevents damage. A hydraulic fuse provides similar protection to a hydraulic circuit by detecting a broken fluid line and closing off the circuit. It is a check valve that closes when a predetermined signal has occurred — generally, a sudden change in pressure or flow. Hydraulic fuses are used most often in critical applications to prevent serious equipment damage and bodily harm. But they can also be used to prevent massive fluid loss in the event of a catastrophic failure, such as rupturing of a hose or tube.

Why aren’t hydraulic fuses as commonplace as electrical counterparts? They were not required by law, so cost seemed to be the main objection.. Even though the cost of a fuse may be less than $1000, not using one could cost hundreds of thousands in litigation, especially if a fuse in a circuit would have prevented a serious accident.

In addition to cost, nuisance trips (closing of the fuse when it is not supposed to) are another reason why hydraulic fuses may not be specified. However, nuisance can be overcome by specifying the right fuse for an application.

Operation and options:

Hydraulic fuse is a general term given to three different types of devices — velocity fuses, quantity fuses, and pressure fuses.

Velocity fuses work by sensing flow across a control orifice when the pressure differential exceeds a predetermined amount. A spring-biased poppet closes, shutting flow to the damaged hydraulic circuit.

A velocity fuse requires a flow potential large enough to meet the differential pressure setting. The flow normally required to trip the fuse is 30% above the rated flow. This usually accommodates flow surges without tripping the fuse. Flow surges can be caused by sudden starts and stops, valve actuations, motor reversals, etc. The fuse allows reverse free flow. Depending on the system requirements, velocity fuses can reset automatically when the pressure is removed or with reverse flow.

An adjustable velocity fuse can optimize the fuse trip setting and can be externally adjusted to provide a flow trip setting without having to disconnect the hydraulic lines. Once the fusing flow is set, the housing can be locked for repetitive operation.

Description: The velocity fuse valve is a normally open valve that automatically closes based upon a pre-determined flow-rate. The valve does not require any external pilot signals or drain ports. Any flow rate available with actual flow test verification documentation. The valve is also very silt resistant and available in any size.

Application: The velocity fuse valve is typically used in applications to protect against excessive flow through a hydraulic system. An example application would be a large cylinder supporting a large load at high pressure. The valve would be installed to protect against an emergency severe loss of load and subsequent excessive flow rate. This would reduce the potential for damaging cylinder velocities. Great for systems needing protection from ruptured hoses to prevent fluid discharge.

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