Lifting the Way: The Unbeatable Advantages of Hydraulic Bridge Systems

With a large vessel wishing to pass under a road which connects two land masses, a standard, fixed bridge, simply will not suffice. Movable bridges, such as the familiar bascule (drawbridge) and vertical lift types become possible solutions. How do we ultimately ensure that these structures will open and close smoothly? The answer is hydraulics. 

For the most part, hydraulic systems represent the "muscle and brains" of bridge operation found in modern movable bridges. Hydraulics offer a range of benefits that revolved cables/good or mechanical teeth cannot. 

1. A Colossal Force Multiplier (the Power Factor)

The number one reason hydraulics dominate the field of bridge operation is their ability to multiply force. 
Pascal's Law: Hydraulics freely use Pascal's principle, which states that a small force applied over a small area creates pressure. That pressure is then transferred to a large cylinder (or ram), resulting in some crazy output force.
Heavy Loads Lifted (Chapter One): Because of this principle, the bridge's drive system comprises motors and pumps that can lift thousands of pounds of steel and concrete with relatively small devices. This force multiplication is essential as the massive weight of a large bridge leaf inherently relies on it.

2. Precise, Smooth, and Controlled Motion

When operating the bridge, the span's enormous, heavy mass should be slowly started and stopped to avoid structural wear and jarring. Hydraulics offers an unrivaled degree of control:

• Smooth Acceleration/Deceleration: If the flow of hydraulic fluid (oil) is controlled properly, the operator will achieve smooth, controlled acceleration and deceleration while avoiding shock loading on both the structure and machinery.
• Positive Locking: Under load, hydraulic cylinders maintain the position of the cylinder indefinitely. This positive locking assurance would hold the bridge leaf open (or closed) safely in the winds, load, or gravity without requiring any complex external mechanical locks.
• Variable Speed: The speed of the opening or closing the bridge process can be infinitely adjusted. This becomes useful in maneuvering the bridge in high winds or with different loading conditions.

3. Reliability and Durability in Extreme Environments

Bridges are out in the elements twenty-four hours a day, seven days a week. The design of hydraulic systems makes them particularly attractive to operate in these conditions as follows: 

• Less Moving Parts: They have fewer main moving components (pumps, cylinders, motors, valves) compared to complicated mechanical systems (gear boxes, shafts, chains, etc.) that use many components and more moving parts. So, there is less to break down, as well as repairs and maintaince is simpler.
• Shock Load Protection: The fluid medium provides a natural shock absorbing capability. Should the bridge experience sudden environmental loads (such as a huge gust of wind), the hydraulic fluid is able to absorb and dissipate loads away from the main drive components. 
• Self-Lubricating: The hydraulic oil provides constant lubrication to the internal moving parts of the cylinders and pumps, reducing friction and extending the life of the equipment.

4. Compact Design and Efficient Power-to-Weight Ratio

Although hydraulic machinery produces enormous forces, the components are relatively small and compact:

• Space Saving: Hydraulic cylinders are long and thin, making them easy to fit in the often constricted space around bridge abutments or towers, and enabling engineers to design thinner, more elegant bridge structures.
• High Power Density: A hydraulic system has a power-to-weight ratio, so the hardware and machinery is smaller and lighter than an equivalent electric or mechanical system capable of creating the same lifting forces.

In summary, hydraulic technology is a delightful engineering marvel, allowing us to engineer our way through the intersection of land and sea traffic. This ensures that when a bridge does need to move, it does so with strength, poise, and dependability.