A certain amount of slack must be left in a flexible hose during installation because, when under pressure, it ________.

• A. expands in length and contracts in diameter
• B. contracts in length and expands in diameter
• C. remains unchanged
• D. becomes brittle

Answer: (B)

When flexible hoses are under pressure, they behave in a way where they contract in length and expand in diameter. This characteristic is crucial for ensuring the longevity and proper function of the hose in a hydraulic or pneumatic system.

As the internal pressure increases, the materials that make up the hose tend to stretch outwards, causing the diameter to increase. Simultaneously, the hose itself may shorten a bit as the material compresses under the tension of the pressure. If sufficient slack is not left during installation, the hose could become overly tight, leading to potential damage, kinking, or failure of the hose under operating conditions.

Proper slack allows the hose to accommodate these dimensional changes without putting undue strain on the fittings or the hose itself. Therefore, leaving a certain amount of slack during installation is essential for ensuring optimal performance and safety of the fluid handling system.