Question 37 1AE01 - First Assistant Engineer

The Correct Answer is B **Explanation for B (Correct Answer):** Option B is correct because hydraulic fluid pressure acts upon all surfaces it contacts. When attempting to tighten a leaking fitting while the system is pressurized, the internal hydraulic pressure (which can be very high, e.g., thousands of psi) pushes the components of the fitting (like the nut and the body) apart. This pressure creates a very strong opposing force to the mechanical force you are applying with a wrench. The force exerted by the pressurized fluid makes it extremely difficult, often impossible, to achieve the necessary metal-to-metal contact required to seal the leak by tightening the fitting. In some cases, attempting to overcome this force can strip threads or damage the fitting without successfully stopping the leak. **Why other options are incorrect:** * **A) dislodge any scale in the tubing, and it will damage the system:** While high pressure *can* dislodge scale, this is not the primary or immediate result of attempting to physically tighten a fitting under pressure. The main immediate effect is the inability to tighten the connection due to the opposing fluid pressure. Furthermore, while scale is undesirable, hydraulic systems typically use filters to prevent widespread damage from dislodged particulate matter. * **C) be successful every time:** This is fundamentally incorrect and dangerous. As explained for option B, the hydraulic pressure actively resists tightening and sealing the fitting. Attempting to tighten pressurized lines is a widely recognized safety and maintenance error in hydraulics. * **D) cause the system to vibrate:** While pressure fluctuations or trapped air can cause system vibration, simply attempting to manually tighten a static fitting under pressure does not directly cause the system to vibrate. The immediate effect is the resistance to tightening.