Question 310General Subjects - QMED

The correct answer is A. The main difference between a stuffing box gland and a mechanical seal is that if the packing in a stuffing box gland fails, the leak can be temporarily stopped by tightening the gland. However, if a mechanical seal fails, the entire seal must be replaced to stop the leakage. Packed stuffing box glands are subject to wear over time and require adjustment, while mechanical seals provide a more reliable seal that does not require adjustment. The other answer choices are incorrect. Packed stuffing box glands are subject to wear, while mechanical seals are not (B is incorrect). The sealing surface of a mechanical seal is perpendicular to the shaft, not parallel (C is incorrect). Both packed stuffing box glands and mechanical seals do not require cooling by the liquid being pumped (D is incorrect).