Maintenance Flashcards

A maintenance technician notices that a roller bearing is running at 180°F (82°C) under normal load and speed. The bearing manufacturer specifies a maximum continuous operating temperature of 200°F (93°C). Which action is MOST appropriate?

Answer: Continue operation and monitor closely, as the bearing is within spec but approaching its limit — investigate root cause such as over-lubrication, misalignment, or inadequate ventilation

180°F is within the manufacturer's limit, so immediate shutdown is not required. The correct response is to monitor and investigate root causes — over-lubrication is a common cause of overheating because excess grease churns and generates heat. Misalignment and poor ventilation are other culprits. Adding more grease would worsen overheating, and increasing speed raises friction and heat further.

A pneumatic cylinder on a production machine is completing its stroke 15% slower than its rated cycle time, but system air pressure at the compressor reads normal. The FRL (filter-regulator-lubricator) unit was serviced last week. What is the MOST likely cause?

Answer: A flow control valve on the cylinder's exhaust port adjusted to limit speed

Flow control valves are commonly installed on cylinder exhaust ports to meter speed. If one was inadvertently adjusted during or after the FRL service, it would reduce exhaust flow and slow the cylinder without affecting compressor pressure readings. Worn seals would typically show inconsistency or pressure drop at the cylinder. A clogged FRL filter would affect pressure downstream of it, and the FRL was just serviced. Lack of lubrication would cause more resistance but not a consistent 15% slowdown.

When performing predictive maintenance using vibration analysis on a rotating machine, a technician detects a frequency spike at exactly 1× running speed. This is MOST indicative of which condition?

Answer: Rotor imbalance

A dominant vibration spike at 1× running speed (1× RPM) is the classic signature of rotor imbalance — a heavy spot on the rotating component generates a centrifugal force once per revolution. Inner race bearing defects appear at BPFI (Ball Pass Frequency Inner), which is a multiple of running speed but not equal to it. Gear mesh frequency appears at the number of teeth × RPM. Cavitation produces broadband, random high-frequency noise rather than a sharp 1× spike.

A V-belt drive system shows rapid belt wear within 500 hours of installing new belts. The sheaves were inspected and found to be properly aligned. Which condition is the MOST likely root cause of premature wear?

Answer: The sheave grooves are worn and have a concave profile, causing the belt to bottom out and lose wedging action

Worn sheave grooves with a concave (cupped) profile are a leading cause of rapid new-belt wear. When grooves are worn, the belt sits deeper and contacts the bottom of the groove instead of the sidewalls, eliminating the wedging action that provides grip. This causes slippage, heat, and accelerated belt degradation. New belts installed in worn sheaves wear quickly because the groove geometry is already compromised. Low tension also causes slippage but typically shows glazing rather than rapid wear. Center distance affects wrap angle, but misalignment, not center distance, is the primary culprit in most belt drives.

A maintenance technician is replacing a hydraulic pump on a system operating at 2,000 PSI. After installation and startup, the system pressure only reaches 1,400 PSI and the pump runs noticeably louder than normal with a rattling noise. What is the MOST probable cause?

Answer: Air is entering the pump inlet due to a loose suction line fitting or low reservoir level, causing cavitation

Cavitation — air or vapor entering the pump — produces exactly this symptom set: a rattling or crackling noise (imploding bubbles) combined with lower-than-expected pressure output. It commonly occurs after pump replacement if the suction line is not properly tightened, the reservoir is low, or the suction strainer is blocked. A mis-set relief valve would cause pressure limitation but not the characteristic noise. Reversed rotation would usually produce zero or very low pressure with no flow. A larger pump displacement would increase flow, not reduce pressure below what's achievable.

During a scheduled preventive maintenance shutdown, a technician is re-torquing bolts on a flanged pipe joint that uses a spiral-wound gasket. The gasket was not replaced. Which procedure is CORRECT?

Answer: Do not re-torque the joint — spiral-wound gaskets must be replaced if a flange is opened; re-torquing a used gasket is not recommended

Spiral-wound gaskets are single-use components. Once a flanged joint using a spiral-wound gasket is opened, the gasket should be replaced — not re-torqued. These gaskets take a permanent set during initial compression. Re-torquing a used spiral-wound gasket risks over-crushing the sealing element, damaging the outer ring, or achieving inadequate sealing because the gasket cannot recover its original thickness or compliance. Industry standards (ASME B16.20, ASME PCC-1) recommend replacement. Re-torquing without replacement is acceptable only for certain gasket types like ring joint (RTJ) in specific conditions.