AMSA Marine Engine Driver Grade 1 (MED1)

Correct: Under United States Coast Guard (USCG) safety standards and typical Safety Management Systems, the immediate priority during a towline failure is to regain control of the barge. Utilizing the pre-rigged emergency towline, which is often designed for rapid deployment without requiring crew to board the barge in dangerous conditions, allows for a connection to be re-established while maintaining a safe distance to prevent a collision between the vessels.

Incorrect: Relying solely on dropping the barge anchor can be hazardous in heavy seas as the anchor may not hold or the windlass could fail under extreme dynamic strain. The strategy of maneuvering the tug directly alongside the barge in heavy weather creates a high risk of hull damage or personnel injury due to the vessels slamming together. Opting to wait for weather improvement is an unacceptable response because an unpowered, drifting barge poses an immediate threat to navigation, coastal environments, and other vessels.

Takeaway: Contingency plans must prioritize the rapid re-establishment of a tow connection using pre-rigged emergency equipment to prevent uncontrolled drifting.

Correct: Bank suction occurs in restricted channels when the flow of water between the hull and the bank is constricted, creating a low-pressure area that pulls the stern toward the bank. Reducing speed is the most effective way to mitigate this effect because the magnitude of the pressure differential is directly related to the vessel’s speed through the water.

Incorrect: The strategy of increasing speed to counter bow dipping is dangerous because squat actually increases with the square of the speed in shallow water, potentially leading to a grounding. Focusing only on bank cushion as a force that pushes the stern toward the bank is a misunderstanding of hydrodynamics, as bank cushion creates high pressure that pushes the bow away from the bank rather than pulling the stern in. Choosing to shift to a towing-alongside configuration based on pivot point movement is incorrect because the pivot point naturally moves forward when a vessel has headway, and changing the tow configuration in a narrow channel during a maneuver is unsafe.

Takeaway: Barge supervisors must recognize that bank suction pulls the stern toward the bank and is best managed by reducing vessel speed.

Correct: The Barge Supervisor must ensure that the weight of the pressure vessels is spread across enough deck area to stay within the structural limits (psf) and that the overall weight distribution keeps the center of gravity low enough for stable operations. This dual focus prevents deck plating failure and ensures the vessel remains upright and resistant to capsizing.

Incorrect: The strategy of placing heavy loads at the extreme ends of the vessel can lead to significant longitudinal stress, potentially causing structural failure through hogging or sagging. Opting to offset weight to one side to counter propeller torque is dangerous as it creates a permanent list that compromises stability and reduces freeboard. Focusing only on the discharge sequence at the destination ignores the immediate safety requirements of maintaining proper trim and structural integrity during the voyage.

Takeaway: Proper stowage requires balancing structural deck load limits with vertical and longitudinal weight distribution to ensure vessel stability and integrity.

Correct: Under 33 CFR 104.225, all crew members, regardless of whether they have specific security assignments, must possess security awareness. This includes the ability to recognize suspicious behavior, packages, or devices and a clear understanding of the communication chain for reporting these concerns to the Vessel Security Officer (VSO) to maintain the integrity of the Vessel Security Plan.

Incorrect: Focusing on the technical maintenance of navigation systems like AIS or radar describes an engineering or operational function rather than a security awareness requirement. The strategy of allowing all crew members to sign a Declaration of Security is incorrect because this specific legal responsibility is reserved for the Vessel Security Officer or a designated person with specific security duties. Opting for training in physical combat or the use of defensive weaponry exceeds the regulatory standards for general security awareness, which prioritize detection, avoidance, and reporting over physical engagement.

Takeaway: United States maritime regulations require all crew members to recognize security threats and understand reporting procedures under the Vessel Security Plan.

Correct: The free surface effect occurs when liquid in a partially filled tank shifts toward the low side as the vessel heels. This movement causes a virtual rise in the center of gravity, which reduces the metacentric height (GM) and the vessel’s overall stability.

Incorrect: The strategy of assuming displacement increases is incorrect because the total weight of the vessel and its cargo remains constant regardless of how the liquid shifts. Focusing only on reserve buoyancy misses the critical stability issue, as free surface effect impacts the vessel’s ability to right itself. Opting for longitudinal stress analysis addresses structural strength rather than the transverse stability concerns inherent in the free surface effect.

Takeaway: Free surface effect reduces stability by causing a virtual rise in the center of gravity through liquid movement in slack tanks.

Correct: Maintaining watertight integrity is the fundamental principle of damage stability under US maritime safety standards. By ensuring that adjacent compartments remain sealed, the supervisor limits the loss of buoyancy to the damaged area and prevents progressive flooding, which is the most common cause of vessel loss after a breach.

Incorrect: The strategy of immediate counter-flooding is often dangerous because it increases the total weight and reduces the overall reserve buoyancy and freeboard of the barge. Focusing only on shifting cargo to the high side can be hazardous if the free surface effect in partially filled tanks is not calculated, potentially leading to a sudden loss of stability. Relying solely on intact stability curves is incorrect because those calculations assume an unbreached hull and do not account for the lost buoyancy or the change in the waterplane area caused by the damage.

Takeaway: The primary defense against sinking after a hull breach is the preservation of watertight integrity to prevent progressive flooding of intact spaces.

Correct: In accordance with US Coast Guard stability standards outlined in 46 CFR, the area under the Righting Arm (GZ) curve represents the energy or work required to heel the vessel. This is known as dynamic stability. A reduction in this area indicates that the vessel has less capacity to absorb energy from external environmental forces, such as wind and waves, before reaching a point of capsize.

Incorrect: Relying solely on the initial metacentric height (GM) is insufficient because GM only describes stability at very small angles of heel and does not account for the total energy absorption capacity shown by the full curve. The strategy of assuming the point of vanishing stability has increased is logically flawed because a reduction in the area under the curve typically corresponds to a decrease in the overall range of stability. Opting to believe a downward shift in the center of gravity would cause this reduction is incorrect, as lowering the center of gravity would actually increase the righting arm and the area under the curve.

Takeaway: The area under the GZ curve is a critical measure of a vessel’s dynamic stability and its resistance to capsizing.

Correct: In accordance with United States Coast Guard emergency response guidelines, the Barge Supervisor must first determine the extent of the damage. Sounding all compartments allows the crew to identify which spaces are taking on water. This information is essential for stability calculations and effective pollution prevention.

Incorrect: The strategy of increasing speed after a suspected breach can force more water into the hull through the damaged area. Choosing to anchor before assessing the damage might result in the vessel sinking in a deep-water channel. Focusing only on shifting cargo to correct trim without identifying the source of the leak can lead to a catastrophic loss of stability.

Takeaway: Immediate damage assessment through sounding is the critical first step in managing a suspected hull breach or grounding incident.

Correct: Performing a Job Safety Analysis (JSA) is the standard professional approach to risk assessment in the United States maritime industry. It ensures that the Barge Supervisor and crew systematically identify how equipment failures could lead to an incident, implement controls to prevent such incidents, and maintain a record of the safety decision-making process as required by safety management systems and United States Coast Guard oversight.

Incorrect: The strategy of proceeding at a reduced flow rate with extra monitoring is inadequate because it ignores the regulatory requirement for functioning vapor control equipment and fails to formalize the risk mitigation. Requesting an emergency waiver from the Captain of the Port is inappropriate for routine equipment maintenance issues that should be handled through the vessel’s own safety and maintenance protocols. Choosing to bypass a required safety sensor based on the presence of shore-side equipment violates federal regulations regarding vessel-specific safety instrumentation and creates a single point of failure.

Takeaway: Formal risk assessment through a Job Safety Analysis ensures all hazards are mitigated and documented before beginning hazardous cargo operations.

Correct: In the event of a cargo shift, the Barge Supervisor must prioritize communication with the tug to coordinate maneuvers and evaluate the vessel’s stability against the USCG-issued Stability Letter. Adjusting the vessel’s heading or speed can reduce the dynamic forces and rolling motions that cause further shifting, while the Stability Letter provides the necessary parameters to understand the current risk of capsizing.

Incorrect: The strategy of sending crew members onto the deck to re-secure heavy cargo during active shifting in heavy seas poses an extreme risk of injury or death. Relying on counter-ballasting without referring to stability data or calculating the impact on the center of gravity can inadvertently decrease the metacentric height or create dangerous free surface effects. Choosing to delay action until a scheduled shoreside report occurs ignores the immediate threat to the vessel’s integrity and the safety of the tow in deteriorating weather.

Takeaway: Immediate communication and stability assessment using official vessel documentation are critical when cargo shifts occur at sea to prevent capsizing.

Correct: Under USCG regulations (46 CFR Part 57), all welding on vital pressure-containing components must be performed using procedures and personnel qualified in accordance with Section IX of the ASME Boiler and Pressure Vessel Code. This ensures that the metallurgical properties and structural integrity of the joint can withstand the high-stress environment of marine steam systems.

Incorrect: The strategy of relying on matching filler metal tensile strength without formal procedure qualification ignores the complex thermal stresses and regulatory oversight required for pressure boundaries. Choosing to use temporary mechanical patches on high-pressure turbine casings is an unsafe practice that violates USCG safety standards for vital machinery. Opting for automated submerged arc welding as a mandatory requirement is incorrect, as various manual and semi-automatic processes are permitted provided they are properly qualified and documented.

Takeaway: All welding on marine pressure boundaries must be performed by qualified welders using procedures that comply with ASME Section IX standards.

Correct: Integral action, also known as reset, is the component of a PID loop specifically designed to eliminate the offset that occurs with proportional-only control. It functions by integrating the error over time; as long as any deviation from the setpoint exists, the integral term will continue to increase or decrease the output signal. This continuous adjustment ensures that the steady-state error is eventually driven to zero, allowing the process variable to match the setpoint exactly.

Incorrect: Relying solely on increasing proportional gain might reduce the magnitude of the offset, but it cannot eliminate it entirely because a proportional controller requires a residual error to maintain a corrective output. Focusing on derivative action is useful for responding to the speed of change and improving system stability during transitions, but it does not correct long-term deviations from the setpoint. Opting to widen the throttling range or adjust the deadband typically decreases the precision of the control loop and may actually increase the deviation from the desired setpoint by allowing more room for error before the controller reacts.

Takeaway: Integral action is the specific PID component used to eliminate steady-state offset by accumulating error over time.

Correct: A Preventive Maintenance Program is designed to proactively manage equipment health. By performing scheduled inspections, lubrications, and part replacements based on time or condition, engineers can detect early signs of wear. This approach minimizes the risk of catastrophic failure during critical operations, such as cargo transfer or navigation in restricted waters, which is a core requirement for maintaining vessel safety and regulatory compliance under USCG standards.

Incorrect: The strategy of running machinery until it fails ignores the significant risks to crew safety and environmental protection required by maritime regulations. Simply conducting replacements at arbitrary intervals without considering manufacturer specifications or actual wear leads to unnecessary costs and potential failures of new parts. Relying solely on redundant systems fails to address the underlying maintenance needs of the primary equipment and does not constitute a comprehensive maintenance strategy as required by professional engineering standards.

Takeaway: Effective preventive maintenance prioritizes proactive inspections and servicing to prevent equipment failure and ensure continuous vessel safety and reliability.

Correct: Positive displacement pumps move a fixed volume of fluid per cycle regardless of the discharge pressure. If the discharge is blocked or restricted, pressure will rise almost instantaneously until a component fails or the motor stalls. Ensuring a clear discharge path and a functional relief valve is the standard safety requirement under USCG engineering standards to prevent equipment rupture.

Incorrect: Throttling the discharge valve is a dangerous practice for positive displacement pumps because it causes immediate and extreme pressure spikes unlike centrifugal pumps. Relying on motor thermal overloads is an insufficient safety measure because the pump casing, seals, or piping will likely fail mechanically before the motor generates enough heat to trip the breaker. The strategy of using a variable speed drive while keeping a valve partially closed is incorrect because it still introduces unnecessary resistance and potential for overpressurization in a system that requires an unobstructed flow path.

Takeaway: Positive displacement pumps must never be throttled on the discharge side and require functional relief valves to prevent overpressurization.

Correct: A cylinder cut-out test is a standard diagnostic procedure used to identify a malfunctioning cylinder. By cutting the fuel to a healthy cylinder, the engine RPM or load will drop significantly; however, cutting fuel to a cylinder with a faulty injector will result in little to no change, confirming it as the source of the issue.

Incorrect: The strategy of advancing the injection timing without verifying the injector’s condition could lead to pre-ignition and severe mechanical damage. Focusing only on increasing cooling water flow merely addresses a thermal symptom rather than the combustion fault. Choosing to adjust the fuel rack linkage to force more fuel into a potentially fouled or leaking injector can lead to incomplete combustion, excessive carbon buildup, and increased risk of a crankcase explosion.

Takeaway: Isolating individual cylinders through a cut-out test is the most effective way to diagnose a faulty fuel injector during engine operation.

Correct: The first-out alarm sequence is a logic feature in marine annunciator systems designed to identify the primary fault in a series of cascading events. When multiple alarms are triggered nearly simultaneously, the system distinguishes the very first alarm by giving it a unique visual characteristic, such as a faster flash rate or a different color, allowing the engineer to identify the root cause rather than the symptoms.

Incorrect: Utilizing sequential event recording involves reviewing a digital or printed log of events with precise timestamps, which is a retrospective diagnostic tool rather than a real-time visual feature of the annunciator panel. Choosing group alarm silencing only mutes the audible alert for a category of faults but does not provide any visual distinction to help identify the initiating event. Relying on time-delay relay integration is a technique used to filter out momentary sensor fluctuations to prevent nuisance alarms, but it does not help organize or prioritize multiple active alarms during a system failure.

Takeaway: First-out alarm logic distinguishes the initiating fault from subsequent alarms by using a unique visual signal on the annunciator panel.

Correct: The Safety Data Sheet (SDS) is the primary regulatory resource for identifying chemical hazards. Determining the vapor density is critical for engineers to understand if the chemical will sink into the lower levels of the engine room or rise, while the flash point identifies the immediate ignition risk to operating machinery.

Incorrect: The strategy of activating emergency bilge suction is incorrect because bilge systems are typically not designed for hazardous chemical compatibility and could lead to internal corrosion or hazardous reactions. Focusing only on adjusting engine combustion settings is a dangerous approach that fails to address the source of the leak and could lead to engine overspeed or mechanical failure. Opting for a gas detector calibrated for methane is a common error, as sensors must be specific to the chemical in question or use appropriate correction factors to provide accurate safety data.

Takeaway: Initial chemical risk assessment must prioritize identifying physical properties like vapor density and flash point using the Safety Data Sheet (SDS).

Correct: Cloverleafing is a specific form of corrosive wear. It occurs when the cylinder oil alkalinity is insufficient to neutralize sulfuric acid from high-sulfur fuel combustion. This acid condenses on the liner surface between the lubricant injection points.

Incorrect: Relying on the theory of abrasive wear from catalytic fines describes a condition that typically results in uniform vertical scoring. The strategy of attributing the damage to adhesive wear or oil film breakdown describes scuffing. Focusing only on mechanical wear from ring tension addresses general liner thinning rather than the localized chemical corrosion pattern.

Correct: The phenomenon described is turbocharger surging, which occurs when the compressor can no longer overcome the backpressure in the scavenge manifold, typically during rapid load changes. This causes a momentary reversal of air flow, leading to the characteristic barking sound and pressure fluctuations. Reducing the load or opening a blow-off/bypass valve helps restore the proper flow-to-pressure ratio, preventing damage to the compressor blades and thrust bearings.

Incorrect: The strategy of increasing the fuel rack setting when a wastegate is suspected of failing open is incorrect as it would likely lead to excessive exhaust temperatures without resolving the underlying pressure imbalance. Focusing only on cooling water flow to address intercooler fouling ignores the specific acoustic and pressure symptoms associated with compressor stall. Choosing to perform a turbine water wash at full load is a dangerous maintenance error, as standard marine engineering procedures require significantly reduced engine parameters to prevent thermal shock and mechanical failure of the turbine components.

Takeaway: Turbocharger surging during load fluctuations requires immediate stabilization of air flow to prevent mechanical damage to the compressor and bearings.

Correct: Non-condensable gases, such as air or nitrogen, tend to collect in the condenser because they cannot be liquefied at the operating temperatures and pressures of the system. These gases occupy valuable space and form a stagnant film on the heat transfer surfaces, which significantly reduces the condenser’s efficiency and forces the compressor to operate at a higher discharge pressure to reject heat. Purging these gases is the standard procedure to restore proper thermal exchange and system pressure.

Incorrect: The strategy of cleaning a restricted filter-drier addresses a pressure drop across the liquid line but would not typically cause a gradual rise in condenser discharge pressure. Focusing on the refrigerant charge level in the receiver is generally incorrect because a high liquid level in the receiver does not impede the condensing process unless the condenser itself is flooded. Opting to manually adjust compressor unloaders might reduce the mass flow of the gas, but it fails to address the underlying cause of poor heat transfer within the condenser unit.

Takeaway: Non-condensable gases in a reliquefaction system insulate heat transfer surfaces, leading to increased discharge pressures that require periodic purging to maintain efficiency.

Correct: The use of a poker gauge is the industry-standard method for measuring the ‘wear-down’ of a stern tube bearing. This tool measures the vertical drop of the tailshaft as the bearing material wears away. These readings are compared against previous records and manufacturer limits to ensure the bearing remains within safe operating tolerances as required by USCG and classification society standards.

Incorrect: Monitoring cooling water discharge temperatures is an operational check that identifies overheating but does not provide a physical measurement of material loss. Performing ultrasonic thickness measurements on the propeller hub is a technique used to detect internal flaws or erosion in the casting rather than bearing clearance. Relying on hydraulic starting pressure is a procedure used to verify the fit and security of the propeller on the shaft taper but offers no data regarding the condition of the supporting bearings.

Takeaway: Stern tube bearing wear-down is physically quantified using a poker gauge to measure shaft displacement relative to the bearing housing during dry-docking inspections.

Correct: In USCG-regulated marine automation, the first step in troubleshooting a PLC fault is to identify the nature of the error. A blinking fault light indicates the processor has detected a specific problem, such as an I/O rack failure or a watchdog timer timeout. Accessing the diagnostic buffer through manufacturer-specific software provides the exact error code, allowing for a targeted and safe repair that maintains the integrity of the vessel’s automated systems.

Incorrect: The strategy of replacing the CPU module immediately is often wasteful and may not resolve the issue if the fault originates in the backplane or an external I/O module. Choosing to manually bridge output terminals is a hazardous practice that bypasses critical safety interlocks and could lead to mechanical failure or fire. Focusing only on increasing supply voltage is incorrect and dangerous, as it can lead to permanent hardware damage and does not address the logical or hardware fault indicated by the status LEDs.

Takeaway: Always utilize diagnostic software to identify specific PLC fault codes before attempting hardware replacements or bypassing safety logic on automated systems.

Correct: Under 33 CFR 151.10, the USCG mandates that oily mixtures discharged from machinery space bilges must not exceed 15 parts per million when the vessel is en route using approved equipment.

Incorrect: Opting for a 10 parts per million limit confuses the standard requirement with more stringent local or voluntary environmental notations. The strategy of using a 50 parts per million threshold fails to meet the primary federal discharge standards for machinery spaces. Focusing only on a 100 parts per million limit is incorrect as this level is significantly above the legal threshold for processed bilge water.

Correct: For service temperatures above 775 degrees Fahrenheit, USCG regulations in 46 CFR Subchapter F require seamless alloy steel, typically containing molybdenum, to provide necessary creep resistance and prevent graphitization of the carbon steel.

Incorrect: Relying on electric-resistance-welded pipe is unsafe for high-pressure steam because the welded seam represents a potential point of failure under extreme thermal cycling. Choosing galvanized wrought iron is incorrect because the material is not rated for high-temperature steam and the galvanizing would fail. Selecting annealed copper tubing is inappropriate as copper loses significant structural strength at high temperatures and is restricted to much lower temperature limits in marine engineering.

Takeaway: Superheated steam systems require seamless alloy steel to withstand high temperatures and prevent long-term structural failure from graphitization.

Correct: In a 3-phase ungrounded system, ground detection lamps are connected between each phase and ground. Under normal conditions, all lamps glow with equal intensity. If one lamp dims, it indicates that the potential between that phase and ground has decreased due to a ground fault or high-resistance leakage on that specific phase. The correct engineering practice is to identify the faulty circuit by momentarily opening branch circuit breakers one at a time until the lamps return to equal brilliance.

Incorrect: Attributing the dimming to a blown transformer fuse is incorrect because a cleared fuse would typically cause the lamp to extinguish entirely rather than dimming. The strategy of tripping non-essential loads to address a phase-to-phase short is misplaced, as a true phase-to-phase short would trigger an instantaneous overcurrent trip of the main breakers rather than a gradual change in ground lamp brilliance. Focusing on the automatic voltage regulator is also incorrect, as a regulator failure would affect the line-to-line voltage across the entire bus rather than the specific phase-to-ground relationship indicated by a single dimming lamp.

Takeaway: A dim ground detection lamp on an ungrounded switchboard indicates a ground fault on that specific phase requiring systematic isolation of circuits to locate the fault.

Correct: Bimetallic transition joints, typically created through explosion bonding, are essential for joining aluminum to steel in a marine environment. These joints provide a metallurgical bond that prevents seawater from acting as an electrolyte between the two metals. If the joint’s integrity is compromised, the aluminum will act as an anode and corrode rapidly in the presence of the steel cathode and salt water.

Incorrect: Focusing only on plate thickness fails to address the electrochemical reaction that causes material loss at the interface. The strategy of using lead-based primers is technically unsound as lead can actually accelerate corrosion in certain aluminum alloys and does not address the underlying bonding requirement. Opting for mechanical fasteners like stainless steel is inappropriate for primary structural bonds because it introduces new galvanic couples and fails to provide the watertight, high-strength connection required for hull-to-superstructure integrity.

Takeaway: Maintaining the integrity of bimetallic transition joints is critical to preventing galvanic corrosion at the interface of aluminum and steel hull components.

Correct: Blowing down the gauge glass is the standard procedure to clear any sediment or obstructions in the water and steam columns. This action confirms that the local gauge glass, which is the primary reference for boiler water level, is providing an accurate and unobstructed reading. In the event of conflicting data between remote and local indicators, the physical verification of the local glass is the most critical step for operational safety.

Incorrect: The strategy of adjusting remote indicator settings while the boiler is operational is hazardous because it assumes the remote sensor is the only faulty component without verifying the local glass first. Relying solely on the low-water cut-off alarm is a reactive measure that fails to proactively manage the water level and could lead to emergency shutdowns. Choosing to manually increase feed water without a confirmed level reading risks overfilling the boiler, which can cause water carryover into the steam lines and damage the propulsion turbines.

Takeaway: Always verify the accuracy of the local gauge glass through a blow-down procedure when water level indicators provide conflicting readings.

Correct: In a fuel oil service system, temperature instability is often caused by poor heat transfer or improper condensate removal. Internal fouling of the heater tubes reduces efficiency, while a malfunctioning steam trap can cause condensate to back up into the heater, significantly reducing the effective heating surface area and causing the regulating valve to hunt or cycle.

Incorrect: Increasing the pump discharge pressure is an incorrect approach because it addresses a symptom of flow resistance rather than the root cause of temperature and viscosity instability. The strategy of bypassing secondary filters is highly dangerous as it allows particulate matter to reach the fuel injectors or burners, leading to potential equipment damage or flame failure. Choosing to rely solely on settling tank temperatures is impractical and unsafe, as settling tanks are not designed to maintain the precise high temperatures required for final atomization of heavy residual fuels.

Takeaway: Consistent fuel oil temperature and viscosity depend on clean heat transfer surfaces and functional condensate drainage within the fuel heating system.

Correct: In naval architecture and USCG stability standards, a slack tank allows liquid to shift toward the low side as the vessel heels. This movement of weight shifts the vessel’s center of gravity (G) off the centerline in the direction of the heel, which is mathematically treated as a virtual rise in the center of gravity (KG). Since GM is calculated as the distance between the metacenter (M) and the center of gravity (G), any rise in G results in a direct reduction of the effective GM, making the vessel less stable.

Incorrect: The strategy of suggesting that liquid movement lowers the center of buoyancy is incorrect because buoyancy is determined by the underwater volume of the hull rather than internal cargo distribution. Focusing only on longitudinal trim ignores the critical danger that transverse free surface effects pose to a vessel’s resistance to capsizing during rolling. The approach of assuming the effect is neutralized at a steady list is a dangerous misconception, as the virtual rise in the center of gravity persists and continues to reduce the righting moment throughout the range of stability.

Takeaway: Slack tanks reduce a vessel’s effective Metacentric Height (GM) due to the virtual rise in the center of gravity caused by free surface effect.

Correct: A high suction vacuum reading is a definitive indicator of a restriction on the inlet side of a positive displacement pump. When the suction is blocked by a fouled strainer or a restricted valve, the pump cannot fill its chambers, leading to cavitation, vibration, and a loss of discharge flow and pressure.