⚠️ Disclaimer: These tasks are guidelines only. They do not include lockout/tagout (LOTO), energy isolation, or other safety requirements. Review and verify suitability for your specific equipment and application. Add all required safety procedures per your company's policies and regulatory requirements before use. You are responsible for the safe and appropriate execution of all maintenance activities.
Positive displacement pumps move fluid by trapping a fixed volume and forcing it through the discharge side. Gear pumps, lobe pumps, piston pumps, diaphragms — they all operate on the same principle, and they all fail the same way: slowly, then all at once. The early signs are there. Pressure drift, noise change, a slight drop in flow. Most PM programs walk right past them.
This checklist covers the inspection and monitoring tasks that keep PD pumps running. Built for maintenance technicians executing the PM and maintenance managers building or auditing the program.
For a broader look at pump PM strategy, see pump preventive maintenance fundamentals.
How to Use This Checklist
Write down what you actually find — not what you expected to find. A pressure reading is only useful if you record the number. A finding that says "OK" tells you nothing in six months.
Good finding: Suction pressure reading 8 PSI, baseline is 10 PSI — slight drop, will trend.
Bad finding: Checked.
Trend your readings over time. A single data point is an observation. Three data points in sequence is a pattern. Patterns are what catch failures before they finish the job.
Field Checklist — Critical Tasks
Visual Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect pump exterior for leaks, cracks, or physical damage. Check all flanges, port fittings, and the casing for signs of fluid weeping. | Every PM | MEC |
Operational Checks
| Task | Freq | Type |
|---|---|---|
| Check suction and discharge pressure gauges (if installed). Record readings and compare to baseline. Abnormal pressure differential may indicate wear or blockage. | Every PM | MEC |
| Listen and feel for unusual noise, vibration, or roughness during operation. Knocking or rumbling can indicate cavitation, worn internals, or bearing failure. | Every PM | MEC |
Mechanical Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect shaft seal or packing for leakage. Minor weeping on packed pumps is acceptable; active dripping or spray is not. Adjust packing gland or flag mechanical seal for replacement. | Monthly | MEC |
| Check pump drive coupling or belt drive for wear, misalignment, and secure fastening. Inspect flexible elements for cracking or degradation. | Monthly | MEC |
| Inspect inlet strainer or suction screen for blockage or debris. Clean as needed to maintain unrestricted flow. | Quarterly | MEC |
| Check all mounting bolts and baseplate fasteners for tightness. Retorque any loose hardware. | Semi-Annually | MEC |
| Verify relief valve (if installed) is set to correct pressure and has not been blocked or bypassed. Do not adjust without engineering authorization. | Annually | MEC |
Lubrication
| Task | Freq | Type |
|---|---|---|
| Lubricate pump bearings per manufacturer type and interval. Do not over-grease. Record lubricant applied. | Quarterly | MEC |
Reference Checklist — Full Task Library
Visual Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect pump exterior for leaks, cracks, corrosion, or physical damage. Check all flanges, port fittings, and casing seams. Record any abnormalities and compare to prior PM notes. | Every PM | MEC |
Operational Checks
| Task | Freq | Type |
|---|---|---|
| Record suction and discharge pressures from gauges or instrumentation. Calculate differential pressure and compare to baseline and design spec. Declining differential pressure may indicate internal wear; rising suction vacuum may indicate blockage or cavitation. | Every PM | MEC |
| Monitor pump operation for abnormal noise, vibration, or temperature. Knocking suggests cavitation or debris ingestion; roughness or grinding may indicate worn internals or bearing failure. Flag any change from normal for investigation. | Every PM | MEC |
| Inspect pump fluid temperature at the outlet using an IR thermometer or contact probe. Elevated outlet temperature relative to inlet may indicate high slip, cavitation, or bypass across worn internals. | Monthly | MEC |
| Perform a flow rate check by comparing actual delivery against rated capacity (using flow meter, tank fill time, or system instrumentation). A significant drop in flow at rated pressure indicates internal wear or bypass. | Quarterly | MEC |
| Inspect pump motor current draw using a clamp meter. Compare to baseline. Rising current at the same load may indicate increased internal friction, cavitation, or drive issues. | Quarterly | ELE |
| Review and trend all recorded data from this PM period — pressures, flow rate, current draw, bearing temps, and defect history. Identify deteriorating trends and adjust PM frequency or scope as warranted. Flag for engineering review if trending toward action limits. | Annually | MEC |
Mechanical Inspection
| Task | Freq | Type |
|---|---|---|
| Inspect shaft seal for leakage. On mechanical seals, any visible spray or dripping warrants replacement. On packed stuffing boxes, verify gland follower is tight and minor weeping is within acceptable limits; adjust packing gland if drip rate is excessive. | Monthly | MEC |
| Inspect pump drive coupling for wear, cracking, or looseness. Check flexible coupling elements, set screws, and keyways. Verify coupling alignment is within specification. For belt drives, check tension and wear. | Monthly | MEC |
| Clean inlet strainer or suction screen. Record debris type and volume — unusual accumulation can indicate upstream contamination or system degradation. | Monthly | MEC |
| Check all mounting bolts, baseplate fasteners, and pump-to-motor feet. Retorque to spec. Inspect anti-vibration mounts for compression set or cracking. | Semi-Annually | MEC |
| Inspect all external piping and connections at pump suction and discharge for vibration-induced fatigue, corrosion, or joint weeping. Ensure piping is properly supported and not applying stress to pump flanges. | Semi-Annually | MEC |
| Verify pressure relief valve (if installed) is set to the correct relief pressure, is operable, and has not been blocked, capped, or bypassed. Test relief valve function if safe to do so per site procedure. Document setting and results. | Annually | MEC |
| Inspect internal pump components during planned downtime — check rotors, gears, vanes, pistons, or diaphragm (as applicable to pump type) for wear, scoring, cracking, or dimensional loss. Compare measured clearances to manufacturer specifications and prior records. Replace worn components before clearances exceed service limits. | Annually | MEC |
| Replace shaft seals or packing on a scheduled interval or upon evidence of excessive leakage — whichever comes first. For mechanical seals, inspect seal faces, O-rings, and springs. Document seal type, lot number, and replacement date. | Annually | MEC |
Lubrication
| Task | Freq | Type |
|---|---|---|
| Lubricate pump bearings per manufacturer specification — lubricant type, quantity, and method. Do not over-grease; over-lubrication causes overheating. Record lubricant type and quantity applied. | Quarterly | MEC |
| Measure and record bearing housing temperature using a contact thermometer or IR gun. Compare to baseline. Bearing temps should not exceed ambient + 40°C or the manufacturer's limit. | Quarterly | MEC |
Failure Modes This Checklist Targets
Internal Wear and Bypass As clearances open between rotors, gears, or vanes and the pump casing, fluid slips back across the pressure gradient. Flow drops. Differential pressure drops. The pump runs — it just doesn't move what it used to. This is the most common long-term failure mode in PD pumps, and pressure and flow trending are the only reliable way to catch it before it becomes a replacement decision instead of a maintenance task.
Cavitation When suction pressure drops below the vapor pressure of the fluid, the liquid flashes to vapor at the pump inlet and collapses violently inside the pump. The sound is distinctive — like pumping gravel. The damage is real: pitting on internal surfaces, accelerated clearance loss, bearing overload. A blocked strainer or a partially closed suction valve is usually the cause. Suction pressure monitoring catches this before the internals pay the price.
Seal and Packing Failure Mechanical seals fail from heat, misalignment, contaminated fluid, and running dry. Packing fails from over-tightening, improper adjustment, and age. Either way, the result is external leakage — which is both a maintenance problem and, depending on the fluid, a safety and environmental problem. Regular inspection catches the transition from acceptable weep to active drip before it becomes a bigger conversation.
Coupling and Drive Failure Flexible coupling elements — elastomeric inserts, jaw couplings, disc packs — absorb misalignment and dampen vibration. When they degrade, that load transfers directly to the shaft and bearings. Misalignment accelerates everything. A coupling inspection that takes five minutes can save a bearing replacement that takes five hours.
Bearing Failure PD pump bearings carry radial and axial loads from fluid pressure, drive forces, and any residual misalignment in the system. They fail from overgreasing, undergreasing, contamination, and overload. Temperature trending at the bearing housing gives early warning before the noise starts.
Relief Valve Bypass or Blockage A relief valve that has been capped, blocked, or set too high is not a safety device — it's a hazard. Relief valves on PD pump systems are not optional equipment. They're the last line of defense against overpressure when a downstream valve closes with the pump still running. Verifying function and setting annually is not bureaucratic procedure. It is the job.
