⚠️ 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.
Diaphragm pumps fail in ways that are slow, obvious, and completely avoidable — right up until they aren't. A cracked diaphragm doesn't announce itself. A worn check valve doesn't trip an alarm. They just quietly degrade until the pump is pushing air instead of fluid and nobody knows why production dropped.
This checklist covers both the every-PM checks that catch active deterioration and the periodic inspections that determine whether the pump is actually doing its job.
For the full context on pump PM programs, including what most checklists miss and why: pump PM fundamentals and program structure
How to Use This Checklist
Record findings with specificity. "Inlet pressure: 8 PSI, down from 12 PSI baseline" is a finding. "Inlet pressure: OK" is noise. Trending data is what turns a checklist into a diagnostic tool.
If you're filling in a checklist without writing a single number, you're not doing PM — you're doing paperwork.
A real finding looks like: "Discharge pressure dropped 15% from last PM. No change in system backpressure. Valve wear or early diaphragm fatigue probable." A checkbox answer looks like: "Pressures checked." One of these things will catch the failure. The other one will explain it at the RCA meeting.
Visual Inspection Tasks
Field Checklist — Critical Tasks
| Task | Freq | Type |
|---|---|---|
| Inspect pump exterior for fluid leaks at diaphragm housing, valve covers, manifolds, and fittings. Note any wet spots or staining. | Every PM | MEC |
| Inspect diaphragm(s) for cracks, pinholes, deformation, or signs of chemical attack. Replace immediately if any damage is found — do not run a compromised diaphragm. | Monthly | MEC |
| Inspect check valves (ball or flap type) and valve seats for wear, cracking, debris, or loss of sealing. Clean and replace as needed. | Monthly | MEC |
| Inspect all wetted-end hardware — manifolds, valve covers, and housings — for corrosion, cracking, or chemical degradation. Torque fasteners evenly per manufacturer spec. | Quarterly | MEC |
| Inspect all fluid hoses, piping connections, and suction strainer for blockage, wear, or leakage. Clean strainer if flow restriction is suspected. | Quarterly | MEC |
Reference Checklist — Full Task Library
| Task | Freq | Type |
|---|---|---|
| Inspect pump exterior for fluid leaks at diaphragm housing, valve covers, manifolds, flange connections, and all fittings. Document any wet spots or staining and compare to prior PM findings. | Every PM | MEC |
| Inspect both diaphragms for cracks, pinholes, blistering, deformation, or chemical attack. Replace as a matched pair regardless of which diaphragm shows wear. Do not run a compromised diaphragm. | Monthly | MEC |
| Inspect all check valves and valve seats. Ball valves: check for ovality, cracking, surface erosion, and seating. Flap valves: check for tears, stiffness, or loss of conformity to seat. Clean and replace components that show wear or leakage. | Monthly | MEC |
| Inspect and clean the suction strainer/filter. Measure or estimate restriction level — a plugged strainer causes cavitation-like symptoms and accelerates diaphragm fatigue. | Monthly | MEC |
| Inspect all wetted-end components — manifolds, valve covers, and pump housings — for corrosion, crazing, chemical attack, or mechanical damage. Torque all fasteners evenly in a cross pattern per manufacturer spec to avoid diaphragm distortion. | Quarterly | MEC |
| Inspect all fluid-side hoses, piping, and fittings for cracking, softening, wear at connections, or leakage. Replace any hose showing signs of degradation. Verify suction line is not collapsed or kinked. | Quarterly | MEC |
Operational Checks
Field Checklist — Critical Tasks
| Task | Freq | Type |
|---|---|---|
| Check and record inlet and discharge pressures at operating conditions. Compare to baseline. Investigate any significant deviation from normal. | Every PM | MEC |
| Listen for abnormal sounds during operation — excessive chattering, irregular pulsing, or sudden changes in exhaust rhythm may indicate diaphragm or valve issues. | Every PM | MEC |
| Inspect air exhaust (AODD pumps) or motor operation (EODD pumps) for smoothness. Erratic or labored cycling can signal a failing diaphragm or stuck valve. | Every PM | MEC |
| Verify pump mounting fasteners are secure and pump is free of excessive vibration during operation. | Quarterly | MEC |
Reference Checklist — Full Task Library
| Task | Freq | Type |
|---|---|---|
| Record inlet and discharge pressures at normal operating conditions. Compare to baseline and prior PM values. A drop in discharge pressure or increase in inlet vacuum may indicate valve wear, diaphragm fatigue, or suction-side blockage. | Every PM | MEC |
| Monitor pump cycle rate (AODD) or motor current draw (EODD) and compare to established baseline. Increasing cycle rate or current at the same flow output indicates efficiency loss. | Every PM | MEC |
| Listen for abnormal sounds during operation — excessive chattering, irregular pulsing, stalling, or changes in exhaust rhythm. Document and compare to prior PM notes. | Every PM | MEC |
| Perform a timed flow check against a known reference volume at defined operating conditions. Compare to baseline flow rate. A greater than 10% decline at the same pressure warrants investigation of valves and diaphragms. | Quarterly | MEC |
| Verify pump mounting hardware is secure — check base bolts, isolation mounts, and bracket connections. Excessive vibration or looseness indicates mounting degradation or internal imbalance. | Quarterly | MEC |
Mechanical Inspection
Field Checklist — Critical Tasks
| Task | Freq | Type |
|---|---|---|
| Check air supply line (AODD) for correct pressure setting and filter/regulator condition. Drain moisture from the air filter bowl. Verify air valve cycles cleanly. | Monthly | MEC |
Reference Checklist — Full Task Library
| Task | Freq | Type |
|---|---|---|
| Check air supply system (AODD pumps): verify regulator set pressure matches application requirements, drain moisture from filter bowl, and confirm air valve shifts cleanly with no hesitation or stalling. Replace filter element on schedule. | Monthly | MEC |
| Inspect the air valve assembly (AODD pumps) for internal wear, spool scoring, or contamination. Clean or rebuild per manufacturer instructions if erratic shifting or stalling is observed. | Semi-Annually | MEC |
| Perform a full wetted-end rebuild — replace diaphragms, check valves, seats, and all O-rings and gaskets. Use a manufacturer-approved kit matched to the fluid being pumped. Document parts used. | Annually | MEC |
| Review historical maintenance data for this pump: leak events, diaphragm life, valve replacement frequency, and any process upsets. Adjust PM frequency or diaphragm/valve material selection if wear patterns suggest an issue. | Annually | MEC |
Failure Modes This Checklist Targets
Diaphragm fatigue and chemical attack. The diaphragm flexes thousands of times per hour. At some point it cracks, blisters, or loses elasticity — faster if the material isn't matched to the fluid chemistry. Once it goes, the pump moves process fluid into the air side or vice versa. Neither outcome is good.
Check valve wear and loss of sealing. Ball and flap valves that don't seat cleanly allow backflow on every stroke. The pump cycles harder to maintain output, diaphragm stress increases, and flow drops while nothing obviously looks wrong until you open it up.
Suction strainer blockage. A restricted inlet creates the same symptom pattern as a worn diaphragm — low flow, erratic cycling, increased stress on wetted components. It's also the easiest thing to fix and the most commonly overlooked.
Air system degradation (AODD pumps). Moisture, contamination, or incorrect regulator pressure causes the air valve to shift erratically or stall mid-stroke. The pump stutters, output suffers, and the diaphragm takes abuse it shouldn't.
Fastener loosening and diaphragm distortion. Manifold fasteners that aren't evenly torqued distort the diaphragm clamping surface. That distortion concentrates stress at the clamping edge, which is exactly where fatigue cracks start.
Hose and fitting degradation. Suction lines that collapse or kink starve the pump. Discharge lines that soften under heat or chemical exposure fail with no warning. Neither shows up unless someone actually looks.
