Moyno® Pump Troubleshooting Guide
Symptoms, likely causes and corrective actions for Moyno® progressive cavity pump startup, suction, capacity, noise, seizure and uneven-flow problems.
This guide is the Moyno-specific troubleshooting resource in the ACCA Pump Engineering Library. Use it when diagnosing a Moyno® installation, including common rotor/stator, suction, packing, joint and operating-condition problems. For manufacturer-neutral diagnosis across conventional progressive cavity pumps, use ACCA’s master troubleshooting guide.
Looking for the General PC Pump Guide?
This page preserves troubleshooting guidance for Moyno® pump installations. For the broader symptom → cause → verification → corrective action → prevention workflow used across conventional progressive cavity pumps, see the Progressive Cavity Pump Troubleshooting Guide.
Before You Start
Confirm the complete pump model, rotation, operating speed, fluid condition, suction conditions and discharge pressure. Never run a progressive cavity pump dry: the pumped liquid provides critical lubrication at the rotor/stator interface.
Quick Diagnostic Index
Pump Will Not Start
Check sedimentation, rotor/stator adhesion, temperature, packing, solids and stator condition.
No Suction
Check rotation, inlet leakage or blockage, suction conditions, viscosity, speed and pumping-element wear.
Low Capacity
Check discharge pressure, entrained air, suction conditions, wear, speed and viscosity.
Excessive Noise
Check packing, suction conditions, coupling, speed, joints and bearings.
Pump Seized / No Flow
Check blockage, excessive head, dry running, foreign material, wear, temperature and stator swelling.
Uneven Flow
Check speed, dry running, suction leaks or blockage, excessive pressure and viscosity.
Moyno® Pump Diagnostic Guide
Pump Will Not Start
| Likely Cause | Corrective Action |
|---|---|
| Sedimentation in the suction housing or stator cavities | Flush and clean the pump. Replace affected components if deposits cannot be cleared. |
| Rotor-to-stator adhesion after shutdown | Remove the stator as required and lubricate the rotor/stator interface with a compatible mild soap solution before reassembly. |
| Fluid temperature too high | Verify actual fluid temperature and confirm that the installed rotor/stator fit and elastomer are suitable for the service. |
| Fluid temperature too low | Verify temperature and fluid properties; provide appropriate process heating where required. |
| Packing gland too tight | Loosen the gland to the correct adjustment and replace unusable packing rings. |
| Solids too large for the pump or inlet | Inspect the inlet, screen oversized material where appropriate, increase the liquid fraction or reduce operating speed as the application requires. |
| Stator swollen | Confirm elastomer compatibility with the pumped fluid and replace the stator with the correct material. |
Pump Does Not Develop Suction
| Likely Cause | Corrective Action |
|---|---|
| Incorrect direction of rotation | Verify required pump rotation and correct the motor/electrical connection as appropriate. |
| Shaft seal or inlet piping leaking or blocked | Locate and correct air leakage, seal leakage or inlet blockage. |
| Excessive suction lift or inlet restriction | Review suction conditions, increase inlet-pipe diameter where appropriate and reduce filter or strainer restriction. |
| Fluid viscosity too high | Verify viscosity at operating temperature and adjust pump speed or system conditions for the application. |
| Pump running dry | Restore product supply and use suitable dry-running protection. |
| Speed too low | Verify that operating speed is sufficient for the fluid and required duty. |
| Speed too high for viscous product | Reduce speed to improve filling of the pumping cavities. |
| Rotor or stator worn | Inspect the pumping elements and replace worn rotor/stator components as required. |
| Drive-joint components worn or damaged | Inspect the joint/connecting components and replace damaged parts. |
Pump Does Not Reach Required Capacity
| Likely Cause | Corrective Action |
|---|---|
| Excessive discharge pressure | Measure discharge pressure and inspect the downstream piping/system for restrictions or unexpected head. |
| Air entering the pumped stream | Inspect inlet piping, seals and packing for air leakage and verify adequate liquid supply. |
| Excessive suction lift or inlet restriction | Reduce inlet losses, review pipe diameter and inspect strainers or filters. |
| Rotor/stator wear | Inspect pumping elements for wear and replace as necessary. |
| Operating speed too low | Verify actual RPM against the required capacity and application limits. |
| Operating speed too high for viscosity | Reduce speed where high viscosity prevents complete cavity filling. |
| Viscosity higher than expected | Confirm actual process viscosity and temperature and review pump speed and suction conditions. |
Pump Is Excessively Loud or Noisy
| Likely Cause | Corrective Action |
|---|---|
| Packing gland too tight | Correct gland adjustment and replace damaged packing. |
| Excessive suction lift or inlet restriction | Review inlet piping, restrictions and available suction conditions. |
| Coupling problem | Inspect alignment and coupling condition; repair or replace as necessary. |
| Operating speed too high | Verify RPM against pump and application limits. |
| Joint loose or damaged | Inspect drive-joint components and replace worn or damaged parts. |
| Bearing noise | Inspect bearing condition and replace failed bearings. |
Pump Is Seized or Produces No Flow
| Likely Cause | Corrective Action |
|---|---|
| Inlet or seal area blocked | Correct blockage or leakage and confirm an unrestricted product supply. |
| Discharge pressure/head too high | Inspect the discharge system for restriction and verify actual operating pressure. |
| Dry running | Stop the pump, restore product supply and inspect the rotor/stator for heat damage before restarting. |
| Foreign object in pump | Isolate the equipment, open the appropriate inlet/pump section and remove foreign material safely. |
| Rotor/stator damaged or worn | Inspect and replace damaged pumping elements. |
| Drive joint loose or damaged | Inspect and replace damaged joint components. |
| Fluid temperature outside suitable range | Verify process temperature and confirm rotor/stator fit and elastomer suitability. |
| Oversized solids | Remove obstruction and review solids size, inlet arrangement and operating speed. |
| Stator swollen | Verify chemical compatibility and replace with the correct elastomer. |
Pump Is Delivering Uneven Flow
| Likely Cause | Corrective Action |
|---|---|
| Speed too high | Reduce RPM when necessary for viscous product to fill the pumping cavities properly. |
| Dry running or intermittent product supply | Verify continuous product level and inlet supply and provide dry-run protection where appropriate. |
| Suction piping or shaft-seal leakage/blockage | Correct leakage or blockage that allows air into or restricts the inlet stream. |
| Excessive discharge pressure | Measure pressure and inspect the downstream system for restrictions. |
| Viscosity too high | Confirm fluid properties and adjust operating speed/system conditions. |
What to Inspect Before Ordering Parts
1. Identify the Pump
Record the manufacturer, complete model designation, serial information and any construction or trim codes from the nameplate.
2. Record the Duty
Document flow, RPM, suction conditions, discharge pressure, fluid, viscosity, temperature and solids information.
3. Inspect the Components
Photograph and inspect the rotor, stator, connecting rod/joints, shaft, bearings, seals or packing and suction housing.
Rotor and Stator Wear Matters
Loss of capacity or suction can result from increased slip across worn pumping elements. A replacement stator alone may not restore performance when the rotor surface is also worn, damaged or undersized for the service condition.
Related Pumps, Parts & Engineering Resources
Need a Complete Replacement Pump?
For complete pump selection and supported replacement models, go to the Moyno® Pumps hub.
Need Replacement Components?
For rotors, stators, joints, shafts, seals, bearings and related components, go to the Moyno® Pump Parts hub.
General PC Pump Troubleshooting Guide
Use ACCA’s manufacturer-neutral diagnostic workflow for symptoms, verification, corrective action and prevention across conventional progressive cavity pumps.
Pump Engineering Resources
Return to the ACCA Pump Engineering Library for selection, maintenance and application guidance.
Still Troubleshooting the Pump?
Send ACCA the complete pump model, application conditions and photographs of the installed pump or worn components. We can help narrow the likely failure mode and identify compatible replacement options.
Moyno® is a registered trademark of its respective owner. ACCA Pumps is independent; model references identify compatible replacement applications.
