Essential Steps When Switching to the Standby High-Pressure Pump| Insights by AQUALITEK

Introduction

In industrial RO systems, dual high-pressure pump configurations (duty + standby) are widely used to ensure:

•Continuous operation

•Reduced downtime

•Improved system reliability

However, improper switching to the standby high-pressure pump can cause serious consequences, including membrane shock, pressure surges, seal damage, and sudden water quality deterioration.

This article outlines the essential steps and best practices operators must follow when switching to a standby high-pressure pump safely and effectively.

Why Proper Pump Switching Is Critical

High-pressure pumps directly affect:

•Operating pressure

•Flow distribution

•Recovery rate

•Membrane mechanical stress

A rushed or incorrect switch can result in:
❌ Instant membrane damage
❌ Pressure gauge shock and vibration
❌ Abnormal permeate conductivity
❌ Pump cavitation or seal failure

Step 1: Confirm the Reason for Switching

Before switching, clearly identify why the standby pump is needed:

•Scheduled maintenance

•Abnormal noise or vibration

•Bearing temperature rise

•Seal leakage

•Electrical or motor alarm

Never switch blindly without diagnosing the original pump condition.

Step 2: Gradually Reduce Load on the Running Pump

Before stopping the active pump:

•Slowly close the concentrate control valve

•Reduce system pressure smoothly

•Lower flow to minimum stable operation

⚠ Never stop a high-pressure pump under full load.

Step 3: Stop the Running Pump Properly

•Follow the standard shutdown sequence

•Confirm pressure drops to near zero

•Ensure no backflow or reverse rotation

Sudden stops under pressure may damage:

•Mechanical seals

•Check valves

•Membrane elements

Step 4: Inspect the Standby Pump Before Starting

Before starting the standby pump, confirm:

Mechanical Checks

✔ Pump casing filled with water (no air)
✔ No visible leakage
✔ Shaft rotates freely

Valve Status

✔ Inlet valve fully open
✔ Outlet valve slightly open (not fully closed)
✔ Check valves functioning properly

Electrical Checks

✔ Correct rotation direction
✔ No active alarms
✔ Normal motor insulation and grounding

Step 5: Fully Vent Air from the Pump and Pipeline

Air trapped in:

•Pump casing

•High-pressure pipeline

can cause:
❌ Cavitation
❌ Pressure fluctuations
❌ Flow instability

✔ Open vent valves
✔ Allow continuous water discharge until air is fully removed

Never start a high-pressure pump with trapped air.

Step 6: Start the Standby Pump at Low Load

•Start with outlet valve partially open

•Gradually increase pressure

•Monitor pressure rise rate

Avoid:
❌ Sudden pressure spikes
❌ Rapid flow acceleration

Step 7: Slowly Restore Normal Operating Conditions

Gradually adjust:

•System pressure

•Concentrate flow

•Recovery rate

Observe:

•Inlet pressure

•Outlet pressure

•Permeate flow

•Permeate conductivity

Allow the system to stabilize for 10–30 minutes.

Step 8: Closely Monitor Key Parameters After Switching

During the first hour, closely monitor:

•Pressure stability

•Pump vibration and noise

•Seal leakage

•Flow balance

•Product water quality

Any abnormal trend indicates:

•Incorrect valve position

•Hidden air pockets

•Mechanical issues

Common Mistakes to Avoid During Pump Switching

❌ Starting the standby pump at full load
❌ Forgetting to vent air
❌ Ignoring rotation direction
❌ Closing outlet valves completely
❌ Skipping post-switch monitoring

Best Practice Recommendation

✔ Perform periodic test runs of the standby pump
✔ Keep pump switching procedures documented
✔ Train operators with real switching drills
✔ Log all pump switching events and operating data

Conclusion

Switching to a standby high-pressure pump is not a simple on/off action—it is a critical operational procedure that directly affects system safety and membrane life.

By following structured steps—pressure unloading, inspection, air venting, gradual startup, and close monitoring—operators can ensure a smooth transition, protect RO membranes, and maintain stable system performance.