How to Troubleshoot a Vacuum Oil Purifier With No Oil Output?

Why a Vacuum Oil Purifier Fails to Filter Oil: Key Causes and Troubleshooting Guide

A vacuum oil purifier failing to filter oil—or delivering very low flow—is rarely due to a single fault. Most failures originate from multiple system points, including the inlet pipeline, vacuum chamber, pumps, and control system.

Before troubleshooting, here is a quick refresher:

How a Vacuum Oil Purifier Works (Quick Overview)?

Primary Filtration:

The oil passes through coarse and fine filters to remove particles.

Vacuum Dehydration + Degassing:

Heated oil is sprayed into a vacuum chamber. Under low pressure, water rapidly evaporates and gases are released, then removed by the vacuum pump.

When any step fails, you may see no oil flow, unstable flow, or very low output.

Main Causes of “No Oil Flow” in a Vacuum Oil Purifier

I. Inlet Pipeline & Primary Filtration Issues (Start Troubleshooting Here)

Inlet valve not open or blocked

Ensure the valve is fully open and the pipeline is not obstructed.

Coarse / pre-filter clogged

One of the most common causes. Dirty filters restrict suction.

→ Clean or ｒｅｐｌａｃｅ the filter.

Air leakage in inlet line

Loose joints, damaged seals, or flange leaks allow air to enter, causing pump cavitation and preventing suction.

Oil inlet pump problems

Gear pump wear (internal clearance too large)

Damaged shaft seal letting air in

Motor faults causing low speed or no rotation

Vacuum System Problems (Core Factors)

Insufficient vacuum level

Without a proper vacuum, the purifier cannot pull oil through.

Common causes:

Emulsified/contaminated vacuum pump oil

Worn vacuum pump

Loose vacuum pump belt

Leaks at the vacuum tank, valves, sight glass, and joints

Exhaust valve not closed (specific models)

If the exhaust valve stays open, the machine cannot build vacuum.

Sprayer or atomizer blockage

Blocked spray nozzles prevent proper atomization, causing:

Excessive oil level in the vacuum tank

Oil is being sucked into the vacuum pump

Inability to feed the discharge pump

Oil Discharge System Problems

Oil discharge pump failure

Wear, seal failure, or low rotation speed prevent oil from exiting the vacuum tank.

Blocked outlet line or closed valve

Check outlet filters, coolers, and valves to ensure smooth flow.

Electrical & Control System Faults

Heating system malfunction

Low oil temperature (<40–60°C): increases viscosity and reduces flow.

Heater failure: Check heating elements, thermostats, contactors, circuit breakers.

Protection system triggered

Level controller malfunction: prevents inlet/outlet pumps from starting.

High differential pressure alarm: indicates clogged filter elements.

Automatic shutdowns triggered by abnormal readings.

Oil Quality Problems

Severely contaminated or degraded oil

Highly viscous, sludge-like, or colloid-rich oil can clog filters, spray nozzles, and pipelines, sharply reducing flow.

Recommended Troubleshooting Process (Simple → Advanced)

1. Observe and listen

Abnormal pump noise? (Possible cavitation)

Is the vacuum gauge within normal range (–0.08 to –0.099 MPa)?

Is the pressure gauge too high? (Filter blockage)

Is the vacuum tank oil level normal?

2. Follow this order

Confirm all valves are open and pipelines connected properly.

Clean or ｒｅｐｌａｃｅ coarse and fine filters.

Check vacuum level and inspect for leaks.

Confirm oil temperature is within the working range.

If still unresolved → inspect inlet pump, discharge pump, or consult the manufacturer.

Summary: Most Common Causes

For most equipment, the issue comes down to:

Clogged pre-filters

Insufficient vacuum level

Low oil temperature/heating failure

Start with these three checkpoints for the fastest diagnosis.