Hydraulic faults causing PLC trips: temp, pressure, filter clog

Introduction — Why Hydraulic Faults Stop Roll Forming Machines

Hydraulic systems are widely used in roll forming machines to power high-force operations such as:

• shear cutting systems
• punch presses
• notch units
• coil handling equipment
• heavy stacker movements.

Because these systems generate large forces, the PLC continuously monitors hydraulic conditions to ensure safe operation.

If abnormal conditions occur, the PLC may stop the machine immediately to protect equipment.

Common hydraulic-related PLC trips include:

• low hydraulic pressure faults
• high hydraulic oil temperature alarms
• clogged hydraulic filter warnings.

These faults are typically generated by sensors connected to the PLC and appear on the HMI alarm system.

Understanding these faults allows technicians to quickly diagnose the root cause.

Overview of Hydraulic Systems in Roll Forming Machines

A typical hydraulic power unit contains several key components.

These include:

• hydraulic pump
• electric motor driving the pump
• oil reservoir
• pressure relief valve
• hydraulic filters
• pressure sensors or switches
• temperature sensors
• hydraulic cylinders.

The pump generates oil pressure, which is directed through valves to hydraulic cylinders performing machine functions.

If the system cannot maintain correct pressure or temperature, the PLC will prevent machine operation.

Low Hydraulic Pressure Fault

Low hydraulic pressure is one of the most common hydraulic-related PLC trips.

The PLC monitors pressure using a sensor or pressure switch.

If pressure drops below a defined threshold, the PLC stops machine operation.

Typical alarm messages include:

• hydraulic pressure low
• hydraulic system not ready
• hydraulic pump fault.

Symptoms of Low Hydraulic Pressure

Operators may notice:

• shear will not activate
• punch cycles fail to start
• machine refuses to enter automatic mode
• hydraulic pump running but pressure not building.

These symptoms usually indicate a pressure loss somewhere in the hydraulic circuit.

Common Causes of Low Pressure

Several issues can reduce hydraulic pressure.

Low Oil Level

If the reservoir oil level is too low, the pump may draw air instead of oil.

Air entering the system prevents pressure from building.

Worn Hydraulic Pump

Hydraulic pumps wear over time.

Internal leakage inside the pump reduces pressure output.

Pressure Relief Valve Misadjustment

The relief valve limits maximum pressure.

If it is set too low or stuck open, system pressure cannot reach operating levels.

Hydraulic Leaks

Leaks in hoses, fittings, or cylinders allow pressure to escape.

Technicians should inspect the entire hydraulic system for visible leaks.

Hydraulic Oil Temperature Fault

Hydraulic systems generate heat during operation.

If the oil temperature rises above safe limits, the PLC may stop the machine.

Typical alarm messages include:

• hydraulic oil temperature high
• hydraulic overheating fault.

Excessive heat can damage seals, pumps, and valves.

Stopping the machine protects the hydraulic components.

Symptoms of Overheating

Typical symptoms include:

• machine stops after extended operation
• hydraulic tank feels unusually hot
• oil appears darker or smells burnt.

High temperatures often indicate inefficient hydraulic operation.

Causes of High Hydraulic Temperature

Several factors may cause overheating.

Continuous Pump Operation

If the pump runs constantly under high load, oil temperature may rise.

Insufficient Cooling

Some hydraulic systems include oil coolers or heat exchangers.

If these components fail, heat cannot dissipate effectively.

Clogged Filters

Restricted oil flow increases friction and heat generation.

Excessive Pressure

Operating at pressures higher than required generates unnecessary heat.

Engineers should review pressure settings and cooling performance.

Hydraulic Filter Clogging Fault

Hydraulic filters remove contaminants from the oil.

Over time, filters accumulate debris such as:

• metal particles
• dirt
• degraded oil residues.

When filters become clogged, oil flow becomes restricted.

Most hydraulic systems include filter differential pressure sensors.

When pressure across the filter becomes too high, a clog alarm is triggered.

Symptoms of Clogged Filters

Typical signs include:

• reduced hydraulic response speed
• increased oil temperature
• PLC filter alarm messages.

Ignoring clogged filter alarms can damage pumps and valves.

Causes of Filter Blockage

Filters may clog due to several reasons.

Contaminated Oil

Dirty oil accelerates filter blockage.

Internal Component Wear

Metal particles from worn pumps or cylinders can accumulate in filters.

Infrequent Maintenance

Filters that are not replaced regularly eventually restrict oil flow.

Regular filter replacement is essential.

PLC Monitoring of Hydraulic Conditions

Modern roll forming machines often include multiple hydraulic monitoring signals.

Typical PLC inputs include:

• hydraulic pressure sensor
• hydraulic oil temperature sensor
• filter clogging indicator
• pump running status.

The PLC evaluates these signals before allowing machine operation.

If any signal indicates an unsafe condition, the PLC generates a fault.

Troubleshooting Procedure

Technicians should follow a structured troubleshooting process.

Step 1 — Identify Alarm Message

Check the HMI to determine which hydraulic alarm triggered the machine stop.

Step 2 — Inspect Oil Level

Verify that the hydraulic reservoir contains sufficient oil.

Step 3 — Check Pump Operation

Ensure the hydraulic pump motor is running correctly.

Step 4 — Inspect Filters

Replace clogged hydraulic filters if necessary.

Step 5 — Verify Temperature and Pressure Sensors

Confirm that sensor signals are accurate.

Hydraulic Sensor Failures

Sometimes alarms are caused by faulty sensors rather than real hydraulic problems.

Possible issues include:

• damaged pressure switches
• faulty temperature sensors
• wiring problems.

Technicians should verify sensor signals before replacing hydraulic components.

Hydraulic Oil Quality

Oil condition significantly affects hydraulic system performance.

Degraded oil can cause:

• increased friction
• poor lubrication
• filter clogging.

Regular oil analysis and replacement help maintain system health.

Preventative Maintenance

Proper maintenance reduces hydraulic faults.

Recommended practices include:

• regular filter replacement
• periodic oil level checks
• monitoring oil temperature
• inspecting hydraulic hoses.

Preventative maintenance extends component life and reduces downtime.

Commissioning Best Practices

During machine commissioning, engineers should verify hydraulic performance.

Typical checks include:

1 verifying pressure sensor calibration
2 confirming correct relief valve settings
3 checking oil temperature stability
4 inspecting filter differential pressure.

These checks ensure the hydraulic system operates within safe limits.

Production Impact of Hydraulic Faults

Hydraulic faults can significantly affect roll forming production.

Possible consequences include:

• machine downtime
• incomplete punching operations
• incorrect cuts
• increased scrap material.

Quick diagnosis and repair help minimize production interruptions.

Benefits of Healthy Hydraulic Systems

Maintaining hydraulic systems properly offers several advantages.

These include:

• reliable punching and cutting operations
• stable machine performance
• longer component life
• reduced maintenance costs.

For roll forming machines using hydraulic systems, regular inspection is essential.

FAQ — Hydraulic Faults in Roll Forming Machines

Why does my roll forming machine show a hydraulic pressure fault?

Common causes include low oil level, worn pumps, misadjusted relief valves, or hydraulic leaks.

What causes hydraulic oil to overheat?

Overheating may result from continuous pump operation, clogged filters, or insufficient cooling.

Why do hydraulic filters clog?

Filters accumulate dirt, metal particles, and degraded oil contaminants over time.

Can faulty sensors cause hydraulic alarms?

Yes. Damaged pressure or temperature sensors can generate false PLC alarms.

How often should hydraulic filters be replaced?

Replacement intervals depend on machine usage but are typically scheduled during routine maintenance.

Why does the PLC stop the machine during hydraulic faults?

Stopping the machine prevents damage to pumps, valves, and hydraulic cylinders.