Hydraulic Pump Prime Loss in Roll Forming Machines – Causes, Suction Failure, Inspection & Repair Guide

Hydraulic Pump Prime Loss

Roll Forming Machine Hydraulic & Pneumatic Failure Guide

Hydraulic pump prime loss is a hydraulic system failure in roll forming machines where the hydraulic pump loses its ability to draw oil from the reservoir, resulting in pressure loss, cavitation, and potential damage to the pump.

Hydraulic pumps are responsible for generating the pressurized oil required to power many functions within roll forming machines.

These pumps typically operate by drawing hydraulic oil from the reservoir through a suction line and then delivering pressurized oil to the hydraulic system.

Hydraulic pumps in roll forming machines commonly supply pressure for:

hydraulic cut-off shear systems
punching stations
press cylinders
coil handling equipment
hydraulic positioning mechanisms
pressure control circuits

When the pump is properly primed, the suction line and pump housing are filled with hydraulic oil.

This allows the pump to create suction and maintain continuous oil flow.

However, if the pump loses its prime, the pump may begin drawing air instead of oil.

This condition is known as hydraulic pump prime loss.

Prime loss may affect roll forming machines producing:

metal roofing panels
metal wall cladding panels
standing seam roofing systems
structural deck profiles
C and Z purlins
light gauge steel framing components

Typical production symptoms associated with pump prime loss include:

sudden loss of hydraulic pressure
loud whining or cavitation noise from the pump
intermittent hydraulic system operation
air bubbles visible in the hydraulic reservoir
delayed hydraulic actuator movement
pump overheating

If pump prime loss continues, cavitation may occur inside the pump, potentially damaging internal pump components.

Maintaining proper suction conditions helps prevent this issue.

Causes of Wear or Failure

Hydraulic pump prime loss usually occurs when air enters the suction line or when oil supply to the pump is restricted.

Several factors may contribute to this condition.

Low Hydraulic Oil Level

Insufficient oil may allow air to enter the suction line.

Suction Line Air Leaks

Loose fittings may allow air to enter the pump inlet.

Blocked Suction Filters

Restricted suction flow may prevent oil intake.

Pump Seal Leakage

Damaged seals may allow air into the pump.

Incorrect Pump Installation Height

Improper positioning may affect suction performance.

Suction Hose Damage

Cracked hoses may allow air entry.

Why It Happened and What Caused It

From a hydraulic engineering perspective, hydraulic pumps must remain fully filled with oil to generate suction and maintain continuous flow.

This condition is known as maintaining the pump prime.

If air enters the pump suction line or if oil supply becomes interrupted, the pump may begin drawing air instead of oil.

Air is compressible and cannot generate the hydraulic pressure required to operate the system.

As a result, the pump may lose its ability to deliver pressurized oil.

Additionally, when air enters the pump, cavitation bubbles may form and collapse inside the pump chambers.

These collapsing bubbles create shock waves that may damage pump components.

Maintaining proper suction line integrity and adequate oil supply helps ensure the pump remains primed.

How to Inspect the Problem

Inspection Procedure

Diagnosing hydraulic pump prime loss requires inspecting the suction system and verifying oil supply conditions.

Step 1 – Check Hydraulic Oil Level

Ensure the reservoir contains sufficient oil.

Step 2 – Inspect the Suction Line

Look for loose fittings or air leaks.

Step 3 – Inspect the Suction Filter

Clogged filters may restrict oil flow.

Step 4 – Inspect Pump Seals

Damaged seals may allow air entry.

Step 5 – Observe Oil Flow in the Reservoir

Air bubbles may indicate suction problems.

Step-by-Step Technician Guide – How to Fix

Correcting pump prime loss usually requires restoring proper oil supply and eliminating air leaks.

Method 1 – Refill Hydraulic Oil

Restore oil level to recommended capacity.

Method 2 – Repair Suction Line Leaks

Tighten fittings and replace damaged hoses.

Method 3 – Replace Suction Filters

Clean filters restore proper oil flow.

Method 4 – Prime the Hydraulic Pump

Fill the pump housing with oil before restarting.

Method 5 – Test Hydraulic System Operation

Verify stable pressure and pump performance.

Preventative Maintenance Tips

Preventing hydraulic pump prime loss requires maintaining proper oil supply and suction line integrity.

Maintain Proper Hydraulic Oil Levels

Adequate oil supply prevents air entry.

Inspect Suction Lines Regularly

Leak-free suction lines maintain pump prime.

Replace Suction Filters

Clean filters ensure unrestricted oil flow.

Monitor Pump Noise

Early cavitation noise may indicate suction problems.

Maintain Pump Seals

Healthy seals prevent air entry.

FAQ Section

What causes hydraulic pump prime loss in roll forming machines?

Low oil levels, suction line leaks, or clogged filters may cause prime loss.

Can pump prime loss damage hydraulic pumps?

Yes. Cavitation caused by air entry may damage pump components.

How can pump prime loss be detected?

Loss of pressure, cavitation noise, or air bubbles in the oil may indicate the problem.

Should pumps be primed before startup?

Yes. Pumps should be filled with oil before initial operation.

Can suction leaks cause pump prime loss?

Yes. Air entering the suction line may disrupt pump operation.

How can pump prime loss be prevented?

Proper oil levels, sealed suction lines, and regular maintenance help prevent this issue.