Introduction

Mechanical seals are widely used in hygienic rotary lobe pumps, centrifugal pumps, and other industrial pumps to prevent liquid leakage while allowing the shaft to rotate.

When a mechanical seal starts leaking, it is often a sign that something is wrong with the pump, the operating conditions, or the seal itself. Ignoring the problem can lead to product loss, equipment damage, and unexpected downtime.

In this article, we'll explain the most common causes of mechanical seal leakage and how to solve them.

1. Dry Running

One of the most common causes of seal failure is dry running.

Mechanical seals rely on the pumped liquid to lubricate and cool the seal faces. Without sufficient lubrication, friction rapidly generates heat, damaging the sealing surfaces.

Symptoms

• Squealing or high-pitched noise
• Burn marks on seal faces
• Sudden leakage after startup

Solution

• Never operate the pump without product.
• Ensure adequate liquid reaches the seal before starting.
• If temporary lubrication is needed during troubleshooting, apply a suitable food-grade lubricant (for food applications).

2. Insufficient Lubrication

High-viscosity products sometimes do not provide enough lubrication around the seal area.

Examples include:

• Peanut butter
• Chocolate
• Tomato paste
• Thick sauces
• Cosmetic creams

Poor lubrication increases friction and accelerates seal wear.

Solution

• Select the proper seal design.
• Verify operating speed.
• Add lubrication if recommended by the equipment manufacturer.

3. Incorrect Installation

Improper installation is another frequent cause.

Common mistakes include:

• Misaligned seal faces
• Damaged O-rings
• Incorrect spring compression
• Scratched shaft sleeve

Even a small installation error can create leakage.

Solution

• Follow the manufacturer's installation procedure.
• Replace damaged O-rings.
• Check shaft alignment.

4. Worn Seal Faces

Over time, the seal faces naturally wear due to continuous contact.

Typical signs include:

• Gradually increasing leakage
• Reduced sealing performance
• Visible wear on carbon or silicon carbide faces

Solution

Replace worn seal components before complete failure.

5. Excessive Pressure

Operating beyond the seal's pressure rating can overload the sealing faces.

Possible causes include:

• Blocked discharge line
• Closed discharge valve
• Incorrect system design

Solution

• Verify operating pressure.
• Install pressure protection devices if necessary.

6. Excessive Temperature

High temperatures reduce seal life.

Heat may come from:

• Hot process fluids
• Dry running
• Excessive friction

Solution

Maintain operating temperatures within the seal manufacturer's specifications.

7. Shaft Misalignment or Excessive Vibration

A rotating shaft must remain stable.

Excessive vibration can cause:

• Uneven seal wear
• Face separation
• Premature leakage

Possible causes

• Worn bearings
• Bent shaft
• Poor pump installation
• Pipe stress

Solution

Inspect bearings, shaft alignment, and piping support.

8. Chemical Compatibility Issues

Not all seal materials are suitable for every liquid.

Incorrect elastomers or seal face materials may swell, crack, or deteriorate.

Examples

• FKM (Viton®)
• EPDM
• PTFE

Always select seal materials compatible with the pumped fluid.

How to Prevent Mechanical Seal Leakage

To maximize seal life:

• Avoid dry running.
• Maintain proper lubrication.
• Operate within pressure and temperature limits.
• Inspect bearings and shaft alignment regularly.
• Replace worn seals before failure.
• Use seal materials compatible with the process fluid.
• Follow the manufacturer's maintenance recommendations.

Frequently Asked Questions

Why is my mechanical seal leaking after installation?

Possible causes include incorrect installation, damaged O-rings, shaft misalignment, or contamination on the seal faces.

Can a leaking mechanical seal be repaired?

Minor issues such as damaged O-rings may be repaired, but worn seal faces usually require replacement.

Does high-viscosity fluid damage mechanical seals?

Not necessarily. However, very viscous products may reduce lubrication around the seal faces, increasing friction and wear if the pump is not designed or operated correctly.

Conclusion

Mechanical seal leakage is usually a symptom of an underlying issue rather than the root cause itself. Dry running, inadequate lubrication, misalignment, excessive pressure, high temperature, and normal wear are among the most common reasons.

By identifying the cause early and performing proper maintenance, you can significantly extend seal life, reduce downtime, and improve pump reliability.