Why Do Chemical Pumps Often Experience Mechanical Seal Leakage? Causes and Prevention Methods

 Why Do Chemical Pumps Often Experience Mechanical Seal Leakage? Causes and Prevention Methods

In chemical processing industries, pumps are required to handle various challenging fluids, including corrosive chemicals, high-temperature liquids, solvents, and fluids containing solid particles.

Compared with ordinary water pumps, chemical pumps operate under much harsher conditions.

One of the most common maintenance problems is:

Mechanical seal leakage.

Many operators find that a chemical pump works normally after installation, but after a period of operation, leakage begins to appear.

Why does this happen?

The answer is usually related to fluid characteristics, operating conditions, seal material selection, and maintenance practices.

1. Corrosive Fluids Damage Mechanical Seal Components

Chemical pumps often transport:

Acids;

Alkalis;

Organic solvents;

Corrosive chemical solutions.

If the mechanical seal materials are not suitable for the pumped medium, corrosion may occur.

Typical problems include:

Seal faces becoming damaged;

Rubber components aging;

Loss of spring elasticity;

Reduced sealing performance.

For chemical applications, mechanical seal materials should be selected according to:

Chemical compatibility;

Temperature range;

Pressure conditions.

Common materials include:

Silicon carbide;

Carbon graphite;

Ceramic;

PTFE;

Fluoro rubber.

The correct material combination is essential for long-term reliability.

2. High Temperature Conditions Accelerate Seal Failure

Many chemical processes require high-temperature fluid transfer.

When operating temperature exceeds the seal design limit, several problems may occur:

Seal face deformation;

Loss of lubrication film;

Aging of auxiliary sealing rings.

A mechanical seal depends on a very thin liquid film between the sealing faces for cooling and lubrication.

If this film disappears:

Dry friction occurs.

As a result:

Seal wear increases;

Leakage develops;

Service life decreases.

3. Unstable Pump Operation Causes Seal Wear

Mechanical seals require stable shaft operation.

However, chemical pumps may experience problems such as:

Excessive vibration;

Bearing wear;

Shaft misalignment;

Coupling alignment problems.

These conditions prevent the sealing faces from maintaining proper contact.

Over time, this can lead to:

Uneven wear;

Seal face damage;

Continuous leakage.

Therefore, mechanical seal problems are often related not only to the seal itself, but also to the overall pump condition.

4. Solid Particles Damage the Seal Faces

Some chemical processes contain:

Crystals;

Catalyst particles;

Solid impurities;

Slurry materials.

When particles enter the mechanical seal area, they can scratch the sealing surfaces.

Possible results:

Increased leakage;

Faster wear;

Complete seal failure.

For these applications, solutions may include:

Harder seal materials;

Flushing systems;

Cooling structures;

Improved filtration.

5. Improper Mechanical Seal Installation

Mechanical seals are precision components.

Incorrect installation may cause early failure.

Common installation problems include:

Damaged sealing faces;

Incorrect compression amount;

Improper installation position;

Damaged O-rings.

When replacing a mechanical seal, technicians should also inspect:

Pump shaft condition;

Shaft runout;

Bearing condition;

Installation accuracy.

Simply replacing the seal may not solve the root problem.

How to Identify Different Types of Mechanical Seal Leakage?

Slight Dripping

Possible causes:

Initial running-in period;

Minor seal surface wear.

Continuous Leakage

Possible causes:

Damaged seal faces;

Incorrect material selection;

Shaft vibration.

Sudden Leakage After Temperature Increase

Possible causes:

Insufficient cooling;

Dry running;

Operation without enough liquid.

How to Reduce Chemical Pump Seal Leakage?

1. Select the Correct Seal Materials

The selection should consider:

Chemical properties;

Temperature;

Pressure;

Solid content.

A suitable seal combination can greatly improve reliability.

2. Avoid Dry Running

Chemical pumps should never operate without sufficient liquid.

Dry running can quickly cause:

Seal overheating;

Friction damage;

Sudden leakage.

3. Keep the Pump Operating Within the Design Range

Avoid:

Frequent start-stop cycles;

Long-term low-flow operation;

Overloading conditions.

Stable operation helps extend mechanical seal life.

4. Perform Regular Inspection

Regular checks should include:

Leakage condition;

Vibration level;

Operating temperature;

Seal chamber condition.

Early detection prevents unexpected shutdowns.

Conclusion

Mechanical seal leakage is one of the most common issues in chemical pump applications.

The main causes include:

Corrosion from unsuitable materials;

High-temperature operation;

Excessive vibration or unstable running;

Solid particles damaging seal faces;

Incorrect installation and maintenance.

Choosing a chemical pump requires more than considering flow rate and head.

A reliable solution must match:

Pump material;

Mechanical seal design;

Fluid characteristics;

Operating conditions.

Shanghai Shangcheng Pump & Valve provides chemical pump solutions for corrosive fluids, high-temperature applications, and industrial chemical processes, helping customers achieve safer and more stable fluid transfer operations.