Reasons why self-balancing pump seals are not wear-resistant

Category: Water pump knowledge

2025-08-15

The wear resistance of the self-balancing pump seal directly affects the sealing effect and service life of the pump. Its lack of wear resistance is the result of multiple factors. It is necessary to conduct a comprehensive investigation based on specific working conditions (medium, temperature, pressure), installation accuracy, material selection, and operation and maintenance to solve the problem in a targeted manner.

I. Problems with the seal material itself

The material of the seal is the core factor determining its wear resistance. Material selection or quality defects will directly lead to insufficient wear resistance:

1. Material does not match working conditions: The seal material (such as rubber, PTFE, metal, etc.) is not selected according to the medium characteristics (corrosiveness, temperature, particle content).

2. When the medium contains hard particles, if soft rubber (such as nitrile rubber) is selected, it is easily worn by the particles "cutting";

3. The use of ordinary nitrile rubber in high-temperature media (such as above 120℃) will cause a sharp drop in wear resistance due to material aging and hardening;

4. If corrosion-resistant materials (such as ordinary rubber) are used in highly corrosive media (such as acid and alkali solutions), the material structure will be damaged and the strength will decrease, and the wear resistance will also decrease.

5. Material quality defects: Insufficient material purity (containing impurities, bubbles) and unreasonable formula (such as poor rubber vulcanization process) will lead to insufficient mechanical properties (strength, hardness) of the seal, which is easily worn during friction.

II. Improper installation process

Stress and positioning deviations of the seal during installation can lead to increased local wear:

1. Uneven force during installation:

The seal (such as O-rings, moving/stationary rings of mechanical seals) is excessively squeezed, twisted, or eccentrically installed, resulting in uneven contact area with the sealing surface (sleeve, gland end face), excessive local pressure, forming "point friction", and accelerating wear.

2. Poor sealing surface fit:

If there are scratches, dents, or excessive roughness on the sealing surface (such as the shaft surface, gland sealing surface) during installation, the seal and the sealing surface cannot be completely fitted, resulting in local gaps or "hard-on-hard" friction, and the wear rate is accelerated.

3. Tool or operation damage:

Using sharp tools to scratch the surface of the seal during installation, or the seal being cut by sharp edges such as shaft shoulders and threads during assembly, damages the surface integrity and reduces wear resistance.

III. Harsh working conditions

Working condition parameters such as medium characteristics, temperature, and pressure exceed the seal's tolerance range, which will significantly shorten its wear life:

1. The medium contains abrasives:

When there are solid particles (such as sediment, metal debris) in the medium, the particles will enter the gap of the sealing surface with the medium, and continuously scrape the surface of the seal like "abrasives", resulting in rapid wear (similar to the effect of sandpaper sanding).

2. Temperature anomaly:

(1) High temperature (such as exceeding the upper temperature limit of the seal material) will soften and age the material (such as rubber hardening, plastic embrittlement), reduce hardness and strength, and reduce wear resistance;

(2) Low temperature will cause elastic materials (such as rubber) to lose elasticity, the fit between the seal and the sealing surface will deteriorate, and local stress concentration is likely to occur during friction, which will aggravate wear.

3. Excessive pressure or large fluctuations:

When the system pressure exceeds the seal design pressure, the contact pressure between the seal and the sealing surface increases, the friction resistance increases, and the wear is aggravated; frequent pressure fluctuations will cause the seal to repeatedly "squeeze-rebound", resulting in fatigue wear.

4. Poor medium lubricity:

Low medium viscosity (such as clean water) or lack of lubricity (such as certain chemical solvents) will prevent the formation of an effective lubricating film between the sealing surfaces, resulting in "dry friction" or "semi-dry friction", the friction coefficient will increase sharply, and the wear rate will accelerate.

IV. Abnormal equipment operating status

The operating stability of the pump directly affects the wear rate of the seal:

1. Excessive or unstable speed:

Excessive speed will accelerate the relative movement speed between the seal and the sealing surface, increase frictional heat generation, and the material will soften due to high temperature and reduce wear resistance; speed fluctuations (such as unstable motor speed) will cause changes in friction frequency and produce impact wear.

2. Vibration and eccentricity:

The radial runout of the pump shaft, impeller imbalance, or shaft eccentricity caused by bearing wear will cause the contact position between the seal (such as the moving ring of the mechanical seal) and the sealing surface (stationary ring) to continuously shift, resulting in "eccentric wear", and the local wear rate is far greater than normal.

3. Dry friction start:

If there is no medium lubrication between the sealing surfaces when the pump is started (such as inlet liquid cut-off, the medium is not full), instantaneous dry friction will occur, and the seal surface will be directly damaged due to high temperature and severe friction (such as rubber carbonization, plastic melting), and the wear resistance will be greatly reduced in subsequent operation.

V. Lack of maintenance

Inadequate daily maintenance will accelerate the wear of the seal:

1. Insufficient lubrication:

The sealing surface (such as the friction pair of the mechanical seal) is not regularly replenished with lubricating grease or the medium lubrication fails (such as the medium viscosity decreases), resulting in increased friction resistance and accelerated wear.

2. Impurities are not cleaned in time:

Medium filtration failure (such as filter screen damage) causes particulate impurities to continuously enter the sealing surface; or deposits (such as scale, silt) accumulated in the sealing cavity are not cleaned regularly, forming a continuous source of wear.

3. Untimely replacement of worn parts:

Wear of parts that work with the seal (such as shaft sleeves and glands) can lead to increased sealing gaps or uneven sealing surfaces, indirectly exacerbating seal wear (such as reduced concentricity of the shaft sleeve with the seal after wear).

6. Unreasonable design

Design flaws in seals or related components may also result in insufficient wear resistance:

1. Structural design issues:

The contact form between the seal and the sealing surface is unreasonable (such as line contact instead of surface contact), resulting in excessive local pressure; or the cross-sectional dimensions of the seal do not match the mounting groove (too loose or too tight), resulting in uneven stress.

2. Improper hardness matching:

If the hardness difference between the seal and the mating part (such as a shaft sleeve) is too large (such as the seal being too soft and the shaft sleeve being too hard), the seal may be "crushed" and worn; or if the hardness is similar, it may cause mutual wear between the two (such as metal seals and metal shaft sleeves having the same hardness).

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