Effects of Mechanical Seal Failure in Pump

Sleeve / Shaft Wear

Sleeve or shaft wear is one of the most common effects of mechanical seal failure in pumps. When a mechanical seal fails, it can allow the pumped fluid to leak along the shaft, causing erosion and wear on the shaft sleeve or the shaft itself. This wear is typically characterized by a uniform reduction in the shaft or sleeve diameter, which can lead to increased vibration, reduced pump efficiency, and ultimately, premature failure of the pump bearings or other components.

Gouging, Denting, Scratching of Shaft

In addition to uniform wear, mechanical seal failure can also cause more localized damage to the pump shaft or sleeve in the form of gouging, denting, or scratching. These types of damage are often the result of debris or particulates in the pumped fluid, which can become trapped between the seal faces or between the seal and the shaft.

Gouging refers to deep, irregular grooves or channels that are cut into the shaft surface, often by hard particles such as sand or metal fragments. Denting, on the other hand, is characterized by shallow, rounded indentations in the shaft surface, which may be caused by softer particles or by cavitation bubbles collapsing near the shaft.

Scratching is another common type of shaft damage, which appears as fine, linear marks on the shaft surface. This can be caused by abrasive particles in the fluid, or by contact between the seal faces and the shaft during operation.

All of these forms of shaft damage can lead to increased wear on the mechanical seal faces, as well as the pump bearings and other components. In severe cases, the damage may be extensive enough to require shaft replacement or resurfacing.

Corrosion of Seal Shaft

Corrosion is another common effect of mechanical seal failure in pumps, particularly when the pumped fluid contains corrosive chemicals or contaminants. When the seal fails, it can allow the corrosive fluid to come into direct contact with the shaft or sleeve, leading to chemical attack and degradation of the metal surfaces.

The type and severity of corrosion will depend on the specific chemicals present in the fluid, as well as the materials used for the shaft and sleeve. Common forms of corrosion include pitting, crevice corrosion, and stress corrosion cracking, all of which can weaken the shaft and make it more susceptible to failure.

Flashing or Etching

Flashing and etching are two additional effects that can occur on pump shafts or sleeves as a result of mechanical seal failure. These effects are primarily associated with high-temperature or high-pressure applications, where the sudden release of pressure or the vaporization of the pumped fluid can cause localized damage to the metal surfaces.

Flashing refers to the rapid vaporization of a liquid when it is exposed to a sudden drop in pressure, such as when a mechanical seal fails and allows the high-pressure fluid to escape. This can cause the formation of steam or vapor bubbles near the shaft surface, which can collapse and create localized erosion or pitting.

Etching, on the other hand, is a form of chemical attack that occurs when the pumped fluid vaporizes and leaves behind concentrated deposits of corrosive chemicals on the shaft or sleeve surface. These deposits can react with the metal and cause shallow pits or grooves to form, weakening the surface and making it more susceptible to cracking or fracture.

Fretting

Fretting is a type of surface damage that can occur on pump shafts or sleeves as a result of mechanical seal failure, particularly in applications where there is significant vibration or relative motion between the seal and the shaft.

Fretting is characterized by the formation of small, localized areas of damage on the shaft surface, typically in the form of shallow pits or fine cracks. These damaged areas are caused by the repeated rubbing or sliding contact between the seal faces and the shaft, which can create high local stresses and lead to the breakdown of the protective oxide layer on the metal surface.

Over time, fretting can lead to more severe damage, such as fatigue cracking or spalling of the shaft surface, which can compromise the integrity and reliability of the pump. In some cases, fretting may also cause the formation of loose debris or particles, which can further accelerate wear and damage to the seal faces and other components.