The life improvement of mechanical seal

The life improvement of mechanical seal 

The life improvement of the mechanical seal can increase the provision of pumps and scale back the price pay for seal maintenance.
Before we have a tendency to seeing the Life Extend of Mechanical Seal, initial we’d like to know the causes of mechanical seal failure.

Causes of Mechanical Seal Failure

As per API 682, the typical lifetime of the mechanical seal is three years. these days the seal manufactures have accrued the mechanical seal life considerably and increase the provision of the pumps for production.

In several cases, the mechanical seal service life will disappoint expectations thanks to the subsequent reasons

• Exposed to contamination

• Outside the planning & in operation conditions of mechanical seal

• Improper flushing arrange choice

• Improper installation of the flushing system

In this article, we’ll use a systems approach to judge the failure reason for the mechanical seal and seal system. Before this analysis, it’s vital to understand the foundation causes of mechanical seal failure.

Root explanation for Mechanical Seal Failure

The premature failure of the mechanical seal can occur for many reasons. the foremost common root causes of square measure

• Outside the in operation vary of pump

• Sudden amendment in pumping fluid properties

• Improper Seal flushing arrange

• Pump with variable speed drive

• Pump vibration

• Improper Installation

Pump operation Range

Usually, the pump rated purpose shall be elite and operated within the most well-liked in operation vary id est., eighty to a hundred and ten you look after pump BEP flow. If the pump operates during this region the pump vibration is a smaller amount. thanks to less vibration, the external force caused by vibration act on the seal faces square measure less and improve the service life of the mechanical seal.

During the pump choice stage, the in operation purpose of the pump is often value more highly to choose on the subject of the pump BEP.

Change in pumping fluid property:

If there’s sharp amendment pumping properties like

• Pump suction pressure

• Fluid temperature

• Solid concentration

• pH variation

• Improper Seal flushing arrange

• Vibration

Suction pressure

If the suction pressure of the pumping liquid is accrued. this may produce massive thrust force act on the pump blade. thanks to this thrust force, the force act on the seal face is additionally accrued and mechanical seal can fail thanks to the too little lubrication between the seal faces.

Liquid Temperature

If an outbreak or decrease in pumping liquid temperature, it’ll have an effect on the seal faces and secondary waterproofing materials.

In most of the cases, the rise in pumping liquid temperature can continuously cause the secondary seal failure (ie., Elastomers). the sharp fluctuation of temperature conjointly creates the secondary seal failure.

Solid concentration

The solid concentration of the pumping fluid accrued or suddenly introduced within the pumping fluid thanks to planting upset conditions. the rise in solid concentration can cause the mechanical seal to face injury.

To avoid this correct seal flushing arrange on to be elite.

pH variation

The variation in pH scale concentration can directly have an effect on the fabric of construction of each mechanical seal and pump. this may be avoided by introducing a pH scale meter within the pump suction and observation the pH scale level of the pumping liquid.

Improper Seal flushing arrange

One of the most important explanations for mechanical seal failure is thanks to improper choice of mechanical seal flushing plans.

To avoid seal failure thanks to this reason, care ought to be taken throughout seal choice. it’s the joint responsibility of each pump and seal manufacturer.

Vibration

They are a great deal of reason for Pump system vibration. The vibration may be elicited from many sources. a number of the explanations square measure listed below.

• External force act on the pump thanks to suction and pipe loading

• Misalignment between pump and driver

• Improper installation

• Impeller unbalance

• Bearing failure

Mechanical Seal Life Extension

The following points square measure to be taken care of mechanical seal style, choice, and maintenance.

Mechanical Seal choice

Selecting the most effective kind of mechanical seal isn’t continuously simple and simple as there’s typically a compromise between economic and technical factors. If the mechanical seal is correctly elite, then an hour of premature seal failure can ne’er occur.

Installation

Proper installation of a mechanical seal can scale back the premature seal failure concerning two hundredths. Here the installation refers not solely mechanical seal and conjointly its seal system.

Nowadays cartridge sort mechanical seals square measure extremely used, due this correct in operation length/working length of a seal is well maintained.

Air Pocket in Seal Chamber

The atmospheric phenomenon in Seal Chamber is thanks to the poor startup procedure of the pump. commonly this downside may be corrected by trauma the air from the seal chamber, before startup, is often an honest procedure. these days most of the OH pumps square measure the self-vented sort. thus this downside can ne’er occur in Overhung (OH) pumps.

But on the opposite hand, this downside can occur in Between Bearing(BB) pumps. A procedure ought to be enforced to confirm that each one the air is bled from the pump and therefore the seal chamber. If this downside continues, a pressure switch could also be put in on the discharge to forestall startup till the flow is indicated.

Bearing Failure

Bearing failure causes instant issues. once an effect fails, it loses its ability to support the rod. thanks to this seal can fail like a shot.

Important Checkings

Following things to be check whereas doing maintenance so as to boost the mechanical seal life

• The total indicated run out, it shouldn’t be over zero.003” (0.08mm) at mechanical seal space.

• The end play (Axial Movement) – most of zero.005” (0.13mm).

• All keyways, threads, and shoulders for sharp edges, that may injury elastomers. spherical edges or tape over before installation.

• Check for shaft circularity to the housing/seal chamber, that ought to be inside zero.005” (0.13mm) most.