The Method Of Extend The life Of Mechanical Seal
Causes of Mechanical Seal Failure
As per API 682, the common lifetime of the mechanical seal is three years. these days the seal manufacturers have increased 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 following reasons
- Exposed to contamination
- Outside the planning & operative conditions of mechanical seal
- Improper flushing set up Select
- 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 important to understand the basic causes of mechanical seal failure.
The root reason behind Mechanical Seal Failure:
The premature failure of the mechanical seal can occur for many reasons. the foremost common root causes ar
- Outside the in operation vary of pump
- Sudden modification in pumping fluid properties
- Improper Seal flushing arrange
- Pump with variable speed drive
- Pump vibration
- Improper Installation
Pump operation vary
Usually, the pump rated purpose shall be chosen and operated within the most popular operative vary id est., eighty to one hundred ten you look after pump BEP flow. If the pump operates during this region the pump vibration is a smaller amount. due to less vibration, the external force caused by vibration act on the seal faces ar less and improve the service lifetime of mechanical seal.
During the pump choice stage, the operative purpose of the pump is usually chosen to choose just about the pump BEP.
Change in pumping fluid property:
If there’s sudden modification pumping properties like
- Pump suction pressure
- Fluid temperature
- Solid concentration
- pH variation
- Improper Seal flushing set up
- Vibration
Suction pressure
If the suction pressure of the pumping liquid is Increasing. this can produce a giant thrust force act on the pump blade. due to this thrust force, the force act on the seal face is additionally raised and mechanical seal can fail due to the insufficient lubrication between the seal faces.
Liquid Temperature
If a raised or decrease in pumping liquid temperature, it’ll have an effect on the seal faces and secondary protection materials.
In most of the cases, the rise in pumping liquid temperature can continuously cause the secondary seal failure (ie., Elastomers). fast fluctuation of temperature additionally creates the secondary seal failure.
Solid concentration
The solid concentration of the pumping fluid raised or suddenly introduced within the pumping fluid due to plant upset condition. the rise in solid concentration can cause the mechanical seal face harm.
To avoid this correct seal flushing set up on be chosen.
pH variation
Improper Seal flushing arrange
One of the foremost reasons behind mechanical seal failure is due to improper choice of mechanical seal flushing plans.
To avoid seal failure due 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 plenty of reason for Pump system vibration. The vibration may be iatrogenic from many sources. a number of the explanations area unit listed below.
- External force act on the pump due to suction and piping loading
- Misalignment between pump and driver
- Improper installation
- Impeller unbalance
- Bearing failure
Mechanical Seal Life Extension
The following points ar to be taken care of mechanical seal style, choice, and maintenance.
Mechanical Seal choice
Selecting the most effective variety 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 chosen, then hr of premature seal failure can ne’er occur.
Installation
Proper installation of a mechanical seal can cut back the premature seal failure regarding 200. Here the installation refers not solely mechanical seal and additionally its seal system.
Nowadays cartridge sort mechanical seals ar extremely used, due to this correct operative length/working length of the seal is well maintained.
Air Pocket in Seal Chamber
The atmospheric phenomenon in the Seal Chamber is thanks to the poor startup procedure of the pump. ordinarily, this drawback may be corrected by bleeding the air from the seal chamber, before startup, is usually a decent procedure. these days most of the OH pumps area unit the self-vented sort. thence this drawback can ne’er occur in Overhung (OH) pumps.
But on the opposite hand, this drawback can occur in Between Bearing(BB) pumps. A procedure ought to be enforced to make sure that every one the air is bled from the pump and also the seal chamber. If this drawback continues, a pressure switch is also put in on the discharge to stop startup till the flow is indicated.
Bearing Failure
Bearing failure causes instant issues. once an impression fails, it loses its ability to support the shaft. due to this seal can fail now.
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 quite 0.003” (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 might harm elastomers. spherical edges or tape over before installation.
- Check for shaft concentricity to the housing/seal chamber, which ought to be among zero.005” (0.13mm) most.
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