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Mechanical seal failure can cause many undesirable effects, such as leaked fluid, unwanted downtime and equipment damage. Though there are many potential causes of mechanical seal failure, there are frequently reoccurring causes as to why it happens. In this guide, we discuss the most common reasons why mechanical seals fail and advise on how you can prevent seal failure from occurring in the future.
Mechanical seal failure can pose a significant hindrance to your application and is a costly and time-consuming occurrence. There is no one cause as to why mechanical seals fail, as failure can occur for a variety of different reasons. The most common reasons for mechanical seal failure are down to misjudgment when first installing the seal and choosing seals with the incorrect attributes and resistances needed for the system.
We address the most common causes of mechanical seal failure in further detail below and provide advice on how to prevent failure from reoccurring in the future.
Mechanical seal failure most commonly comes down to a few reasons:
Incorrectly installed seals.
Seal deterioration from high heat.
Poor resistance from the seal materials against the fluid sealed.
Restricted seal motion with the faces opened.
Incorrect installation of seals is a very common cause of mechanical seal failure, leading to premature failures and failures at initial start-up. It is essential that you carefully follow the manufacturer&#;s instructions when initially installing a seal, as doing so will prevent many common problems from occurring.
Alternatively, cartridge seals, as a result, are an effective method of averting incorrect seal installation due to their pre-assembled design. Additionally, they provide the benefit of protecting seal faces from contamination.
&#;O&#;-rings often fail due to their heat resistance, meaning that failure often occurs when seals are heated beyond their recommended temperature. The reason this occurs is due to their manufacturing methods.
After the chosen material is put in a mould and cured, the seal will assume the moulded shape and vulcanise.
When the O-Ring is in service it will undergo physical and chemical degradation due to mechanical, thermal and chemical ageing. This will cause the O-Ring to undergo permanent deformation (known as compression set) and thus the sealing force of the O-Ring reduces. When the sealing force is reduced below a critical point fluid can bypass the seal, resulting in a leakage. The rate at which an &#;O&#;-ring takes a compression set is primarily related to temperature, strain and chemical effects. Some materials will fail in service after high temperature exposure due to their thermal instability which makes them brittle and hard. When comparing datasheets between materials the technical datasheet should be reviewed and long term compression sets should be compared. A lower result can indicate a longer expected service life.
Due to industrial applications commonly experiencing high temperatures, this is a commonly occurring problem. The best method to protect against high heat, therefore, is to use balanced seals as these will minimise heat generation. Choosing low-friction face materials is also beneficial, meaning that frictional heat generation and degradation are reduced. You should also use a clean liquid flush or product recirculation to carry away heat in your system.
It is vital that the applicable materials are chosen for your &#;O&#;-rings as selecting the incorrect material can lead to issues. When incorrect materials are used, &#;O&#;-rings can swell and cause the mechanical seal to lock up. This then results in rapid deterioration and corrosion of metal seal components.
You must choose the correct material type for your &#;O&#;-rings to provide the needed resistance against the specified fluid in your system. By checking our chemical resistance guide, you can find out which &#;O&#;-ring materials are compatible with the substances in your application.
One of the causes of mechanical seal failure is when the spring-loaded, dynamic seal face constantly moves to maintain full face contact with the stationary seal face. Some reasons as to why this movement occurs are that:
The pump has bearing end play. This means the shaft moves back and forth a few thousandths of an inch at frequent but random intervals.
Thermal shaft growth and pump vibration are affecting the seal.
The stationary face is not perpendicular to the pump shaft.
The pump is operated away from its BEP, causing side loads on the shaft.
An impeller unbalance is causing shaft whip.
In addition, these are the most significant conditions that can restrict the movement of the spring-loaded mechanical seal&#;s face:
The spring compression is inadequate due to incorrect installation.
Solids have collected in the seal or around the dynamic seal ring.
Solids in the stuffing box, gasket protrusion or other foreign material have restricted the motion of the dynamic seal ring.
The sealed fluid has caused the dynamic &#;O&#;-ring to swell.
Checking your system for any signs of the above-mentioned conditions and promptly resolving any of these issues will prevent mechanical seal failure from reoccurring.
We hope this guide will equip users with the knowledge to put preventative measures in place to reduce mechanical seal failure within their systems. To reduce the likelihood of mechanical seal failure further, investing in resistant and reliable &#;O&#;-rings is a way to ensure your system will be leak and damage-free.
At TRP Polymer, we can provide you with custom-made &#;O&#;-rings that are designed specifically for your system&#;s requirements. We can design custom materials specifically to resist heat and chemical wear and keep your system running flawlessly. These include our custom moulded rubber seals and FFKM &#;O&#;-ring and seals.
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For more information on our products and how TRP can assist your business, please contact us. Our technical team is ready to provide expert advice and solutions tailored to your needs.