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the mechanical seal of non lubricants

by:DMS Seals     2019-10-16
When we discuss mechanical sealing, the lubricant is defined as a fluid with a film thickness of at least 1 micron (0. 000039 inches)
Under its operating temperature and load.
If the product we are sealing is not a lubricant, we will be forced to use
Lubrication properties for the manufacture of a carbon/graphite mixture on the sealing surface.
The key to this self-lubricating is that carbon can form a strong chemical bond with gases such as water vapor.
The adsorbed gas then weakens the staggered binding force, which in turn reduces friction.
Many other types of steam and gas can be easily adsorbed by carbon/graphite, and in some cases inorganic compounds can be added to carbon/graphite if there is no adsorbed gas, or in short supply.
Graphite of carbon (
Heat to 5000 degrees Fahrenheit or 2750 degrees Celsius)
It is another method of self-lubricating.
In the sealing business, we face the challenge of sealing three types of non-lubricant.
I will solve these problems based on the difficulty of these problems: Non-lubricated liquefied hot water and many solvents belong to this category.
Insufficient lubrication of the sealing surface will cause the carbon surface to wear faster.
This surface of carbon is actually a combination of carbon and graphite, which is a good dry lubricant.
With the wear of the sealing surface, graphite is deposited on a hard surface (
You can see the black ring)
Keep the carbon
The function of a hard surface is to give graphite a place to store.
The test shows that when we seal the lubricating oil, the lubricant will be trapped between these stains (
When graphite is deposited on a hard surface, it leaves)
In many cases it turns into steam, separating the two running surfaces.
Lack of lubrication between the sealing surfaces can also lead to a form of destructive vibration called a \"slide bar.
If there is no proper lubrication, the overlapping sealing surface tries to stick together, but when the sealing drive mechanism engages to drive the lugs, \"slide\" and inertia accelerates the surface of these lugs.
Face will slow down due to poor lubrication.
This alternating \"slide\" and \"paste\" can cause serious vibration, resulting in \"debris\" of the outer diameter of the carbon surface, as well as wear and tear of the driving lugs and slots.
The amount of wear experienced by the carbon/graphite mixture is affected by the following factors: the surface speed of the sealing surface. (
Combination of Axis rpm.
Sealing surface diameter).
PV numbers don\'t really work because carbon is sensitive to \"P\" but not to \"V.
The spring load on the sealing surface and the area on the sealing surface.
Packing Box pressure.
Keep in mind that this number may vary during pump operation.
Quality and grade of carbon/graphite surface.
Surface finish and hardness of hard surfaces.
Cleanliness of sealing fluid.
Accuracy of initial installation dimensions.
Hydraulic balance designed to the face.
Hardness of carbon.
Thickness of lubricating film.
Influence of centrifugal force and hydraulic force on surface load.
There is little chance of excessive development between the sealing surface and the packing box area, because the heat generated can be taken away by the conductivity of the non-lubricating liquid around the sealing.
All of the above means elastic material (o-ring)
It may not be affected by the extra heat generated between the sealing surfaces, because the Fluid lubrication performance of your seal is poor or there is no lubrication performance.
This app has all the issues related to non-sealing
Lubricate the liquid, but now you have an extra heat problem because the gas is a good insulator to a large extent, does not let the heat generated between the surfaces dissipate into the surrounding product and metal filling boxes.
Heat can affect the seal in several ways: the filled carbon surface may be damaged depending on the selected filler or adhesive.
If the gas cannot be adsorbed into carbon/graphite, the graphite is released to provide dry lubrication, there is a special filled carbon. The elastomer (rubber part)
Probably the most sensitive to heat increases.
In dry running applications, it is very important that it is close to the sealing surface.
Heat causes initial compression-
A set of elastic materials and eventually complete destruction.
Each rubber compound has a temperature limit and is sensitive to certain chemicals and compounds.
Most fluids are affected by increased heat.
They can: crystallize, solidify, lose viscosity, evaporate, or form a film.
In each case, the sealing life is affected.
The corrosion rate of most corrosive fluids doubles at 18 degrees Fahrenheit (10°C)
The temperature rises.
Changes in the temperature of the stuffing box can affect the flatness of the seal, surface load, carbon extrusion, elastic interference, and many other tolerances.
Mixers and trailers designed with bottom stuffing boxes are particularly sensitive to this issue.
Try to locate the seal inside the mixer and outside the narrow packing box, otherwise there will be a problem with the solid packing around the outer diameter of the mechanical seal.
In this application, clean air or suitable gas flushing rarely works because air passes through a dry solid, or the container pressure will be equal to the incoming air pressure that stops flowing.
In many applications, the introduction of air into the split seal at the bottom of the gland has achieved good results.
If the seal is indeed blocked, it is easy to remove the seal for bulk cleaning.
In some applications;
It is acceptable to use compatible grease in the packing box to prevent solid entry. A balanced o-
The ring seal running at a lower motor speed should not generate enough heat to affect the lubrication quality of the grease.
Most of these applications are slow (
Below 500 rpm. )so a non-
The blocked mechanical seal works well.
If you are ready to clean it between batches with air or other gas, an external seal of non-metal can be used.
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