6 Technical data
It is important to observe the technical data during installation, operation and maintenance.
Inform personnel about the technical data.
6.2
Technical information and description of mechanical shaft seals
General considerations regarding mechanical shaft seals
The basic working principle of a mechanical seal is that the seal faces are cooled and lubricated by the process media
or the flush media.
If the seal faces are not cooled and lubricated, the temperature of the faces will increase to be above the temperature at
normal running conditions. This is referred to as “dry running”.
Dry running will shorten the lifetime of the seal and eventually cause the seal to fail. Dry running is not allowed in ATEX
applications.
Due to this working principle, there will be a small controlled leakage from the seal during normal operation. This leakage will
increase if seal failure occurs. When a seal is failing the degree of leakage can go from a drop leakage to a flush leakage
depending on the type of failure.
Note: The risk of leakage from a failing seal must be considered if pumping flammable products or other products where
leakage can lead to hazardous situations.
Single mechanical shaft seal (SSS)
The SSS is cooled and lubricated by the process media.
The process media must always be present during operation to avoid dry running.
The Critical temperature range and the minimum flow rate of the process media are stated in chapter “2 Special conditions
for safe use”.
Double mechanical shaft seal (DMS)
If continuous presence of process media cannot be guaranteed or leakage of the process media is unacceptable, a DMS
should be applied.
The DMS is cooled and lubricated by the process media and/or the flush media.
Flush media must always be present during operation of the pump to avoid dry running.
Requirements for minimum flows and max temperatures of the flush media are stated in chapter "2 Special conditions for
safe use”.
There are two basic flush principles for DMS:
-
Buffer fluid system having a pressure lower than the pumped media.
This principle will flush away possible solidifications and residues from the primary seal. It is the product media which
lubricates the primary seal faces and the flush media lubricating the secondary seal faces.
-
Barrier fluid system having a pressure of minimum 1bar above the pump inlet pressure.
This principle will cool and lubricate both the primary and secondary seal.
The barrier principle can be used in many applications but should be used if the seal configuration is SiC/SiC and the
process media viscosity is less than 1cP.
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Summary of Contents for LKHex UltraPure 10
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