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
All mechanical shaft seals are dependent upon sufficient lubrication and cooling of the sealing surfaces. Otherwise increased
temperature will occur.
Due to the lubrication of the seal faces, all mechanical shaft seals will generate a small leakage. This leakage will increase in
case of failure of the seal.
Due to the mentioned leakage, the use of a single shaft seal is not recommended when pumping flammable or other products
where leakage can lead to dangerous situations.
Single shaft seal (SSS)
The single shaft seal is cooled and lubricated by the product pumped through the pump. The lack of sufficient cooling
or lubrication will cause the seal to fail. If the shaft seal fails, it will start to leak and in some cases exceed the temperature
class. If sufficient cooling and lubrication cannot be ensured in any other way, a combination of flow rate and temperature
should be monitored.
Double mechanical shaft seal (DMS)
If continuous lubrication and cooling cannot be guaranteed or leakage of the pumped fluid is unacceptable, a double
mechanical shaft seal should be used together with an additional auxiliary support system.
There are two basic types of support system; a buffer fluid system having a pressure lower than the process pressure or a
barrier fluid system having a pressure of minimum of 1bar above the process pressure in all situations. If the viscosity of
the processed fluid at process temperature is less than 10cP when using silicon carbide versus silicon carbide only barrier
fluid system must be used.
To ensure that the temperature, flow rate and pressure are within the specified limits, these should be monitored on both
support systems:
-
Temperature should be measured on the outlet from the seal housing ensuring that the temperature of the fluid supplied to
the seal arrangement is within the specified limits.
-
Flow rate should be measured on the inlet of the seal housing ensuring that the correct flow rate is applied to the seal
arrangement.
-
Pressure should be measured on the inlet of the seal housing ensuring that the pressure applied to the seal arrangement
does not exceed the specified limits.
To prevent hazardous reaction between:
-
The buffer/barrier fluid and materials of construction the materials of construction shall be suitable for the application.
-
Processed fluid and buffer/barrier fluid the buffer/barrier fluid shall be suitable for the application.
All equipment and systems used for checks and monitoring must be ATEX compliant and comply with
EN 13463-6: 2005 or equivalent relevant standards.
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