PROPERTIES OF SEALANTS
Water is the most commonly used sealant in liquid ring vacuum pumps. Other fluids may be used to obtain process
compatibility. In these applications special consideration should be given to the properties of the sealant, which may affect pump
performance. Some of the properties of sealant which should be considered, are:
•
Specific Gravity
•
Specific Heat
•
Viscosity
•
Vapor Pressure
Additionally, the solubility of process gas in the sealant can be of significance and should be evaluated especially if the partial or
full recovery system is used. When water is the sealant its chemical content should be evaluated since certain conditions will
affect the service life of the pump. Generally if water is suitable to drink it is suitable for pump use. Hardness greater than 500
PPM will result in internal plating and fouling of pump parts. Service with hardness of less than 500 PPM depends upon operating
temperature and the nature of the salt deposit. Naturally occurring well water with organic acid of pH-5 or higher is generally
suitable, however pH of 7 or higher is preferred. Chemically treated water with sulfur content requires pH-7 or more. Water, which
has a pH less than 5 should be treated, or the pump should have special materials of construction. If internal scaling affects
performance, a water treatment specialist should be consulted. TVBS recommends that sealants and sealant systems be
carefully evaluated and we invite you to discuss them with your TVBS Sales Professional or our Application Engineers.
Sealant Temperature
The rated volumetric capacity (ACFM) of a pump is based upon the use of incoming seal water at 60° F (15° C) . Seal water
temperature affects the pump capacity. Table 2 provides data which when applied to the below formula will give the pumping
capacity on dry air at water temperature other than 60° F (15° C) . To calculate volumetric pumping capacity (ACFM) or to
approximate the capacity when using water at other than 60° F (15° C) the following formulas apply:
S
a
= (S
60
)(P
1
-P
c
)
(P
1
-13.3)
Where: S
a
= Actual capacity in ACFM, at P
1
S
60
= Pump capacity with 60° F (15° C) sealant at P
1
This data is shown on our Liquid Ring Vacuum Pump Brochure
#4120.
P
1
= Inlet pressure in Torr
P
c
= Vapor pressure of sealant at actual sealant temperature
Table 2 on the facing page shows the vapor pressures of water at various temperatures.
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