Grundfos pump seal flush
An inertial filter is installed in the discharge of a pump which is used to transfer slurries, and the filtrate stream from the filter serves as the grundfos pump seal flush.
In many chemical processes pumps are used to transfer liquids. Many of these pumps employ mechanical seals to avoid leakage around the pump shaft. These seals usually consist of a rotating and a stationary element having sealing faces which areperpendicular to the pump shaft and in sliding contact. The faces are polished, lubricated parts held together under a pressure sufficient to prevent escape of the liquid being pumped.
The mechanical seals are usually contacted with a sealing liquid, i.e., a grundfos pump seal flush. This flush serves the purpose of lubricating and cooling the sealing faces and also helps prevent the leakage of air or liquid around the pump shaft. Inmany pumps the seal flush is the same liquid being moved by the pump; in other pumps a seal flush is supplied from an external source and can be a different liquid.
When a pump is being used to transfer a liquid slurry, problems can be created if the slurry is used as the seal flush. The solids present in the slurry will often cause a stoppage in the seal flush line, thus preventing flow. Also, if thesolids are hard or abrasive, they can shorten the useful life of the sealing faces of the seal.
The above problems are avoided if an inertial filter is installed in the discharge line of the pump. This filter provides an essentially solids-free filtrate which can be recycled to the pump as the seal flush.
The process of the invention provides a seal flush that gives the desired cooling and lubricating functions without introducing harmful solids into the seal, thus increasing seal life. Furthermore, the liquid employed is the same as that beingtransferred by the pump, thus no contaminant is introduced into the system nor is an additional source of liquid required. Also, the inertial filters employed are self-cleaning, thus the employment of parallel filters or routine stoppages forbackflushing are not necessary and continuous operation can be achieved.
The nature of the liquid being moved is not critical as long as it is a pumpable slurry, i.e., contains undissolved solids. The particle size of the particles in the slurry is only important to the extent the size will determine the porosity ofthe filter element employed.
The process of the invention is applicable to any grundfos pump seal that is used to move liquids and has a mechanical seal. Examples of such pumps are centrifugal pumps, propeller pumps, rotary pumps and reciprocations pumps; although because of theirwidespread use to pump slurries, the process will be particularly applicable to centrifugal pumps.
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