Dickow Hot Oil Pump Sealless

PUMP CONCEPTS

Low-cost pump concepts normally use standard foot-mounted ductile iron volute casings with a standard single mechanical seal that is separated from the hydraulic parts by an air-cooled intermediate casing. The temperature limit is typically 350°C. However, in applications above 320°C this standard foot-mounted casing can be overstressed and deformed by typically unknown forces and moments generated by the piping system during heating of the plan. For temperatures above 320°C (up to 400°C) a pumping concept based on the chemical standard pump hydraulics is often a better solution. The pump casings can be equipped with centerline mounting, the material can be improved to cast steel and different sealing systems can be used. When cast steel is used, it is also possible to use welded drain pipes which are getting more common nowadays.

SEALING SYSTEMS

Especially for low viscosity and high temperature synthetic oils (e.g. Dowtherm or Diphyl), sophisticated tandem seal arrangements or magnetic couplings are required. In Figure 3, an ideal tandem seal arrangement is shown. In order to minimize the influence of solids (such as cracking particles) on the seal lifetime, the seal face combination is SiC against SiC (silicium carbide is a very hard ceramic material), the bel- lows are rotating in order to prevent clogging and the seal chamber is designed as large as possible to prevent the accumulation of solids. The two seals (on the product and atmosphere side) are lubricated by a pressureless aircooled thermosiphon vessel which also prevents damage to the seals, even during
dry running conditions. A constant lubrication and circulation flow is generated by a pump ring. Failure of the product
seal can be detected by a level switch in the vessel and the atmosphere seal will prevent leakage. For applications above 350°C, it is possible to have additional water cooling with a cooling coil inside the thermosiphon vessel.

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Dickow Hot Oil Pump Sealless