Unigas KPBY70, Manual Of Installation - Use - Maintenance

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PART II: INSTALLATION
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Recommendations to design heavy oil feeding plants
This paragraph is intended to give some suggestions to make feeding plants for heavy oil burners. To get a regular burner operation, it
is very important to design the supplying system properly. Here some suggestions will be mentioned to give a brief description.
The term “heavy oil” is generic and summarises several chemical-physical properties, above all viscosity. The excessive viscosity
makes the oil impossible to be pumped, so it must be heated to let it flow in the pipeline; because of the low-boiling hydrocarbons and
dissolved gases, the oil must be also pressurised. The pressurisation is also necessary to feed the burner pump avoiding its cavitation
because of the high suction at the inlet. The supplying system scope is to pump and heat oil.
The oil viscosity is referred in various unit measures; the most common are: °E, cSt, Saybolt and Redwood scales. Table 3 shows the-
various unit convertions (e.g.: 132 cSt viscosity corresponds to 17.5°E viscosity).
The diagram in Fig. 24 shows how the heavy oil viscosity changes according to its temperature.
Example: an oil with 22°E viscosity at 50°C once heated to 100°C gets a 3 °E viscosity.
As far as the pumping capability, it depends on the type of the pump that pushes the oil even if on diagram in Fig. 24 a generic limit is
quoted at about 100 °E, so it is recommended to refer to the specifications of the pump provided.
Usually the oil minimum temperature at the oil pump inlet increases as viscosity does, in order to make the oil easy to pump. Referring
to the diagram on Fig. 25, it is possible to realise that to pump an oil with 50°E viscosity at 50°C, it must be heated at about 80°C.