Dangers of operating a centrifugal pump at low flow rates
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Our company has a centrifugal pump of the model ISR80-50-230, with a flow rate of 60, a head of 54, and a designed operating temperature of 55°C. Later, due to process requirements, it was changed to a heavy oil blending pump. The pump operates for extended periods at low flow rates, with flow rates around 7-10, and the medium temperature is approximately 70-90°C. This pump requires frequent repairs, with seal leakage and bearing damage (on the side of the pump body) being the most common issues! There is no return line, but there is a crossover at the outlet that spans over the inlet. I would like to ask fellow sailors: how much damage can running the pump under such conditions cause to the pump itself? Where is it specifically reflected? Does the medium temperature affect the mechanical seal? By the way, are there any good oil-resistant O-rings (for gasoline and diesel)? Thank you all!
If the pump operates at low flow rates for an extended period of time, it is functioning at its inefficient point; simultaneously, this causes uneven stress on the components inside the pump, leading to wear or damage of these components. As a result, in practical use, the bearings, wear-resistant rings, or mechanical seals are prone to damage! If the poster needs it to operate in this way, they could consider using that frequency converter or an impeller-type cutter pump for this purpose! The export pressure conditions need to be taken into consideration specifically!
Continuous backflow leads to increased shaft power consumption, resulting in wasted effort. Furthermore, the backflow causes the liquid temperature to rise, which has a significant impact on non-metallic components and shortens their lifespan.
Continuous backflow leads to increased shaft power consumption, resulting in wasted effort. Furthermore, the backflow causes the liquid temperature to rise, which has a significant impact on non-metallic components and shortens their lifespan.
At a certain minimum flow rate, severe backflow of the fluid occurs within the pump, which leads to temperature increases and vibrations; this in turn shortens the lifespan of the bearings and mechanical seals and causes damage to them
If it operates at a low flow rate for a long time, wear between the components is inevitable since it is not working at its optimal operating point. It is recommended to replace the impeller in order to change its optimal operating condition; otherwise, another pump could be used – IS pumps are not very expensive these days.
It is mainly due to uneven stress, backflow inside the pump, and worn components.
Firstly, when operating at low flow rates, the pump vibration increases, and the axial forces are not properly balanced, which reduces the service life of the bearings. Inadequate flushing of the mechanical seal also reduces its service life. Additionally, backflow can raise the temperature, causing some non-metallic components to be easily damaged.