【2026 Transmission Equipment】Centrifugal pump does not deliver flow after starting
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Why doesn’t the centrifugal pump deliver flow after it is started (with zero outlet pressure)? The main reason why a centrifugal pump does not deliver flow is either an \"unfilled inlet medium\" or a \"blocked flow channel\"; the four most common causes along with their solutions can be applied directly. Common causes: ① Air leakage in the inlet pipeline, resulting in air locking (such as damaged flange gaskets) ； ②The inlet filter is clogged (impurities have accumulated by more than 50%), preventing the medium from being drawn in ； ③The impeller is damaged (blades are broken or the wear exceeds 3mm), and thus cannot generate centrifugal force ； ④The pump body does not exhaust air completely, leaving residual air in the flow channels. Solutions: ① Replace the sealing gasket of the inlet pipeline, check for leaks using soapy water to ensure there are no bubbles ； ②Disassemble and clean the filter, and replace the filter element (filter precision shall meet the process requirements) ； ③Inspect the impeller; if wear is beyond the acceptable limits, replace it. In a certain refinery, a centrifugal pump used in the catalytic unit failed to deliver fluid due to a broken impeller, but normal operation was restored 30 minutes after the impeller was replaced ； ④Before starting, fully open the pump’s exhaust valve until continuous liquid is discharged, then close it.
Below: Centrifugal pump vs. axial flow pump, for reference. Centrifugal pump: Uses centrifugal force to \"fling\" water out. Axial flow pump: Functions like a propeller, \"pushing\" water forward. One relies on flinging, the other on pushing; their principles are completely different, and their application scenarios vary greatly as well.
I. Axial flow pump: The “propeller” in pipelines, moving in a straight line. Axial flow pumps belong to the category of vane pumps, and their main feature is that the liquid flows in the direction of the pump shaft, without any turning or change in direction.
1. Working principle: The impeller of an axial flow pump is similar to a marine propeller, with blades in the shape of wings. During rotation, the blades generate lift and thrust on the liquid, directly \"pushing\" the fluid forward in an axial direction. No radial ejection, no 90° turns, a straight path the entire way.
2. Core structure: Rotor: The component that performs the work; it has propeller-like blades that generate axial thrust. Guide vane: Installed behind the impeller, it straightens the rotating water flow, eliminates vortices, and converts kinetic energy into pressure energy. Straight-through flow channel: The inlet and outlet are on the same straight line, with the fluid undergoing almost no turning.
3. Features: High flow rate, low head; small footprint, high efficiency. Widely used in circulating water systems, flood drainage, and high-flow transportation
II. Centrifugal pumps: The most common type of \"water-dispelling pump.\" Over 90% of the pumps used in chemical plants are centrifugal pumps. Their working principle is well-known: water is drawn in axially and discharged radially, first being accelerated and then pressurized.
. Working principle: Suction: Liquid is drawn in from the center of the impeller, creating a low pressure at the center. Acceleration: The high-speed rotating impeller uses centrifugal force to throw the liquid toward the edges, achieving maximum velocity. Pressure conversion: High-speed liquid enters a volute shaped like a snail shell; as the flow channel widens gradually, the flow velocity decreases, and kinetic energy is converted into pressure energy, which is used to push the water out. Simply put: the impeller is responsible for acceleration, while the volute is responsible for pressurization.
2. Features: Low to medium flow rate, high head pressure; capable of generating high pressure and delivering fluid to high locations (distillation towers, reactors, surge tanks). It has the widest range of applications and can be used with various types of fluids
The most vivid analogy: Centrifugal pump: like a wringer, which flings water out; Axial flow pump: like an electric fan, which pushes air (water) straight forward