Obstructions in piping layouts affect flow velocity, which changes fluid pressure, which can cause cavitation. Good piping layouts prevent cavitation by helping to maintain constant velocity.

Pipe length, diameter, and flow rate all affect friction loss. Higher velocities can create more friction and more noise.Īs fluids pass through a pipe, friction between the fluid and the inside surface of the pipe causes turbulence, which slows the fluid and results in a pressure drop. In general, keep suction pipe velocities below 2 m/s. Larger pipework requires a reducer before the pump inlet and must be designed carefully to avoid turbulence and creation of air pockets at the inlet. Suction-side piping is commonly one or two sizes larger than the pump inlet - never smaller than the pump’s inlet. Also, the piping arrangement must not cause strain on the pump casing, so pumps can never support the piping for suction or discharge. Connecting an elbow directly to the pump flange, for example, draws fluid towards the outer curve of the elbow instead of directly into the eye of the impeller. Do not include elbows, reducers, valves, or strainers within the final length of pipework.

To maintain laminar flow, connect 5-10 pipe diameters of straight piping to the pump inlet. In general, you want 12 cm of straight pipe for every centimeter of pump suction diameter. Disrupted or poorly executed processing lines can cause suction or discharge pressure to fall, which leads to cavitation. In the case of cavitation, this formation and collapse is both rapid and violent. The bubbles collapse when they reach areas of the liquid where the pressure is above the vapor pressure. As the pressure inside the pump falls below the liquid's vapor pressure, bubbles form. Under normal atmospheric pressure conditions, fluids have predictable vapor pressure.

When pressure acting on the liquid (Net Positive Suction Head Available) is too low, bubbles form, and as the liquid accelerates because of impeller rotation, pressure increases and the bubbles collapse. The eye is where fluid is drawn into the impeller and where the rotation of the impeller begins to act on the fluid. For positive displacement pumps, the lowest pressure occurs just prior to rotor meshing for centrifugal pumps, lowest pressure is near the eye of the impeller.Ĭavitation is possible in all pump types and since its principles are essentially the same, we will focus on centrifugal pumps. The inlet, or suction side of a pump is the point of lowest pressure in a given pump. Pumps are designed to work with a full flowing water supply, but in some cases a flooded inlet is not enough to maintain pressure required to prevent cavitation.

View all Corrosion-Resistant Super Alloys™.

Temperature Gauges, Transmitters & RTD Components.

Streamline In-Line Filters and Strainers.

View All Tubing, Fittings, Installation.

Etank positive