Why do pumps cavitate

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What is pump cavitation? Suction Cavitation When a pump is under low pressure or high vacuum conditions, suction cavitation occurs. Make sure it is running at its best efficiency point. Running the pump off its best efficiency point not only causes excess recirculation, expect excessive heat, radial loads, vibration, high seal temperatures, and lowered efficiency.

Re-evaluate pipe design - Ensure the path the liquid takes to get to and from your pump is ideal for the pump's operating conditions. Both result in suction problems and pump cavitation. Struggling with a cavitation problem? Ask us about it! We gladly provide technical assistance to businesses in Wisconsin, Minnesota, Iowa and Upper Michigan.

Previous Story. Next Story. Equipment Maintenance. September 29, When suction lift is too high to maintain pressure, move the pump closer to the fluid source or move the fluid source closer to the pump. Enlarging suction lines can also be effective. In some obvious cases, a blockage occurs in piping or hoses near the pump. Clear those blockages to resolve the issue. Clean suction lines by clearing debris. The best way to prevent cavitation is to select the right pump for the application.

Cavitation increases as pump head falls or as capacity increases, so selecting the correct pump to maintain a positive margin of NPSHa above NPSHr is the best first move. NPHS at the inlet depends on atmospheric pressure, friction losses in the suction piping, and flow velocity. Discharge cavitation occurs when pressure at the discharge end of the pump is too high. High discharge pressure limits the volume of fluid flowing out of the pump, causing high-velocity fluid to recirculate between pump impeller and housing, causing cavitation.

After proper pump selection, regular maintenance is the best way to avoid cavitation. Routine maintenance extends pump life and consistent performance. The best ounce of cavitation prevention is pump selection and system design for maintaining pressure and flow. The goal of installation is therefore to maintain net positive suction head available NPSHa at greater than net positive suction head required NPSHr by considering four key variables:.

Physically install the pump so the water flows into the pump suction inlet smoothly. Make sure that the suction lines leading to the inlet of the pump are adequately sloped to ensure that the pump housing is flooded.

Pumps, and especially centrifugal pumps, work most efficiently when the fluid travels in a smooth, laminar flow, and turbulence of any kind reduces pump efficiency, so positioning the pump as close as possible to the fluid source makes sense. In general, you want 12 cm of straight pipe for every centimeter of pump suction diameter. To maintain laminar flow, connect pipe diameters of straight piping to the pump inlet. Do not include elbows , reducers , valves , or strainers within the final length of pipework.

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. 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.

Higher velocities can create more friction and more noise. Suction lift can place higher than necessary energy demands on pumps, increase turbulence, and decrease NPSHa. The solution is to install the pump below the water level of the supply tank and meet standards for piping design.

As 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. Pipe length, diameter, and flow rate all affect friction loss. Good piping layouts prevent cavitation by helping to maintain constant velocity.

Obstructions in piping layouts affect flow velocity, which changes fluid pressure, which can cause cavitation. When your pump, pipe, or hose sounds like marbles or gravel are circulating, you're witnessing cavitation and need to take immediate action or risk severe damage to components.

When cavitation does occur, you need a trusted partner that can diagnose the cause, provide a long-term solution, and repair or replace parts that are damaged. CSI's pump service and maintenance program is designed to take the irritation and guesswork out of dealing with pump cavitation. Each audit and repair that CSI completes include an evaluation by an OEM-trained pump technician, a report on the findings, and all the materials required to perform the service.

Call us today to schedule your next system audit or pump repair! Central States Industrial Equipment CSI is a leader in distribution of hygienic pipe, valves, fittings, pumps, heat exchangers , and MRO supplies for hygienic industrial processors, with four distribution facilities across the U. CSI also provides detail design and execution for hygienic process systems in the food, dairy, beverage, pharmaceutical, biotechnology, and personal care industries.

Specializing in process piping, system start-ups, and cleaning systems, CSI leverages technology, intellectual property, and industry expertise to deliver solutions to processing problems. More information can be found at www. This guide is intended for engineers, production managers, or anyone concerned with proper pump selection for pharmaceutical, biotechnology, and other ultra-clean applications. A clogged filter or strainer, for example, can easily restrict flow and lead to pump cavitation.

Similarly, a restricted or flimsy inlet hose might collapse and cause issues. Fluid viscosity is a major contributor, too, especially when combined with the wrong hose.

Imagine drinking a milkshake through a thin straw: the combination of the thick viscosity, pressure, and weak structure of the straw causes it to collapse and restricts the flow. Or consider if that straw has a pinhole in it; the leak would also affect flow and pressure. Similar phenomena can occur in pump systems. If you use a solid metal hose or a system is plumbed with hard PVC or copper piping, it could cause water hammering.

Finding the right combination of dampening with a strong yet soft inlet hose or flexible PVC is ideal. Here at Pumptec, we use pulse hoses with metal springs inside them to add strength and rigidity.

The position of the reservoir tank also makes a difference. If the tank is positioned below the pump, the pump will need to decrease pressure to draw the fluid vertically through the inlet piping. The longer the inlet hose and the farther the vertical distance between the tank and the pump, the greater the chance of creating a vacuum and cavitation. Heated liquids are a major contributor to cavitation, too, especially as the hot fluid approaches the boiling point and creates additional vapor pressure.

The easiest way to achieve this is to have the tank containing the heated fluid elevated above the pump so that it is gravity fed into the pump system. In all these instances, the flow is being disrupted or poorly executed, causing the discharge pressure to fall. The pump is basically being starved of fluid, resulting in cavitation.