Why is Cavitation Damaging to your Pump?

Cavitation is one of the biggest troubles faced by pump owners. Unfortunately, most pump owners blame the pump for the issue, when the actual problem lies elsewhere. In 9 out of 10 pump system failure, the root cause of the trouble is not the pump but other issues like cavitation, lack of maintenance, or poor system design. While we have previously written about the causes of cavitation, in this post, we take a look at the damages caused by cavitation.

What is cavitation?

Cavitation or entrapped gas inside the pump leads to problems with pump performance. Cavitation occurs when the liquid inside the pump turns into vapour due to low pressure. This transformation occurs when there is not sufficient pressure at the suction end of the pump. As a result of cavitation, air bubbles form inside the pump at low pressure. When the liquid moves from the impeller’s suction to the delivery end, the bubbles break. This generates a shockwave that hits the impeller creating vibrations and mechanical damage to the pump. When left unchecked, cavitation could even lead to complete failure of the pump system.

Why is Cavitation Damaging to Pumps?

Very often, pump owners ignore cavitation until it becomes a severe issue. After all, cavitation is nothing but a few vibrations, right? No! Let’s take a look at the various damages to pumps caused by cavitation.

#1: Damage to the Mechanical Seals of the Pump

Mechanical seals are a vital part of a pump, as it prevents dirt and other foreign objects from entering the casing. It also prevents the pumped liquid from escaping into the environment. Damages to the pump’s mechanical seals increase operating costs and reduce the efficiency of the pump. Cavitation is damaging to the seal faces. When left unchecked, it causes the seals to run dry without sufficient lubrication or cooling. Cavitation leads to wear and tear of the mechanical seals, as well.

#2: Damage to Shaft Alignment

Shaft misalignment can occur due to several reasons. However, the primary cause of shaft alignment is vibrations caused by cavitation. As a result of these vibrations, the pump shaft expands, leading to misalignment.

#3: Damage to Bearings

Bearing life is significantly reduced due to the vibrations caused by cavitation. The vibrations in the pump shaft are passed on the bearing housing from the casing. This causes the rollers and balls in the system to block the raceways, which, in turn, leads to multiple bents. When left unchecked, the raceways resemble a corduroy fabric, with plenty of bents. This, in turn, cuts down bearing life, leading to frequent repairs.

#4: Damage to the Pump Impeller

When the pressure in the impeller’s eye falls below the vapour pressure of the transferred fluid, it leads to the formation of gas bubbles, which causes cavitation. These bubbles implode (collapse) as the pass from the low-pressure zones in the pump to high-pressure zones. As the air bubbles collapse, the transmitted liquid hits the metal parts of the casing, with the velocity of sound. You can quickly identify cavitation in the pump by looking out for this sound – the sound of marbles or pebbles rattling inside the pump. The technical term for this sound is “water hammer.” The force of these shockwaves hitting the inside of the pump can cause permanent damages to the impeller over time.

How to prevent these damages?

Pump cavitation, when left unchecked, can severely impact the efficiency and performance of your pump. You can prevent these damages by keeping cavitation in check. For that, you need to understand the root cause of cavitation in your pump. We also recommend that you refer to the pump operational curves provided by your manufacturer. This helps you to know the limits of the operational boundaries of your pump. This gives you a clear insight into what’s going wrong with your pump, helping you pinpoint the cause of cavitation in the first place. To correct cavitation, you need to start by calculating the total dynamic head of the pump. This has to fall within the operating range of the pump. Also, ensure that the pumping system is appropriately designed to avoid suction cavitation. To correct cavitation on the discharge end, you need to reduce the head or increase the flow. You can also try to change the operating speed of the pump to eliminate cavitation. Suction cavitation is mostly caused due to an NPSH (Net Positive Suction Head) problem. To rectify this issue, you need to identify the source of the high vacuum. If the suction line is plugged, clean it and do not blowback the dirt into the liquid source, as it will come back again to block the line. If the suction life is too high, it should be moved closer to the liquid. Also, if the suction lines are too long, then they should be shortened. On the other hand, if it’s too small, it needs to be enlarged. For over three decades, Sintech pumps have manufactured high-quality and high-performance pumps for various industrial sectors. To know more about the causes of cavitation in your system, get in touch with our pump experts.