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Get in-depth information about Blackmer pump and compressor technologies while learning why our solutions are the ideal choice to help solve your most critical fluid-handling applications.

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Blackmer® is the leading global provider of innovative, high-quality sliding vane, centrifugal, screw and regenerative turbine pump, and reciprocating gas compressor technologies for the safe transfer of liquids and gases.

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Blackmer provides innovative product transfer solutions for many markets and applications, including in the chemical process, energy, transport, military & marine; general industrial, and oil & gas industries.

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What is Pump Cavitation?

Pump cavitation is a phenomenon in which a pumping system’s net positive suction head available (NPSHa) is not in balance with the net positive suction head required (NPSHr). When an NPSH deficit is created, it leads to the formation of vapor bubbles in the liquid. When these vapor bubbles are subjected to higher pressure during a pump’s pressure stage, they implode. This implosion causes the liquid walls to collapse and produce shock waves of incredible force that cause destruction upon impact.

Reasons Why Pump Cavitation Happens

There are a number of pumping setup conditions that can result in a dangerous NPSH scenario. These conditions include:

  • Excessive suction-lift requirements
  • Long piping runs
  • Flow restrictions at the inlet, such as the presence of a piping elbow
  • A clogged strainer
  • Partially closed valves that can restrict flow
  • Unnecessarily high flow velocities that are caused by undersized piping
  • Pumping liquified gases
  • Non-vented applications
graphic_Excessive Lift

Excessive suction lift

graphic_Long Pipe Run

Long piping runs

graphic_Flow Restrictions

Flow restrictions at inlet

graphic_Clogged Strainer

Clogged Strainer

graphic_Undersized Piping

Undersized Piping

Signs that Pump Cavitation is Happening

The most obvious signs of pump cavitation are vibration and noise during system operation, often sounding like the pump is being filled with bits of gravel. Other signs of cavitation include a reduction in discharge pressure or flow, increased power consumption and debris in the discharge liquid.

Applications that Feature Cavitation

While pump cavitation can occur in a wide variety of applications, it most often occurs when transferring fluids with high vapor pressures, such as liquefied petroleum gas (LPG), anhydrous ammonia (NH3), gasoline, acetone, various types of refrigerants and condensates, and those that are highly viscous. These applications are more susceptible to cavitation because the vapor pressure of these liquids is greater than any NPSH provided. In other words, these applications operate at a deficit from the start: the liquid demands more than what the system could ever provide.

Negative Effects of Cavitation on Pumps

If cavitation-causing conditions are present in an operation and allowed to persist, damage to the pump and its components is almost certain to occur. In fact, cavitation damage could set off a chain reaction of negative effects that can include loss of operational efficiency, elevated maintenance and part-replacement costs, pump downtime and, in the worst-case scenario, total pump failure.

Dynamic components are especially sensitive to cavitation. Specifically, the pump’s mechanical-seal faces will briefly separate as the implosions occur. The shock-wave pulsations create a condition known as “chattering,” which leads to premature wear and failure of mechanical seals. Additional failure should be expected in other wetted parts, such as bushings, impellers, back covers, volutes, casings, heads, gears, idlers, and vanes.

graphic_Noise Level

How Blackmer Sliding Vane Pumps Solve Cavitation

The key to eliminating pump cavitation and its harmful side effects is setting operational parameters so that the NPSHa will always meet the NPSHr. However, most systems require a bulletproof solution designed for the worst conditions – a one-of-a-kind technology designed for unforgiving physical constraints and inevitable vapor formation. Blackmer has found a solution with the development of the Cavitation Suppression Liner.

graphic_Blackmer CSL

The Cavitation Suppression Liner defeats cavitation through a design that defuses or mutes destruction before vapor implodes. This unique feature creates internal recirculation jets that break apart vapor bubbles before implosion. While the vapor levels are not reduced, the size of each vapor bubble becomes a fraction of what it would have been. The fact is this: smaller bubbles yield smaller implosion reactions.

The Cavitation Suppression Liner also allows a controlled amount of fluid at discharge pressure to bleed back toward the suction of the pump. This breaks the larger vapor bubbles apart into smaller vapor bubbles before they have a chance to implode. The net result is less noise (up to 15 dbA), less vibration, less wear, and less chance that the pump will be susceptible to disruptive failures.

graphic_Blackmer CSL From Animation