1. Cavitation Demystified
This is a nice short and hopefully informative presentation on cavitation. I put this together because so many customers I visit mistake

2. Phase Diagram of Water STP (Standard temperature and pressure)
I’m quite sure everyone in the room is familiar with the three phases of water; solid, liquid, and gas. For this example we’ll be starting at STP (standard temperature and pressure). Water is most commonly boiled by heating it at constant pressure [click]. What is less intuitive is that water can also be boiled by dropping the pressure at a constant temperature [click]. Indeed, any change or changes in temperature or pressure that move across the normal boiling curve result in a transition from liquid to gas [click].

3. Cavitation – A Simple Process
Cavitation is the formation and subsequent implosion of vapor bubbles in a fluid
Caused by significant pressure gradients within process equipment
Pressure gradients typically generated by high velocity flow around
Valves – throttling (partially closed valves)
Vanes – moving portions of pump impellers
Protrusions – pitot tubes, vortex shedders, etc.

4. Pressure Gradient Formation
Arrows indicate flow direction
Fluid is compressed above vane creating a high pressure region
Fluid is rarified below vane creating a low pressure region
Behind this low pressure region is another high pressure region

5. Impeller Cavitation Regions

6. Typical Impeller Cavitation Pattern

7. Cavitation Demonstration

8. Microjetting Vapor bubbles do not implode symmetrically
Because of pressure gradients, they tend to implode towards hard objects

9. Microjetting – High Speed Photograph
Microjet has formed
Vapor bubble is in the
process of imploding
towards the nearby hard
surface
Shockwaves generated by microjetting can be up to 145,000,000 psi
This pressure vastly exceeds the compressive strength of any metal alloy

10. The Alternative to Rigid - Elastic
Cavitation energy can be dissipated two ways
Into a rigid metallic substrate
Plastic deformation
Ultimate compressive failure
Into an elastic substrate
Hook’s Law
We modified our Durable & Abrasion Resistant Elastomer to better withstand cavitation

11. Belzona 2141 (ACR-Fluid) Project sprung from a US Coast Guard request
Products had to survive 16+ hours in a high speed test
At the time, the best product lasted 12 hours
Second formulation Belzona submitted lasted 20 hours
Coast Guard currently in the process of coating all rudders with Belzona 2141 (ACR-Fluid) to resist the severe cavitation of their service

12. Equipment Problem Solution
Hydro Runner at a small Canadian Power Plant
Problem
Mild cavitation was decreasing generating efficiency
Scored shafts are most commonly repaired with Belzona 1111 (Super Metal) which here is applied via a split former technique.
Solution
Runner was coated with Belzona 2141 (ACR-Fluid Elastomer) to restore and maintain efficiency. After 2 years it is still in perfect condition.

13. Equipment Problem Solution ITT 3480 Impeller
Severe cavitation was necessitating a full rebuild every 3 months
Scored shafts are most commonly repaired with Belzona 1111 (Super Metal) which here is applied via a split former technique.
Solution
Impeller received two coats of Belzona 1321 (Ceramic S-Metal) and a final coat of Belzona 2141 (ACR-Fluid Elastomer). Impeller now lasts 28 months between rebuilds!

14. Questions?
Thank You Very Much