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Cavitation Demystified. Phase Diagram of Water STP (Standard temperature and pressure)

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Presentation on theme: "Cavitation Demystified. Phase Diagram of Water STP (Standard temperature and pressure)"— Presentation transcript:

1 Cavitation Demystified

2 Phase Diagram of Water STP (Standard temperature and pressure)

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 Mild cavitation was decreasing generating efficiency 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 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


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