Transcript Cavitation - Carbon Fiber Props Contur Composite Carbon

Cavitation
Demystified
Phase Diagram of Water
STP (Standard
temperature and
pressure)
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.
Pressure Gradient Formation



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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
Impeller Cavitation Regions
Typical Impeller Cavitation Pattern
Cavitation Demonstration
Microjetting
 Vapor bubbles do not implode symmetrically
 Because of pressure gradients, they tend to
implode towards hard objects
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
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
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
Equipment
Hydro Runner
at a small
Canadian Power
Plant
Problem
Mild cavitation
was decreasing
generating
efficiency
Solution
Runner was coated with Belzona 2141 (ACR-Fluid Elastomer) to
restore and maintain efficiency. After 2 years it is still in perfect
condition.
Equipment
ITT 3480
Impeller
Problem
Severe cavitation
was necessitating
a full rebuild
every 3 months
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!
Questions?
Thank You Very Much