Help with Cavitation
localenergystrategies
Cavitation is the formation of vapour cavities in a liquid – i.e. small liquid-cavitation-free zones ("bubbles" or "voids") – that are the consequence of cavitational forces acting upon the cavitational liquid. It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low. When subjected to higher pressure, the voids implode and can generate an intense shockwave. Cavitation is a significant cause of wear in some engineering contexts. Collapsing voids that implode near to a metal surface cause cyclic stress through repeated implosion. This results in surface fatigue of the metal causing a type of wear also called "cavitation". The most common examples of this kind of wear are to pump impellers, and bends where a sudden change in the direction of liquid occurs.
If this is the failure mechanism then I expect our acoustic leak detector should pick this up.
So what is the fix? What are the options?
1) flash the condensate from high pressure to low in various building basement mechanical rooms and intentionally segment the campus from complete steam outage to repair, and avoid by design the single point of failure
2) find welding "compatible" alloy that is cavitation resistant to cut in and replace elbows with.
Any other fixes or ideas?
Maciejczyk, Joseph
Question: What is your hp condensate pressure?
Joseph P. Maciejczyk, PE
Associate
Structural Integrity
Associates, Inc.
Experts in the prevention and control of structural and mechanical failures
804-502-2820 Cell/SMS/Viber/WhatsApp
E-mail:
jm...@structint.com
Web Site: www.structint.com
--
You received this message because you are subscribed to the Google Groups "Distribution Forum" group.
To unsubscribe from this group and stop receiving emails from it, send an email to
distribution-fo...@googlegroups.com.
To post to this group, send email to
distribut...@googlegroups.com.
Visit this group at http://groups.google.com/group/distribution-forum.
For more options, visit https://groups.google.com/d/optout.
Izzy Rivera
We make a clamp-on ultrasonic flowmeter. Our meters are aeration sensitive, we have a diagnostic that detects aeration. So our meter can tell when the liquid is aerated. Cavitation tends to occur when pressure is not high and the liquid already is carrying compressed air, air that is compressed from the pressure. Pressure drops cause decompression of the air, i.e. cavitation. Elbows do not cause cavitation to the degree that we pick up the aeration in the liquid. Valves are the highest source of cavitation, but you are far more likely to see cavitation when the liquid is already holding a lot of compressed air. Cooling tower water brings lots of air, and condensate at low pressures can contain air. Elbows may cause some micro cavitation, and elbows will get the abrasions from profile swirls. Condensate pipe have a tendency to scale up heavily. Sometimes we struggle to find a good signal through the scaling and we find that we can get a much better signal closer to an elbow. That’s because the abrasive effect of the swirls keep the scaling off the internal pipe walls near the elbow.
Regards,
Izzy Rivera
Product Sales Manager
Service Manager
Flexim Americas Corp.
250V Executive Drive
Edgewood NY 11717
631-492-2300 Main
631-495-1857 Cell
Maciejczyk, Joseph
HP condensate elbow failures due to cavitation damage – comments
In most component failures, we would perform a forensic assessment at our metallurgical laboratory to isolate the exact damage mechanism.
Assuming this failure is from a cavitation damage mechanism:
· Some system design changes that may help are increasing the radius of the troubled elbow and/or increasing the pipe diameter to reduce flow velocity. Both of these changes would tend to reduce the intensity of the cavitation thus mitigating the failure mechanism.
· Some material changes that may help would be using a harder carbon steel component or changing the component to a stainless steel; both options would tend to mitigate the issue.
I hope this helps. Please contact me if you have any questions.
Regards,
Joe
Joseph P. Maciejczyk, PE
Associate
Structural Integrity
Associates, Inc.
Experts in the prevention and control of structural and mechanical failures
804-502-2820 Cell/SMS/Viber/WhatsApp
E-mail:
jm...@structint.com
Web Site: www.structint.com
From:
distribut...@googlegroups.com [mailto:distribut...@googlegroups.com]
On Behalf Of localenergystrategies
Sent: Tuesday, November 25, 2014 11:06 AM
To: distribut...@googlegroups.com
Subject: {Distribution Forum} Help with Cavitation
Hi everyone,
--