Cavitation?

Hi All

Some time ago, I reported unstable conditions in a condensate pipe that fed into a flash tank. The problem was simply a large pressure drop across the valve, which caused bubbles in the pipe. These bubbles immediately collapsed creating the instability.
The problem was solved by relocating the valve right next to the flash tank, hence the bubbles had little opportunity to form inside the pipe, but were expanded into the large flash tank. This solution worked perfectly. My thanks to Phil Thompson, who supported this remedy.

In another area, a "similar" problem appeared due to plant modifications. We're gravity feeding water into a contact heater that operates under sub-atmospheric pressure 0.5 bara, (7.25 psia). When the control valve begins to open, violent banging and clanking takes place for a few seconds, violent enough to cause damage to welds along the pipe.
With the same problematic symptoms as in the previous example, we elected to apply the same "solution". We moved the control valve 5 meters downstream and relocated it 0.5 meters from the contact heater. The results were not as dramatic, there is still some hammering, but not as severe as before.

Is 0.5 met proximity to the contact heat exchanger sufficient?(The piping is 150 mm or 6")
Given the limitation of my description of the problem, is anyone able to suggest areas that we may have overlooked, or suggest another theory that we could examine?

Thanks
Ahmed Vawda
Process Engineer
Al Khaleej Sugar - Dubai

[Non-text portions of this message have been removed] Received on Sat Sep 15 08:47:00 2001