Vibration from flashing valve

I am a retired mechanical engineer, after working for 34 years for Swenson Evaporator Company in Harvey, IL, USA. I believe that using a gate valve in a flashing condition is a mistake.

We used globe control valves to handle flashing liquors or condensate from evaporators to flash tanks for many years. We then decided to eliminate the control valves and installed orifice plates only. The plates were bored to handle the maximum expected liquor flow (normal flow, GPM, times 1.3) with a maximum allowable pressure drop, PSI, of 0.2 times the absolute upstream pressure, psia. The upstream piping was sized for 4-6 feet per second velocity. The vapor piping was immediately increased after the orifice plate and was sized for a vapor velocity of 100-150 feet per second. That pipe size was run to the inlet of the flash tank. The orifice plate was located near and below the flash tank.

We also experienced problems when a gate valve was installed in saturated steam control valve bypass piping. The control valve was a globe valve and we opened the gate valve to increase the steam flow. We experienced vibration and a great, unbearable amount of noise.

Best Regards,

Dick Anderson

[Non-text portions of this message have been removed] Received on Thu Jul 04 15:59:00 2002