RE: Fwd:Vibration from flashing valve

From: <Steve>
Date: Wed Jun 26 2002 - 21:02:00 EDT

Hi there

this seems an unusual application for a (Valtek?) ShearStream valve as you are dropping all your pressure at one point and flashing. You will get less noise and vibration either by going to a multiport valve such as MegaStream, Tigertooth or Channelstream, but at considerable cost.Some of these styles are suitable for flashing service. If the flow is fairly constant, you could look at a Megastream plate diffuser to take out some of the sting.I have never used one in flashing service,however. Note that all the above have small passages. If your liquid is dirty, blockages may be a problem. In this case you will probably have to use a choke tube, but this is only effective at constant flow, and the valve will have to do the work at reduced flows. The alternative is a series of series staged valves - very expensive and may be difficult to design for flashing service. I assume you have checked that the vibration is not a resonance problem. If it is, a large lump of concrete or steel will quiet things down. Finally, you may need to check that you are not getting gas pockets upstream of the valve. It may be causing slugging. If you can eliminate the gas, things may settle down.

Cheers

Steve McKenzie

-----Original Message-----

From: Paul Bowers [mailto:pbowers@pipingdesign.com] Sent: Thursday, June 27, 2002 3:17 PM
To: PipingDesign@yahoogroups.com
Subject: [PipingDesign] Fwd:Vibration from flashing valve Importance: High

____________________Forward Header_____________________

Subject: Vibration from flashing valve Author: KV Ravichandran
Date: 6/25/02 8:55 AM

Hi,
Can any one give guidelines for quelling vibrations from flashing control valve.
This is my problem
There is in one 8" Zirconium line carrying acetic acid/ catalyst from reactor
to flash tank. At the flash tank side the line has one flashing control valve ,
gate valve and a conical expander section of about 4.6m long where the pipe dia
increases from 10" to 26" and connects to the flash tank eccentrically.The source of vibration is the flashing control valve (shear stream ball valve)which
throttles from 26 bars to 2 bars. The liquid flow velocity is about 8.5m/s at
the valve.Operating temperature of the line is 193 deg C. During the original design two phase flow and vibration was considered and the
line is supported with TICO Vibration isolation pads and U bolt clamps.

Now the platform from the flash tank as well as the structure supporting the piping near the flashing valve is vibrating.

To have an idea about the magnitude of the vibration following is the latest measurements at the flashing valve.

Fcy      Velocity
Hz       mm/sec
4.405       1.418
8.811       1.049
13.22       .6426
22.03       .6278
48.46       1.876

Thanks in advance

Regards,

K.V.RaviChandran
Senior Piping Engineer
Foster Wheeler Eastern Pte. Ltd.

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