pipingdesign: RE: Dumb Question about Gate Valves [bcc][faked-fr

From: <Steve>
Date: Fri Jan 30 2004 - 16:29:00 EST

Thanks Bruce
my feeling is that the original bypass was oversized and we may be able to save some money by fitting a smaller one. Rough sums suggest 12" is marginal. However if I knew the old valve opening I could estimate the original friction loss, and size th new bypass accordingly. Unfortunately orifice plates dont help much because the process needs to be shut down to change, and the flow requirement will change from day to day at certain times of the year. Ald log readings reflect this. Will use a butterfly valve as they are cheap and the duty is compatible.

Cheers

Steve

-----Original Message-----
From: Bruce Bullough [mailto:bbullough@sebesta.com] Sent: Saturday, January 31, 2004 3:37 AM To: <a href="/group/PipingDesign/post?postID=ZF0NEgAjas_RTDCMaemnI_yJKCUVcyu2keMCzRAb2uwlhaAXI_wdkSN1dJH1zVZJ9-hF_K8N9TkKrmHkaTl2n_cb0w-_apQ">PipingDesign@yahoogroups.com</a> Subject: RE: [PipingDesign] Dumb Question about Gate Valves [bcc][faked-from][bayes]

Steve:

Might I suggest that the precise valve isn't so important? I propose this because, 1) the plant has run for some time without it, but there is some optimization gained with using it; and 2) the valve, if it was installed and run for years in a partially opened manner, it probably changed over time anyway (erosion, etc.).

Replace the bypass including a gate valve, and install a flanged spoolpiece in which to include (or just allow for) an orifice.

If there is a concern about finding just the right size orifice, use a slide-gate weir in the place of the orifice plate and try a variety of settings on the gate 'til you find the "sweet spot", and design a few orifices with flow characteristics based on the what you found from testing with the slide-gate (all but one as spares) to more permanently install in the bypass.

... Bruce D. Bullough ...
Sebesta Blomberg & Associates
2381 Rosegate
Roseville, MN 55113 USA
651-634-7344 direct
651-634-7400 FAX
www.sebesta.com

-----Original Message-----
From: Steve McKenzie [mailto:mechproj@xtra.co.nz] Sent: Friday, January 30, 2004 5:12 AM
To: <a href="/group/PipingDesign/post?postID=ZF0NEgAjas_RTDCMaemnI_yJKCUVcyu2keMCzRAb2uwlhaAXI_wdkSN1dJH1zVZJ9-hF_K8N9TkKrmHkaTl2n_cb0w-_apQ">PipingDesign@yahoogroups.com</a> Subject: [PipingDesign] Dumb Question about Gate Valves [bcc][faked-from][bayes]

Gents
On a process plant I am looking at, they used to have a 16" gate valve fitted to a bypass valve which normally ran at about 4 turns open according to old logsheets.
The bypass line was deemed unnecessary and it and the valve were pulled out and dumped. Thats all I know about the valve. I reckon the line needs to be reinstated (to improve plant performance), but possibly smaller if I could find out what percentage open the valve was. This is easy to do if I knew how many turns open to closed the original valve required. A similar 12" valve (no name) is fitted elsewhere on the plant and is 12 turns open to closed - two start thread. My guess is that the 16" valve would therefore be somewhere between 12 and 16 turns O to C.
Just wondered if there is a standard or something covering this.

Cheers

Steve

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Received on Fri Jan 30 16:29:00 2004

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RE: Dumb Question about Gate Valves [bcc][faked-from][bayes]