RE: B 31.3 Grass Root natural gas cpmpressor station

From: <elie>
Date: Thu May 19 2005 - 23:25:00 EDT

I worked for many natural gas companies and most of them prefer flanged valves all the time, including below ground valves. All of the hot taps I made below grade were flanged with 6' extentions.

ET.

Steve McKenzie <Mechproj@xtra.co.nz> wrote: Hi Paul

weld valves are exceedingly popular in industries where blowouts and fugitive emissions incur severe penalties beit internal (opex) or external(litigation).

There are three issues with them that I know of: 1) Body damage often requires cut out and reweld new body. The procedures, certification, material match and approvals can be horrendous. The line may have to be fully retested and possible design checked.
2) You are over the barrel for new trim. The valve supplier can charge what he likes. I often find a new valve costs about the same as a retrim except with retrim you still have an old body. 3) Engineers specify flange joints without thinking. The cost of two flange pairs can be enormous compared to two butt welds, but some just don't understand. Breaks my heart sometimes.

Cheers

Steve

-----Original Message-----
From: PipingDesign@yahoogroups.com [mailto:PipingDesign@yahoogroups.com] On Behalf Of Paul Bowers
Sent: Friday, May 13, 2005 11:06 AM
To: PipingDesign@yahoogroups.com
Subject: Re: [PipingDesign] B 31.3 Grass Root natural gas cpmpressor station

elie altawil wrote:

> .Plant piping may me above grade or on a pipe rack.

Sleepers, you mean?

> .Welded or flanged valves

I've always assumed that most gate valve guts were accessible/replaceable via a bolted bonnet. If this is true, why are welded-end valves not more popular?

Paul

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[Non-text portions of this message have been removed] Received on Thu May 19 23:25:00 2005