This is a dumb question.
Answer #1 - Place the valve at the bottom of the vertical portion.
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Answer #2 - Place the valve at the top of the vertical portion.
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Answer #3 - Put the valve at the place where the operator can reach it.
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Answer #4 - Ask the Process Engineer where the valve should be located
Sometimes its possible to do all the right things and still get bad results
It really depends on whether there is a freeze risk. In country prone to freezing, I am very careful to avoid block valves on the vertical, but when I can't avoid them I put them as close to the top tee as humanly possible (i.e., put a flange or short threaded nipple on the branch of the tee. I have never had a properly placed valve freeze and break, but improperly placed valves on natural gas well tubing/casing cross connect lines freeze and break by the hundreds every year in the Rockies.
LittleInch,
Gas will always gravity-separate through a liquid column if given the opportunity. A shut valve on the vertical is creating a dead end that will foster condensation and gravity separation. Over time, even in a 3-phase line, if there is room you will have water on the bottom, condensate above that and gas above the condensate. This dead-leg is very quiet and very much subject to freezes. Like I said above, we see hundreds of broken valves and broken pipes each winter in the U.S. Rocky Mountains from vertical cross connects between tubing and casing lines on gas wellheads.
We also see solids like frac sand and coal fines collect in these dead legs if there is room. The key is to not allow space for very large accumulations.
In many ways, a simple "ball valve" is the absolutely worst style to use in a vertical line: A globe valve disk does not rotate strongly (friction will tend to rotate the disk as it lifts, but the main travel is vertical away from the seat so solids may wash past the seat.)
Trapped debris, particulate solids, condensed solids, or biologics) will be less squeezed into the sealing surface and rubbed across the disk-to-seat interface of a globe valve. Butterfly valve (bad) or ball valve (worst!) WILL rub every particle right across the sealing surface. Scratches and future leaks are near-certain much faster with a ball valve unless your system is "perfectly clean and condensate free"
rackookpe1978,
I would put a very different priority of valve selection for vertical valves. You were looking at a single facet of the problem (scoring of the seat), but there are other considerations. From best to worst in my opinion (realize that I am limiting my consideration to block valves, not throttle valves, that are in a vertical run of pipe and that will normally be shut, and rarely operated--a frequently operated valve or a valve in throttle service would change the priority):
[ol 1]
[li]Ball valve. High potential for scoring if operated frequently, but very low potential for sticking. In high dP vertical applications the low sticking potential outweighs the high scoring potential on all infrequently operated valves. In low dP vertical applications the scoring potential is nearly a non-issue.[/li]
[li]Gate valve. Very low potential for scoring, but for an infrequently operated gate valve it has a very high potential for sticking from debris accumulation. In high dP applications they can be nearly impossible to unseat.[/li]
[li]Plug valve. Very high tendency for solids to score seats, and very high maintenance. If not properly maintained can be nearly impossible to operate in an emergency.[/li]
[li]Butterfly valve. Poor sealing characteristics make butterfly valves a poor choice in any but the lowest priority service. In a freeze situation, it is normal for the disk to fail and open the path it is intended to seal without a clear indication of failure.[/li]
[li]Globe valve. A valve designed for throttling should never be considered viable for on/off service, especially normally-shut on/off service.[/li]
[/ol]
Thank you to all...especialy to Mr. David Simpson, PE...
As for Little incg - fluid is Hydrocarbonm and Client asked for some portion of pipe this position of valve...it is reachable, but requeast was to be vertical (ball or globe), but vertical...and I wonder why.
without seeing the piping configuration or why they think this is a good idea it is difficult to argue the case. I can only assume you means trunnion mounted ball valves - floating balls may not seal well under low DP if the pressure comes from vertically up.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Little inch, thank you for your efforto. My attention was to ask, but some issues were more important. Next time...
Thank you ones mnore to you and the guys.
My guess is that clients intention regarding vertical position is related to lever/hand wheel for operation and the valve should be in horizontal line. Valves in vertical lines are more difficult to remove for maintenance and unless Process dictates to be in vertical, don't recall any instances, I try to avoid although not always possible. I find it is a common client comment related to maintainability in 3D model reviews and unless you can justify results in rework.
