Symbol on side of Globe Valve 4

[jeni333]

Hello all,

I ran into a question today concerning a symbol located in the casting of a globe valve. In fact it is on every globe valve we are installing.

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I hope the symbol above makes sense to someone out there. We have been racking our brains all day searching catalogs and the net to no avail.

Any help would be appreciated!

Thanks!
-Jeni333

 

[zdas04]

It is showing the flow through the seating surface (the horizontal line). Normally you'll install a globe valve with flow up through the seat (i.e., from right to left) to keep shut-in pressure off the packing, but this is not required by the manufacturer and is not a universal rule.

Manufacturer's usually call a globe valve a bi-directional valve since the throttling characteristics are the same in either direction. In steam plants we were really careful to ensure the flow was up, but in Oil & Gas it is rare to find someone who knows what the symbol means.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

The harder I work, the luckier I seem

 

[TBP]

On the valves I'm familiar with, it will show you the orientation of the valve after it's in-line. If the flow is right to left, in your diagram, then it would enter the valve, come up under the disc, and exit. This is the traditional orientation, and allows you to close the valve, and repack the stem without depressurizing or draining the upstream piping run. On other applications, it is sometimes desirable to have the flow acting on top of the disc, and tend to drive it to the closed position, should it come off the stem. This orientation won't allow simply closing the valve, to repacking it, though.

 

[grandnobi]

jeni333,

IMHO this symbol does not represent the flow through the seat as mentioned by zdas04, but the internals of the valve in a cross-sectional view. The horizontal line represents the disc.
Thus the normal flow (up through the seat) would be from left to right.

See also the pictures shown from this link:

http://www.gammontech.com/gg24.htm

Regards,
grandnobi

 

[zdas04]

Dang, every time I rely on my memory and convince myself that something seems too logical to have to look-up I messs it up. Of course grandnobi has it right and I had it backwards.

David

 

[jeni333]

Thanks zdas04!

This is what I had in my mind and had a slew of pipers telling me different. I will pass the information from your link on to others.

Thanks again!

-Jeni333

 

[codeeng]

I came across this problem once before. At first glance I assummed this showed the flow path but in actual fact the opposite is true as it shows the orientation of the bridge walls - very confusing! A star for grandnobi for pointing this out.

 

[jeni333]

OK, so I'm new to the board and thanked the wrong person. Thanks Grandnobi!

 

[TBP]

I guess what they say is true - you're memory is the second thing to go...