Number of Turns to Open/Close a Gate Valve

[McDermott1711]

Recently, I was reading thread164-168796 (

http://www.eng-tips.com/viewthread.cfm?qid=168796).

In that thread, "bimr", with reference to AWWA, said that number of turns equals NPS times 3 plus 2 or 3. But I saw in AWWA M44-96, Fig. 3-1, that for 6" valve number of turns is 26. Actually, with numbers in the table, number of turns is NPS times 3 + 10. Am i right?

 

[zdas04]

To hear the guys in the field tell it, the number is 26,000 turns for a 6-inch, but I think they exaggerate.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.

 

[Shawner]

From what I've seen in our system, it's like bimr quoted, size x 3 + 2 or 3 (give or take).

Every 6 inch I've ever closed has been 18-22 turns.

 

[BigInch]

The multiplier depends on what you're standing in at the time. In 4' of shi* or 2' of gasoline 23 might easily seem like 23,000.

What would you be doing, if you knew that you could not fail?

 

[jgailla]

I've also heard X3 + 2 or 3, but I've only operated a gate valve a couple of times, and haven't thought to count the turns.

 

[hydrae]

The 3x+2 or 3 works for most modern valves
exceptions
some older valves (50+ years) have a shallower thread pitch, 4x or 5x
also some older valves operate as a left hand
gate valves mounted sideways will also have a gearbox, this is to overcome the crud that must be pushed out of the way instead of just crushed, I know of 24" 1960 era valves with 158 turns, and when they have not been operated for 20 years take three men an hour to exercise

Hydrae

 

[cvg]

I have seen large size gates take up to half an hour with a motorized operator. these were 72" rectangular, rising stem gates. there was a lot of operating torque, requiring significant gear reduction