Manual Valve Closing Times

[sshep]

My Friends,

I am working on a project which has many large gear operated valves.

Is there any standard or reference on how long it takes to open valves of different sizes and types, standard gearing ratios, etc? Any help is appreciated.

best wishes,
sshep

 

[zdas04]

"Standard" is a slippery term. I worked on a system in the '70's that had a minimum closing time of 2 minutes. I've worked on compressor stations where the maximum closing time was 4 seconds. I always look and the requirements and specify the closing time for the application.

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.
The plural of anecdote is not "data"

 

[gr2vessels]

Typically, the valve closing time is derived from the hydraulic (water) hammer formula. Is function of material, piping arrangement, fluid properties, etc. This applies to normal valves. The ESD valves have to close quickly, but without damaging the piping and equipment. For example, 80% is a quick closure of the ESD and the last 20% is slow, to prevent water hammer. Even in long, large diameter gas piping, you have to consider the pressure increase due to rapid closure.
Google water hammer and do your research on the opening/closing time for valves.
As far as large manual, geared valves concerns, how long is the piece of string? How fast can you spin the handwheel? Typically, these valves are much slower than the actuated ones, so I wouldn't worry too much on the closing time. You can get these time figures from the valve supplier or you can work with him to determine the actuating time.
Cheers,
gr2vessels

 

[sshep]

I probably should have given more detail but was hoping for a general reference or practice, even an ergonomic reference might help- i.e. similar questions are sure to follow.

My immediate case was to answer how long it would take to fully open 20" manual gate valves, which I anticipate will be gear operated. I know from my own experience that it can be tiring- i.e. the gearing is usually that it turns easily, but that it takes many many turns. I guess I tire easily because if there were more than one or two big valves, we usually did it as a team so that there was a chance to rest. In this particular case the valves must be opened on an emergency basis. They will have at least 45-60 minutes notice, but not all of this time will be spent spinning the valves- i.e. travel time and other actions. This is where the question came from.

Anyway, thanks for the advice so far.

best wishes,
sshep

 

[racookpe1978]

Emergency basis?

Is it an "emergency" action to open? Or to shut?

What happens if they don't open/don't shut? (Fire continues? Lube oil is not supplied from alternate tank? Nerve gas keeps leaking? Oil keeps flowing into river? )

Are you manned 24 x 7 with a truck available? What happens if the crew can't get there? If only one person is available? How long does it take to get to the platform or the staging to turn the valve?

.... So any or all of those would be reasons to put in an automatic valve or a remote-controlled valve operator.

Why not? Expense of purchase, install, maintain, test, backup power, actuating power, etc.

 

[sshep]

It is a backup water supply from a second source if we lose our primary supply. In the ultimate case the main plant supply pumps will lose suction. Cooling water make-up will stop, boilers will lose BFW, or (if a fire is driving demand) the firewater supply pond will be exhausted. The existing reservoir is 4 hours, so it isn't a clear case that something bad happens immediately or that their isn't time to do something. Even if the low alarm sounds they still have probably an hour to get the supply restored. I am just trying to answer a question that came up in a P&ID review.

 

[maddocks]

This is pretty vague. I recently worked on a 16"-300# gear op valve and the damn thing took hundreds of gear spins with the stupid wheel. I bet it was over 3 minutes of furious cranking and swearing...

 

[LittleInch]

sshep, Unfortunately not as there are simply too many variables such as torque needed to close the valve, pressure rating of the valve, size of hand wheel, rotations to close, has the gearing / screw been maintained/greased etc etc. If you type in "manual valve closure time hand wheel" into google there are a couple of valve suppliers sheets which seem to show an acceptable rim force of around 450N or 100lb. The valve manufacturer then plugs that into his max torque figure requirement (which is normally quite conservative) and then gets a gearing ratio. Turns to close even for the same size valve could vary from 16 to over 70 based presumably on the torque requirement. Hence many valves start opening / finish closing with a bit of an effort and then almost free wheel to the end point, but take forever because the gearing is designed for the max torque value, not the running torque which is usually much less.

If you try to shift a valve which hasn't been opened for a long time though, forget the free wheeling bit.

So, you need to get the valve suppliers data sheet for his manual actuator for your particualr valve(s) and find out how many revolutions it takes to open / close and then guess a bit as to how long each revolution of the hand wheel would take - for a 12 to 16" one, my estimate would be about 5 seconds per revolution for an easy well maintained valve and 10 seconds for a worst case.

If its a lever operated vlve then it's about 2 seconds open to close....

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[athomas236]

why not just ask the valve supplier?

 

[steamdog]

You should get from the gear operator and valve information the total number of turns required. I once did a job at a chemical plant where they put electric actuators on the large gear operated steam gate valves because they actually timed a guy trying to close the valve and it was over 3 minutes and that was not acceptable. The valve actuator has a simple push button to open and close, and of course there is a manual gear override just in case.