Number of turns to operate large ball or plug valve 1

[mch22112]

Hello,
For a typical 32" quarter turn (ball or plug valve) with gearbox, does anyone have an approximation for the number of handwheel turns required to fully open or close?
Thanks

 

[LittleInch]

Somewhere in the region of 100 to 200, but depends quite markedly on the pressure rating and hence closure / opening torque required.

Many valve suppliers will have this on their data sheets.

My motto: Learn something new every day

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

 

[Ryguy1988]

It depends on the gearbox you are using. The larger the gearbox the more turns are required.

 

[mch22112]

Thank you for the reply gents. I will contact a valve vendor.

 

[JohnGP]

As others have basically said, it depends on valve design and operating conditions, as well as allowable maximum force to operate. The valve manufacturer will then size a gearbox to suit. We have some Class 900 36" full bore ball valves which require 360 turns to operate fully closed to fully open, 36" reduced bore balls and 30" full bore with 240 turns.
Cheers,
John

 

[Dean8573]

It will mainly depend on the operator fitted, if it is a standard gearbox the chances are high that the ratio is poor an the operation time is very high with multiple turns of the hand wheel. Gearbox multiplier or ratio boxs can be fitted that will increase speed of operation along with reducing the number of rotations required. Do you need it to operate in certain number of handwheel operations? Operman mastergear or Rotork websites will provide further details.

I work for a valve company so we often work with this issue.

Thanks
Dean

 

[mch22112]

Thanks Dean,
I need to purchase the valves and am really trying to determine the shortest time in which they could be operated. The valves will be used for switching streams on a multiproduct manifold, so fast operation in beneficial.
Cheers
Mark

 

[LittleInch]

A 32" manifold valve?? That's some sized flow you have there.

I think you could afford an actuated valve to do this as fast as you can or you're going to end up with a large interface or an off spec tank depending on which end if the system you're working in

Fast operation isn't just "beneficial", it's required and manual operation at that size just isn't going to cut it. Any cost saving will be wiped out by excess slops created or out of spec product whilst you sweat trying to close it manually whilst opening the next valve at the same time....

As I'm sure you know, a ball valve basically does nothing against flow until about 85% closed.

My motto: Learn something new every day

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

 

[mch22112]

Thanks Little Inch,
We have been able to scale back to smaller valves, but still quite large (10" - 24"). For the 24" valves we have the option of duplicating lines to further reduce diameter and minimise operating times (i.e. achieve the required flow using two smaller lines rather than a single large line). The valves will all be actuated and flows will be slowed as interface approaches the manifold.

 

[LittleInch]

Slowing multi-product lines can increase your interface size - you probably want to look at just increasing the actuator power / speed to close it a bit faster. Normally you interlock the valves in the control system to prevent two being open together and so to change product you command the next one (slops or the next product) to open and while it's doing that the previous open one is closing.

When you work out interface size, the initial interface generated by dual valves being open can be a considerable proportion of the final interface size even after long distances in the pipeline. Just get a range or closure speeds from the actuator suppliers then decide which is the best one for you. I've had 18" valves close in 3 seconds (a spring return admittedly, but closure speed is up to you - there's some "normal" speeds floating around, but I've not come across any hard and fast rules. If you need it to close and open fast, then just specify it. Watch the surge pressures, but for a long pipeline the closure speed is normally irrelevant unless it takes minutes.

My motto: Learn something new every day

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

 

[mch22112]

Thanks LittleInch, that's very helpful advice. I should be able to come up with a workable solution now.

 

[gerhardl]

If the operational time is the most critical issue, it seems natural to start the with a normal constructional description with answering the central questions:
- Minimal/best closing time
- Maximum acceptable closing time
- All necessary flow data (pressures, max, min and normal flow, fluid data, pressures etc)

With lower diameter than original it seems you already are on this track, as you either have increased flow speed or reduced flow amount.

The central question is if you also already have considered cost/usabillity of other types of valves, piggable or non-piggable, with 90 degree closing.

In this size you will have several constructions to considered with several types of fast-closing actuators. The fastest, but also highest priced, would be weight loaded for closing, hydralic for opening, types used par example as turbine inlet valves for hydro-electric plants. Theese could also be used with oil-hydraulic or electrical actuators. For other fluids you will find a multitude og higher priced eccentric, 90 deg constructions, both BFL, ball and plug valves, all at standard or shorter building lengths as the one proposed by you.