Valve for controlling drilling cuttings 1

[Bjarte]

Hi
I have a problem. I need a valve for controlling the flow of drilling cuttings. I can't use a ball valve cause it will block up with drilling cuttings. In fact, all valves that control the flow by "strangle" are out of the question.
I need a valve that can handle small rocks and stuff without blocking up.


The pressure will not be high. Max 0,5 bar.

I have thought of a valve designed like a whater weel (or turbine). I can then control the rotary speed of the weel and then the flow rate. I don't know the name of such a valve (if it excists) or who might manufacture such a valve. So I need help with this. If someone have a better solution to my problem this is greatly appreciated too.

-Bjarte

 

[JimCasey]

Normally one regulates the flow of the coolant to the drill BEFORE it gets to be a slurry with the cuttings. COntrolling the coolant INTO the drill is relatively simple. Controlling the slurry coming OUT of a drill sounds like a job for a pinch valve. Take a look at

http://www.redvalve.com.

 

[MikeHalloran]

At half a bar, a standpipe would work just fine as a valve. Use either two nested vertical pipes and adjust their composite length, or use one long pipe and tilt it to regulate the head required to spill over the lip.



Mike Halloran
Pembroke Pines, FL, USA

 

[Ashereng]

Bjarte,

Your water wheel or tubine sounds like a screw conveyor. You speed up the screw or slow it down to control flow. Is that what you meant?

Jim's pinch valve may also work. One thing to keep in mind is that the pinch valve has a soft "pinch" material. Your drill cuttings may cause abrasion/erosion (I am not sure what the word is) of this material. You may need to look deeper into this.


Mike's solution is really neat I think. It is certainly simple.

My 2 cents worth is to add a set of parallel pipes with a on/off valve to each. This way, flow is controlled by the number of parallel pipes in use. With 5 pipes, you can control by 20% increments. With 2 pipes, you can control by 50% increments. An on/off full port ball should be okay as it only has to open or close.

 

[abscott]

If you can not find a reasonable solution to your problem and are forced to use some type of "standard valve" such as a globe or ball valve I suggest that the control system incorporate a "quick jog open" so the valve can to pass the accumulated debris. This is not unusual in processes that have entrained solids in the flow stream.
Hope this helps.

 

[JimCasey]

Ashereng,
I believe the "water wheel" Bjarte mentioned is describing a rotary valve normally used as an airlock in pneumatic conveying of dry particles. It's the same principle as a revolving door, but industrial ones are powered, run up to about 20 rpm, and have from 6-10 vanes depending upon the severity of the service and how much the customer is willing to pay. Take a look at premierpneumatics.com

Not a good valve for rocks and sand suspended in a liquid. If you are ever in a flour mill, don't put your fingers into one.

The pinch valve is designed specifically for lumpy slurries, and the sealing/throttling element is a reinforced rubber hose. Rubber is nicely resistant to erosion/abrasion, as demonstrated by auto tires that easily last 50,000 miles.
There are pneumatic pinch valves that use air pressure in a chamber on the outside of the tube to collapse the tube shut. With this method the tube is free to conform around rocks and chunks. Without the air pressure, the process pressure inflates the tube to an essentially round, obstructionless flowpath. And, if you are wondering, I do not work for a pinch valve company.

Halloran's idea is clever. It would need enough velocity to keep the heavy chunks from staying in the bottom, otherwise it would become an inverted sand filter.

 

[Ashereng]

Jim,

Thanks for the clarifications.

On the pinch valve, what is the typical thickness of the rubber sealing/throttling element? Part of what makes a tire last so long is the thickness of the rubber. In a valve, if the rubber is too thick, it may be tough to pinch?

 

[Bjarte]

First of all thank you all for your answers. They have been of great help.

I have taken a look at the pinch valve. And that is a very neat design. However, what if you open the valve to say 20 percent. Won’t the opening then be so thigh that it will clog up with debris?

Ashereng mentioned the screw conveyor. But can you have a screw conveyor witch stops the flow when you turn it of? Won’t the cuttings and the mud just flow right through it?

The "whater wheel" I thought of is indeed the one Jim explained. The one in the bottom of this drawing is much like the one I have thought of in my mind:

http://premierpneumatics.com/visuals/cycloneCut.jpg

The advantage with this solution is that you can control the flow by the rotating speed of the “wheel” And you can then also stop the flow by stopping the wheel. As there is no throttling there is not the problem with debris clogging the “valve”. A problem might be that debris can be caught in between the “paddles/wings” of the wheel and the edge at the valve entrance. But by having a rounded edge here the problem might be a solution to that problem. What do you think of this solution? And could you please explain to me why you don’t think this will be a good solution for rocks and sand?

 

[JimCasey]

Ashereng: The inner lining of the tube in a pinch valve is pretty thick rubber for resiliency. THe reinforcing fibers are in the outer layers. And they are not as tough to pinch as you might think because they are molded pre-pinched.

Bjarte: If the pinch valve is automated, the control system does not look at the 20% position of the valve as much as it is looking at the commanded 20% flowrate. If the valve starts to strain out debris, the automatic control will just sense that te flow is below setpoint and open the valve a bit---releasing the boulders. The the control loop will drive the valve back closed. If the valve is not automated, you can do the same thing manually.

You hit on the exact reason why a rotary vane valve is not appropriate. Rocks and debris can catch between the housing and the tips of the vanes. This will lead to increased wear, scoring, mechanical damage, or jamming of the valve. They work well for metering fine granular nonabrasive solids such as flour, sugar, or polymer granules. The flow in solids is always downward initially by gravity. A pie-shaped cavity will fill with powder, rotate around through the housing, and dump its contents out the bottom. The outlet can be at higher pressure than the inlet(up to 50 psi) , so the valves are useful for feeding powder into a pneumatic conveyor. The volume of the cavity is known, and adjusting the rpm determines the number of cavities dumped per unit time. FLow vs rpm is pretty linear up to the point where centrifugal force starts becoming significant. This keeps the chambers from filling completely and thru-put drops off at higher RPMs.

The tips of the vanes are usually square, sharp-edged, so there is a capillary seal between the tip and the housing. If the powder to be metered melts easily (sugar, plastic pellets) then the tips are relieved/beveled so there is more clearance behind the leading edge and they don't hold local granules between the tops and the chamber long enough to melt them. Rounded tips would aggavate the trapping of particles between the tip and the housing with no good effects I can think of.

Rotary valves such as this are highly unusual in liquid services, if they are used at all.

 

[Ashereng]

Bjarte,

Yes, you are correct. The screw conveyor will not stop flow - it is a conveyor. Your original posting is for throttling - for this, a screw conveyor may work.

To stop the flow, you still need a "valve" of some sort. The problems you encounted with throttling should be less with an on/off valve, as you only need to operate it when you want to open or close (infrequently).

Jim,

Thanks for the information on pinch material. I haven't used one - don't see them in my industry.