Pipe Flow from resovior to machining center 1

[farmENGR]

Hi all,

I want to acheive a velocity of 28-32m/sec on our coolant lines to our grinding centers. We have a resovior(transor system) that pumps fluid to our grinding centers.

We performed a 'bucket test' yesterday to determine the liters/minute which is the volumetric flow rate of our oil. How can i figure out the velocity of the oil. I want it to be between 28-32m/sec.


We will pour the contents into a large measuring bucket to determine how many liters we have aquired. We filled up the bucket for one minute.

We are having our transor system re-engineered so that each machine will be able to be controlled by one pump. Right now Machine 1 and 2 flow rates are much greater than machine 3 because it is not connected to the transor system.

If you have any additional questions i can try to provide them.

Thanks

 

[micalbrch]

When you know the flow in l/min and the required velocity in m/sec then you just need to know the pipe diameter D.

v (m/sec) = Q (l/min) x 0.004 x 1/(188.5 x D²) with D in meter

But I think that is not the solution for your problem. You have pumps between the reservoir and the grinders? You can't tell a pump that it shall convey the fluid with a certain velocity.

 

[farmENGR]

yes we have pmps from the reservoir to the grinders. OUr parent company has it set up with one pump governing each grinding center.

I have calculated the volumetric flow rate at 2.24E-4 m^3/sec.

 

[farmENGR]

From what you say i have a velocity of 3.14m/sec. This has been determined from a 8mm pipe ID(0.008m) using your equation.

Our flow rate is about 9.5 liters/minute.

Funny this is that we give our grinder a velocity of 28m/sec but i do not calculate that using your equation. Can you explain?

 

[farmENGR]

I have made a mistake. The correct velocity calculated is 12.59m/sec. I need to decrease the pipe ID huh

 

[micalbrch]

Yes, and that (decreasing the pipe diameter) can cause the next problem - with the pumps you have. What kind of pump is (are) installed?

 

[farmENGR]

high pressure pumps by Grundfos 50 HZ 3Mot. filter pump is a mtr15-12/2. what does this mean? The lines coming off the pumps are bigger and seem to have a thicker wall than coolant lines in the machines.

There is a filter pump, fast fill pump, presure flash pup and cooler pump.

 

[farmENGR]

Only 1 feedpump runs at a time. The other is a autobackup.

Feed opening lines are 2'' female parts. I calculate my velocity to be between 22-32m/sec with either a 3m or 2.5mm OD pipe ID. To acheive the second velocity i will need to increase the velocity of the machine or increase the pressure on the corresponding pump?

Note: In a week or so each machine will have its own pump; they currently do not.

What is critical now is to find the correct size pipe ID.

Thanks.

 

[MikeHalloran]

I can understand wanting a high velocity on the discharge nozzle that sprays coolant on the grinding wheel, and a fairly uniform velocity across the face of the exit aperture, typically a slot.

Unless the coolant has some magic particles in it that you trying to keep suspended, I don't understand fussing much about velocity in the coolant distribution except, except to keep the velocity _down_ far enough that you don't waste pressure drop just getting it through the pipes, and have enough _flow_ to be sure that each discharge nozzle gets all the flow it needs to maintain its discharge velocity.

I.e., I think you are trying to solve the wrong problem, in the wrong way.



Mike Halloran
Pembroke Pines, FL, USA

 

[farmENGR]

we need a certain velocity so that as the material is ground it is removed in the same pass. To do this we must match the grinding wheel speed to the velocity of the oil.

I think we can use the same piping. All we have to do is increase the velocity of the pumps inside the machines to increase the velocity. Once we have found 28-32m/sec velocities we can save the velocity of the pumps(inside the machine) to the program. this will prevent us from increasing the pressure on the resvoir pumps or changing the piping.

How can i check if this is an effect method re: pressure drops or other factors?

 

[cvg]

what kind of pump are you running (posative displacement, centrifugal, etc.) It makes a difference in how you approach this problem.

do you have the pump curves? (If you are getting new pumps, you need the new curves)
have you calculated the system loss curve? If you are installing new piping, you will need the system curve for the existing and proposed arrangement)

and do you have a requirement for minimum flow rate or pressure? Decreasing pipe size will generally also reduce the flow rate and discharge pressure.

without more information, you will continue to spin your wheels. simply reducing the size of the pipe will likely not solve the problem.

 

[farmENGR]

I could probably get the pump curves if needed.

System loss can be calculated as well then.

I believe our parent company had our supplier of the resovior modify their design so that each machine has its own pump. I don't know how they approached the problem but they are just telling us to measure the flowrate with simple bucket test. Based on our pipe ID we should have a flow rate that gives us 28m/sec.

Specifications of the filter unit says the clean oil flow rate is 30GPM +-10%. I do not know if ours is at 30GPM. I may call the supplier of the machine to find the min flow rate.

 

[farmENGR]

pumps are centrifugal

 

[farmENGR]

cvg,

The machinings have their own pumps as well. I think we can use the same piping and simply turn up the velocity of the pumps in the machines. There is a value you can change on the controles. Then we can measure the flow rate. I am looking for 84l/min with the given pipe flutes i have to achieve 28 m / sec.

My current velocity is 3.1m/sec using a flow rate of 9.5L/min and a pipe ID of 0.008m.

What will i need to check on when proceeding with this method?

Thanks for your help.

 

[cvg]

no, you probably can't just spin the dial and make it work to your satisfaction. But you can certainly try that and see what happens!

you are proposing to greatly increase the pump speed which will increase the discharge. this will result in a drop in discharge pressure due to the increased pressure drop in the piping (from both the reservoir and from the booster pump at the grinder). Have you confirmed that operating at the new flow rate, the pumps will have sufficient discharge capacity and pressure and that the pumps can even operate at the proposed new point? Can your existing piping handle the pressure? Will you have sufficient suction head to prevent cavitation? What about the driver? can it handle the load?

 

[farmENGR]

Ha. I understand you know more about this than i do.

I will need to consult with the machine maker? about the discharge capacity as well as the operating point.

I don't quite understand the direction i need to go in.

I believe our parent company reduced the size of the pipes and made sure all other technical details were satisfied or met so none of the systems failed.

 

[bimr]

Why don't you call Transor?

 

[katmar]

It is only the velocity at the discharge that is required to be high - the velocity in the feed pipes could be lower. You should use larger bore piping from the pumps to the grinding machines to lower the pressure drop, and then fit narrow nozzles or slots at the end to achieve the high velocity onto the grinding wheel.

Achieving this discharge velocity will consume 4 or 5 bar of head (as velocity head). Whatever discharge pressure you can achieve from your pumps you must size the piping so that there is this 4 to 5 bar available for the discharge losses.

Is the velocity the only specification? Do you not require a minimum flow as well?

30 m/s is a very high velocity for a liquid. You are going to get some severe splashing.

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[BigInch]

And erosive action on whatever it hits.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[CastMetal]

"we need a certain velocity so that as the material is ground it is removed in the same pass. To do this we must match the grinding wheel speed to the velocity of the oil."

While admittedly I'm not aware of your setup this statement seems incorrect. I am imagining a setup similar to a surface grinder in a machine shop and when you refer to the "wheel speed" you mean the speed the wheel is traveling across the workpiece surface not the speed of the surface of the wheel (because 30m/s would be very very slow).

In this case the speed ground material needs to be removed is independent of the travel speed of the wheel and instead is determined by how quickly the wheel returns to the previously ground area.

Say the grinding wheel is moving at 30m/s and moves 6in beyond the workpiece before reversing direction. Oil flowing perpendicular to the grinding wheel would only need to be fast enough to move the ground material the width of the grinding wheel during the .01seconds before the grinding wheel returns. With a one inch wide wheel this is only 2.5m/s. This disregards the efficiency of moving the ground material (overcoming friction / viscous forces among other things) but I would think it safe to assume three times this number would be more than sufficient. That is still just 7.5m/s.

The situation may be very different from what I am picturing but I think it is worth finding where the 30m/s requirement came from and if that is necessary.

Comprehension is not understanding. Understanding is not wisdom. And it is wisdom that gives us the ability to apply what we know, to our real world situations