Sensors Measuring powder flow.

[Tharon]

I know air is already there BUT the more you use the more demand you put on the system. Whether its pulsing air or an air leak it adds to the demand of the system; which in effect causes more power to be used.

An example of sorts, others can offer more precise information, a simple air leak or small air line (even pulsed) can use 5HP (3.7KW). Calculating a years use of the power involved may show an ROI for another method.

They do make specifically engineered air fittings for blow offs, that get maximum results for minimum usage.

But, I agree about the expense of air. I think one of the other engineers here told me a few weeks ago that Air was one of the most expensive utilities around the shop. (Even though Operators waste it all the time, using the air lines to sweep the floor, and blow themselves off, and anything else they can think of, including putting it down their pants when they are hot )

 

[TConnolly]

One of the most expenive?

I think it is the single most expensive utility by a large margin. A compressed air system transmits only about 10% of its consumed energy. The other 90% of the energy is turned into heat. And half of that transmitted 10% is lost to wasteful use, like you said, sweeping the floor, etc. (one of the reasons I'm not a fan of vortec cabinet coolers, but thats another topic)

 

[rsdoran]

I mentioned this because he mentioned he had an AccuRate system but thought it may be too expensive to incorporate into the system. It was not that you could not get the "air wipe" situation to work but in the long (or short)run, is it the most efficient and cost effective method.

Another thought, since he mentioned it being so dusty is whether they are allowing too many "open" points to the process. I know from working with dry material that dust means you are losing material; which means a loss of product. In many, if not most, vacuum systems with baghouses are incoporated to re-capture the "dust" for use in the product. This "veiwport" may be an open point that is allowing the dust to be released into the atmosphere instead of being recaptured.

Just had another thought, instead of air if there is a vacuum system involved may want to look at using it.

Its all just "food for thought" to offer different ideas or areas to look at.

 

[atifplus]

Awesome I will look into the re-capturing of product its a nice idea i think it is all gypsum floating arround.
Never thought air could be that expensive. But in my plant the air is constantly blowing on the lens to keep it clean :| that is why i thought must modified the design.


aaa another thing if i am using the PLC to do the pulsing air shots. what if i try the shots when there is an alarm if the alarm disappear means lens is clean and if not then there is no product flow.

But hey good to know all the options

 

[milldrone]

I have been in the lumber industry for 35 years and I have see several scheemes to solve the dust problems. Some worked some didn't.

Constantly blowing air and pulsing air from different directions yeild different results.

Some of the tactics were already mentioned by Tharon, rsdoran, and Alaric. I would like to add a little twist on Tharon's pulse of air. Some of the best results I have seen were blowing across the lens but not actually touching the lens. Sort of like using the induced vaccum from the jet to suck the debris from the lens. Also having a flush lens is a must (not one with "valleys" for the optics).

If this was already mentioned please excuse this next question. What type of sensing are you using? Diffuse? Your drawing shows "one" photocell so I'm presuming this is what your using. A "convergent" style might work. The "convergent" style will ignore objects near the lens and have a fairly fast cut off. A Banner SME312CV2 is an example. This unit also has a teach function (you use a plc output to teach the sensor when it should see and not see). So to recap this sensor will ignore from the surface of the lens to one inch, then sense from one inch to 3.5inches and ignore the rest. Plus the gain can be adjusted via the teach function by the plc.

OkiePC recomended a thru beam style This might work if the starch is opaque enough. From your drawing it appears the starch is falling and you are trying to sense it's presence as it's falling. There are emitter receiver pairs that have the power to "burn through" 20 to 30 sheets of paper when the pair is mounted only a few inches apart. One application is to burn through two layers of cardbord to sense the level of cereal in a closed box. I have never used a teach function on a through beam pair so I can't comment on that.

I have also seen photo eyes mounted in a manifold/pipe with air from a blower purging out the same hole the eye is looking. I'm thinking this might be very messy for your application. Unless you were able to use a very small fan with filtered air. Just enough air to keep moving the dust away from the eye.

 

[John Soltesz]

For a different way of sensing this may be worth looking into.
We have used these products to detect dust from dust collector leaks. It uses static charge to monitor the air flow for particulates and doesn't have the problems optical systems have. Our sensors are 2 wire loop powered that give an analog signal not just on/off. I would give them a call with your specific application and see if it can work.
http://www.auburnsys.com/products_1.html
They also show these uses:
Process Applications:

Air Slide Flow Monitoring

Catalyst Feed Injection

Cyclone Flow and Overflow

Flow/No Flow Detection

Fly Ash Handling Systems

Gravity Feed Monitoring

Lime and Powder Injection

Particle Flow Velocity

Pneumatic Conveying

Screw Conveyor Flow

Spray Drier/Fluid Bed Driers

Vacuum Systems

http://www.auburnsys.com/products_1.html

 

[atifplus]

"induced vacuum"

Will search on this topic on google... hummm

What type of sensing are you using? Diffuse?

Just sensing the presence of Starch falling into mixture. I could give you the details tomorrow of Photo eye used looks like convergent style. There is a knob on the sensor to adjust the sensitivity. From talking to the operators I found that the system was working properly and just started giving lots of problem and false alarms. I suspect humidity is one of the possible reason.

From your drawing it appears the starch is falling and you are trying to sense it's presence as it's falling.

Exactly

I have also seen photo eyes mounted in a manifold/pipe with air from a blower purging out the same hole the eye is looking.

It is possible

I'm thinking this might be very messy for your application. Unless you were able to use a very small fan with filtered air. Just enough air to keep moving the dust away from the eye.

a haa nice idea using a small fan J



Here that was my plan..

 

[rsdoran]

Personally do not care how fancy you get with an air blow system, it will always be a "fix" to get it working now. Your talking to people that have been there done that (BTDT) so all this is old stuff that in the long run does not work effectively.

 

[atifplus]

true

Seems like this task will require a lot of research.
I will discuss with the other engineers ( if they are free ) and operators see what they have to say and then i will decided what path i will takin ..

it is getting complicated already

 

[rsdoran]

Seems like this task will require a lot of research.
I will discuss with the other engineers ( if they are free ) and operators see what they have to say and then i will decided what path i will takin ..

it is getting complicated already

It always does.

 

[atifplus]

Alright Found that we have a
Acrison's "Weight-Loss-Differential" Weigh Feeders Just a step back from the eye also monitoring the strach. I will see if it is connected to PLC. Then there will be dual monitoring of strach flow one by weight difference and other by eye
Still need to find the series number and other detials .. today's task go over the diagrams and specs of this feeder .

Also, what could be the cheapest solution for measureing water level. i need Digital Ouput ( if level is high thats all)

Thanks for suggestions and posting and ur time.

Atif

 

[Mark Buskell]

One of the cheapest I have seen is very similar to a toilet bowl float.

 

[CheezSarge]

Hi,


I would not pursue a photo eye with trying to monitor a powder in a dusty environment. Try going with a mass flow type detector. I did a google search and here is one site I found that mentions several manufacturers of these units. Yes the initial cost will be higer but if set up properly you will have far fewer false trips. http://www.clrwtr.com/Flow-Sensors-Monitors.htm Good luck.

Darrell

 

[wdd0422]

Could you enclose the sensor in a small sealed enclosure with a hole just large enough to operate the sensor and then apply a positive pressure with air to keep the powder out?

 

[atifplus]

Sure can do ..



But I haven't still able to figured out how much is the cost for air and the more i looked at the surrounding the more i feel it is really hard to avoid dust.



In my final design for the photo eye method i have a encloser. just to prevent the dust entering in.



The more stress is on the photo eye because that is the point where the stratch is mixed with other product, so if we dont sense the stratch we for sure know right away the mixture we are getting is not correct and we could stop the production line .



On the other hand the at feeder the weight will be changing for a while but the product could be getting stuck in the line and by the time we will figured out it be late and we might have produce some products with wrong ingredients.

The arrangement under use is shown below