I don't know if there's any mileage in the concept used here....

http://www.jh.nl/en/volumemeting/index.htm ■

Originally Posted by SteveDavis

Real time level mapping of coal in a large bin

Hi all and Seasons Greetings,

We have a requirement to monitor the level of a sized product coal bin that is rectangular profile, some 7m wide and 14m long with vertical sides 9m high and two square conical discharges. The bin is single point feed, and there are two conical discharges. Flat top.

The bin level is continuously changing as it is filled and emptied, and the surface profile is extremely variable. A single point measurement is of little use. The fill rate is about 4 times the discharge rate, nominally 9kt/h and 2.5kt/h

We have found a system that appears to work giving a 3D surface map of the bin content, but there is a 5 minute delay in producing the output. This will not work in our control application where we wish to know the content in real time. We will be exploring whether the software can be amended.

The bin is fully enclosed, obviously an extremely dusty environment, temperatures from 5-55 Centigrade inside. Expect a relatively high humidity but we can't measure this. Coal is all minus 50mm.

Mechanical systems and anything nuclear are not viable options. There is reasonable access to install instruments on the top and sides of the bin and voltages etc. are "standard" Australian.

Any suggestions? We would prefer a self contained system that outputs a profile in a digital form to the main control system.

Thanks

Why is it the mercury tilt switches/bindicators are not viable?,

why make a mountain out of a mole hill or termite mound

and turn it into Ayers Rock when you can simply have signal lights

tied into the bindicators paddles?

Square D has communications systems that tie tilt switches

into computers systems.

Installing mercury tilt switches to locate high mid and low bin limits

with paddles is easy enough why complicate it? ■

We use a combination of ultrasonic level indicators on some bins and load cell on the legs of other bins.

We have a 400 Ton bin with a single conveyor feeding it and 2 separate discharge points. We found the load cells on the legs work the best for controlling the feed conveyors. ■

OK so we are at still at this point;

One loading point, two drawpoints when and

if the coal wants to play nice, said customer

wishes to monitor the bin.

The numb, dumb, stupid, bullet proof approach

to avoiding the deer in the road is this;

One very large diameter telescopic loading tube

sized for the conveyor feed tonnage-ours was 450 T.P.H.,

using a fabric tube and a winch cable with limit switch

padddles to direct, control and monitor the coal

load coming in and leaving the bin.

The telescoping loading tube will utilize a lattice frame

or pipe to allow it to have vertical unrestricted movement

up or down in the bin.

The telescoping loading tube will raise and lower as fast as

the material enters or leaves the bin.

The simplest most basic Square D belt conveyor software

programable logic controlers using fiber optic cable can

monitor and control it if needed.

I have to circle the wagons and bed the horses down now

as its time for bed.

Happy New Year ■

Hi Steve,

Trust all is well.

I have come across similar problems and not found an off the shelf solution. The first issue is dust. If the material is not dusty lasers will give the best result. Davies Engineering in Esperance WA have developed a liner that incorporates a counter sunk bolt where a level detector could be included in the core of the bolt. What this does is give you the opportunity to create a monitoring array and 2-3 critical levels that could then be set to an on-line alarm/control system. I believe you will need to do a bit of design and work yourself to get it exactly right. I am not fan of anything that dangles in side chutes or hoppers, too many things can go wrong unless they can be positioned away from the material flow yet still do their detection work.

Cheers

Colin Benjamin

Gulf Conveyor Systems P/L

colin.benjamin@gcsm.com.au

www.conveyorsystemstechnology.com ■

I fail to see where a telescoping loading chute

which uses brattice cloth to create the flexible

tube that rides up and down the pile hieght with

paddle type limit switches to control bin ore hieght

would be inflicting any problem.

(brattice cloth is what is used to create pathways

for fresh air in underground mine ventilation and to

direct stale polluted mine exhaust air away from the

mine face).

The flexible tube load directing system I mentioned

has been use since 1989 and is still in use.

The brattice fabric telescoping tube also limits the

creation of fugitive dust as the discharge is controlled by the

vertical movement of the flexible tube in operation.

The flexible tubing type loading tube allows simplicity in its

design limits the bin to a simple cone within the confined

area of the bin sidewalls to the very top of the silo

under the discharge head pulley.

Sorry to hear you are putting the telescoping

tube loading spout on the back burner though.

Going back the earliest types of weight measurement-

perhaps the simplicity of a wiegh lock measurement

system which would solve all the issues of control and

end any discussion of measurement guesses should be pursued.

The wiegh lock measurement being non nuclear, non electric,

non toxic, non explosive, passive in activity, with accuracy

second to none, it should be considered as the bin wieght

would be the dead wieght tonnage, and the active loading

would be the laden wieght, and as a result the measurement

is accurate at all times and infallable, using water displacement

measurement for wieght determination which is legal for trade

and is used in the Erie Canal Corridor, and is used on the

Panama Canal for wieght charges since the Panama Canal was

opened in 1914 if I remember the year correctly.

The same type of wiegh lock measurement is used to determine fuel

and water tank tonnage volumes with and without floating covers.

The wieght-counter wieght displacement method of factual wieght and volume

measurement is even simpler than a telescoping tube and has an

unmatched reputation in accuracy.

As long as the counterwieght liquid wieghs more than the bin and

payload dead weight tonnage, the accuracy of payload volume is

without question.

The history and reliability of paddle type mercury tilt switches used

for bin controls and measurement have been reliable in operation

for over 65 years as well and have used reliably in coal burning

power plants for many years.

Perhaps it would be more productive to examine the bin sidewalls and install

slippery liner material to allow the continuos discharge of material as there would

be no hanging material left to create rat holes and bridging from temporary compaction events. ■

Originally Posted by SteveDavis

Hi Izaharis,

We have a bin that has no mechanical components inside and works perfectly. Why would I want to put a cumbersome mechanical device inside it, where I can hardly see it and have little access to maintain it? The dust is enclosed by the bin, so also not an issue.

The bin exists, therefore any consideration of a weigh lock is irrelevant, interesting though the concept may be.

We could consider sealing the bin and introducing a water displacement system. This makes the discharge somewhat interesting and we need a lot of water and fast fill and overflow facilities and of course a method to instantly measure the water overflow and water feed and integrate to a mass of coal. Just a thought, but I am sure this could work. Lots of side issues though. Messy. I think this concept goes back to a bloke called Archimedes and has been around for 100s of years. Must be ok.

Side wall lining is also not an issue as the bin self empties, perhaps assisted by the vibration from the discharge feeders. Sized coal generally flows nicely especially if it hasn't been standing for more than a few minutes.

We do not want to control the amount of coal in the bin we just want to know accurately how much is left at any stage during the process.

Looking for a straightforward 21st century non contact instrumentation solution to a fairly simple problem. The solution will be simple, I am certain.

I have used and will keep using low tech solutions such as mercury tilts and so on where applicable. This is not one of those situations.

Perhaps another thread on the many diverse and strange ways in which a mercury tilt switch fails to perform as expected? I can recall a few, I am sure others have similar experiences.

All the best for 2011

To further explain and proof;

The retracting fabric telescoping tube is controlled in its ascent by the mercury tilt switces at the base of the ring which carries the the tube up and down via the winch cables.

the paddle switches are completely safe from entrapment by the material being discharged as the are indirectly contacting the cone as it ascends.

as compared to High middle and low limit paddle switches mounted on poles that swivel and that are secured to a rail below the bin roof line and

directly within line of the head pulleys discharge trajectory.

The hieght of the cone in the salt shed determines when the feeder belt stops the loading with the upper tilt switch at the roof line of the salt shed.

The fabric tube is reinforced with a wire rope sprial that raises and lowers within the fabric to add wieght and maintain its shape.

The fabric tube is continually transmitting the location of the tubes base collar at all times to the Square D PLC system that is 20 years of age at this time with the mercury tilt switches.

To further illustrate:

1. If one was to take a 2 gallon chilled ice milk carton used for soft ice cream base and remove the top and simply cut a hole in the base of the carton to represent the drawpoint.

2. the use of a simple paper towel roll tube aids in the illustration to the viewer wherein;

A large funnel with a wide opening is placed inside the paper towel tube to represent the transfer point above the silo and the transition to the bins chute the funnel would be directing the full flow and KNOWN volume being carried by the feeder belt to the BIN and then in a slightly exagerated way the filled funnel which has already filled the base of the paper towel tube is raised with the funnel allowing the material (which could be useable soft coal fines in the example; wherein

the cooal level and volume escapes the base of the tube as it raises and finds it level as it slows down when it reachs the silo's side walls and theis continues until it is full and when the carton is raised above the table it begins to discharge which in turn lowers the bin level and the paper towel tube representing the retractable collapsing loading tube lowers and continues to fill it until the paddle tilt switch has the momentary contact to tell it it raise until the momentary contact is lost again and it again ascends until it is closed and again raises until it loses the contact repeatedly until the collar at the base of the fabric loading tube reaches its top and the limit paddle for the winch control creates a closed contact and the feeder belt and winch stop.

The winch cable is no different than a mine winder/ slope tugger/ vertical hoisting system.

The winch cable being a single lay wire rope has length, thickness and location to deterimine the EXACT position of the collar or ore skip or mancage or slope railcars at any time because the vertical DISTANCE/HIEGHT/ VALUES are a known quantity and FINITE.



AN identical winch cable with a wieght block attached to the winch shaft used to raise and lower the collapsing loading tube can be successfully timed to duplicate the position of the collar at all times as the collar is secured on a rail which allows it freedom of ascent and descent as it is directly to the side or rear of the collar ring attached to the flexible fabric collapsing loading chute.

The bin volumes are a know quantity, the draw down system has a known draw down capability, you have stated the bin walls are a zero issue, mine hoist controls and location values have been used for decades with simple measurement values.

The parallel winch cable could be secured with a weight attached pole rail along the bin exterior to pass sealed electric magnet location sensors along the vertical path with limit switches at the top to stop it and transmit a filled bin message via the PLC and at base to alert one of a zero fill condition via the PLC as well.

About the weigh lock methodology:

The methods used for the Erie and Panama Canals are not messy in any way just simple.

The bin would be the load on a small floating concrete raft with the water volume greater in wieght and proportion than the silo and payload in total at all times and the simple act of displacement created by the loading and unloading sequence provides the user with total loading of the barge and position/height of the coal pile in the silo with the water column height created by the displacement.

As long as the total wieght is a known value for the silo and payload the displacement is the wieght value used to obtain the correct bin condition at all times.

There are a lot of concrete barges that still work this way one hundred years on, and a properly constructed concrete barge or raft will not sink as it displaces water.

the only thing left too debate would be the meniscus level when atmosperic pressure changes but thats not much of an issue in the scheme of things. ■

I saw this and thought of your problem

http://www.acuitylaser.com/line-scan...hipmeter.shtml ■

Originally Posted by SteveDavis

Hi Izaharis,

I did think about not responding further, but your response is so symptomatic of issues I have seen in the last 30 odd years I felt compelled:

Firstly, you obdurately refuse to accept that the problem raised does not fit into the solution that you would like to use and continually harp on the perceived benefits of a system that does not address the key requirements.

Secondly, you focus on complex out of date technology that admittedly may yet have it's uses.

"A. the technology is not out of date and is used for shiploading this very day as well."

Thirdly, your solution does not consider the impact on the user, other than it works in your experience.

"B. It goes up and goes down on a stationary railing with immediate communication of its position with the high limit low limit paddle switches only affected by the lower paddles sensing the cones increase in hieght which close the contact for the winch motor to operate until the paddle switch

contact closes."

Given the description of your winch propelled feeder tube, which you have described well, I ask - if this were a new project would we blindly copy your method today or would we seek alternate solutions that are simpler, cheaper and use today's technology?

"C. Why not? They are commecially available, have worked for years, and what is so complicated about a collapsing and expanding cable reinforced abric loading chute that also is a dust control method that works with limit switches ?".

To your credit, you have not stated that my problem cannot be solved.

I am going to leave it as is. It seems that the many suppliers of instruments that have offered solutions to my thread do not participate much in these forums, and no-one who has solved a similar problem has read the thread or wishes to comment.

I appear to have several options, all of which will cost less than $100,000 installed and programmed, with very short down time, but none of which appear to be proven in a similar operation. We may eventually trial one or two.

"D. If you would like a contact for the manufacturer............................"

Thanks to all who gave constructive inputs, and thanks Izaharis for the entertaining discussion.

Cheers Steve

I glad you were entertained with my explanations.

If your client is so worried about volume and bin level why did they not install a battery of weigh dump scales at the discharge point if they are that worried, simple flawless perfection using gravity that has been in used for over 65 years in the steam plant up the road from me.

The pulverised coal plants erected by Combustion Engineering have batteries of weight loss feeder scales to verify the tonnage leaving the elevated bunkers prior to the coals delivery to the small apron feeders and final grinders prior to the coal being blown into the combustion chambers.

The 4 coal bunkers still use the same ancient reliable methodology involving mercury paddle switches for high, middle and low limit to deliver 100 tons an hour to the two boilers it uses to make steam for cogeneration. ■

Reading the starter to this thread it seemed a reasonable request, to surface map the bin contents and use this to establish the stored volume.

Yet most discussion seems to have been on a tangent i.e. NOT related to surface mapping.

This may be a new technology, but nothing stands still. What didn't work yesterday tends to work tomorrow. What was an arm and leg yesterday is cheap as chips tomorrow.

And leads have been posted regarding surface mapping to establish the volume of containers. ■

Just my opinion...

6 loadcells, a iQube2 digital junction box, and a Rice Lake 920i controller.

This should run about $9-10k in parts.

Bring the loadcells in by sections, and you can display what is over each end and get a total for the whole bin.

It would probably take a custom program in the 920i, but it would be pretty simple. ■

Dear Steve,

just take a brief look at indurad - they are offering 3D Stockpils Solutions and installed their sensor already on hopper cars for 3d bunker inventory in chilean copper mines in the dusty atacama desert or on coal Stacker/reclaimers. They combine their unique 2D iDRR Radar with their unique 1D iATR Radar Hopper Localisation to a 3D model considering the site specific geometry. If you send them a drawing+picture about your application, they should come up with a solution.

Cheers

Michael ■

In the USA, we apply strain gages to all support legs via a bolt on assembly made for this purpose. The gages are pre-assembled into a weather proof package that has the bolt connections set at factory. Kistler-Morris is one such company:

http://www.kistlermorse.com/

You empty the bin, then drill and bolt per manufacuturers instructions. Each leg will give a portion according to the loading pattern. The signals are then summed and wala you have a reading on bin and its contents. ■

Surface mapping can only be done if the dust concentration is sufficiently low.

Ultrasonics and laser measurements need a reasonably clear path to see the true surface.

One way to achieve a reasonably clear path is to mute or agglomerate the dust (nebulize or other moisture addition) . Since we do not know the particle make-up, I offer a suggestion that may or may not work according to your specs. When material is charging the bin, the material is passed through a chute configuration that induces a negative pressure in the stream mid-center region using the principle of Vena Contracta (VC). The chute needs a two part assembly. The outer containment wall surface uses the general flow of the VC. An inner surface aids in establishing the negative pressure field within the stream. The is a gentleman in New Zealand that might have applied for the patent, this I am not sure. I do believe either Newcastle or Woolongong did some theorectical work a few years back.

I admit to only knowing of this concept and have not personally practiced its principle. However, we do have the granular flow and gas model that could attest to a theorectical solution of dust abatement for the sake of measuring the content surface as well as mass.

Please let us know of your success. ■

The contents vary with charging, reclaiming, or a combination of both. Thus, a single point reading does not map the surface. Some modern "distance mapping" codes work on a statistical averaging basis. In this way, the mean strongest measurement/signal is found from many samples and the software filters out the lighter variances about the mean. Find a laser or ultrasonic mapping that can filter such noise (dust) to a high level and you might find your answer. ■

Since you can seal the system, I have been wondering if you could not measure the ullage by a gas pressure technique?

Something along the lines of METHOD AND APPARATUS FOR MEASURING THE ULLAGE OF A VESSEL United States Patent 3744306 .

This would not provide the surface, but might provide a measure of the contents. Calibration via the existing system would seem possible. I am not sure if there is a commercial version of this available. A quick search did find a range of ullage measurement devices. ■