Comptrol makes an impact weigher that uses the material horizontal velocity rather than the vertical freefall. Think of it as a gravity impact meter laying on it’s side.

Your 5 m/s belt speed should be more than sufficient. Click www.comptrol.com/headweigh15b.htm for information on their HeadWeigh 15B Series Belt Scales.

Delmar Schmidt

Melfi Technologies

www.melfitechnologies.com

Attachments

15b (GIF)

■

We can offer a nucleonic wighing solution. Totally non contact but with the obvious regulations to be observed. The choice is of course the users as to whether they use it, but it does have some advantages and gamma radiation systems are already widely used for moisture detection for example in the coal handling industry.

Article below refers:

Continuous monitoring of the mass flow or weight of solids is a vital area of process control in solids measurement, particularly in quarries and aggregates handling. The challenges for instrumentation are many, e.g. dust, abrasion and impacts, varying bulk densities, changing moisture, build up, particle sizes and vibration.

‘In line’ weighing systems in the aggregates and quarrying industries come in a variety of technologies depending on the product and conveyor type, formats include ‘Loss in weight’ systems, impact and dynamic belt weighing systems. They all involve various levels of process contact and/or precious plant space for isolation of process for the weighing of material at a point in time, and all involve some mechanical, moving parts. Not ideal when handling abrasive products.

Another option is the indirect measurement of product flow though screw and drag conveyors via motor load consumption, acoustics or suspending conveyers and chutes on load cells have proved generally unreliable and high in maintenance and demand regular recalibration.

These factors can make many existing systems’ cost of ownership high. Lost production, time and money spent on repair, unscheduled maintenance and specialist recalibration - depending on the device, material and environment they are used in.

Another way ‘around’ the problem

There is another highly reliable alternative to consider, by using a completely externally mounted, low energy, high sensitivity nucleonic system ‘around’ the conveyor, with no intermediate machinery or additional space needed. Although the installed cost may be higher, the benefits of this type of system are clear:

·No moving parts - no mechanical wear or drift

·Installation on screw, chain or belt conveyors without major modifications

·Little space required - no relaxation section required for mass flow

·Measurement possible even during free fall of product

·Low source activity due to the use of highly sensitive scintillation detectors

·Extreme long-term stability due to digital electronics and decay compensation

·Check of calibration on the empty conveyor system by a standard absorber

·Determination of the dry weight possible with existing moisture signal

·Proven in thousands of applications worldwide

‘Concerns over the use of radiation’, is the normal answer. However it is worth considering a little more carefully in light of the potential benefits outlined above and the demand for more predictive maintenance and ‘fit and forget’ equipment.

Go to http://www.vegacontrols.co.uk/casest...ixedRangeID=06 ■

MB,

I would be concerned with build up and the wear factor of using an impact flow meter for raw coal. Using a single idler belt scale at 5 m/s (984 fpm ) would hurt the expected accuracy. If you are only looking for 1-2% you would probably be OK. Mounting on 1 meter centers means the scale would be seeing the coal for 1/20th of a sec. Most single idler scales are rated for +/- 1/2% when installed in approved applications. ■

Hello Mr Biggs

The most cost effective/accurate and reliable way of measuring mass flow on conveyors is without doubt using a single or multiple idler belt weigher.

An idler pitch greater than 1m will give greater weight discrimination than a short weigh-length and multiple weigh idlers fitted will give even more accuracy. We have supplied and fitted 3 idler set systems and acheived long term accuracy of better than 0.1%.

Accuracy depends largely on the condition of the conveyor rollers and bearings, alignment of weigh idlers and whether there is any belt tracking and flexing of the conveyor.

The weight integrator/display can can also be used to control the infeed flowrate via a user programmable set point. An analogue signal is transmitted to control the feeder system flowrate or to control the speed of the weigh conveyor, thereby matching the flow-rate with the set demand. ■

Hello Mr Biggs,

I am intrigued to know why you are looking for an alternative to a traditional belt weigher.

The application you have is a very difficult one.

I have done a quick calculation which indicates that you would require a weigh length in the order of 4.9 metres in order to get any sort of reasonable accuracy and repeatability. The calculation also shows that the volumetric utiliation is only 63%. This would indicate that you could afford to run the belt at a lower speed, say 3.8m/sec. This would reduce the required weigh length, increase the resident time of material in the weigh area and probably improve the wear and tear on your conveyor system.

If you simply increase the weigh length by placing the idlers further apart you run the risk of the belt bellying and causing higher side impact on the weigh idlers.

Jon Scarrott ■

Hello turnyourbassdown.

treble only.

1. Determine the C.S.A. of the material using the nominal surcharge angle of the material and the angle created by the idler trough and the belt.

2. Calculate the cosine of the conveyor angle. This becomes the De-rate Factor. (not exact but close enough).

3. Use the first formula to calculate belt speed for 100% Volumetric Utilisation

.

max t/hr

.

3600 x C.S.A. x De-rate factor x bulk Density(t/cum)

4. Use this second formula to calculate actual volumetric utilisation

Volumetric Utilisation = (Calculated Speed / Actual Speed) x 100

Hope this helps

Any trouble with the above and I'll run the calcs for you.

Jon Scarrott ■

Hello turnyourbassdown.

I originally gleaned all of this material from various conveyor design manuals, and put together some design software that ultimately calculates weigh lengths for belt weighers. This was about 20 years ago and would guess that some belt manufacturers such as Dunlop would still supply this information.

The surcharge angle for crushed limestone is 25 degrees. Agricultural limestone of -1.00mm is 20 degrees.

I have a table to indicate csa for various conveyor sizes. If you would like a copy, email me.

Jon Scarrott ■

Hello turnyourbassdown

We manufacture belt weighers and I can supply you with all the information you could need on the above subject if you wish to send me an email. There are very simple ways of doing all the calculations for the above.

Best regards

Martin Hindle

email: martin.hindle@hkprocess.co.uk ■

Kindly go through the link below

href="http://www.ktekcorp.com/dnn20/Default.aspx?tabid=67&productID=108" target="blank">http://www.ktekcorp.com/dnn20/Defaul...&productID=108

Its LM2D Two Dimensional Laser Scanner

for Non-Contact Volumetric Measurement of Belt Conveyed Materials

Attachments

lm2d-0202-1%20datasheet (PDF)

■

Further to your request for more information with regards to the Impact Plate Flowmeters

for coal flow measurement.

The impact plate flowmeter is a Mass flow meter which is ideal for use with solid products. We

have numerous installations in a variety of industries were our flowmeters are used together with various

flow modulating techniques, to measure and regulate system throughput for effective plant management.

The impact plate flowmeter would be suitable for use with your application.

Impact Plate Flowmeters are suitable for systems with throughputs of 50 - 250,000 kg/hr. Accuracy of flow

measurements are to +/- 5%. Incorporating an Impact Plate Flowmeter into an existing system is usually

a simple process. The nature of the flowmeter only requires that it be placed into the process line were

product is falling under gravity. With no moving parts there is little maintenance.

For more information on our SOLO range Impact Plate FLowmeters please follow these links:

Continuous Weighers Brochure, Page 3: http://www.rospen.com/downloads/ContinuousWeighers.pdf

Impact Plate Flowmeters Web Page: http://www.rospen.com/ImpactPlateFlowMeter.html

If you could contact me I would be happy to have a discussion with you about you requirements and give a quotation for a suitably sized flowmeter.

I trust that this information is suitable for your requirements, and look forward to hearing from you.

Regards

Dan Liptrott

Mass Measuring Ltd

Dan@mass-measuring.com

+44 (0) 161 304 5700 ■

Totally correct!

But, if there's a hard way to do a job somebodies will find one. ■

Originally Posted by mbiggs

I am after an alternative to a traditional belt weigher.

Is it possible to get some kind of impact weigher to work in a hood and spoon chute at a 90 degree transfer between two conveyors?

I need one that will not intefere with the chute geometry. Maybe mount the entire chute on load cells and measure the reactions?

The conveyor will run at 5 m/s, with throughputs between 1000-3000tph. 1600 wide belt, 45 degree trough, 1100mm between head pulley and centre of out conveyor.

Or else, what about a single idler belt weigher at say 1m idler spacings for feedback control purposes. Who makes these and how accurate/reliable are they?

Dear Friend,

Kindly let me know the conveyor length & a sketch of the Conveyors. We should be able to help you.

Regards

Sundar

+91 9483527761

sundar@orangecare.in ■