Re: Belt Weigher
we use Merrick gravimetric scales (weightmeters) for Stacker/Reclamimers boom (45 meters, +12/-16 degres). they use an inclinometer to determ the angle correction factor. They work since 1984 faily well.
At present we are moving to a non contact type (radiometric or laser scanner) in order to avoid error due to belt conveyor tension change (it use a hidraulic take-up).
bye ■
Untitled
Dear Mr. Ignacio,
Could you describe for "gravimetric scales and non contact type (radiometric or laser scanner)" principally.
Currently, we need the optional scale to measure flowrate for blending purpose and will be placed at Stacker/Reclaimer.
And then please advise me the supplier/manufacturer web address for subject above.
Regards
Achmad Zabir Ula ■
Re: Belt Weigher
The belt weigher / scales are regularly installed on horizontal portion or straight incline portion of conveyor. The belt weighers are also regularly installed on straight incline conveyor but varying inclination (like boom of luffing type stacker)
The Belt weigher cannot be installed in concave / convex portion of belt conveyor, because variation in belt tension will vary the belt pressure (force on idler) and reading will not indicate true weight force (i.e. mass). The belt tension in conveyor continues to fluctuate depending upon instantaneous conveying rate (loading).
Regards,
Ishwar G Mulani.
Author of Book : Engineering Science and Application Design for Belt Conveyors.
Email : parimul@pn2.vsnl.net.in ■
Re: Belt Weigher
Dear Mr. Mulani,
Thank you for your reply. Can you provide or suggest the method and supplier who is supplying the weigher that can be installed on inclined conveyor.
We are having the conveyor with fixed inclination of 8.5 ° and capacity of 400 TPH.
Rgds,
Jigishu Shah
MUNDRA PORT ■
Re: Belt Weigher
Dear Jigishu Shah - MUNDRA PORT
Please inform your email address to provide you required information.
Regards
Ishwar G Mulani
EmailID: parimul@pn2.vsnl.net.in ■
Incline Weighers
Many suppliers can offer mechanical (load cell) weighers for installation on straight inclined belt conveyors.
Like all mechanical weighers they need to be calibrated using a measured quantity of the correct material. OIML R-50 and NIST handbook 44 give some calibration details for certification, which could be adapted for non certifyable use. The accuracy of the weigher will be largely dependant on the quality of the installation of the belt in which the weigher is installed, and the method by which you calibrate.
There are a variety of weighers available, ie single roll, two roll etc., and some units have been type approved. This information should be available from suppliers.
Trust this helps ■
Re: Incline Weighers
Originally posted by Steve Davis
Many suppliers can offer mechanical (load cell) weighers for installation on straight inclined belt conveyors.
Like all mechanical weighers they need to be calibrated using a measured quantity of the correct material. OIML R-50 and NIST handbook 44 give some calibration details for certification, which could be adapted for non certifyable use. The accuracy of the weigher will be largely dependant on the quality of the installation of the belt in which the weigher is installed, and the method by which you calibrate.
There are a variety of weighers available, ie single roll, two roll etc., and some units have been type approved. This information should be available from suppliers.
Trust this helps
■
Re: Belt Weigher
Application Guidelines for belt scales ( belt weighers) can be found at this address: http://www.siemens-milltronics.com/p...981GA01.pdfss;
For a variable incline conveyor, such as a stacker conveyor, an incline compensation device should be used. Siemens Milltronics offers such a device that compensates for angle changes by raising and lowering the belt scale load cell excitation voltage,
With such a device, it is still important to keep consistent belt tension by using a gravity take-up on the conveyor, if it is all possible.
Ralph Closs
Product Manager
Siemens Milltronics Process Instruments ■
Re: Belt Weigher
The milltronics manual gives some good advice on the basics of a belt weigher installation, and many weigher suppliers offer similar advice.
An issue not covered is that of belt speed used to integrate the weigher output signal into a weight reading. This can be measured several ways, but the norm is either a wheel on the return side belt or a tachometer on a pulley shaft. The wheel method is inherently less accurate for various reasons, but may be acceptable depending on requirements. The pulley tachometer can suffer from inaccuracy due to lagging wear over time, but planned re-calibration will reduce this and most of the other variations in conveyor condition generated with time.
Installation of a weigher on a variable incline beltwould not be a first choice for ultimate accuracy. The issue being that unless the weigher is calibrated with material at each incline, there is no real way in which the accuracy of the incline correction device, be it electronic or mechanical, can be confirmed. The approximation may be adequate for weighing where ultimate accuracy is not required.
A straight, horizontal conveyor is preferred for accurate weighing, with the weigher just after the single load point in a well aligned, well founded conveyor with gravity take up. Wind protection fences or a full enclosure also help. A similar fixed straight incline conveyor is likely to be slightly less accurate. ■
Belt Scales
Belt Scale accuracy whether on a horizonatal or sloping belt depends upon the design if the weigh frame. There are many weigh frames on the market for which tight accuracies are claimed however since belt weighing applications vary from easy though to very difficult sometimes they work and sometimes they dont. Their failing is a 'one size fits all' philosophy which fails to take into account the differences between applications.
Many of the comments in this forum are based on the idea of putting a belt scale in an ideal position to make it work while we have found that it is possible to design a weigh frame to work in almost any situation or at least to get near the desired precision and then to tell the customer exactly how well it will work.
We have many belt scales with accuracies from 0.25% to 1.0% on slopes of up to 17 degrees, but these are normally 4 idler fully suspended units. We also have over 50 units around Australia on Stacker-Reclaimer booms which evidently work in the 0.5% to 1.0% accuracy range, we continuously measure the angle of inclination and compensate the result at all angles using a simple trigonometric rule. The secret again is a good multi idler weigh frame which is senstive only to forces perpendicular to the conveyor.
For Weights and Measures jobs there is a need for live load calibration, however we get very good agreement between dead weight calibration and live load performance using our multi idler fully suspended weigh frames. ■
Belt Weigher For Inclined Conveyor
Dear Mr Shah
I believe that your original question was concerning placement of a belt weigher on the inclined portion of a conveyor rather than on a variable incline coneyor.
The truth of the matter is that some belt weigher designs yield more accurate results than others when placed on inclined (or declined) portions of a belt conveyor.
Belt weigher location is often a trade-off between ideal location and requirement / performance.
I would be please to discuss your application with you if you cotnact me at mike.tallevi@siemens.com
Regards
Mike Tallevi ■
Scales For Inclined Belts
It is no problem to install the Rembe Uniband Beltscale in an inclined belt (the product should not slide back). For conveyor belts, that change the inclination, we supply an additional inclinometer option, which is able to compensate for the different belt slope. ■
Re: Belt Weigher
The old school of thought that more idlers are better might lead one to purchase 4 idler belt scales when a less expensive, high performance single idler, or dual idler belt scale may do the trick.
On fixed incline conveyors there is more freedom for selection.
Siemens Milltronics offers a unique design of single idler belt scale where the weighing idler is actually applied directly to 2 triple beam parallelogram load cells. The results have been very rewarding. This model, MSI, has been certified for trade by SABS (South Africa) and Measurement Canada. The combination of two of these belt scales as a two idler system (MMI) has been certified by NTEP and Measurement Canada. In our opinion, the MSI single idler belt scale can easily provide the accuracy of a 2 idler conventional belt scale and the MMI (2 MSI units) can easily provide the accuracy of a conventional 4 idler belt scale. Please check our web site for more specific details on these products.
http://www.siemens-milltronics.com/
To address variable incline conveyors, such as stacker conveyors, a multi-idler belt scale can be more forgiving with regards to the great variation in belt tension, which is created due to the changes in conveyor slope. We generally elect to go with a 2 idler (MMI), or a 4 idler belt scale on these applications, depending on the desired accuracy. If a gravity take-up can be used on such conveyors in order to reduce the variation in belt tension, it will greatly enhance the performance of the belt scale system. An electronic incline compensating device, where measurement of incline angle and automatic compensation of conveyor load readings is performed, remains a must.
Hope this helps.
Ralph Closs
Product Manager
ralph.closs@siemens.com
(705) 740-7603 ■
Re: Belt Weigher
Another probem not spoken of that was brought to light by Hendrik Colijn: back sliding of materials on incline planes. He measured and demonstrated the errors of weigh scale systems applied to incline planes. He has published in Bulk Solids Handling on the subject.
Lawrence Nordell
Conveyor Dynamics, Inc. ■
Inclined Belt Weigher
In principle belt weighers can be installed on inclined conveyors without any problems. Most scale carriages nowadays (at least ours) have been designed to operate on inclined conveyors without effecting the accuracy. In general the accaracy is improved when using multiple weighing idlers.
We advise not to install belt scales on convex/concave conveyors. Or at least 12 - 15 meters away from the start/end of a curve.
Calibration on an inclined conveyor might only be more difficult if you use static weights. But since strain gauge loadcells have a difined calibrated output/sensitivity, calibration can be carried out be means of electronic simulation (R-Cal).
On conveyors with variable inclination an inclinometer is used to compensate for this effect. Accuracy however will be less (2 - 3%).
Regards, Jimmy Grootegoed (Thermo Ramsey Germany) ■
Re: Belt Weigher
The question of using an inclined conveyor for a weighing conveyor is not a simple yes or no. If the proper conditions are met, accurate weighing is possible. Both HB44 and R50 scales can be installed on an incline---they need to be carefully installed and carefully calibrated. Most approved scales are multiple idler scales--usually 4 or more.
Manufacturers of approvbed scales such as CST (Australia), Ramsey (Australia and US), Milltronics (Siemens) and Merrick (US) have approved scales and publish a handbook of recommendations.
I work as an independent consultant on belt conveyor scales.
P W Chase ■
Re: Belt Weigher
Dear Jigishu,
I will try to answer your questions to the best of my knowledge.
In a perfect world, we like to see belt scales on flat idler-no incline conveyor applications, for a nice even belt load. In hopes of making it a perfect world...
The belt should touch the idlers at all times and track fairly evenly, at least two idlers before the scale idler and two idlers after the scale. (Even when there is no material on the belt) Also, as long as the incline portion of the conveyor isn't so steep, that the material rolls back down the belt and over the scale weigh bridge. (One idler before and one after)
Trough rollers are acceptable up to approx. 25 degrees.
Please see the attached PDF file of our Belt-Way Scale manual, for recommended "Conveyor Design Requirements" (page 40 and 41) Also, please review page 2 of the Belt-Way Scale Manual, for more details on placement of a belt scale on your conveyor.
If you have any further questions please feel free to contact us.
Sincerely,
Melissa Johnson
Sales & Service
Belt-Way Scales, Inc.
One Belt Way
Rock Falls, IL 61071
(815) 625-5573 phone
(815) 625-5593 fax
sales@beltwayscales.com ■
Re: Belt Weigher
to Jimmy Grootegoed
hello---e-mail me when you have a chance
Paul Chase
mjc@emily.net
Hope you remember me
Paul ■
Re: Belt Weigher
Belt Scale,
Jenson & Nicholson,India Have installed belt scale
in a inclined conveyor in Tata Iron & steel Plant ,INDIA in 1989 with cosine correction factor & the same is working well.
Atanu Banerjee
M.N.Dastur & co (p) Ltd.
KOLKATA
INDIA ■
Belt Weighters
May I ask why a weighter would be used in configuration with a materials moving belt and not in a location isolated from the number of variables associated with transportation of bulk materials on a conveyor.
If the weighing mechanism were located at a position in the structure related to support of the conveyor, the variable, material weight being transported would be correlated with the constant Time.
Thus eliminating the weight of the structure above the weighing mechanism supporting the conveyor, does it not seem that a plant operator would be able to measure the weight of material being processed over a specific point in corelationship with time?
I'm very new in this business, so please forgive me if this is a rather "stupid question".
thank you
Tominer ■
Re: Belt Weigher
Dear Tominer,
It seems you are suggesting to install load sensor below conveyor structure instead of below the platform supporting 2 / 3 idlers. In this case, the load sensor will be sensing large magnitude of dead weight plus small magnitude of concerned weight. This type of arrangement will be less accurate because accuracy is related to total weight. As you say dead weight can certainly be bypassed, however accuracy will continue to be an issue.
This is like; if you wish to weigh a person, better we weigh him directly rather than weigh the car when he is sitting inside the car, and then deduct the car weight.
Regards,
Ishwar G Mulani.
Author of Book : Engineering Science and Application Design for Belt Conveyor.
Email : parimul@pn2.vsnl.net.in
Tel.: 0091 (0)20 5882916 ■
Inclined Belt Weigher
Dear Sir,
I have installed on conveyor having 15 deg. inclination without any probleb in accuracy. Now cosin factor is taken care of by the electronics. So without giving second thought you may install belt scale in a inclined conveyor.
Regards.
A.Banerjee ■
Belt Weigher On Inclined Belt.
I have seen belt weigher (load cell type) on inclined belt conveyors since 1966. They had to be calibrated once in a while. The belt-weighers work well on belts with fixed inclination. ■
Inclined Belt Weigher
Dear Mr. Vinayak,
What about accuracy level at that time. Was it 0.5%?
Regards.
A.Banerjee ■
Simple Answer Previously Mentioned
The belt weigher industry has been weighing on inclines for years. Most good scales have incline imput in their software. The big question is what is the material and at what angle does it begin to slide back on the belt. If you are weighing marbles, no incline. ■
Belt Weigher
Hi All,
Normally the belt weighers / scales are installed in horizontal position only since the calibration is easy..
I would like to know that whether they can be installed in inclined portion of conveyors? Any suppliers for this? Method of calibration?
Jigishu Shah ■