Hi Mike,

There are a number of self adjusting plows available.

Richwood Industries has a very positive air controlled system that uses a thick rubber blade for belt cleaning.

Martin engineering has a system that uses a polymeric tensioner.

Other systems use gravity tensioners to maintain contact of the cleaner on the belt.

Major considerations for the cleaning system required include: material being cleaned from the belt, belt speed, space availability for the cleaning system, and likelyhood that the cleaner will be properly maintained. (NO CLEANER WILL WORK FOR LONG PERIODS IF IT IS NOT ADJUSTED AND MAINTAINED ON A REGULAR BASIS.)

With plows, consider using more than one. The first plow will clear the majority of material and the second, or third, will clear the rest.

I believe that both Martin and Richwood have web sites and can be easily found -- if not, send me an e-mail and I will give you contact information.

Regards, ■

I have to disagree with Dave... It is possible to design a belt cleaner with enough intelligence and reliability that will work for long periods of time without any intervention.

The major problem is that most people does not want to pay for those solutions and I'm not so sure that it can be justifiable unless safety and well being are issues.

A cleaning system whatever in a belt or roll needs to be customized or at least properly integrated. Since continuous monitoring and adjustment is needed, the system must be safe and operator-friendly to inspect and adjust.

Can a system be automated to engage and release? I think that the additional cost to provide these features is minimal.

Antonio Reis

www.vitrom.com ■

Although I hate to admit it, Antonio is correct.

Cleaners can be designed so that minimal PM work is required. All that would be required is to include two separate I/O (Input/Output) devices in the control system -- one to advise when the plow has reached its Minimum Height and one to advise if material has become lodged between the plow and the belt.

I am in agreement with him that these solutions are rarely used.

A more expensive alternative is to place a camera for monitoring the plow, if the control station is manned.

Regards, ■

Your question mentions plows, and as mentioned by you, it is required for scrapping the bulk material off the belt. Your word plow is getting mixed-up (confused) with internal scraper. I would like to clarify about generally used following names :

Plow : To discharge material from carrying run belt

V Type internal scraper : It looks like V-type plow but it is of lighter duty and used for return run belt cleaning purpose.

It would be easier for readers to respond to your question, if you mention whether you are referring to plow discharge or V-type internal scraper.

Regards,

I G Mulani.

Author - Book 'Engineering Science and Application Design for Belt Conveyors'

Email : parimul@pn2.vsnl.net.in ■

Mike

Seems like you hit another funny bone and another two cents on the definition. By plow, are you refering to the normal or conventional condition of scaping material from the belt underside or pulley cover surface at the tail?

This type of equipment is sometimes used at the head end, as well, to protect drive or takup pulleys from trapping rock.

My following comments are related to the conventional definition of plows:

Even though these "self cleaning" v-plow or single blade slant plows profess to be long lived (automated to compensate for wear) don't believe it.

There are many types. The reason is that they only partialy work. Some are designed to work under tension ( be pulled by the belt or belt pulls plow againt a restraint) and others in compression ( the plow pushes against the belt). The latter type is worse in that it can more easily set up vibration, on belt contact, passing muck and splittle, and digs into belt cover - leading to belt damage if unattended. Look at the linkage articulation kinematics. The VEE is preferred because it has "balanced" forces" symmetric about the center (maybe). Spittle has to move half as far to be dumped or half as long to dig at the plow....

As previously stated, spittle can get by. When the belt vibrates, it passes small pebbles under the plow and bouncing big rocks over the plow. Eventually, this can unevenly wear the plow surface leading to the passing of ever bigger pebbles and abrasive muck. The wear action is dependent on the duty, material, environment, maintenance,...... Ice is another difficulty.

It should become an axiom - All horizontal plows will pass muck and spittle. Observing the wear mechanism will tell you that.

One way to partially overcome this pebble bypass problem is to put in a reverse VEE idler set, assuming a full turnover is not justified. Place the plow just before the VEE idler, or better, between two VEE idlers. Incoming pebbles and muck get a gravity boost before hitting the plow and after it. The vibration issue disappears. This concepts needs a little extra space to negotiate.

I have examined too many belts with broken tensile structures (fabric and steel cord) to believe in the effectiveness of the plow without other aids.

Regards,

Lawrence Nordell

Conveyor Dynamics, Inc.

www.conveyor-dynamics.com ■

Mike:

I agree with I.G. Mulani, on a second read you seem to be asking how to scrape or plow product from the carry side belt. I also agree with Mr. Brinko, and the atributes he notes - flat bed, et. al.

If you are interested in plowing carry side product, then as others will tell you, it is only prudent if you have an acceptable material ( soft relative to digging the belt cover or fine grain such as fine sand and related products) and the belt speed will be below the vibration and wear tolerance levels. The general duty

should not be in the 24 x 7 class.

We have designed and built such plows for coal and coke environments. We have also used the articulated and fix tripper pulley arrangement to faciliitate discharge with greater efficiency.

If cost or space are big issues, and the rest is compatible, then the design is not difficult.

We have built a plow that removes the product in two stages. It has a two blade system or twin plows. The first stage = first blade assembly removes the bulk of the material. It is built like a "cow catcher". It has space between blade and belt to let about 20% of flow to pass under, depending on rock size. The trick here is to make it flexible to allow rock to pass under it when it begins to bind. Sufficient space allows the second stage , wiper plow to remove the remainder within interaction with the first stage. The second plow becomes more efficient because it does not have the high stagnation pressure and lateral shear resistance of the single plow.

Lawrence Nordell

Conveyor Dynamics, Inc. ■

Dear Mikemcbain

I would like to inform you / readers, following design issues for belt cleaners (belt scrapers) and plow discharge, for general benefit of readers.

1.0 Belt scrapers cleaning blade / medium will exert particular pressure during static condition (when conveyor is not working).

2.0 Belt scrpaer cleaning blade / medium will exert different pressure during dynamic condition (when conveyor is operating). Again this cleaning pressure will have variation such as

2.1 There is no material on / with belt and hence actual scraping / cleaning of material is not present.

2.2 Average expected material is on / with belt and corresponding scraping resistance.

2.3 Max expected material is on / with belt and corresponding scraping resistance.

If the scraper is properly designed, it needs to maintain only positive pressure during all the above situation. If it is so, the item will function steadily without chatter (in most of the situation). The chatter signifies that the pressure is fluctuating from positive to negative, and could mean wrong choice or wrong considerations in design or faulty design.

Also, the hing-point / critical support should be located such that turning moment due to varied drag resistance should create minimum effect on blade pressure. The chapter - 9 of my book adequately describes this aspect in thought provoking manner.

Regards

Ishwar G Mulani, Book Author - Engineering Science and Application Design for Belt Conveyors.

Email ID: parimul@pn2.vsnl.net.in ■