Originally Posted by Joseph A. Dos Santos

Though I have had much experience in conveying widely varying materials

I have no experience in handling salt. I was asked for general guidelines on conveyors to handle salt so I would

like to pose this to the experts in this forum.

I imagine that most of the guidelines will deal with corrosion as salt should not prove to be difficult in handling

but I do welcome any insights related to handling as well.

I do remember learning from a friend who sold to underground salt mines that equipment did not suffer bad

corrosion when underground.

However the minute it was brought to the surface it would immediately begin to corrode at a much accelerated rate.

I welcome the comments of all readers of this thread.

Joe Dos Santos

About conveyor belts for salt:

Cable Supported or Steel Supported Conveyors used

for transporting Deep Mined Halite Salt and Solar Salt

overland or into Buildings/salt sheds on the surface will

suffer dearly with corrosion NO matter the latitude.

Surface Conveyors handling Deep Mined Halite or Solar Salt

will require a continuos conveyor belt cover to prevent

local winds from blowing the finished salt off the

conveyor belt line.

The other issue is surface water pollution from naturally occuring

chlorides in the salt product.

In my example the New York State Department Of Enviromental

conservation requires that overland mounted conveyors for salt

have cast in place gutters for salt water collection.

Any salt conveyor run mounted on towers with steel supported

works requires conveyor belt covers.

Surface operations require enclosed transfer points for conveyor belts on

the surface handling finished salt.

The transfer pointsfor filling silos also require closed transfer points.

The overland transfer points will have to be cleaned periodically with a pressure washer

due to the build up of salt dust and minus 30 mesh salt fines.

.

To give you a good example eye opening view about salt related corrosion you should

visit the Windsor Salt Mine in Windsor, Ontario and the Canadian Rock Salt Company

mine in Pugwash Nova Scotia Canada if you have the time and the shallow Halite mine

opened in the gulf of St. Lawrence in the late nineteen seventies which is wholly owned

by Canadian Rock Salt.



The Windsor Salt Mine is shallow(below 1,200-1,300 feet underground) and owned by Canadian Rock Salt

which is wholly owned by Morton Salt Inc.

The Cargill Salt Mine at Avery Island, Lousiana which was formerly owned by International Salt Company

has to use wood to mount some of their underground conveyors due to the high humidity. The conveyor

used to load barges is also made of wood if I rememeber correctly for the same reason.

As far as handling salt it all depends on whether the salt has a lot of rock in it as the shale will wear on

the ore side of the belts.

Our two different sized run of mine belts carry 450 to 900 tons per hour-36 and 42 inch.

Mechanical splices are used normally on rapidly advancing belt lines depending on tonnages.

They will fail prematurely from Run Of Mine Ore impact damage.

The splices leak dust back to the return side which carries back to the tail pulley which has a plow scraper

on it to divert the fines riding on the belt. The beater pulleys help some but if you have a large amount of

fines as you would from the use of AMFO which creates a lot minus 30 mesh fines the drive units and tail

pulley are prone to being buried in fines if they are anchored close to the floor. this also creates a huge

power drag on the drive units.

Simple shoveling becomes difficult when the dust is packed under the drive units.

The mine I worked at had one vulcanised conveyor run which operates on a

twenty one degree slope for finished salt (minus one inch) that is almost

2,000 feet long on a cable supported belt system.

The splice or splices are replaced annually during shut down periods.

The head end of the drive units will become buried in fines quickly even with daily

shoveling as the transfer point in enclosed.

Head pulley cleaners work well but the issue is and always will be the minus 30 mesh fines.

A belt conveyor for salt is a means to an end but they are only fifty percent efficient.

There is at least one Halite/Potash mine in Germany that still uses a high efficency rail

network underground.

I would also recommend visiting Irish Salt Incorporated in Ireland as thier mine is shallow and mines

salt and potash and uses Joy brand continuos miners to mine the Halite Salt and Potash both.

The Halite is broken by a belt feeder breaker (typically WR Stamler-now owned by JOY MINING)

or (Long Airdox) and the broken ore is fed on to a tail pulley and transferred to the screen plant for further crushing

and screening. ■

Hi Joe

I have worked in salt for over 30 years. I look at our underground operation basically like a rock quarry so handling rock salt is really no different than handling rock and gravel except for the corrosion factor. We do our milling underground so we only hoist finished products. So after primary crushing you can expect 8" minus material to be conveyed. Secondary and tertiary crushing in the mill reduces the finished product to 1/2" minus. We use bulk densities of 90 lb/cu ft for primary crushed and the finished product varies from 76 to 78 lb/cu ft. In situ density I believe is around 135 lb/cu ft. The angle of repose can vary from 32 to 34 degrees depending on the moisture content of the salt and the amount of fines in it. We have conveyors handling up to around 2500 TPH underground and up to 5000 TPH on surface.

Your information on minimal corrosion underground is correct in most cases. Constant low humidity and constant temperature 68 to 70 degrees F do not prolong corrosion. There is some slight corrosion but it only tends to go so far and then stops. We typically only coat steel with a primer for underground or a standard enamel paint coat for color. We will use stainless steel for chute work underground because we get a condition which a now retired colleague of mine liked to term it as "corrosion erosion" the chute walls would corrode to a certain point and then that corrosion would erode away starting the corrosion process over again. Most people confuse this with a wear problem but salt is classed as a soft rock and wear is very minimal.

Areas close to the shaft prior to the ventilation doors should be treated the same as surface especially near downcast shafts. My experience is that steel underground tends to become impregnated with the salt and yes when it comes to surface this salt impregnation becomes extremely active causing almost immediate corrosion once exposed to the higher moisture levels and temperature fluctuations on surface.

Now surface is a totally different story. Moisture plays a major factor in the corrosion process as I am sure you well know. The best protection for surface (other than expensive stainless steel) is a 2 part epoxy paint system (I can give you my recommendations if you need them). The most critical part of any good coating system is the surface preparation as it must be to a near white blast to SSPC SP10. In choosing any stainless steel components I would suggest to avoid 304 SS and go with 316 SS. The carbon content is much higher in 304 verses 316 and will start corroding over time.

All the above information is solely based on my experiences over the years. I would be more than happy to answer any other questions you may have. ■

I do not recommend galvanizing anything used for a salt application. It simply will not stand up.

As far as idler frames and rolls. We use standard frames but we use an all PVC roll and I highly recommend a good labyrinth seal for the bearings - do not rely on bearing seals by themselves. Frames will corrode but the high cost of SS frames does not justify the cost of simply replace them over time. You could expect to get 5 to 7 years out of frames maybe more.

Pulleys we do not do anything different except we use SAFD (D=ductile iron which stands up quite well in the environment) bearing blocks fully sealed with end caps or LOR seals when the shaft extends out of the bearing block. We do spec a minimum 1/2" rim thickness with no lagging or ceramic lagging is most preferred vs rubber lagging .

The only place I would use aluminum is for guarding. Even then it must be separated with some rubber from contact with any more noble steel to minimise any galvanic reaction. The aluminum with disappear starting at those contact points gauranteed. ■

Joe

One further note you may want to consider.

I always specify seal welding of all welded joints. Stitch welding will prevent sandblasting at the location between the 2 pieces will allow corrosion to occur at that location in the joint. So absolutely no stitch welding permitted. ■