A 'self propelled' maintenance trolley raises many questions which have never been addressed over the fullness of time. The method by which motive power is supplied needs to consider what tractive effort is required to carry the maintenance equipment. This will determine the gradient ability of the vehicle in question. If the rails are wet enough then the tractive effort will be seriously compromised.

Maintenance very often demands the replacement of weighty items which are far beyond the limit of legally acceptable manual handling requirements: so a crane should be supplied. Similarly, a ruptured belt requires that a meaningful maintenance trolley would be able to transport a full reel of belting weighing around 20 tonnes. Will your gantries carry that? Give over!

A maintenance trolley belongs to a bygone age when follies could be ignored and self gratification was expected. If I was in the business again I would introduce microphones to listen to idler condition and remote cameras to observe other troubles. The price of such equipment is very attractive and their reliability and effectiveness exceeds that of a motley gang sitting on a remote trolley and watching videos on their mobile phones. Of course dispense with walkways: but do it properly. Mobile cranes can even be hired when required. ■

Conveyor Dynamics, Inc. (CDI) has installed many long and undulating overlands with self powered maintenance trolleys. There are multiple ways to exceed the standard norms of slope stability. Many have trolleys with slopes to 14 degrees. There are multiple methods to take the trolley to 20 degrees and higher such as with pipe conveyors that can negotiate 30 degree slopes.

Me thinks Mr. Gateley is in the fog of older days/years. Think what ski lifts do today as they negotiate the Matterhorn. ■

CDI has recently designed a 210 km OLC with individual flights over 30 km. The OLC is completely elevated and fully fitted with self powered maintenance trolleys. I do not know any client that would go back to conventional wisdom of ground based assemblies and their environmental and human interactions on large overlands. No road maintenance, higher productivity, reliability, and availability with better inspection technics, better access, and better install/removal of idler assys.

By example, Dangote Cement, Nigeria has 3 elevated OLC conveyors (7, 8, 10 km) in near parallel operation, coming from different limestone sources, designed by CDI starting in 2004-2012. They are all fitted with self-powered trolleys. Other examples include, Adani in India, at their Mundra and Dahej OLC installations spanning many years, in Brazil and China a large assortment of trough and pipe conveyors with self-powered trolleys.

Self-powered maintenance trolleys are the new norm for long overland where reliable, fast, safe and easy maintenance preferred with difficult terrain. Witness Dopplemayr, Flying Belt, and CDI publications.

There are new advancements in belt conveyor more efficient power, strength, and reliability. Elevated conveyors are becoming the preferred configuration with self-powered or cable pulled trolleys. ■

In 1972, Krupp installed the Phosbucraa 96 km overland Sahara desert OLC consisting of 11 flights. All were equipped with self-powered maintenance trolleys.

Unfortunately, the conveyors suffered from unanticipated dynamic response that caused the belt to whip like a wounded snake. The belt threw ore up into the belt covers ripping them from the stringer/trolley rail supports. Then the trolley ran into the dislodged conveyor support. The operator was not looking directly ahead. The belt covers caused the trolley to derail and fall from the structure, fatally injuring a maintenance crewman. This happened more than once. The owner then removed all trolleys from service and sent them to the scrap pile. The conveyor is now maintained from the ground with difficulty. The structure is elevated to allow sand dunes to pass under like ocean wave.

Krupp did install a self-powered maintenance trolley at Skyline mine in Utah, USA. This installation is an 11,000 ft downhill pipe conveyor. The conveyor is installed on the foot of a mountain side, quite removed from easy foot access. It went through some teething issues due to ice and downhill run. The initial power & brake design failed to stop the trolley when the operator applied the brakes. Gave the operator a thrill. Rework of the drive and brake apparatus was successful and there were no further trolley mishaps. ■

Since when has a gadget put into service in 1972 just now justified the description "the new norm"?

Methinks the previous thread ignores the word 'maintenance' and gives no reference to the load carrying capacity of the trolley.

Conveying overland is mired in the dark ages and ignores newer technologies.

So a belt is severely ripped halfway along one of these airborne gadgets. Is anyone seriously suggesting that a reasonably sized replacement belt can be offered to the break point by an aerial carriage?

How do you examine the lower rollers on a pipe conveyor from an overhead vantage point?

These trolleys have more gaps than the deck of the Bismark: just ask Krupp! ■

Originally Posted by johngateley

Since when has a gadget put into service in 1972 just now justified the description "the new norm"?

Methinks the previous thread ignores the word 'maintenance' and gives no reference to the load carrying capacity of the trolley.

Conveying overland is mired in the dark ages and ignores newer technologies.

So a belt is severely ripped halfway along one of these airborne gadgets. Is anyone seriously suggesting that a reasonably sized replacement belt can be offered to the break point by an aerial carriage?

How do you examine the lower rollers on a pipe conveyor from an overhead vantage point?

These trolleys have more gaps than the deck of the Bismark: just ask Krupp!

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I offer answers one-by-one.

First, if the 1972 trolley did not have the fatalities, the remote location, Bedouin-Arab war and its dangerous intermittent operation, the maintenance trolley concept would have happened must sooner. Next came South Africa where Mr. Phil Staples, my partner at the time (1990's), applied my maintenance trolley & triangular truss concept on many installations. Then came Skyline Mine in Utah, Dangote in Nigeria, Mundra and Dahej in India, now many in China, .... copy-cats are now abundant.

Please enlighten us on newer more effective methods. Strictly professional comments will be read. Constructive & informative criticism is welcome.

Load carrying capacity of the trolley, aside from its dead tare weight, is about 1000 kg including tools and replacement rollers. Replacement rollers number about 5 on each side, but, depend on conveyor length traversed by trolley. Since the conveyor is inspected every few days, idlers are marked for repair and crew have knowledge on quantity. When the conveyor is designed, the replacement rate is calculated on Useful-Life probability curve. It works.

Broken belts are not a problem. On one of the later elevated conveyor installations, the client hired a unqualified belt splicer. Later all splices had to be cut out and replaced. During this event, some splices were corrected remote to the central splice station. NO problem and done in an as efficient manner as ground based conveyors.

Top and bottom belt strands are readily accessible for roller bearing inspection and roller replacement from the maintenance trolley platform. You do not seem up to date with modern methods. Become informed.

Since the maintenance crew can travel up close to the rollers, have necessary inspection and replacement tool, and have less drama replacing the rollers, the belt operating availability is improved. In addition, inspection is more reliable, is less stressful on the crew, and is done on a controlled schedule, the process is faster than conventional ground based systems. In fact, some operators have applied this process to ground based installations. More are coming. More have an open mind to better reliability and operator safety.

There are methods developed that will allow the conveyor to operate without a shut-down due to idler roll failure. This significantly improves longer overland (>30 km) availability.

I offer this to those interested in proven technical advancements. Those not, are often too old to know better.

CDI have the world record for length, downhill capacity, for both trough belts (27 km) and pipe conveyor (17 km). We have pioneered rubber low rolling resistance, rubber compounding, improved belt wear life using advance chute design methods (+2-10 times life), improved belt splicing techniques to achieve ST-10,000 N/mm with high endurance, developed safer and more effective brake controls, developed new comminution methods for crushers and mills, new methods to control shockwave impulses, new horizontal curve techniques, elevated conveyor methods, air-supported conveyor technology improvements, and so on.

What has your "foot & mouth method" achieved that advances belt conveyor science?

Today there are newer methods that advance beyond yesterday's practices.

Enquires are welcome. ■

Hello,

As I know Krupp Germany has supplied 100 km long conveying system comprising of 11 flights, possibly around 40 years back in Sahara. This system has maintenance trolley.

Maintenance trolley track (conveyor) inclination will depend whether it is only 4 wheels for friction grip on rails or also grip by gear wheel and stationary rack, or sprocket engaging with the stationary chain. I am not aware about exact mechanism there.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis is ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 2012.

Author of Book: ‘Belt Feeder Design And Hopper Bin Silo’

Advisor / Consultant for Bulk Material Handling

System & Issues.

Pune, India. Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com ■

Originally Posted by I G Mulani

Hello,

As I know Krupp Germany has supplied 100 km long conveying system comprising of 11 flights, possibly around 40 years back in Sahara. This system has maintenance trolley.

Maintenance trolley track (conveyor) inclination will depend whether it is only 4 wheels for friction grip on rails or also grip by gear wheel and stationary rack, or sprocket engaging with the stationary chain. I am not aware about exact mechanism there.

Ishwar G. Mulani

Author of Book: ‘Engineering Science And Application Design For Belt Conveyors’. Conveyor design basis is ISO (thereby book is helpful to design conveyors as per national standards of most of the countries across world). New print Nov., 2012.

Author of Book: ‘Belt Feeder Design And Hopper Bin Silo’

Advisor / Consultant for Bulk Material Handling

System & Issues.

Pune, India. Tel.: 0091 (0)20 25871916

Email: conveyor.ishwar.mulani@gmail.com

Website: www.conveyor.ishwarmulani.com

================================================

Dear Mulani,

Suggest your read prior posting. 96 km long, installed in 1972 (46 years ago), Krupp did not design/install vertical lift preventers. When support wheels hit ore deposits and/.or damaged hood covers on stringer/rails, they upended the trolleys. This problem was caused by erratic belt dynamics.

Trolleys were sold as junk in 1980's-1990's after fatalities.

Site had many hiccups with war between Bedouins and Arabs. Bedouins used/crossed conveyor path as part of their nomad trails. CDI visited the installation in early 2000's when the belts were experiencing big splice failures due to rubber strength loss with heat and being parked for long periods with the war. Eventually, ContiTech supplied a new reduce cord count belt to solve splice failures.

UN have a peace keeping force in the area to control hostilities. Maybe resolved today. ■