Uncategorized – Condra

Condra’s design team wins through

Designers — Mon, 15 Apr 2024 15:22:21 +0000

PROBLEM SOLVED – I

Double bogeys fitted to the end-carriages of this overhead crane represent the key to a puzzle recently solved by Condra: how to meet customer specifications while still being able to install the completed crane in a factory with no roof access and insufficient headroom. Conventional installation of a crane of this type is usually executed by first lifting the disconnected end-carriages onto the gantry, then attaching the girders to form the frame of the crane, and finally lowering the crab and hoist into position from above.

The problem in this case is there is not enough factory headroom to do that, even though the crane has already been designed with a lowered profile to achieve maximum lifting height.

Condra’s solution was to fit bogeys to each end of both 12-metre-span steel girders, four bogeys in all, and to develop a different installation sequence. By fitting the girders with bogeys, an additional 20 millimetres of headroom is freed up through reduced wheel loading and consequent smaller diameter wheels.

Integral bogeys also allow the girders to be placed on the factory gantry as the first step of installation. The girders will be moved apart and the hoist lifted into position between them, instead of being lowered into position from above. The girders will then be closed up and their bogeys linked and fixed, resulting in two double-bogey end-carriages and a completed overhead crane.

Condra specialists will carry out this installation at the customer’s Johannesburg factory this month (April).

PROBLEM SOLVED – II

The unusually large rope drum on this hoist, seen here nearing completion at Condra’s Germiston factory, has been designed to hold and manage nearly 700 metres of rope, winding and unwinding it at high speed during very high lifts of 150 metres within a narrower-than-normal mineshaft. Careful calculation of rope drum dimensions and winding sequence was the focus of the drum’s design.

Drum PCD (pitch-circle-diameter) is 1600mm. A 4:2 centre-lift reeving arrangement will avoid snagging the mineshaft sides.

The drum will carry 676 metres of 18mm rope, lifting and lowering loads at 30 metres per minute, almost ten times faster than lifts in standard overhead crane workshop applications.

Condra’s design team had to coordinate the drum width with a PCD and reeving arrangement that will precisely control and restrict lateral movement of the four ropes moving vertically as they lift or lower the load. The rope will wind onto or unwind from the drum in opposite directions as the drum rotates.

The hoist features improved drives, gearboxes and safety devices, and enhanced operation by remote control. Motor design is such that the load placed on the electric motor will remain manageable despite the non-stop nature of the work at the mineshaft.

Crab span is 6972mm with a wheelbase of 3400mm. Crab and hoist disassemble to fit into a standard 12-metre shipping container.

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NEW CONDRA CRANE FOR DISSOLVING PULP PLANT

Designers — Mon, 27 Nov 2023 15:10:29 +0000

Condra has completed manufacture of a service and maintenance crane for Saiccor Mill’s Feed Three pulp dryer line at Umkomaas on South Africa’s KwaZulu-Natal south coast.

The double-girder electric overhead travelling crane will replace an existing machine from a rival firm, and has been designed to incorporate three hoists: a 25 ton main lifting unit and two 12,5-ton auxiliaries, all of them mechanically synchronised for tandem operation as well as offering individual lift.

Dimensions and capabilities are impressive. Able to service all machinery on the dryer line’s floor area of 80 x 25 metres, the crane’s 25-metre span will deliver a maximum capacity of 50 tons and a lift height of 16 metres. Alternatively, the crane will lift up to 25 tons using the main hoist while, simultaneously, two independent loads of up to 12,5 tons can be managed by each auxiliary.

A typical double-girder electric overhead travelling crane undergoing load test at Condra’s Johannesburg factory. Photo inset shows fabrication of the operator’s cabin.

Condra undertook the contract as a turnkey project that will include installation through the plant’s roof. Manoeuvrability on the dryer line floor is limited by in situ machinery, making conventional access and installation impossible. Production will continue uninterrupted while installation takes place.

To execute this complex operation, three Durban-based companies will work in close collaboration as subcontractors to Condra. They are Yellow Dot Coatings, Lovemore Bros, and Natal Cranes. All components of the new crane, including end-carriages, 25-metre-long box girders, crabs and hoists, will be lowered through an aperture in the plant’s roof and precisely positioned for in-situ crane assembly.

Yellow Dot Coatings has been appointed to open the plant’s roof, after which Lovemore Bros will rig all components and use its 550-ton mobile crane to luff them one by one above and through the roof opening, lowering them precisely into position for crane assembly by Natal Cranes, Condra’s Durban-based agent.

After installation, Natal Cranes will also oversee commissioning.

Condra’s 12,5/25,0/12,5-ton electric overhead travelling crane was ordered as part of Sappi’s 7,7-billion rand upgrade and expansion of the company’s Saiccor Mill at Umkomaas in KwaZulu-Natal, which has made the mill one of the biggest dedicated dissolving pulp plants in the world. Global demand is increasing for this key input in textile manufacture, food processing and pharmaceutical production.

The pulp dryer line to be serviced by the new Condra crane is noted for a corrosive environment resulting from the use of steam-heated drying cylinders to dry the sheet-form pulp ahead of packing and shipping.

Manufacture of the crane from carefully selected materials and the use of anti-corrosion finishes will afford protection. All motor and electric panel insulation has been protected to Standard IP65, while the panels themselves and all handrails are of stainless steel. Crane platforms have been fitted with fiberglass grating instead of steel chequer plate, and all crane components coated with a special anti-corrosion finish.

The crane’s load lifts are failsafe, its three hoists fitted with secondary emergency brakes on the rope drums to back up standard brakes on the electric motors.

The new crane, which replaces a machine supplied some years ago by a rival European firm, will become Condra’s second to work at Feed Three, joining a single-girder overhead crane manufactured by Condra in 1984.

Competition for the contract was keen. Five companies from Europe and Africa submitted tenders. The proven reliability of Condra’s existing installation is thought to have reinforced a competitively priced bid to secure the turnkey contract for this Johannesburg-headquartered company.

Sappi’s new crane is scheduled for commissioning at Saiccor Mill early in 2024.

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MILL TURNS TO CONDRA TO RECOVER LOST PRODUCTION

Designers — Mon, 10 Jul 2023 10:02:25 +0000

Price should never be allowed to unduly influence the purchase decision. A wrong choice of capital equipment can prove costly not only in downtime and lost production, but also in unnecessarily increased expenditure when new equipment must be bought to replace the failed original.

This caveat comes from Marc Kleiner, managing director of crane manufacturer Condra, who says that buyers should exercise caution if they notice tender appraisal paying undue attention to price rather than product capability and overall lifetime cost.

He was commenting on a recent order to manufacture an overhead crane as replacement for a competitor’s machine that failed inspection and load testing. The rapidly deteriorating crane is now adversely affecting production in the millhouse where it is installed.

The order for the replacement was placed by Natal Cranes, authorised Condra distributor in KwaZulu-Natal and the firm behind the winning tender to replace the failed machine. In the same millhouse, Natal Cranes has been servicing a 10-ton Condra maintenance crane installed in 1987 on the same gantry as the rival crane now needing replacement. The 10-tonner is still working reliably after 36 years.

Condra received the order on June 6 and is committed to a delivery date of six weeks from drawing approval. After installation and commissioning, the failed crane will be scrapped.

OLYMPUS DIGITAL CAMERA

The new crane will be a physically large machine of double-girder electric overhead design, spanning 21 metres and equipped with two hoists: a 35-ton main unit and 5 ton auxiliary, both mounted on the same crab and delivering lifting heights of 15 and 16 metres respectively.

Maximum long travel speed will be 31 metres per minute, with 15,4 m/min on the cross travel. Control will be by mobile pendant.

The crane will feature a full-length walkway, dual-speed controls on all functions, binder brakes, stainless steel panels and IP65 dust and waterproofing for the motors. Paint finish will be to high-specification anti-corrosion standard.

Commenting on the order, Kleiner said the mill’s need to replace a failed machine was a good illustration of lost production and additional expenditure being the direct result of a buying process where price exerted undue influence.

“The old adage that the proof of the pudding is in the eating is relevant even in the market for overhead cranes,” he quipped.

“Condra’s product quite simply has more depth and durability. Our sales pitch might sometimes not be as polished as our rivals, but the mettle of our products is well proven, witness Condra’s 10-tonner on the same gantry as the failed crane, and still working even though it was installed almost forty years ago, years before the failed machine.”

A complete range of spare parts remains readily available, he added.

Kleiner explained that Condra’s tender price could in many cases not be the lowest, because the product represented a first-rate, top-quality offering.

“But the longevity of our installations around the world justifies the investment made in them. These are robust, reliable cranes.”

Condra’s managing director, Marc Kleiner.

Condra has in recent years captured an increasing share of the lifting equipment market in Africa south of the Sahara, with the company’s success in securing orders against determined competition from European rivals seemingly set to continue.

Company management claims the highest local content of any overhead crane manufacturer in the region. The product range encompasses capacities from 250 kg to 500 tons with a fully automated option offered on all machines. Manufacture is to ISO 9000 standard.

Research and development at the company is ongoing and includes a commitment to environmental improvement. Design engineers are currently researching the effect of different rotor and rotor winding configurations – silumin among them – on motor torque and efficiency, the aim being to contribute to environmental improvement by reducing energy input requirements.

The company has additionally installed solar panels at its Germiston and Cape Town factories to provide an estimated 70 percent of electricity requirements.

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UNIQUE SUSPENSION CRANE

Designers — Wed, 15 Mar 2023 06:46:16 +0000

Condra is to manufacture a 15-ton suspension crane of unusual configuration as one of two overhead cranes ordered for underground use at a Botswana diamond mine. The second machine is of conventional overhead design.

The arrangement of the suspension crane is rarely seen: two I-beams defining its area of movement will be bolted to rock-bolt flanges anchored in the roof of a mine chamber after blasting, excavation and preparation as a service workshop. The I beams will hang from the chamber’s ceiling, whereas they are more usually the topmost side components of a fixed gantry constructed from the ground up.

The wheeled 11-metre-span crane girders will then run suspended from the lower flanges of these two long-travel I-beams, with the crane’s crab mounted atop the girders to provide the cross-travel. The whole structure of the crane becomes suspended, running along and across the roof of the chamber.

Condra designed this crane to specifications supplied by the project’s consulting engineers. By suspending the crane, it will deliver the greatest possible lifting height, reducing the volume of rock needing to be blasted and excavated to form the chamber. After installation, the 11-metre span, 15 ton crane will have a lifting height of 9 metres.

Condra has previously manufactured similar suspension cranes for mines in central Africa.

The second crane for the diamond mine will have a 35-ton capacity and 9,2 metre span. Of conventional overhead design, it will work in a larger existing chamber. Lifting height will be 12,7 metres.

Condra underground suspension crane similar to that to be manufactured. Not the same crane as in this story.

For both cranes, Condra’s design team had to calculate balance points for individual components, precisely positioning lifting lugs on the sides of component assemblies so that they will hang precisely vertically below the cage that will lower them down the mineshaft. Similarly, lifting lug positions atop the components will ensure balance during crane assembly and installation within the confined spaces of the service chambers.

It is thought that competitive pricing, rapid response times during the tender process and a reputation for on-time delivery of completed machines contributed to Condra’s winning this order against competition from rival companies in South Africa and abroad.

Commenting on the latest contract, a Condra spokesman said that the 15-tonner’s special configuration would make for an inspiring project on the factory floor.

“Few companies in Africa, or indeed abroad, have the design and manufacturing skills for a suspension crane of this complexity,” the spokesman said.

“It’s a very nice order to get. These are big machines, and the unusual design, welding and finishing specifications will make for interesting manufacture outside the norm.”

To minimise chipping and rust, Condra will apply an edge finish, grinding all angular steel to circular section before the application of a customer-specified protective coating.

The cranes will feature flame-proofing, stainless steel panels and full weld seams in place of the more usual space-welding along the lengths of steel joints, including the girders.

Control of both cranes will be by mobile pendant. The suspension crane will feature a flashing light and siren for safety.

The consulting engineers specified brake logic to avoid overuse of the pushbuttons on the mobile pendants. Operators are prone to repeated and rapid use of this control, causing excessive heat and wear on the braking system. With brake logic, as soon as the button is pressed twice in quick succession, a two-second temporary block is activated, overriding the operator and correcting his use of this control.

Typical overhead crane under test in Condra’s factory.

The cranes will be used for service and maintenance applications, the suspension crane being installed in a chamber close to the orebody, where it will work on machinery used for drilling, blasting and ore removal. Such a location will save the time and cost of moving the machines over a greater distance to workshops closer to the shaft.

The cranes are scheduled for delivery in 2024.

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UNDERGROUND JIB CRANE WILL RECOVER SPILLED ORE

Designers — Mon, 13 Sep 2021 06:31:13 +0000

Condra has designed and manufactured a very large jib crane for bulk recovery underground of ore spilled at an unnamed mine.

Delivered last week, the 5-ton crane has a lifting height of 9 metres, a slewing radius of 5 metres, and is equipped with an orange-peel grab and electromagnet combination that allows bulk ore to be gathered, lifted and positioned while simultaneously separating out the iron ore within it by means of the electromagnet.

After installation and commissioning at surface level for trials, the crane will play a key role in a prototype ore recovery process. Permanent installation underground will take place after six months of tests.

The mine’s surface-level prototype solution comprises five different types of machines working together.

Ore spilled along the conveyor lines will first be recovered by small articulated loaders which will place it on dump trucks for depositing in a purpose-built pit. The jib crane will then retrieve the ore from the pit by means of a combined grabbing, magnetising, lifting, slewing and travel functionality, depositing the ore into a feed hopper from where a secondary conveyor belt will transport it to re-join the main ore stream on its way to the crushing plant.

The Condra jib crane is the key to this solution, and has been designed and built to withstand a harsh underground working environment with minimal maintenance. It comprises a pillar-supported double-girder beam topped by the crab-mounted hoist, an arrangement that maximises the grab’s lifting height and optimises productivity in the execution of a repetitive but complex lifting task within the spilled ore recovery process.

Condra’s jib crane for bulk ore recovery underground, shown here at the company’s Johannesburg factory prior to delivery. The five-tine hydraulic grab has an electromagnet to allow bulk ore to be gathered, lifted and positioned while simultaneously separating out the iron ore within it.

The crab itself is jam-packed with equipment, holding not only the 5-ton variable-speed-drive hoist, but also the hydraulic power pack, two hydraulic hose reels serving the opening and closing functions of the orange-peel grab, and the cable-reeling drum serving the electromagnet.

Slewing action is delivered by power from three swivel drives, and limited by rotary limit switches defining and limiting travel extremities.

The crane’s lift, swivel and crab movements, and all hydraulic grab and release functions, can be operated by either remote control or back-up pendant.

Commenting on the newly completed crane, Condra’s managing director Marc Kleiner said that that the large size of the machine and the complex task of designing it to achieve optimal productivity, had excluded most crane manufacturers from competing for the contract.

“The jib crane market is very competitive at its entry level or small-machine end, and we do not actively compete in that segment,” he said. “But as crane size and complexity increases, Condra becomes difficult to beat in terms of engineering and design expertise.

“We have worked hard over many years to achieve an ability to align with both end-users and multiple third-party suppliers to deliver the required solution,” he added.

Principal co-suppliers for Condra’s ore recovery crane were Rec-O-Quip, which designed the overall multiple-machine concept process, and MMH Recycling Systems which supplied the five-tine hydraulic grab.

Asked about Condra’s future plans for the jib crane market, Kleiner said that increasing manufacturing efficiencies within the production process for this type of crane would make the company more competitive in bids for smaller, standardised designs.

Final assembly of the crab at the top of the jib crane, with the 5 ton hoist itself (green, central), hydraulic power pack behind the hoist, two hydraulic hose reels (between power pack and hoist) serving the five-tine orange-peel grab, and the cable-reeling drum serving the electromagnet (foreground).

“These efficiencies will also reinforce Condra’s position as the manufacturer of choice for large jib cranes such as the machine just completed,” he said.

Further jib crane orders are anticipated.

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The Official Mining in Africa Country Investment Guide – Interview with Marc Kleiner and Kyle Kleiner, Condra Cranes

Designers — Tue, 22 Jun 2021 10:22:45 +0000

Interview with Marc Kleiner (MK), Managing Director and Kyle Kleiner (KK), Sales Director, Condra Cranes
Selections of the approved transcript may be included in the final editorial

What milestones has Condra achieved since 2020?

MK:Condra Cranes has a vast network of end-users and consultants that have been involved in many different projects over the past 18 months. We are currently working on a specialized double-boom jib for an underground application and hope to make 12 additional units with the same design. We are also working on a coil-handling crane project that requires various technologies in monitoring, data logging and information capture, which will better enable the client to maintain his equipment by identifying the precise location of any fault in the crane system. These contracts came to us due to the durability of our products and our ability to finish designs and projects under tight deadlines. Another noteworthy contract came from Botswana, where we delivered a 60-tonner and 20-tonner for gold production.

KK: The reason our equipment has been so successful in the current sales environment, which is difficult, is partly due to the recent boom in resource prices. The mining industry is trying to move mineral commodities as fast as possible while the prices are strong. This is why lead times make such a huge difference. If you can deliver quickly enough, you are more likely to get the contract. Condra Cranes supplies the central and southern African market from South Africa and can thus get to the client and his mining site quicker than other companies who manufacture abroad, especially now with the onset of the pandemic. Shipping costs are also increasing dramatically, and thus we have an advantage in supplying the African market from our factories in South Africa. While we do import some components such as motors and ropes from Germany, we hold stock of these in South Africa where all crane design, hoist design and all manufacture take place. We also have a production facility in Bulgaria from where we import certain prefabricated steel components, as steel is currently very expensive in South Africa, having approximately doubled in price over the past year.

The mining industry is currently the market of greatest significance to Condra. Although we are not seeing many new mining projects coming on stream, there is a considerable amount of activity in crane upgrades, refurbishments, maintenance and after-sales service at the mines while the mining industry takes advantage of the commodity super-cycle.

With regards to technological advancements, to what extent are sensors becoming crucial in overhead cranes?

MK: With sensor-driven cranes, there is a requirement for service-driven maintenance of the installed technology on the part of the supplier, and with mines being very far apart this becomes challenging. We do offer a fully automated option on all our cranes, but we also issue a cautionary where the mines are concerned, as it is sometimes difficult to respond quickly to service requirements once the cranes are in the field. The job itself is not the challenge, but the travelling time to remote locations is. Thus, it is not always the best decision to have highly automated and sensitive machines that rely heavily on maintenance in the African market.

KK: We are working on virtual maintenance and service videos to address this challenge, but this does not entirely solve the problem as you still need that element of experience when it comes to maintenance and servicing, especially when they are technology-rich. The cranes for the coil-handling project are smart and do have encoders and sensors, but these machines will be installed in a major city and can be accessed very quickly.

With Condra having been in the crane and hoist industry for 56 years, how would you describe the current health of the South African mining industry?

KK: I believe that, globally, mining companies might have been drained by government regulation of some of their passion for building, creating, and contributing to society. This regulation is a distraction from what they do best. There are now statutory regulations on sustainability, the environment, social contribution and corporate governance criteria. The mining companies have complied with all of it – they have the documentation and they are doing what they have been told to, but the passion has been lost, and this is clear. We need to again find the desire to contribute to society. Companies need to be allowed to uplift communities by doing what they do best, and with the minimum possible bureaucratic interference and paperwork.

MK: The South African mining market has been dormant in terms of greenfield projects for the last several years. New mines are needed to unlock the potential of South Africa’s secondary and tertiary sectors.

What is Condra Cranes’ strategy to facilitate growth and consolidate the company’s market share?

MK: The strategy is to continue developing our export market, which has been difficult to do due to the pandemic. The Southern African market for cranes is relatively small because it is mining focused and there is currently not enough new investment in this sector. We want to enter fresh markets both in Africa and overseas to facilitate company growth.

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Condra adds crane refurbishment to new-machine manufacture

Designers — Wed, 18 Mar 2020 07:08:39 +0000

WHEN TO REPLACE, AND WHEN TO REFURBISH

Is it better to replace or refurbish an overhead crane reaching the end of its life?

At least one South African firm reckons that there are advantages to both options, and Condra, a specialist in new crane manufacture as well as crane refurbishment, believes that the choice should be very carefully considered.

According to Marc Kleiner, the company’s managing director, refurbishment allows the customer to immediately realise a cost saving over buying new, and carries the additional advantage of providing an as-new machine already familiar to his operators, avoiding any need for re-training. Production can continue as before, with no change to established procedure.

Buying new, on the other hand, offers the advantages of lower operating costs quickly realised, a reduction in projected overall lifetime cost, and more efficient operation as a result of newer cranes’ increased speeds, lower weights and lower electricity consumption. According to Kleiner, hoists today are as much as 50% lighter than they were 30 years ago, and the consequent reduction in crane weight also reduces the rate of wear on the overall factory structure.

Signs that an overhead crane will soon need either refurbishing or replacing include brittle electrical cable loop systems, failing contactors, extreme wheel wear, structural cracks and a general increase in maintenance costs.

If the customer should decide to refurbish, then the procedure generally comprises a dismantling of the crane followed by inspection of all brakes and mechanicals, a change of bearings, and an assessment of the overall crane structure using MPI to inspect critical sections for rust. Crane girders and crabs are also re-aligned, and the girders checked to ensure that they remain true. All main components are then shot-blasted, reassembled and painted.

Condra refurbishes not only its own cranes, but also competitors’ machines.

Kleiner explained that competitor crane refurbishment is becoming increasingly popular because it allows the circumvention of delays caused by long component lead times of up to 18 months. Such delays are common among European companies because they have to import their spares.

Refurbished 20-metre-span Condra crane for Implats

As an example, Kleiner pointed to a 20-ton crane originally manufactured by a German company but soon to be refurbished at Condra’s Germiston factory, which will either re-engineer or re-manufacture any parts that are either no longer available or which will take too long to import.

Recent refurbishments of Condra’s own overhead cranes have included an 80-ton machine for Sishen, and two hoists and a 25-ton, 20-metre-span crane for Implats, the latter involving conversion of the existing electrical configuration from 525V to 400V. The refurbishment of Sishen’s 80 tonner was more routine, with all bearings, ropes and brake linings being replaced, and the usual checks and inspections carried out before the crane was re-painted and delivered back to the mine.

Besides its own machines and competitors’ cranes, Condra also refurbishes overhead machines originally supplied by companies that have recently closed.

Kleiner explained that the benefit Condra gains during refurbishing, whether one of its own machines or one from a rival firm, is that its engineers can ascertain from a technical perspective precisely how the machine has been performing.

“If the crane is our own, then we get the chance to look inside it, examine wear rates and make projections of expected component life,” he said.

“One thing we’re seeing is that Condra’s component life expectancy presently far exceeds the international norm, and we will be reducing the size of some of the components for our 2025 models to improve efficiencies and reduce power consumption, especially within the gearboxes.”

Kleiner explained that overhead cranes are sent back to the factory for refurbishment anywhere between 15 years and 30 years after commissioning, depending on the operator’s maintenance policy and how hard the crane has been working.

He pointed out that Condra offers the option of changing both crane capacity and span during a refurbishment by fitting new hoists, changing the rope and modifying the gear reduction.

“Whatever the case, whether upgrade or refurbishment of a Condra crane or a competitor’s crane, or one from a company that has closed, we work closely with the client on a solution that will deliver back a fully reliable, fully refurbished machine that will work happily for many years into the future,” Kleiner said.

Condra crab and hoist unit (new)

He pointed out that refurbishment is not always the better option, with the cost sometimes outstripping the benefits. Examples are when a crane is very old (35 years or more), or when a crane has been working in the open and rust has established itself inside the girders.

“So the customer first has to consider the estimated price difference between new and refurbished,” he said, “and then he has to weigh the extra cost of a new crane against the benefits of increased crane speed and consequent gains in productivity.

“To help him with this decision, we supply a range of solutions offering varying productivity gains, with alternative costs for each one.”

Kleiner said that customers were almost always offered the option during refurbishment of technically upgrading their machine. He explained that the productivity of cranes of 20 years or older can usually be improved through increased speed and easier acceleration and deceleration, all achieved through the installation of variable frequency drives. Enhancements can also be fitted, such as a digital read-out on the load, or remote control if the machine does not already have this option.

“So with refurbishment we can give back to the customer a crane that is much faster and much lighter than it was before, and we can fit a frequency drive on the long travel to speed it up, and we can incorporate in the refurbishment any kind of modern technology that he wants, including hoists of different capacity,” he said.

“We can also automate the crane during refurbishment, in which case we often improve the mechanicals to incorporate the new electrical equipment needed for automation.

“These options are offered across the board, from standard 2M workshop cranes to the higher performing machines such as Class 3 and Class 4.”

Kleiner said that the time needed to refurbish a standard workshop crane was approximately two weeks, while heavier-duty cranes need anything up to six weeks including time for re-painting.

All refurbishments carry a warranty of two years on machines originally manufactured by Condra, and one year for cranes made by a competitor.

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HORSES FOR COURSES – ARE BIGGER WAREHOUSES WORTH IT?

Designers — Tue, 03 Dec 2019 11:37:00 +0000

Factories and warehouses are wider than ever, and existing buildings are being extended to make them longer. Both trends beg questions about increases in productivity – are they in proportion to the higher costs of construction?

Crane manufacturer Condra claims to provide at least part of the answer, supplying the overhead travelling machines that service these larger buildings.

Though the company still delivers many cranes with traditional spans of around 17 metres, there are orders for an increasing number of double-girder machines greater than 25 metres in span, and managing director Marc Kleiner says that he has in recent years seen buildings measuring as much as 26 metres by 28 metres served by a single crane.

His opinion is that the economy of building factories of such a size is debatable, because as the span of the overhead crane increases to match factory width, so too does the cost of the factory structure needed to support its weight.

“And the crane itself also becomes more expensive,” Kleiner added.

“For example, the 3-ton girder needed for a 17-metre span increases in weight to 12 tons when the span becomes 25 metres – a fourfold weight increase to service a 47 percent increase in factory width – and additional power is also needed to move the heavier crane.”

Very wide-span crane nearing completion in Condra’s Johannesburg factory

In the case of factory extensions serviced by a second overhead crane, a similar question hangs over whether the intended increases in productivity are actually achieved, because cranes operating in tandem can lead to production logjams.

Kleiner explained:

“The thinking is that you put up the initial building which is, say, a two-bay layout, and incorporate planning to extend it at a later date and install a second crane to service an additional two bays.
“But what often happens is that goods in Bay One cannot be moved to Bay Three because of the second crane working in Bay Two,” he said.
Turning to factories with more modest widths, Kleiner said that single-girder overhead cranes are often a cost-effective alternative to the double-girder ideal.
In Bulgaria, Condra’s subsidiary there has recently delivered single-girder cranes to an engineering company (a 5-ton machine), and to a steel trading company (two machines with capacities of 5 tons and 3,2 tons). Spans of these cranes range between 11 and 13,8 metres. More single-girder machines are under manufacture.

Kleiner emphasised the functional design of this type of crane:

“The single-girder design is both durable and robust, and is an effective solution in standard factory applications.
“Of course, the double-girder design provides the advantages of greater stability, lift precision and lifetime durability, but these benefits come at a higher initial price that is later justified many times over by a much extended useful life.

“A tight budget may therefore dictate consideration of the single‑girder design, which in many cases will be adequate.”

Kleiner said that single-girder designs were usually fitted with Titan short-headroom (SH) series hoists, underslung to maximise vertical lift by absorbing the dimensions of motor and cable drum into the space of the girder depth.

SH-Series hoist profiles are some 20 percent less than that of other underslung hoist models.

Titan hoists lift a maximum load of 16 tons, and incorporate refinements such as automatic rope tensioning, smooth travel, built-in load limiter, standardised direct drive and universal carriage.

Design of all Condra cranes, both single-girder and double-girder, takes place at Condra’s Gosforth Park factory outside Johnnesburg, where design teams examine the application and compare the suitability of the two alternatives.

Manufacture to specification is carried out using selected components from some 250 sub‑assemblies, the main ones being hoists, drives, end-carriages, brakes, gearboxes and motors.
Hoists are assembled from standard Condra parts, and fitted with either hooks, grabs, magnets, ladles, buckets or spreaders according to requirement.
All manufacture is carried out in accordance with the quality management standards of ISO 9001:2015.

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