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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Non Classé – Condra

Condra’s design team wins through

NEW CONDRA CRANE FOR DISSOLVING PULP PLANT