Tell us your workshop conditions and get a tailored solution within 24 hours.
Get a Quote →
A steel processing plant in Kenya had four double girder overhead cranes that were still structurally sound but mechanically worn out. The main girders were fine. The runways were fine. The hoist trolleys were not.
The customer set the boundary in their first email, before anything had been quoted: replace the hoisting machinery and the travel drives, and leave everything else alone. This case study is about what it takes to work inside that boundary — and why, on a site with no OEM service network within reach, the decisive engineering question turned out to be whether the plant’s own maintenance team could carry out the changeover themselves.
The plant processes hot rolled coil and runs several tube mill lines. Cranes there work around the clock, lifting for roughly 60% of each day, with loads regularly reaching 90% of rated capacity, on a site handling 7,000 to 10,000 tonnes of coil a month. That is not a workshop duty cycle. It is continuous heavy service, and it is why the customer specified A7 (equivalent to ISO M7) rather than a general purpose classification.
Four cranes were in scope, serving the tube mill bays and one adjacent production bay. Three constraints shaped everything that followed.
The structures still had years of life in them. Replacing complete cranes would have meant scrapping main girders and end carriages that were in good condition. On a retrofit, the structure is the asset you are trying to keep.
The shutdown window was short. On a line moving that tonnage, lost production costs far more than the equipment does. Every hour a crane is out of service has to be justified against output.
There is no OEM service presence nearby. Any solution that depended on foreign engineers flying in and staying for a multi-week installation would be uncontrollable on both schedule and cost — and would overrun the shutdown window regardless of how good the machinery was.
The customer did not ask for better cranes. They asked for the worn parts of four working cranes to be replaced without touching the girders, the runways or the building — and to be able to do the work with their own people.
| Project Type | Crane modernization — hoist trolley and travel drive replacement |
| Crane Type | Double girder overhead cranes, existing, retained in place |
| Quantity | 4 cranes, delivered in two phases |
| Rated Capacity | 10 t (three cranes), 7 t (one crane) |
| Span | 13.00 m / 13.08 m / 15.18 m / 15.18 m |
| Cross Travel Rail Gauge | 1050 mm / 1400 mm / 1400 mm / 1400 mm |
| Lifting Height | 6 m |
| Duty Classification | A7 (FEM/DIN), equivalent to ISO M7 |
| Hoisting Mechanism | Winch type hoist trolley — rope drum, gearbox and brake on the trolley frame |
| Hoisting Speed | 0.5–5 m/min, variable frequency, 10:1 range |
| Control | Radio remote control with pendant backup |
| Operating Regime | 24-hour continuous, approx. 60% lifting time, load factor to 90% |
| Supply Scope | Hoist trolley assembly, electrical control panel, wheel blocks or end carriage, long travel drive, radio remote |
| Excluded from Scope | Main girders, runway rails, building structure — all retained |
| Installation | Carried out by the customer’s own maintenance team, with remote technical guidance |
| Wiring | Pre-made looms with aviation plug connectors — negligible field wiring |
| Application | Steel coil processing and tube mill material handling |
| Location | Kenya, East Africa |
The four cranes have two different cross travel rail gauges — 1050 and 1400 mm — and four different spans. There was no single trolley design copied four times. Each one was built to the rail gauge of the specific crane it had to sit down on. This is the part of a retrofit that is most often underestimated at quotation stage.
A7 / ISO M7 with 24-hour operation and load factors reaching 90% places the hoisting mechanism near the top of its service classification. Rope, drum, gearbox and brake were sized against that spectrum. Standard duty components would carry the rated load without difficulty and still reach the end of their life years early — which on this site would mean repeating the whole exercise.
The original units were winch type hoist trolleys, with drum, gearbox and brake mounted on the trolley frame. The replacements keep that architecture. This was not conservatism. Keeping the mechanism type is what makes the interface with the existing cross travel rails and girders identical, and a direct changeover possible. A retrofit that changes the machine type turns into a structural project.
Hoisting speed 0.5 to 5 m/min under VFD control. The top speed protects cycle time on a line that cannot afford to slow down; the creep speed is what lets an operator set a load down accurately. On the old machinery a single fixed speed had to serve both duties.
The operator can stand where the load is actually visible, rather than working from a cab position fixed decades ago when the bay was laid out differently. On coil and bundle handling this matters more for safety than for productivity.
Every loom between trolley, control panel, travel drives and remote receiver was made up and tested before shipping. On site the connections plug together. Almost no field wiring is the single decision that governs how long the crane stays out of service — and it was the shutdown window, not the machinery, that was the binding constraint here.
Clear drawings and unambiguous wire numbering, so the plant can trace a fault on its own three years from now. On a site without OEM support within reach, documentation quality is part of the machine, not an accessory to it.
The changeover was carried out entirely by the plant’s maintenance crew, with remote technical guidance from our engineers. No engineers were deployed to site. Per crane the sequence was: lift off the old hoist trolley, lift the new one into place on the existing cross travel rails, connect the plugs, energise and test.
The customer’s own description of the package was that it was easy to handle.
That is worth stating plainly, because it is the part most often glossed over in retrofit proposals. Whether a modernization project succeeds on a site like this depends less on how good the new machinery is than on whether the people who already work in the building can install it. If the answer is no, both the schedule and the cost belong to someone else.
The first enquiry gave us three capacities, a lifting height and a duty class. That is nowhere near enough to engineer a retrofit, so the questions we asked back were about the application rather than the product.
| What we asked | What it determined |
| What is lifted, and in which bay | Lifting attachment and bay allocation |
| Hours per day and load factor | Confirmed A7 / ISO M7, not standard duty |
| Monthly tonnage and unit weight | Confirmed high cycle, heavy service |
| Cross travel rail gauge, crane by crane | Trolley frame width — different on almost every crane |
| Photographs and drawings of the existing cranes | As-built interface verification before manufacture |
This is the structural difference between a new crane and a retrofit. A new crane is built to a specification. A retrofit is built to the interfaces of equipment that is already hanging in the building, and every question left unasked is a risk that the new trolley will not sit down on the rails.
From first enquiry to order took around seven months. Verifying as-built dimensions crane by crane, and scheduling shutdown windows around a continuous production line, is not a process that compresses.
Retrofitting is not automatically the cheaper option, and we would rather say so before quoting than after.
If the main girders show fatigue cracking, significant section loss to corrosion or permanent deflection, replacing the hoisting machinery buys you a new mechanism on a structure that is closer to the end of its life than the mechanism was. If the required capacity has increased since the crane was installed, the girder was never designed for the new load and no trolley change fixes that. And if the runway itself is worn or out of alignment, that has to be dealt with first — a new trolley on a bad runway wears out early, and it will look like a supplier problem.
The honest test is whether the structure is genuinely sound. Where it is, replacing the hoist trolley is usually better economics by a wide margin. Where it is not, it is money spent twice.
The progression is the result worth reporting. One trial unit earned the four-crane programme. Four working cranes earned an order for new machines.
If the girders and runways are still in good condition but the hoisting machinery has reached the end of its service life, replacing the trolley alone is usually the better option. Send us the following and our engineering team will come back with a feasibility view, a configuration and a budget figure:
TO TOP
