Case study
Building Vrtlište, fourteen years before rebuilding it
The plant our 2025 modernisation replaced — designed, supplied, programmed and commissioned across thirteen months, from the transformer station to the SCADA screens.
- End client
- RMU "Kakanj" d.o.o.
- Location
- Kakanj, Bosnia & Herzegovina
- Sector
- Coal mining · material handling
- Delivered
- Jun 2011 – Jul 2012
564,000 KM
Contract value
13
Months, start to commissioning
1 MVA
Transformer station supplied
0
Complaints recorded on completion
The plant
Everything a coal transfer system needs, at once
Vrtlište is a transfer system: coal arrives, is processed, and is loaded onto wagons. Nothing about that is gentle. Conveyors run long and dusty, the material is abrasive, and the whole line is a chain — when one machine stops, everything upstream of it backs up and everything downstream starves.
Comex came in as subcontractor to Rudstroj on the electrical and control side of the build. That meant the full stack rather than a component: bringing power onto the site, distributing it, building the cabinets that switch it, writing the software that decides when, and giving operators a screen that shows what the plant is doing.
A build like this has one hard constraint that a retrofit does not: nothing exists yet to test against. The commissioning window is where design assumptions meet real conveyors, real motors and real dust for the first time.
The scope
Five workstreams, one contract
From the incoming supply to the operator's screen — the whole electrical and control package for the plant.
- 01
1 MVA transformer station
Supplied and commissioned — the plant's incoming power, sized for the full connected load of the transfer system.
- 02
Low-voltage distribution
Designed from scratch, with the distribution cabinets built and delivered to match.
- 03
Control cabinets
Designed and supplied complete with the automation equipment inside them — the switchgear and controllers that actually run the plant.
- 04
PLC and SCADA software
The complete control software for the plant, and the supervisory system operators use to watch and drive it.
- 05
Video surveillance and IP telephony
Built and delivered alongside the control system — the plant is spread out, and operators need to see and speak across it.
The plant
Nine machine groups, two lines, one chain
Vrtlište takes coal off trucks, screens and sorts it, stacks it in a depot, then reclaims it and loads it into wagons bound for the TE Kakanj power station. Every machine depends on the one before it — which is why the control system is the plant, not an accessory to it.
Line 1
Receiving, processing and stackingGRO_AUT in the transformer station · RDO_L1 in the depot hall
- Receiving hopper with radar level measurement, and a traffic light that tells a driver when tipping is permitted
- Chain conveyor on two mechanically coupled 30 kW drives — its speed sets the capacity of the whole line
- Vibrating screen, 22 kW, speed monitored
- Picking table, 15 kW, its speed tied to line output
- Main conveyor to the depot, 45 kW, soft-started — and downhill, so it generates
- Reversible stacking conveyor, 15 kW, positioned on 2.2 kW wheel drives and held by brakes
Line 2
Reclaim and wagon loadingRDO_L2 in the depot hall · KBO in the control cabin
- Four dosing conveyors beneath the depot, 22 kW each
- Conveyor to loading, 45 kW
- Loading conveyor feeding a surge bunker — the buffer that keeps material flowing while one wagon leaves and the next arrives
- Wagon shunting device, 15 kW, drawing the rake under the chute while coal discharges
The two lines can be stopped independently, but they are not unaware of each other: when the reversible conveyor sits at the position where it transfers straight onto the outbound belt, software has to hold Line 2 — a physical overlap that only logic can police.
“The services were performed in accordance with the rules of business and the situations were duly concluded. There were no complaints or objections regarding the quality of work, the delivery deadline, the payment terms, or the conduct of the personnel.”
Customer satisfaction certificate, Rudstroj — main contractor
Contract 5B-002-132/2011 · end client RMU “Kakanj”
The sequel
The same client, fourteen years later
Control systems have a service life. The one built here was rated for ten years and ran for fourteen — which is the best thing that can be said about a plant control system, right up until the point it becomes the problem.
In 2024 RMU Kakanj tendered its replacement. Comex won it, and rebuilt the control and power electrical systems across both technological lines without stopping production once. Two contracts, fourteen years apart, with a signed confirmation from the client at each end.
At a glance
Project specification
- End client
- RMU "Kakanj" d.o.o., Kakanj
- Main contractor
- Rudstroj — Comex as subcontractor
- Contract
- 5B-002-132/2011
- Object
- Supply and installation of the complete automatic control system on the Vrtlište transfer system
- Contract value
- 564,000.00 KM
- Period of performance
- 1 June 2011 – 10 July 2012
- Scope
- Design · equipment supply and installation · programming · plant commissioning
- Delivered
- 1 MVA transformer station · LV distribution design and cabinets · control cabinets with automation equipment · complete PLC and SCADA software · video surveillance and IP telephony
- Completion
- No complaints on quality, deadline, payment terms or conduct
Building a plant from the incoming supply up?
Transformer station to SCADA screen, under one contract. Tell us what the plant has to move and we will tell you what it takes.