Electrifying results, Keestrack promoting alternative plant drives
KEESTRACK promotes alternative plant drives
To reduce operational costs and optimize the sustainability of processing plants KEESTRACK intensively works on alternative drive concepts for all models across its range. Diesel-electric technologies with “hybrid” or “full-hybrid” operation are playing a key role. At their official debut in late October the new cone and jaw crusher concepts H4e and B4e formed part of a remarkably fuel-saving “plug-in”-production line.
Since several years KEESTRACK is intensively working on the implementation of alternative electric drives in its mobile processing plants. As a result, most of the KEESTRACK crushers, screeners and stackers are today available as conventional diesel-hydraulic units, but also as “e-“versions with on-board diesel engines and flanged generators to supply electric motors on screens, conveyors, compressors and other components. With plug-in-option, those “hybrid” plants can be externally supplied via mains, another machine in the processing line (eg. crusher) or via separate gen set.
The obvious reason for replacing numerous hydro drives on conventional mobile plants, and reducing with that to a large extent hydraulic power needs, oil volumes and pipework on machines is direct cost-cutting. And indeed, KEESTRACK is reporting for the e-versions up to 30 % lower fuel consumption compared to the same models with modern load-sensing hydraulic systems. This might not seem too dramatic at the end of a shift, but live-time-cost analyses clearly show, that minor additional investments for the e-versions pay off quite shortly, even in recent times of moderate fuel pricing.
This turns even better, focussing on some other important advantages of the hybrids as enhanced environmental compatibility, better availability and ease of operation and maintenance even under difficult conditions. Smaller hydraulic networks minimize the risk of leakage, which is particularly important for operations in protected areas. It also avoids production downtime. Lower oil volumes prevent temperature problems, fewer filters and coolers reduce daily or regular maintenance. And even the service life of on-board diesels can be extended significantly, when the engines run under lower and more regular loads or only have to be started to move the tracks or manipulate conveyors on KEESTRACK’s “plug-in” screeners or stackers.
Consequently the exhaust-free operation of the crushing units was the next challenge for the KEESTRACK engineers. Quite common on smaller machines or for very large quarry crushers the all-electric or “full-hybrid” drive concept had to be adapted to the requirements of highly productive mobile units in the 30- to 60-tonnes segment. “We didn’t want to compromise neither the high production rates, nor the extreme versatility and mobility of our crushers,” KEESTRACK owner Kees Hoogendoorn shortly explains the engineers’ task. “Our e-versions give to the customer the choice and freedom, to start the engine and work conventionally wherever and whatever the job is. But if there’s mains available or an external gen set makes sense, why not bringing down diesel rev to zero, reducing fuel costs instantaneously and boost live-time profitability of your machinery investments?”
To meet the scope of the project which is mainly defined by high power demands of the crushing units, the weight-sensitive integration of respectively strong additional electric motors and – above all – the indispensable availability of the “key machine” crusher, the KEESTRACK engineers started on a clean sheet, instead of changing well proven machine concepts.
First result was the tracked cone crusher KEESTRACK H4, developed in close co-operation with a renowned cone specialist. The 35-tonne machine with an innovative compact frame design features an electrically driven cone crusher (132 kW, max. 200 tph). Optional 1-deck pre-screen* (*not available in the United States) and 3-deck after-screen modules convert it into a highly efficient but very compact secondary or third stage production plant (max. weight: 46 tonnes). The hybrid version debuted at Bauma 2016, now KEESTRACK presented the full-hybrid H4e. According to emission regulations both machines feature 328/346 kW on-board diesels powering the 330 kVA on-board generator for the crusher drive and ancillary components (side conveyors, magnet, etc.). For full electric operation from mains or external gen set the new H4e is equipped with an additional electric motor/hydro pump unit to supply the hydraulic driven feeder, the large after-screen module, the tracks and all hydraulic cylinders.
The brand-new tracked mobile jaw crusher KEESTRACK B4/B4e operates on a similar principle. Completely re-designed it follows the successful Apollo/B4, which for years set industry standards with high production rates in flexible recycling applications or medium-sized quarry operations. Accordingly, the new frame structure incorporating elements of high-strength Domex steel qualities guarantees low transport weights (approx.. 42 – 49 tonnes) and good static properties on site. Optionally the B4/B4e can be now equipped with a 1-deck afterscreen module with oversize and recycling conveyors.
The plants feature an active 2-deck prescreen and the re-designed KEESTRACK 1100 x 700 mm jaw crusher with hydraulic gap adjustment during operation and the patented overload-protection “Non-Stop-System” (N.S.S.), which automatically detects non-crushable material. To let pass the obstruction, the intelligent N.S.S. opens the swing jaw only to the necessary extent and immediately resets to the initial C.S.S. (45 – 160 mm). This reliably prevents break-downs and ensures constant quality of the end product. Different strokes (hard stone: 29 mm, recycling: 32) allow the adaptation of the eccentric throw to specific applications and maximise the production of the hydraulic driven 18-tonne crusher unit (recommended feed size 600 mm).
The diesel-hydraulic B4 is driven by an on-board diesel (210/242 kW acc. to emission regulations) and a modern load sensing hydraulic system. Diesel power on the all new B4e is converted by an 225 kVA on-board generator to supply the separate electric motor for the crusher (110 kW), all other electric components and drives and a second electric motor (55 kW) with flanged hydraulic pump for the installed hydro drives (feeder, pre-screen, after screen modules), hydraulic cylinders and tracks. This now allows a full plug-in operation of the whole plant without starting the diesel engine. Once connected to an external power source the whole energy management is controlled automatically including the supply of a secondary unit (screen, stacker).
Both new machines debuted on the impressive autumn customer show of KEESTRACK’s Norwegian/Swedish dealer Fredheim Maskin in late October this year. With over 40 machines on static display and active demonstration the traditional show attracted once again many visitors from Scandinavia and other European regions. Certainly one of the highlights was the full-electrical granite processing line with KEESTRACK’s B4e as primary and H4e as secondary crusher with 3-deck after-screen producing the first two end fractions. Completing the line were a KEESTRACK stacker S5e for stockpiling pre-screened material 0/20 and the 2-deck tracked screen KEESTRACK K3e for the finer end products. The complete electrical power was supplied by a single external 500 kVA gen set.
Following a production layout for two different sets of five end products (0/2 … 16/22; 0/4 … 16/22) tests were run with feed size 0/600 at 180 tph (estimated granite work index: 16). The results of consumption analysis even surprised KEESTRACK’s own experts: the whole “plug-in”-line consumed around 55 litres per hour.
“These results are impressing,” states Kees Hoogendoorn. “Even if they are just valid for this specific case, we’re convinced that our full hybrid concepts are more than interesting for our customers. Compared to conventional diesel-hydraulic or hybrid diesel-electric machines, fuel cost savings of 30, 50 or even 70 percent are definitely possible, depending on the external energy supply.”