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Wed 17 Dec 2008 04:00 AM

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The exchange rate

An increasing number of plant managers are choosing to exchange, rather than scrap industrial engines.

An increasing number of plant managers are choosing to exchange, rather than scrap industrial engines.

What's the worst sound in the world? We could pontificate all day, but somewhere near the top has to be the ominous knock of a doomed piston, which is generally followed by clouds of black smoke.

The sinking feeling is that you will have to buy a new machine, or at least have to buy a new engine. However, there is a more wallet-friendly option in getting a remanufactured exchange engine.

Interestingly, while the ‘exchange' method, so called because you exchange your old unit and some cash for one that has already been rebuilt, has been known for many years in Europe, with stand-alone ancillaries such as radiators and alternators also being available for exchange, the process appears to be relatively new everywhere else.

In fact, local company Taurus Engines, under the banner of parent company Technical Solutions and Services have been rebuilding engines for well over twenty years, but they have only been offering an exchange programme for four of those, and a fully branded operation began in early 2008.

We have come across exchange programs many times before, but have always wondered what the process actually is.

Answering the question is Rakesh Tekwani, a manager at the Al Quoz-based company. "It is a six-step process" he says.

Engine Core

So what happens when your dud engine comes in for exchange. For a start, the firm refers to unrefurbished engines as ‘cores'.

While the majority of the stock comes from locally exchanged units, a surplus of stock is kept by buying in scrap ‘cores', mostly from America, where reuse is surprisingly uncommon, or from individuals who wish to sell their dud motors, in which case each engine core taken in by Taurus is inspected by a qualified technician.

The core is inspected for broken parts and bits that might be missing. After inspection, it is logged onto the database, and joins the que for refurbishment with the rest of the stock in the inventory.

"There are four major brands which we do at the moment. These are Catepillar, Perkins, Cummins and Detroit Diesel" Tekwani says.

"We are also adding Deutz and John Deere to our portfolio" adds Yogesh Chotaliya, also a manager at the firm. "All the machines are for industrial applications, though some are for marine use." This is an important distinction, because though marine engines are similar to their onshore counterparts, they tend to be more lightly engineered, so it is important not to mix the two up.

Disassembly

"We get the old cores, from customers or from the USA and after we have inspected it, we dismantle it" Tekwani says. During the process, the engine stripped bare, even the core and galley plugs (stops that were put in the engine during the manufacturing process) are removed.

The cylinder head, block, crankshaft, camshaft and subassemblies then go their separate ways to different machine shops at the Taurus complex. A decade or more of grime and contamination is then removed in parts washers before machining can begin.

"Sometimes the engine comes in and it is uneconomical to repair" says Tekwani. "For example, if the block is cracked. In that case we would remove any parts we could remanufacture, and sell them as separate units.

Machining

Each cylinder block is checked for cracks, while all required dimensions are recorded and measured for machining purposes. The block is then line bored to ensure the main journal bearings are on the same centre line. Doing this reduces bearing wear and improves oil pressure and performance.

The cylinders are then bored to spec, and then carefully honed to perfection. After this, the block deck surfaces are checked in reference to the crankshaft centreline.

The block is then de-burred and all bolt holes are re-tapped. After this kind of attention, it is reasonable to assume there will be a certain amount of swarf, so the block goes through a high-pressure wash to clean all galley holes. The casting is then processed up to the original spec. Crankshaft

Each crank is checked for cracks and measurements recorded. Oil holes are cleaned out thoroughly and micro-polished. The shaft itself is checked for alignment. "Any shaft that won't grind is discarded" Tekwani confirmed.

After grinding the crankshaft, it is micro polished to remove peaks that are created during the process.

Cylinder head

The heads are completely dismantled. All water and oil galley plugs are removed. The head is then measured for thickness and it is then resurfaced. Valves are inspected with a gauge and vacuum tested, though generally they are replaced, as any not meeting original standard is discarded. As a matter of course, all valve seats, guides and copper tubes are replaced. After that, the head is put back together.

Injectors

A high-tech approach is taken to rebuilding the fuel system. There is a whole workshop at Taurus dedicated to the engine management and injection systems. Simply put, the injectors need to be checked on a specialised test bench.

Older and more basic diesel engines have a mechanical injection system, and these have a machine dedicated to testing the flow rate and so on. However, modern electronic injectors run at a much higher pressure, so the way they are engineered is very different.

As a result, the company has invested in some very high-tech equipment, which keeps a computer log of all the diagnostic tests carried out. It takes specially trained technicians to use this type of equipment.

Rebuild

Of course, it also takes specially trained technicians to bolt the refurbished parts back together again. Using special callipers, pistons are checked for perfect cylinder wall clearance. Each piston ring is checked in bore for proper end gap. The crank and the main bearings are installed in block, and the bearing clearances are checked. The cam is shimmed up and installed and checked for the correct clearance.

Dyno test

The final stage is a test on a dynamometer. Taurus are particularly proud of the computer controlled unit it has bought from the UK, said to be the only one of its type in the Emirates.

Whatever the load is on the engine, the machine will produce all these facts, which we can then give to the customer" Tekwani says, as a giant twelve-cylinder generator engine is manoeuvred into position.

Besides providing torque peak graphs and the usual data about the health of an engine, this system also incorporates a pressure test among various other reports that will be shipped with an engine.

After this, the engines are packed and shipped. While it is usual in this industry to mark a remanufactured engine with an extra letter after the original engine number (Most often an X) However, Taurus fit its own plate on each unit, stating where and when the rebuild took place.

So next time you have a machine with an ailing motor, don't worry about the time it might be off site for costly repairs - instead consider an exchange.

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