Particularities

The engine speed control is automatic without external intervention. Only the commands for start and stop of the motor can be adjusted on the mechanical speed controller. This means that the diesel engine works externally without any auxiliary voltage.

The engines of this type were formerly used in smaller vessels of inland shipping. The low speed of 1500 rpm used by these motors results in long service intervals and high life cycle times.

Turbocharging and intercooling are foreign words for machines of this age and type. The application of a pure suction motor brings a very decisive advantage. Most technically interested surfers have certainly come across the term "turbo lag". When changing from idle to full load, the turbocharger needs a certain amount of time to reach full speed. Such a load change now occurs when the load is switched on. Once the generator requires the maximum power from the diesel engine, this can not be provided in the expected performance. The speed breaks down and it can even happen, that the diesel engine stops. This can happen mainly when the generator should start large electric motors. 

Particularities

The generator is a two-pole compounded synchronous machine.

The compounding is used for voltage maintenance. The principle can be simplified as follows:

A load connected to the generator provides a current flow through the windings of the generator. Since these windings have an ohmic resistance, a voltage drop occurs at this resistor. This means that the voltage at the terminals of the generator drops. A light bulb connected to the terminals would be brighter or darker, depending on whether consumers are switched on or off. The load current of a load is passed through a (compound) transformer. This transformer controls the excitation current through the windings of the exciter field. If the load current increases, the current of the transformer is also increased and thus the excitation field is amplified. A strengthened excitation field in turn ensures increased voltage at the terminals of the generator. The voltage is thus kept approximately constant. For new machines, the voltage is kept electronically constant.

What has been changed on the generator?

The generator was not as busy as the engine. Only the grease of the ball bearings, which was rather crumbly than greasy, had to be renewed. For this purpose, the generator was removed and disassembled. The rotor was pulled to make the bearings easier to access. Of course, the generator main line to the main distribution has also been replaced by a new H07RN-F 5G50 line.

Particularities

The special thing about the original controller was, that there was no controller.

There was no monitoring of oil pressure, oil or water temperature.

Once started, the engine ran just as long as fuel was available, the oil went out or anything gave up its live once and for all. That was something we did not want to leave unchanged! For this reason, we have installed a controller that monitors the main functions of the engine. In the event of a fault, the controller is thus able to drop the load, slow down the engine speed or stop the engine in an emergency. Only then can you operate such a device without constant supervision for several hours or days at a time.

With a PLC, we have realized this monitoring.

What did we change on the diesel engine?

Paintwork

Basically, the entire unit was in a very dirty state when handed over to the THW. After some layers of dust and soot, that had accumulated over the years were removed, a reasonably painted engine came out. For this reason, we decided not to repaint the engine, as this would be an extremely big expense. Meanwhile, we got used to the sky blue color.

Control

The speed control of the diesel engine is done via a mechanical speed controller, which is firmly connected to the fuel injection pump. If now the engine is started or stopped, this is changed via a lever on the speed controller. Previously, this was done via a Bowden cable from the machinist. Today this task takes over a windscreen wiper motor, which is controlled by a programmable logic controller (PLC). The required position signals are detected by inductive proximity switches and processed in the PLC.

Cylinder head gasket

Once the unit was received, it had to pass numerous test runs first. Such a short-term operation is known to be not very good for combustion engines. So what came to happen: The cylinder head gasket leaked and had to be replaced. Some pictures of this action can be found in the picture gallery.

Wasserpumpe

Als wir schon sehr weit mit unseren Arbeiten waren und das Aggregat offiziell vorstellen wollten, trat eine Woche vor dem “großen Tag” ein Lagerschaden an der Wasserpumpe auf. Dieser machte sich dadurch bemerkbar, dass Wasser aus der Pumpe austrat und der an der Wasserpumpe befestigte Kühlerlüfter gegen den Kühler schlug. Wie durch ein Wunder schafften wir es aber doch noch die Pumpe bis zur Präsentation durch eine neue auszutauschen. Allen, die sich hierfür mindestens ein Bein herausgerissen haben, danke ich an dieser Stelle noch einmal recht herzlich.

Ausgleichsbehälter

Im Betrieb hat sich dann herausgestellt, dass der Kühlwasserausgleichsbehälter vom Motor zu klein dimensioniert ist. Wir der Motor auf Betriebstemperatur gebracht, drückt Kühlwasser aus dem Überlauf. Bei kalter Maschine liegt der oberste Teil der Kühllamellen trocken. Um diesen Zustand abzuschaffen und um eine Erfassung des Kühlwasserstandes für die SPS zu ermöglichen, wurde ein größerer Ausgleichsbehälter angebaut.

Öldruckmessung

Um im Fall eines defekten Öldruckschlauches einen Motorschaden zu vermeiden, wurde eine elektronische Öldruckmessdose eingebaut. Vor dieser geht eine Störmeldung ebenfalls auf die SPS.

Wasser-/Öltemperatur

Diese beiden Parameter werden ebenfalls durch elektronische Instrumente erfaßt und Störungen zur SPS weitergeleitet.

Drehzahl

Die Drehzahl des Motors wird über einen induktiven Näherungsschalter erfaßt. Dadurch ist es möglich sicher zu sagen, ob der Motor läuft, oder still steht. Dies ist wichtig, um zu verhindern, dass der Anlasser betätigt wird, solange sich der Motor bewegt.

Kraftstoffvorwärmung

Um bei Betrieb im Winter dem Versulzen des Kraftstoff vorzubeugen, wurde eine Durchflusskraftstoffheizung eingebaut. Diese erwärmt den Kraftstoff, bevor er durch die Filteranlage gepumpt wird. Die elektrische Energie hierfür wird dem 24V-Bordnetz entnommen.

Lichtmaschine

Der Einbau der oben beschriebenen Kraftstoffheizung machte den Austausch der alten 12V Lichtmaschine erforderlich. Die Leistung dieser Maschine war viel zu klein, so dass diese durch einen leistungsstarken 24V Drehstromgenerator ersetzt wurde.

After we were able to convince the full-time administration of the benefits of the new power generator for our local section, the THW supported us with the trailer. There were at least 100 trailers on a site of the Bunderwehr. There we should go and find a suitable trailer. There was no more information. I was already worried that it is probably about 100 identical trailer. That was true, but it was just the type we were looking for.

That was really a direct hit.

After the paperwork was clarified a few weeks later, we were able to pick up "our" trailer.

What has been changed on the generator?

Since we wanted to make the generator modern, it was clear that some parts of the trailer were no longer needed.

The side walls came away, as did the wall at the front. Because the trailer used to belong to the Bundeswehr, the color of the frame did not fit the THW. Olive green had to turn black. The workshop of the Bundeswehr had done a great job and preserved the trailer clean with wax. But you can not paint on wax. So all the crap had to go down first. With wire brush, solvents and sandpaper, we spent several weeks preparing the trailer. Then it was primed and painted twice.

The wooden boards were in good condition and needed only sanding and then repainting. So the trailer soon looked like new again. It was time to make the breakthroughs for attaching the generator frame to the trailer (see "Wedding" section). In addition, we have sawn an opening for the oil change in the ground. In order to protect the wood from rain and, of course, to enhance the appearance of our generator, we have used corrugated aluminum.

We have covered the parts that are not protected by the new noise insulation later on.

Then the trailer was ready.

Generators are certainly operated for a long time at a stationary site. Such a site may well be in a residential area or near inhabited areas. In order for the residents to find their rest at night, we wanted to build a noise protection for the power generator in any case. There was a lot of discussion in this regard. Of course because of the cost. So far the support association of our local association had borne all costs for the conversion. The advocates for noinse protection were fortunately in the majority. A company built the sound insulation according to our specifications, and just a few weeks later we were able to pick up the finished element.

What has been changed on the generator?

Since we had to save costs, we painted all the individual elements ourselves. There were also a few minor changes to the side doors. Originally there was only one flap at the rear, which could be opened. On the sides you could take out the element only. I then rebuilt an item on each page so that you could open it easily. This turned out again and again as a great advantage.

When the painting was done, the noise protection was placed on the trailer and also bolted to the frame of the trailer. Here we have again used the same system that we had previously decided for the wedding of generator and trailer with the expert of the TÜV.

One of the most important milestones in the construction of our power generator was the so-called wedding between generator and trailer. We spent a lot of time thinking about what we can do and what we need to do to achieve a secure and stable connection between the two parts.

To firmly weld the unit to the frame of the trailer was out of the question. Because of the heat during welding, the material changes the trailer. We probably would not have received a certificate from TÜV for such a connection. So we had to think of something else. With the expert of the TÜV, we then agreed on a screw connection. The unit is screwed with threaded rods to a small subframe underneath the trailer and tightened.

Thus, the way was paved for the wedding.

The big day came when the unit was lifted onto the trailer.

 In the same way we later also screwed the soundproofing with a trailer.