flight systems
Development of the Flight Systems Engine Saver
Eighteen years ago Norman G Clark (A/Asia) Pty Ltd introduced to the Flight Systems Engine Saver® to Australia. It quickly attracted interest for several reasons. The unique early warning features built into the design was one of them. But more importantly, it was the first time a system was generated to offset the inherent faults associated with existing engine protection systems.
Temperature sensitive sensors had been the preferred method of detecting engine faults.
This situation changed with the installation of a large fleet of 2000 HP diesel engines in haul trucks in South Africa. These engines were protected by conventional systems, and during early operations, there were coolant-related problems, which were not detected until after serious engine damage had occurred.
The engine failure rate highlighted the fact that temperature sensing was not a sufficient basis for a large engine protection system. An alternative sensor system was considered as an answer, but no one had any idea how pressure sensing could be introduced. This was before Flight Systems’ involvement.
As the major problem was coolant related, it was given immediate consideration. Almost all modern diesel engines are cooled by liquid, which circulates in a pressurised and sealed container. A coolant pump circulates the coolant around the system and there are approximately five distinct pressures at different points in the engine. The maximum pressure in the system is at the outlet of the pump. It therefore made sense that this would be the point where coolant pressure was monitored.
In almost any developing problem there will be no indication on in-cab gauges. Engine Saver will give an EARLY WARNING of trouble.
Inside the Engine Saver box there are several pressure sensors. For coolant, there is a very accurate adjustable transducer. This is constantly monitoring the pump output pressure whenever the engine is running. It is also comparing the actual pressure with the set trip point through the Electronic Module.
The pump maintains a very constant series of pressures for the range of pump RPM. Something that cause a change in pump output pressure is pump speed change. This can be caused by slipping fan belts, pump impeller damage, reduction in coolant volume, a loose or missing radiator pressure cap and coolant temperature increase. With the Flight Systems Engine Saver, the problem will be detected immediately and shut down action can be initiated.
Oil pressure was not a significant cause of engine failure, but it was decided to allow for this anyhow. The circuit was arranged the same as for coolant, and the set trip point was adjustable for accurate setting.
RPM was the main controller of the electronic component, and it was adjustable for overspeed. If the set speed was exceeded, the engine would be shut down in 0.5 seconds.
Flight Systems also included a sensor measuring turbo boost. This can be a back up for RPM failure. Apart from its other functions, RPM sensing also enables the electronic components and ensures that they maintain coolant and pressure control accuracy.
Finally, crank case pressure was monitored by a highly accurate switch which was operational anytime the engine was turning. In excess of 10” WG, pressure would be shut down instantly. This function was responsible for the detection of many faults and saved a lot of engines from destruction. There was no adjustment on this trip point, but if required, alternative sensors up to 15” WG were available.
In the beginning, a Level 4 Engine Saver was fitted to about 200 units to Cummins and Detroit diesel engines. A surprising observation coming out of this was the variation between the two makes in pump output pressure. Caterpillar’s pump output pressure was also significantly different. It became obvious that a bigger range of adjustment would be required if suitable trip points for all engines were to be obtained.
In Engine Savers up to Level 6, it had been customary to set one trip point. This was usually about mid RPM range for the engine. This setup was flawed because of the unacceptably large change in pump output pressure from idle RPM to high idle. All engines increased and decreased pump output in a curve. So it was difficult to select and set a point which allowed protection right through the pressure curve.
Level 6 incorporated an electronically ramped pressure control. While RPM is linear, the pump pressure is curved. The ramped feature allowed the Trip Point selection to be set at both low RPM and at high RPM. The ramp kept the trip point right in the RPM range close to actual operating pressure. The method for setting this is the topic of another report. Most importantly though, the system was highly efficient in practice. Faults in pressure were detected very quickly and the saving of engines happened early and frequently.
The Level 6 model has only recently been superceded by Level 7; a very different device. It still includes all the old tried and tested features, but it has special functions and incorporates other systems.
Basically the Level 7 Series C has been upgraded electronically so that it is practically immune to spike problems. Flight Systems have arranged for a heavy upgrade of the transducers and sensors. So there will be a much improved field life even in the face of severe conditions.
The new design includes monitoring from analog and digital signals. This allows crank case pressure, previously a fixed trip point, to be adjusted to different settings. This feature can prove advantageous in many circumstances.
A standard electronic module is part of all Level 7 Series C models. However, there is a possibility of monitoring two (2) auxiliary operations such as transmission or differential temperatures. The settings for this are adjustable, and if exceeded the engine shut down can be initiated.
A development with the Level 7 Series C is the possibility of extracting engine operational information to an external source. This is achieved with a matching unit (known as Service Advantage) plugged into the accessory port. It is then possible to collect information on an engine’s state from downloaded information at regular intervals.
A less exotic version for presenting information is the Digital Enunciator. This is a hand held tool which also plugs into the accessory port while the machine is working. By selecting the circuit that is to be checked, a digital read out will be presented which indicates what is happening to the engine while working. Although this information is available from the internal Engine Saver display, the Digital Enunciator is much more convenient as it can be used in the Operators cabin.
For a number of years Norman G. Clark has carried a substantial stock of all components for the various Engine Saver models. More recently, we have offered a rebuild facility for Level 7 models. This has been used extensively and there are regular users throughout the mining industry.
If you have an old Level 7 that requires repair, it can be recycled as an “as new” 7C and we will be happy to quote on any version of the current model. There is quite a lot of interest in this facility and we would be happy to demonstrate the advantages of this service. Attached is some information relating to the Level 7C attachments, which are highly recommended as a Service or Operators Tool.
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