by Doug Woodyard
condition monitoring
Growing market for electronic pressure indicators
G
erman cylinder pressure measurement specialist IMES reports that another major enginebuilder has adopted its
hand-held EPM-XP electronic indicator instead of traditional mechanical devices. Hyundai Heavy Industries, the world’s largest builder of low speed two-stroke engines, will supply the equipment for periodic monitoring of cylinder pressure on the MAN B&W MC/MC-C and Wärtsilä RT-flex models it builds and sells under licence.
Earlier co-operation between the companies saw the joint development
of a cylinder
pressure monitoring system for HHI’s Himsen medium speed four-stroke engines (in 2008) and a number of two-stroke engines in 2009/2010. The aim is to offer engine operators the precision and user-friendliness of advanced electronic equipment. By October last year IMES had sold over 600
EPM-XP devices and targets a total of 1,500 electronic engine indicator sales by the end of 2012.
An EPM-XP unit provides accurate information on key operating parameters immediately after data acquisition on the engine, with recorded values swiftly downloadable to a PC or notebook computer via a USB cable. The information can then be distributed as data files over the Internet to interested parties such as the shipowner, enginebuilder or ship manager. “In this way, both enginebuilders and end- users can be confident that engines in the field are set up according to their guidelines and will thus run more economically and reliably,” says IMES company owner
Dipl.Ing. Stefan Neumann. “For example, the electronic data recorded directly during periodic measuring by the EPM- XP can be compared with electronic data from the engine’s factory test runs and the ship’s trials. As well as enabling the optimisation of fuel consumption, an evaluation of the cylinder pressure pattern allows the calculation of mean effective pressure for all cylinders. This feature is
of special significance, given
the2011 introduction of IMO Tier II NOx emission limits.” The IMES evaluation
and visualisation
software package delivered on a CD-Rom with each EPM-XP device is menu-guided and largely intuitive, and allows graphical representation of key values in various forms. Following download from the hand-held device to a PC or laptop, the
www.mpropulsion.com
acquired data can be processed at leisure. Visualisation includes x-y axis graphs for the pressure patterns of all cylinders, which can be superimposed for making comparisons and depicting spreads and deviations from data recorded during engine factory testing and sea trials. Trends can also be derived and visualised from the comparative data. Significantly, too, the processed data can be input immediately into an over-riding onboard monitoring and diagnostic system. The EPM-XP cylinder pressure indicating device is designed for handling up to 160 measurements per cylinder over a maximum of eight output steps in a load range from 25 to 110 per cent on engines with up to 20 cylinders. The relevant engine speed ranges are 40 to 300 rpm for two-stroke engines and up to 1,500 rpm for four-stroke engines. Cylinder pressures can be recorded in a range from 0 to 300 bar with a claimed precision deviation of only 0.5 per cent (full scale). Up to 20 data acquisition cycles per cylinder can be realised on an engine for each of the eight output steps, each on the basis of the mean value of up to 10 complete pressure cycles per cylinder. Supplied with a strong instrument carrying case, the hardware involved in the system comprises: • a hand-held measuring device with LCD
display arranged in a robust protective casing and powered by a rechargeable block battery, the USB port of the device serving for both data transfer and battery recharge • an IMES HTT pressure sensor with flexible armoured hose incorporating a sprung Thompson adapter for swift connection to the indicator cock • a USB cable.
IMES firmware stored in the EPM-XP device enables acquisition of a complete testbed run in eight steps from 25-110 per cent engine load and simultaneous storage of all values in a data file. The CD-Rom contains dedicated software allowing the data acquired and/or calculated per load step by the device to be evaluated and visualised offline on a PC or laptop. The capabilities comprise the calculation and depiction of complete pressure patterns per measured cylinder: the maximum compression pressure and maximum pressure rise (Palpha); and the indicating cylinder output and indicated mean effective pressure (imep).
Further advanced data processing embraces a compensation function for mean pressure (Pmean) in which deviations from the derived values
for maximum cylinder pressure are calculated and visualised for all cylinders. In the Pmean visualisations function all medium pressure curves for all cylinders are superimposed in order to give a graphic representation of deviations in combustion pressure patterns. To check its accuracy according to ISO 9001,
the EPM-XP can be loaded with static pressure from a pressure testing device and recalibrated via the software.
Central to the performance of the indicator is the accuracy, reliability, robustness, longevity and cost-effectiveness of the IMES HTT pressure sensors exploiting TION thin film technology. The sensor has been produced in large quantities by IMES since the company’s foundation 16 years ago for series applications in permanently installed cylinder pressure monitoring systems and cylinder pressure- based control systems.
An IMES hand-held EPM-XP electronic cylinder pressure indicator
On engines running 24 hours a day in a range of applications, IMES reports, the sensors have regularly reached over 500 million load cycles. The proven reliability has earned the HTT sensor five type approvals from classification societies. MP
Marine Propulsion I February/March 2012 I 81
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