Acuerdos y técnicas para representar objetos geométri cos y condiciones para interpretar tales representaciones

Initial investigation of abnormal engines focused on PJB 114 and 132 at Elouera Colliery, albeit for different reasons. The raw exhaust carbon monoxide reading on vehicle 114 was found to be 2,000 ppm CO, well above the statutory limit of 1,500 ppm. At the same time the raw exhaust elemental carbon concentration was only 28 mg/m3, which was somewhat of a surprise.

During the connection of the sampling hose to the gas point on the engine manifold, it was noticed that the engine appeared to have a very high backpressure. A pressure gauge was used to measure the backpressure between the engine and the water-filled spark arrestor (scrubber tank).

The backpressure recorded was 170 kPa, many times the engine manufacturer’s recommendation. Pressure tests across the inlet and outlet of the scrubber tank indicated a restriction and as a result the unit was removed and replaced with a reconditioned unit from the store. Immediately the raw exhaust elemental carbon result increased from 28 to 121 mg/m3 and the carbon monoxide from 2,000 to >2,500 ppm. The high carbon monoxide concentration suggested over-fueling and the fuel setting was adjusted to a lower rate. Immediately the elemental carbon concentration dropped from 131 to 45 mg/m3 and the carbon monoxide concentration reduced from >2,500 ppm to 690 ppm.

Following an evaluation by Elouera Colliery mine site engineering personnel it was decided to replace the fuel injectors to establish if better power performance could be achieved. As a result, elemental carbon concentrations barely moved (Table 5.4); however carbon monoxide levels were reduced by over 50% (Table 5.6). This provided the opportunity to readjust the fuel setting to give more power, resulting in a final raw exhaust carbon monoxide concentration of 600 ppm and 40 mg/m3 elemental carbon.

The initial scrubber tank was returned to the vehicle manufacturer, where the base of the unit was cut open for inspection. As can be observed in Figure 5.3, the majority of exhaust downpipes were blocked with a carbonaceous material thus creating a severe restriction. Discussions with mine site personnel indicated that some time previously a decision had been made to cease placing a chemical cleaning agent in the water bath. The basis for this decision is unclear; however it has obviously proved to be incorrect.

Figure 5.3

Internal View of Scrubber Tank from PJB 114 at Elouera Colliery

Examination of PJB 132, which had a raw exhaust elemental carbon concentration of 139 mg/m3 _{and carbon monoxide of}

1,250 ppm, revealed a similar situation to that of PJB 114. Backpressure on the engine arising from the scrubber tank was found to be excessive, however in the interests of time a chemical cleaning agent was dosed into the scrubber tank and the vehicle driven for approximately four hours. At the same time a new fuel pump was fitted and the raw exhaust re-tested.

Elemental carbon dropped from 139 to 46 mg/m3, carbon monoxide from 1,250 to 690 ppm and backpressure on the engine from approximately 170 kPa to <1 kPa. The vehicle returned to service the same day with minimum loss of availability.

It is clear that these two cases have highlighted the importance of ensuring scrubber tanks are maintained in a clean condition and that a simple backpressure test would have highlighted the issue.

The availability of the mobile gas laboratory and the R&P Series 5100 diesel particulate analyser greatly assisted the diagnostic process.

Investigation of the other vehicles with unacceptable exhaust emissions resulted in the following outcomes:

• Ram Car 194 – The engine in this unit has been found to have many hours of operation under high load (>6,000 hours). The fuel injectors were changed and the unit re-tested, with a resultant raw exhaust elemental carbon concentration of 71 mg/m3. Site engineering personnel did not consider it worthwhile progressing the matter beyond this point as the vehicle is scheduled to be scrapped in 2004 as the mine approaches closure. Nevertheless the process of replacing the injectors reduced the raw exhaust elemental concentration by over 55%. It is also interesting to note that the raw exhaust carbon monoxide concentration was reduced by 140 ppm by this basic maintenance procedure.

• PJB 103 – Investigation of maintenance records established that this engine had been a reconditioned spare left over after the closure of Tower Colliery. It is understood that the tappets were found to be incorrectly set upon the vehicle’s arrival at Dendrobium Mine and site engineering personnel thought that this may have caused permanent damage. As a first step, mine site personnel changed the injectors, cleaned the scrubber tank and air intake system. The engine was re-tested with a resultant elemental carbon concentration of 61 mg/m3, which is below the 95% UCL for KIA engines. The raw exhaust carbon monoxide concentration was also reduced by 305 ppm.

• SMV 5073 – A review of the history of the vehicle indicated that the unit had been purchased “second hand” from Queensland. This unit, together with SMV 5100 and MPV 98 have been scheduled for investigative maintenance, however to date operational requirements have delayed this process.