Analysis of Heat Sources in a Large Mechanized Development End at Mount Isa Mine

Abstract

The T62 decline at Mount Isa is a nominally 5.5 m wide and 4.7 m high heading driven at a grade of one in eight which is to be used as a main electric truck haulage for the 3000 and 3500 orebodies below the current shaft hoisting systems. The measured and expected virgin rock temperatures are 48°C at the main tipple 1000 m below surface and 58°C at the main loading loop 1500 m below surface. The portion of the decline considered in the study comprised a 75 m long face section between the face and the first storage bay and a 300 m long tunnel section from this storage bay to a point of through ventilation. This heading was one of several available to the same development crew, advanced an average of 3.5 m/day and was worked intermittently during the three shift operation. The face was drilled using a two boom electric hydraulic drill jumbo and was blasted using ANFO explosive. A 231 kW diesel powered loader was used to clear the face to the storage bay recess. This was also used to load a 287 kW diesel powered truck which removed the broken rock from the heading to a waste rock pass 700 m further up the decline. Two 1.22 m diameter flexible ventilation ducts were used to supply ventilation air to within 30 m of the face. Two observers were continuously present during the 120 hour study period and they completed 37 air quantity and air temperature surveys covering both the face and the tunnel sections of the development. The observers also monitored and timed the period of operation of the various items of mining equipment in both sections of the heading. Measurements of the average heat produced by the diesel powered equipment whilst undergoing typical load cycles were taken prior to the main study by measuring the fuel consumption. A bucket hydraulic line pressure transducer which was calibrated using lead weights was used to determine the average broken rock load in the bucket. An analysis of the measurements taken during the study clearly demonstrated the storage and release of heat by the rock surfaces when the diesel engine is operating and stopped. The average amount of beat removed from the heading was 254 kW of which the rock contributed less than half at 118 kW, diesel powered equipment 105 kW, electric equipment (excluding the ventilation fans) 11 kW, explosives 9 kW and the broken rock removed from the heading 12 kW. The study showed that where cyclic mining operations take place using diesel powered equipment, using a heat load averaged over 24 hours will provide a reasonable estimate of the conditions that may be expected when the diesel equipment is not in use. During the short periods of diesel equipment operation, multiplying the average heat load by a factor of between two and three will indicate the maximum temperatures that may be expected. Hot environments at Mount Isa are managed by the use of shortened shifts as a warning and stopping work completely when the limiting heat stress condition is encountered. The normal design is therefore to provide optimum ventilation and cooling relative to thermal productivity for the mining operations where diesel powered equipment is not used and, to confirm that this design will not result in six hour shift conditions when the diesel powered equipment is in use.

Meeting Name

5th International Mine Ventilation Congress (1992: Oct. 25-30, Johannesburg, South Africa)

Department(s)

Mining Engineering

Keywords and Phrases

Mount Isa Mine; Heat Sources; Rock Temperatures

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1992 Mine Ventilation Society of South Africa, All rights reserved.

Publication Date

30 Oct 1992

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