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PROJECT REPORT July 2014

Productivity assessment for a Caterpillar 305.5D CR hydraulic mini-excavator (mini-hoe): a case study at the Slave Lake Mulch Research Area Steven Hvenegaard, Rex Hsieh

INTRODUCTION

In February 2014, Alberta Environment and Sustainable Resource Development (ESRD) completed a 30 ha fuel treatment within the Slave Lake Mulch Research Area near the town of Slave Lake, Alberta. We attached a MultiDAT1 to a Caterpillar 305.5D CR hydraulic mini-excavator, commonly referred to as a mini-hoe, to capture real-time data from the machine while it was working. We then calculated its productivity and utilization rate.

METHODS

Machine Description The Caterpillar 305.5D CR mini-hoe (Figure 1) is a rubber-tracked 31 kW (42 hp) hydraulic mini-excavator with a ground pressure of 30.2 kPa (4.1 psi). The standard boom can extend 5.79 m (19 ft) from the centre of the cab and is equipped with a thumb.

Figure. 1. The Caterpillar 305.5D CR mini-hoe.

1 MulitDAT is a system for recording and reporting information about the activities of forestry machines.

http://www.castonguay.biz/

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Fuel Treatment Site The Slave Lake Mulch Research Area (Appendix A) is 4 km southeast of the town of Slave Lake, Alberta. The area was designed to study mulch fuel treatments and the productivity of the equipment. The Caterpillar mini-hoe was used in four study plots: 3A, 3B, 5A, and 5B. Crews from the Alberta Wildland Fuels Inventory Program measured the stand characteristics (Table 1 and 2) and collected fuel load data before treatments began. The study plots were flat and the ground was frozen with approximately 50 cm of snow. The stands were dominated by Black Spruce.

Table 1. Species composition of the study plots processed by the mini-hoe.

Study Plot

Black Spruce

(%)

Balsam Poplar

(%)

Larch (%)

3A 99 0 1

3B 98 2 0

5A 100 0 0

5B 99 0 1

Table 2. Stand characteristics of the study plots processed by the mini-hoe.

Study Plot

Plot Area (ha)

Stand Density (stems/ha)

Average Tree

Height (m) >9 cm DBH <9 cm DBH Total

3A 1.9 1425 3750 5175 8

3B 1.5 1950 4875 6825 9

5A 2.5 1400 3887 5287 8

5B 1.5 1087 6500 7587 7

Fuel Treatment Activities Two common forest fuel treatments are strip mulching and inter-tree spacing. Strip mulching is commonly used in high density Black Spruce stands where stems have a small diameter. The mulcher punches through the forest leaving strips of mulch behind. Inter-tree spacing is used to reduce the stand density by leaving only larger and healthier stems standing. In dense stands with small diameter stems, inter-tree spacing is sometimes modified to space clumps of small trees instead.

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Study plots 5A and 5B were strip mulched, study plot 3A had inter-tree spacing, and study plot 3B had clump spacing. The main function of the Caterpillar mini-hoe in these treatments was to pull pockets of woody debris and fallen stems from adjacent standing timber that resulted from the first stage of mulching (Figure 2, 4, and 5) and pile it in the mulch strip (Figure 3). This was called the cleaning phase.

Figure 2. Pockets of woody debris and fallen stems in standing timber after strip mulching.

Figure 3. Cleaning phase in mulch strips with the mini-hoe.

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Figure 4. Woody debris remaining after inter-tree spacing before cleaning with the mini-hoe.

Figure 5. Woody debris remaining after clump spacing before cleaning with the mini-hoe.

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RESULTS

We collected data on the mini-hoe over four days from February 18 to 21, 2014. Most of this work was conducted in temperatures ranging from -15oC to -30oC. The productivity rates of the mini-hoe are summarized in Table 3. The table also includes measured forest stand characteristics that could have had an effect on productivity.

Table 3. Productivity rates of the Caterpillar mini-hoe at the Slave Lake Mulch Research Area.

Plot Treatment Activity Productivity (ha/PMH)

Stand Density (stems/ha) Average

Tree Height

(m) >9 cm DBH

<9 cm DBH Total

3A cleaning after inter-tree spacing 0.87 1425 3750 5175 8

3B cleaning after clump spacing 0.26 1950 4875 6825 9

5A cleaning after strip mulching 0.23 1400 3887 5287 8

5B cleaning after strip mulching 0.21 1087 6500 7587 7

The machine utilization rate is equal to productive machine hours divided by total scheduled machine hours multiplied by 100:

(PMH/SMH x 100)

The utilization rate for the mini-hoe during this study was 83%.

DISCUSSION

The wide spacing between individual stems (4–6 m) in study plot 3A made it easy for the mulcher to process most of the woody debris on its first pass. Consequently, very little debris was left to be cleaned by the mini-hoe. As well, the openness of the stand made it easier for the mini-hoe to manoeuvre. These two factors are reflected in a relatively high productivity rate for the mini-hoe in study plot 3A (0.87 ha/PMH).

There was a sharp difference in the stem height and density within study plots 3B and 5B: at the northwest end of these plots the stand was tall and dense, but at the southeast end the stand was shorter and less dense (Figure 6). The effect of this difference on productivity could not be determined.

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Figure 6. Accumulation of lodged stems in dense stands (left) and sparse stands (right).

The volume of woody debris and stems lodged in the adjacent standing timber appeared to be greater in areas with taller and denser trees. ESRD fuels managers and the equipment contractor agreed that this was problematic. Increasing the width of the mulch strips might reduce the amount of stems and pockets of woody debris in adjacent timber. Wider mulch strips would also make it easier for the mini-hoe to manoeuvre and increase its overall efficiency.

Lodged stems and debris accumulation were less common in areas with low density Black Spruce, so in stands like these the cleaning phase and the final mulching phase may not be required. In areas with distinct differences between high density and low density Black Spruce, it may be more cost-effective to split the treatment area and treat the low-density stands without the cleaning phase and final mulching phase.

CONCLUSION

This assessment provides a snapshot of the potential productivity of the Caterpillar 305.5D CR mini-hoe in a cleaning operation as part of a mulching fuel treatment in Black Spruce. We caution readers against relying on these results to estimate the cost of their fuel treatment project, or to expect a certain production rate from their equipment. Generally, productivity assessments are conducted over much longer periods, but because forest fuel treatments are small and variable this is difficult to achieve. We continue to look for opportunities to conduct these assessments for different machines and in different types of fuel treatments.

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APPENDIX A

Slave Lake Mulch Research Area

Map courtesy of Mistik Environmental Services Ltd.