.

Previous PageTable Of ContentsNext Page

6. STUDY METHODOLOGY AND ANALYSIS OF DATA

Work and time studies to assess the efficiency of felling and extraction operations were undertaken in accordance with generally accepted forest work study procedures (IUFRO 1995). The study methodology used for all time studies was cumulative timing exclusively, with the time for each work element subsequently obtained by subtraction.

Although the skidding machine operator was studied independently from other harvesting activities, information on other crew members was collected to support the analysis of time consumption and interpretation of the time distribution of work elements.

The postharvest assessment of environmental impacts associated with harvesting was limited to a survey of skidtrails in order to quantify soil disturbance caused by the operations.

6.1 Work and time studies on felling and extraction

Cutting comprises a set of activities undertaken to fell standing trees and prepare them for extraction. Extraction is defined as the process of moving trees or logs from the felling site to a landing or a roadside where they will be processed into logs or consolidated into larger loads for transport to the processing facility or other final destination (Dykstra & Heinrich 1996).

Depending on the harvesting system applied, these activities vary with respect to their frequency of occurrence. Nevertheless, a sequence of regular work elements can be found for felling that constitutes the normal work cycle. The same applies also to extraction. The normal work cycle comprises a sequence of work events that are repeatedly applied to every work object (IUFRO 1995). A work element is sub-division of a given work task and is delimited by break points. Depending on whether or not it occurs in every work cycle, a work element can be considered as a repetitive or an occasional element.

Only workplace time, which is defined as the portion of the total time that a production system or part of a production system is engaged in a specific work task (IUFRO 1995), has been considered in estimating production rates. Although meal time is part of the workplace time, it has been excluded from estimations because it varied considerably during the study.

Figure 7 shows the conceptual structure of work elements as generally applied in forest work and time studies. The nomenclature shown in the figure was used in this study.



Figure 7. Structure of workplace time concepts (Source: IUFRO 1995).

 

6.1.1 Work and time study on felling operations

The classification and percentage of workplace time, excluding meal time, as observed for each work element in felling operations can be found in Appendix 3 for both study sites, M38/SBLC and BL14/VFP. General data from the felling studies may be summarised as follows:

Subject of Observation

Set-up M38/SBLC

Set-up Bl14/VFP

Work time

15 h 21 min

11 h 54 min

Non-work time

1 h 36 min

47 min

Workplace time

16 h 57 min

12 h 41 min

Trees felled

   

    Marked trees

31

35

    Unmarked trees

8

---

Trees crosscut only*

1

2

Trees harvested

40

37

Trees rejected

8

2

Utilisable volume

236.0 m

214.2 m

Volume/tree

5.9 m

5.8 m

Note: Workplace time excludes meal time

* Trees crosscut only:

Work elements (Classification)

Set-up M38/SBLC

Set-up BL14/VFP

[min]

%

[min]

%

           

Felling

(MW)

8.02

37.33

4.78

27.50

Bucking and delimbing

(MW)

5.42

25.23

5.18

29.84

Location of tree

(CW)

2.63

12.26

1.38

7.95

Felling preparations

(CW)

1.97

9.15

1.13

6.50

           

Productive work time

(PW)

18.04

83.97

12.47

71.79

           

Consideration

(OP)

0.69

3.21

0.23

1.35

Repair time

(RT)

-   

-   

-   

-   

Maintenance time

(MT)

0.61

2.84

0.60

3.43

Refuel time

(RF)

0.85

3.96

0.74

4.27

Site clearing

(AW)

0.82

3.82

0.18

1.05

Cut free saw

(AW)

0.47

2.20

3.15

18.11

           

Supportive work time

(SW)

3.44

16.03

4.90

28.21

           

Time required to fell a single tree

21.48

100.00

17.37

100.00

           

Subject of Observation

Set-up BL14/VFP

Sub-Sample 1

Sub-Sample 2

Work time

10 h 35 min

-

Non-work time

4 min

-

Workplace time

10 h 39 min

16 h 16 min

Logs skidded

39

40

Utilisable volume

219.3 m

214.2 m

Volume/tree

5.6 m

5.4 m

   

Set-up BL14/VFP Sub-Sample 1

Work Elements (Classification)

[min]

%

Attach cable to log

(MW)

2.63

16.20

Winching

(MW)

0.83

5.08

Skidding log(s)

(MW)

4.11

25.28

Unhook

(MW)

0.70

4.29

Landing operation

(MW)

0.66

4.05

Unloaded travel on primary skidtrail

(CW)

1.52

9.32

Locating logs

(CW)

3.83

23.52

Productive work time

(PW)

14.28

87.74

Consideration

(OP)

0.67

4.12

Repair time

(RT)

-   

-   

Maintenance time

(MT)

-   

-   

Refueling time

(RF)

0.17

1.04

Clearing landing

(AW)

1.16

7.10

Supportive work time

(SW)

2.00

12.26

Time required to skid a single log

16.28

100.00

Study site

[Set-up]

Number of observations

Volume per tree felled [m]

Felling time per tree [min]

Productivity

[m/h]

Ania-Kapiura area

[M38/SBLC]

40

5.9

25.43

13.92

Basu-Leitre area

[BL14/FVP]

37

5.8

20.57

16.91

Study site

[Set-up]

Number of observations

Volume per load [m]

Skidding time per load [min]

Productivity

[m/h]

Basu-Leitre area

[BL14/FVP]

79

5.5

20.44

16.15

Sub-sample 1

39

5.6

16.38

20.51

Sub-sample 2

40

5.4

24.40

13.28

 

Subplot BL14/VFP

Description

[m]

%

trees

Felled stems

499.9

100.00

129

Losses due to:

     

      unsatisfactory topping

3.8

0.76

1

      splitting of stems

18.6

3.72

5

      undiscovered decay

18.8

3.76

4

Total losses

41.2

8.24

10

Extracted sawlogs

458.7

91.76

119

 

Subplot BL14/VFP

Classification of

Width

Length

Length

Area

Skidtrails

[m]

[m]

[%]

[m]

         

Primary skidtrails

4.5

2,360

79.9

10,620

        Planned & marked

 

195

6.6

 

        Unplanned

 

2,165

73.3

 
         

Secondary skidtrails

4.5

594

20.1

2,680

         

Total skidtrail length

 

2,954

100.0

13,200