6.1. Felling operation
As explained above, the felling phase was not included in these time studies because felling had already been completed before logging by construction crane began.
But according to the stand characteristics, given in Table 1, the following productivity rate could be estimated:
Team: Chain-saw operator
· Estimated production at study area A: 3.6 m3/h
· Estimated production at study area B: 3.5 m3/h
These production figures for felling have to be considered as standards and are calculated according to value tables of coniferous timber felling by means of chain-saws. These tables should enable the forester to predict felling productivity under particular site and stand conditions in order to make arrangements with the fellers.
Stated productivity rate for study area A includes felling, delimbing and cutting the trees into assortments, mainly long logs. At study area B the trees were felled and in case the feller estimated that the weight of a tree would exceed the permissible load weight of the crane the tree was cross-cut once. For this reason the productivity rates, stated above, are quite similar although the mean tree volume at study area B amounted to roughly half the tree volume at study area A.
6.2. Logging operation
The production during the crane operation was recorded for the three installations (2 settings on study area A and 1 setting on study area B) totalling 178.12 m3 of timber. The crew was the same during the whole logging operation.
Team: Crane operator and two assistants
· Production: 178.12 m3 : 14.29 h = 12.46 m3/h
The time distribution between the different work phases of the crane operator based on the studies at the three construction crane settings was as follows:
Work phases Total
Crane movement unloaded 18.60 % 17.86 %
Lowering the hoisting equipment 12.08 % 11.59 %
Hooking the load 7.91 % 7.59 %
Crane movement loaded 56.41 % 54.15 %
Unhooking the load 4.73 % 4.54 %
Cross-cutting 0.27 % 0.26 %
Total work phases 100.00 % 95.99 %
Sequence of operation delays 44.14 % 1.77 %
Personal delays 34.52 % 1.38 %
Delays due to getting new order 9.13 % 0.37 %
Equipment delays 12.21 % 0.49 %
Total delays 100.00 % 4.01 %
Grand total 100.00 %
There were no major delays resulting from a defect of the construction crane or the hoisting equipment. But three short delays between five and ten min occurred because the rope jerked out of the pulley attached to the end of the boom. This happened when the boom was not aligned to the load. The adjustment to the load is not only important in preventing delays but it also is a very important safety measure in the operation because lateral pulling of the load might cause the crane vehicle to be overturned.
The following work phases were not included in the calculation of the productivity rate:
· Setting up the construction crane
The average time consumption for setting up the construction crane was 27.8 min with a range from 11.2 to 44.2 min. The longest time involved for setting up was that which was necessary to discuss the job order and operation method, in general, prior to setting up the crane.
· Dismantling The average time consumption for the three dismantling operations was 14.98 min with a range from 12.8 to 18.7 min.
6.3. Processing operation
The production data for the processing operation have been obtained from other time studies of wood processor operations where the one-grip crane processor STEYR KP 40 was mounted on a skidder. All settings where time studies were carried out were on the road so that conditions for comparisons are given. According to the results of these studies, productivity depends on the diameter of the trees and the required assortments which call for different amounts of cross-cuts.
Figure 4 shows the performance of the STEYR KP 40 which can be expected according to the mid-diameter.
- - -- Assortment method - short --- Assortment method - long
Figure 4. Performance of the STEYR KP 40 wood processor (FPP 1991).
FPP (Kooperationsabkommen Forst - Platte - Papier) (1991): HARVESTER / PROZESSOREN,
Maschinen in der Durchforstung, Einsatzmöglichkeiten - Verfahren, Leistung - Kosten; Wien; p. 32