of test series I was to determine the impact 

 of a log weighing 1,362 kg (6.1 m long and 

 0.92 m in diameter) against the screen as a 

 factor of three approach velocities, 0.15, 0.6, 

 and 1.2 m per second (mps). Travel rate of 

 the screen was matched to each approach velo- 

 city. Test series II was to determine whether 

 logs (6.1 m long and 40.6 cm in diameter) with 

 1.2-m long stubbed branches extending through 

 the loops of the cable netting would be released 

 from the screen as the log entered into the by- 

 pass, just prior to the screen's return upstream. 

 Test series III was to determine the horsepower 

 requirements of the debris screen when it was 

 traveling without water in the canal in contrast 

 to traveling with water moving at various ve- 

 locities of approach. No special test materials 

 were required. 



Water depth for all tests was held as constant 

 as possible at 1.7 m (4.7 ft). For each test 

 the logs were dropped into the canal at the up- 

 stream end and allowed to be carried by the 

 flow onto the screen. 



EFFECTIVENESS OF TRAVELING 

 DEBRIS SCREEN 



We conducted 128 tests in the three test ser- 

 ies. Of these, 21 tests (test series I) were 

 related to the study of log impact against the 

 net. Table 1 shows that the horsepower re- 

 quired to move the screen did not increase 

 through impact of the 1,362-kg log against it 

 and indicated the ease with which large debris 

 could be handled. 



Forty-four tests (test series II) were con- 

 ducted to determine the possibility of log hold- 

 up on the screen. Without exception, all 

 stubbed branches enmeshed in the cable loops 

 slipped away as the screen started its travel 

 around the end turn. 



Table I. Comparative horsepower requirements of traveling debris screen as 

 factor of water approach velocity and debris load (travel rate of screen 

 matched to velocity of approach). 



Hater approach 

 velocity (raps) 



without log 



Horsepower renuircr.?nt r. (hp) 

 with logl/ incre 



0.15 

 0.61 

 1.22 



O.llO 

 1.00 

 3.00 



o.uo 



1.00 

 3.00 



■ Theoretical hp requirement 



* Screen operating dry - actual hp requirements 



• Screen operating in water ol water velocity of 



10.43 mps and 1.5-tn water depth 

 1 0.8-mps woter velocity ot I 5-m water depth 



TRAVEL RATE OF DE8RIS SCREEN Imps) 



Figure 6. Curves t>f drag forces on debris screen. 



The results of 63 drag tests (test series III) 

 are plotted in Figure 6. (Each of the 21 plotted 

 values in Figure 6 represents the mean of three 

 tests.) We found that only 3 hp were needed 

 to move the screen at 1.0 mps in a water ap- 

 proach velocity of 0.8 mps and that an extensive 

 drop in horsepower requirements could be 

 achieved by reducing the travel rate of the 

 screen: A 50% reduction in the screen travel 

 rate (0.5 mps) reduced the horsepower require- 

 ments to a minimal 0.5 hp (Figure 6) . 



Although water reaction forces" against the 

 debris screen were not appreciable because of 

 the extensive open area of the 35.6-cm diameter 

 loops, it did become necessary at higher veloci- 

 ties to add weights to the bottom of the net 

 to prevent undue deflection from the vertical 

 position. Weights were required only at ve- 

 locities above 0.9 mps. 



In the fall, long streamers of moss passing 

 downstream with the flow became enmeshed 

 with the cable loops. To release the material, 

 hand picking was required. 



During the 7-month period of testing, the 

 debris screen traveled a distance of 5,474 km 

 over a period of 1,900 hr without breakdown 

 or call for maintenance. 



SUMMARY AND CONCLUSION 



During a 2-year period of intermittent op- 

 eration, it was clearly indicated that the travel- 

 ing debris screen combines all the advantages 



1/ Weight, 1,362 kg; length 6.1 m; diameter 0.92 n. 



6 Water reaction force is the sum of water friction 

 and water pressure against the screen. 



