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Table 2.5.1 List of protective height H, sensor length J and steel pipe L
Number
of
beams
Detection
capability
14mm
Detection
capability
20mm
Detection
capability
30mm
Detection
capability
40mm
Beam spacing
10mm
Beam spacing
15mm
Beam spacing
25mm
Beam spacing
35mm
H
J
L
H
J
L
H
J
L
H
J
L
6
175
190
500
8
175
190
500
245
260
500
10
225
240
500
315
330
500
12
165
180
500
275
290
500
385
400
750
14
195
210
500
325
340
750
455
470
750
16
150
165
500
225
240
500
375
390
750
525
540
750
18
255
270
500
425
440
750
595
610
1000
20
190
205
500
285
300
500
475
490
750
665
680
1000
22
315
330
500
525
540
750
735
750
1000
24
230
245
500
345
360
750
575
590
1000
805
820
1000
26
375
390
750
625
640
1000
875
890
1200
28
270
285
500
405
420
750
675
690
1000
945
960
1200
30
435
450
750
725
740
1000
1015
1030
1200
32
310
325
500
465
480
750
775
790
1000
1085
1100
1500
34
495
510
750
825
840
1200
1155
1170
1500
36
350
365
750
525
540
750
875
890
1200
1225
1240
1500
38
555
570
750
925
940
1200
1295
1310
1500
40
390
405
750
585
600
1000
975
990
1200
1365
1380
1750
42
615
630
1000
1025
1040
1500
1435
1450
1750
44
430
445
750
645
660
1000
1075
1090
1500
1505
1520
1750
46
675
690
1000
1125
1140
1500
1575
1590
2000
48
470
485
750
705
720
1000
1175
1190
1500
1645
1660
2000
50
735
750
1000
1225
1240
1500
1715
1730
2000
52
510
525
750
765
780
1000
1275
1290
1500
1785
1800
2000
54
795
810
1000
1325
1340
1750
1855
1870
56
550
565
750
825
840
1200
1375
1390
1750
1925
1940
58
855
870
1200
1425
1440
1750
1995
2010
60
590
605
1000
885
900
1200
1475
1490
1750
2065
2080
62
915
930
1200
1525
1540
1750
2135
2150
64
630
645
1000
945
960
1200
1575
1590
2000
2205
2220
66
975
990
1200
1625
1640
2000
2275
2290
68
670
685
1000
1005
1020
1200
1675
1690
2000
2345
2360
70
1035
1050
1500
1725
1740
2000
2415
2430
72
710
725
1000
1065
1080
1500
1775
1790
2000
2485
2500