1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136 
'Incredible specs on some trucks'
Page 105
If you've noticed an error in this article please click here to report it so we can fix it.
• INCREDIBLY, certain truck manufactures delete the air drier for the UK market for reasons of cost, but do not compensate for this by fitting a larger wet tank, David L Rim mer, chairman of the Institute of Road Transport Engineers council, told the Road Transport Forum.
In a talk entitled "The role of maintenance roads and vehicles" given at the Institution of Mechanical Engineers, he said today's air-brake systems for tractive units can be broken into three parts: compressor, control valves and brake actuators.
Air driers are fitted to many chassis on production and many are retrofitted, he said. But for the UK certain manufacturers, while deleting the air drier, do not fit a larger wet tank. These chassis produce copious amounts of water, and valve contamination is inevitable.
"The design is available," he said, "but the commercial interests are obvious but unacceptable in the maintenance aspect of operation. The designs for air systems are well known and it is important that we accept the proposed changes which will improve reliability and maintenance.
"Among improvements are improved compressors — smaller and more efficient air driers — more compact air actuators. Electronics will play a major part in improving reliability and con
trol of the systems and will also aid diagnosis and of course limit maintenance."
In his introduction, Rimmer said legislation in the UK and Europe is disjointed and the industry in a dilemma as to the way forward. Take suspension — whether trailer suspensions are steel, air or hydraulic springs. We have as yet no performance criteria to meet which is meaningful in any aspect of performance with regard to road wear. Work is advanced, but there are no conclusions.
For load equalisation, air is superior to steel he said, but defective valves, contaminated air lines, incorrect valve settings and inadequate dampers failing early cause maintenance problems.
The normal current operating pressures are up to a nominal eight bar, he said, and problems of water ingress and contamination by oil mist in control valves are well known.
"From a design point of view and to limit maintenance could not a revised steel suspension — may be two or leaf parbolic spring type — together with more responsive equaliser parts and dampers give the same result in equalisation and continue to give a far superior road wear factor on a more consistent basis than air?" Minimal maintenance would not need the high costs on ongoing maintenance of air or hydraulic springs.