Buderus Manual on Trenchless Installation of Ductile Cast ... - Duktus

Longitudinal force-fit joints and technical rules for trenchless installation
The results obtained in these tests showed there to be a threefold safety margin in
comparison with the figures given in Table 2.1. FEM calculations carried out by Prof.
Bernhard Falter [2.9] showed very good agreement with the experimentally determined
figures for permitted tractive force. The very safe nature of the figures which
were given for the permitted tractive forces on positive-locking joints in ductile cast
iron pipes in the DVGW rules had two consequences:
1. In its internal technical rules, BWB made a very large increase in the permitted tractive
force from the figures given in the DVGW rules. This was because practical experience
of a wide variety of kinds had convinced it of the high performance of the joints
(see Table 2.2).
2. A footnote was added to the tables in the DVGW rules saying that, with pipelines
following straight paths and with an angular deflection of less than 0. ° ( = a radius of
curvature of 87 metres), the permitted tractive force could be increased by 0 kN
(see Table 2.1)
Table 2.2: Permitted tractive force for positive-locking joints in cast iron pipes
(source: internal standard WN 322 of Berliner Wasserbetriebe)
Nominal size
DN
[mm]
Component
operating
pressure PFA
[bar] 1)
Permitted tractive
force F perm
[kN] 2)
Capacity for angular
deflection
of sockets [°]
Minimum permitted
elastic
bending radius
R min [m]
80 100 2) 3 11
100 2 0 1),2) 3 11
1 0 0 320 1),2) 3 11
200 0 00 1),2) 3 11
2 0 3 00 2) 3 11
300 30 00 2) 3 11
00 2 8 3 11
1) Determined by tractive tests (see report)
2) The tractive forces given apply only to Berliner Wasserbetriebe and to DN 80 - DN 250 BLS ®
joints with high-pressure locks.
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