DELIVERABLE 2.8 - urban track

2.3. BREMEN (BSAG)
D0208_STIB_M24.doc
TIP5-CT-2006-031312 Page 13 of 44
URBAN TRACK Issued: August 13, 2008
Quality checked and approved by project co-ordinator André Van Leuven
The practice at BSAG is similar to Brussels with the exception that they do not perform the pre-emptive
build-up welding. BSAG installs the rail as is and welds in the field when necessary. Until about 20
years ago, BSAG also did pre-emptive build-up welding before bending the rails. This gave problems
during the bending as the two different metals (bimetal) behaved differently and caused the weld to split
off from the rail. The welding is now performed by an outside contractor in which BSAG owns 51%. The
60% of paved track is Ri59 and previously Ri60, all of Q700. The 40% open track is 49E1 (earlier S49) of
Q900 and before S41 of Q700.
Another difference is the track design, which prevents wheel from touching the lip of the rail. The lip
cannot be used for guidance. That means that BSAG only has (lateral) wear on the railhead. The
introduction of the new low floor trams in 1996 has changed the wear pattern. Before there was only
wear on the outer rail in curves with a radius below 40 m. Now the wear is distributed with 1/3 on the
outer rail and 2/3 on the inner rail. On new rails, the inner rail needs treatment first. This is also due to
the selection of the rail: NP4am (and also Ri60) has a groove of 34 mm, whereas Ri59 has a groove of
42 mm. The extra 8 mm make that there is less contact with the flange. BSAG designs its tracks to avoid
flange wear on the back of the wheel. BSAG used to remove up to 9 mm lateral and 7 mm vertical. This
caused problems when welding again. When the rail wears in the vertical direction, the weld may split
off.
BSAG was also experimenting with Q900 rail to avoid welding. Now Q700 grooved rail is used; they still
see normal wear on the railhead with lateral wear of 6 mm after 12 to 18 months before re-welding. The
next re-welding then takes place when the wear is 7 mm, i.e. when it is more than the layer added in the
previous re-welding process. In the next step a wear of then e.g. 8 mm is allowed, then 9 mm etc where
BSAG allows a maximum gauge widening of 20 mm.
BSAG also introduced wheel flange lubrication. The second welding now takes place after 2 to 3 years
with a material of the same quality as Q900. It is normal practice to do the build-up welding 8 times,
using the same material as Brussels. Rail life this way can be extended to about 15 to even 20 years.
The main advantage of not welding pre-emptively is the cost of machining the rail.
Since 1996 all vehicles are equipped with wheel lubrication which has generated a reduction in welding
costs of 15% with the added benefit that squeal is eliminated.