dk nkf - Nordisk Konservatorforbund Danmark

sold to the Falkland Islanders and remained as a
floating storehouse. This was extremely fortunate
because she would almost certainly have been sold
for scrap if she had been too expensive to repair in
the Northern hemisphere.
In 1937 the harbour master became concerned
about her condition. He ordered that she should be
removed from the harbour and scuttled in a nearby
cove (see Figure 11). There she stayed until, in
1970, she was salvaged and returned to the Great
Western Dockyard in Bristol, the dockyard that
Brunel had built for her construction. Owned by
a trust, operating as an independent museum, she
was partially restored between 1970 and the mid
1990s. At this point the trustees decided that she
should in future be treated as a museum object, and
that the traditional shipyard approaches used in her
restoration should be replaced with conservation
methods.
Fort Brockhurst Bridge, by contrast, was built by
the army from a kit of parts in 1862. Several similar
examples, dating from the period, are located
nearby. The bridge provides access over a moat to
Fort Brockhurst, one of a number of forts built in
the 1860s to protect Portsmouth and its strategically
important harbour. The fort remains physically
largely unaltered, although it currently serves as a
store for objects from English Heritage’s extensive
reserve collections. These include stonework,
textiles, jewellery, and furniture from many periods.
It was crucial that the fort retain safe vehicular
access.
Condition and Treatment ~
Fort Brockhurst Bridge
The bridge had lasted for almost 150 years before
receiving conservation treatment. As can be seen in
Figure 2, the bridge was re-inforced on at least two
occasions before receiving full conservation and
restoration to its original function in 2004.
The bridge was constructed from a combination of
wrought and cast iron. Generally, cast iron was used
for elements such as the support columns, hand-rail
stanchions, bridge-deck plates and the landing beam
of the drawbridge. Riveted wrought-iron beams were
Figure 3. Corrosion of the wrought iron
used where tensile strength was required. The owners
of the bridge, English Heritage, had specified the
design life of the treatment should be as long as was
reasonably practicable. For this reason, it was decided
to dismantle everything except the cast iron columns
and treat the bridge in the conservation workshops.
The main conservation issues to be addressed were
corrosion of the wrought iron and some fracturing
of the cast-iron elements.
The main structural elements of the bridge were
composite riveted wrought iron I-beams. These
were constructed from plates and angles.
The horizontal plates, particularly the upper ones,
were heavily corroded. It was decided to de-rivet
the beam and to cut down plate No. 2 to become a
new plate No. 1. A new plate No. 2 was made from
mild steel because wrought iron is in very short
supply in the UK and it can be next to impossible
to obtain high-quality replacement material in the
large sizes.
The engineers had determined that if more than 60%
of the thickness of a material remained then it could
be left un-repaired. Minor areas that were below this
threshold (small holes for example) were repaired
by welding in small patches or the application of
weld metal to build up the required thickness.
Cast-iron elements were visually inspected and dye
penetration tests were conducted if fractures were
suspected. Fractured cast-iron elements were metal-
stitched together.
All iron elements were cleaned to SA3 and zinc
metal-sprayed.
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