Insight – Issue thirty

Mounted permanently at roof level, a BMU is the safest and most comprehensive type of suspended access system, providing full lateral, horizontal and vertical movement of the working platform. BMUs are automatic, remote controlled or mechanical devices which carry window washing operatives or mechanical robots to maintain or clean the covered surfaces. Units range from small, simple devices used by a single operative to larger outreach units used on high-rise buildings.

Integral Cradles, PTSG’s London-based cradles installation specialist, which provides permanent façade access equipment for a wide range of significant buildings, has provided bespoke access solutions for some of the capital’s most iconic – and architecturally challenging – buildings.

One such building, The Scalpel, is a 190-metre tall tower, named for its unique, angular shape. PTSG’s expert engineers were called upon to design and install two complex BMUs at the site, as well as a series of intricate moving roofs to house them, enabling the safe and easy storage of this access equipment.

The two BMUs are eight storeys tall – approximately the height of ten cars stacked one on top of the other. They are installed on either side of The Scalpel, on the east and west elevations. The larger unit on the west side has an impressive 19-metre operating radius, is 49 metres in height, weighs 41,300 kg and has a 1,000-kg glass replacement capacity.

The project’s requirement for such a unique design allowed the PTSG team to provide a BMU that worked harder for the building, serving it in more ways that just maintenance. The east BMU was designed with a roof panel comprising photovoltaic solar cells, which move and slide in tandem with the unit’s operation. The cells provide renewable energy for the building, a valuable extra benefit of the system.

Building Information Modelling (BIM) was used by PTSG designers and engineers throughout the project at The Scalpel. This enabled any problems to be detected and resolved quickly and easily with the use of 3-dimensional imagery. The digital modelling and information for the BMUs produced via BIM were used as part of the training process to show the client how to operate the units.