Vitrex exported vitreous enamel steel panels to create a uniquely twisting cladding system for an airport tower in Oman.

To construct the unusual and innovative cladding system for the Air Traffic Control (ATC) Tower at Muscat International Airport in the Sultanate of Oman, Ekurhuleni-based Vitrex designed and supplied unique twisted vitreous enamel steel panels to cover an area of about 4 000m2.

The Vitraclad heavy-gauge panels were installed by the project’s main contractor, Carillion Alawi LLC, to form fins around the tower.

Cristian Cottino, sales and marketing director of Vitrex, says the company developed the cladding system for the challenging, complex design in close collaboration with Quality Architectural Systems LLC (QAS) in Dubai and QFS B.V. of the Netherlands.  

“The design is very unusual as the position of the leading edge of the fins – located on the four corners of the tower – changes progressively over the height of the structure, coming in towards the corner of the structure from ground level to Level 18, and then going out again thereafter, along the edge of the petal up to its tip on Level 23.

“However, at the same time, the trailing edge of the fins remains at the same position along a true vertical line, over all the levels. The face of the cladding across the fins therefore changes from true vertical at the trailing edge to sloped at the leading edge, thus creating the twist, with the angle of the face, as measured from the true vertical, changing from level to level.”

A calculated design
The Vitraclad vitreous enamel steel panels and cladding system had to be designed in detail to create the twist effect across the width, and over the height, of the fins.

A mathematical analysis of the architect’s design allowed for the degree of twist to be determined over the full height of the fins and, based on this analysis, Vitrex was able to approximate the architects’ design by gradually twisting individual, rectangular, flat panels at each position by a given amount. The maximum twist at any given point was 13mm.

The use of flat, rectangular panels also enabled Vitrex to substantially reduce the number of panel types required.

The panels were twisted when secured to purpose-made, adjustable brackets during installation on site.

“To connect the panels to the special brackets, each panel was factory-fitted with a pair of full-height aluminium frame profiles produced in the specified aluminium alloy and with a natural anodised aluminium finish, here in South Africa,” says Cottino.

“The frame profiles were chemically bonded to the rear of the cladding panels using a pre-tested sequence of bonding agents. The application of aluminium elements directly to panels with a vitreous enamel finish was a first for Vitrex,” he adds.

Managing the weight
To reduce the overall weight, the panels were constructed with an aluminium honeycomb core, resulting in a total mass saving of 10kg/m2. The aluminium honeycomb core was bonded to the rear face of the panels using a two-part polyurethane adhesive. A dedicated lamination line, which includes electronic dispensing equipment for the adhesive, was commissioned by Vitrex for this contract.

Matching the colour
In addition, the colour of the vitreous enamel coating had to be specifically matched for the project and a design requirement for a reduced gloss level had to be achieved.

The Oman Civil Aviation Authority specified the need for a reduced gloss level (RGL) due to concerns that a highly reflective finish over such a large surface area may create issues for pilots during the approach and landing.

“The colour RGL Tower Grey (VIT-411) was developed in-house by Vitrex and then tested in our laboratory to determine its functional characteristics and ensure that the coating was appropriate for the intended application,” states Cottino.

“To ensure an objective assessment of colour and consistency in production, strict quality control procedures form part of Vitrex’s ISO9001-certified Quality Management System. The colour of each individual panel produced was measured electronically, using a colour meter combined with compatible software, and compared to that of the approved colour master plate,” he explains.

Fit for the environment
Since the tower is located close to the coast, it is exposed to high corrosion levels. In addition, the cladding would also be subjected to wind-blown sand and high levels of ultraviolet (UV) radiation. While aluminium cladding panels are customary in the region, Vitraclad vitreous enamel steel panels provided an ideal solution for this application.

“The design and manufacture of the panels were undertaken in line with Vitrex’s own recommendations for the use of vitreous enamel steel cladding in highly corrosive environments,” Cottino adds.

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