Monday 18 July 2011

HBA damage

The HBA tile antennas are quite robust when fully deployed. The polystyrene frame locks into place and is held securely by the polyurethane covers. However, during transportation and installation, the tiles are open, folded or otherwise supported in ways that are not part of the end design. As a result, they are fragile in this state and are susceptible to damage. Additionally, the actual process of handling them can lead to errors. Although rare, these incidents do happen, and then we need to implement field repairs to set things right.

Normally, damage is limited to the the odd polystyrene structure, which snaps under an abnormal load direction. These are easily replaced. However last week we encountered a different problem. Here one of the huge metal tines on the forklift caught and ruptured the black underside cover of one of the tiles.

Gash in the base bag of Tile HBAT-01009-00035.

Unlike the polystyrene, which is in multiple parts, this meant replacing the entire bag. We considered trying to patch it, but were not convinced that the seal would be sufficient and the tear was too low down to be effectively covered by the top cover. This meant replacement.

However this too would be problematic, as the base cover actually holds many of the components together. Without it, they would be even more delicate and, given the high wind conditions, this is not a good state to be in.

In the end we decided to add a second base cover to the tile. Fortunately we had one to hand. This was the surviving base cover from the destroyed test tile.

A cover and a partly assembled tile.

We had to clear this base cover up first, but it was soon ready to be attached.

Hauling the second base bag under the damaged tile.

With the cover in place, we could then lift the tile onto the array. However, the additional weight of this cover made that operation a little trickier than usual. Still, we have the tile in place, as robust as the rest of them.

Photos: D. McKay-Bukowski

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