The objective of the tests was to determine the water distribution characteristics using different water pressures and sprinkler spacing of two selected Extended Coverage sprinklers. The sprinklers may be used for the protection of the Muskö tunnel and the test set‑up simulated a freight truck trailer positioned inside the tunnel.

Adequate sprinkler coverage would require that sprinklers are positioned close to the peak of the ceiling. A relatively short vertical distance from the sprinklers and the ceiling is also essential for proper thermal activation. These requirements are best met by the use of upright sprinklers. Two extended coverage upright sprinklers with a K‑factor of 363 (metric) and 202 was selected for the tests.

For the extended coverage upright K363 sprinkler (Tyco model EC‑25), a sprinkler spacing of 4.0 m is recommended, in order to account for the fact that full coverage of the freight truck trailer was not achieved at the tested 4.2 m spacing. A density of 10 mm/min requires an operating pressure of around 0.7 bar at this particular spacing.

The tested extended coverage upright K202 sprinkler (Tyco model EC‑14) provided a wider water discharge pattern, with a proper water distribution on the top of a freight truck trailer positioned offset in the tunnel at sprinkler spacing up to 5.0 m. For an actual installation, a K202 sprinkler designed for a density of 10 mm/min require an operating pressure of around 3.6 bar at this particular spacing.