Tall masts withstand extreme conditions over the long term

21 September, 2023

Many of the masts maintained by Teracom have been in service for nearly 60 years. It is therefore essential to assess their condition and determine when they must be replaced. Swerim has been contracted by Teracom Samhällsnät to carry out unique testing of the dismantled TV and radio mast Tåsjömasten.  

"Since many of the masts are very tall, over 300 metres, they are subjected to extreme loads, particularly under hard wind conditions," explains Teracom's mast specialist. “It is therefore important to determine how much service life remains after 60 years of use.”

Preventative maintenance is standard

Teracom conducts preventative maintenance on an ongoing basis. Non-destructive testing has been carried out to find potential cracks in Tåsjömasten, but when it was decommissioned in 2020, new opportunities for testing arose. This has allowed the possibility of using the mast's components for more extensive testing. Since many other masts from the same period are still in operation, the study of Tåsjömasten provides the basis for a general assessment of the condition of the other masts.

The mast, built in 1961, was a 330-metre-tall framework structure. Initial FEM computations revealed that the most critical points are the external welded joints connecting the framework elements to the flanges, high up on the narrowest side of the mast. The metal research institute Swerim has therefore carried out fatigue testing of the framework elements taken from near the top of the mast.

Great condition, for a 60-year-old!

Fatigue testing at Swerim
Fatigue testing of framework elements at Swerim in Kista.

"It has been very exciting to investigate the status of the mast", comments Pontus Rydgren, who has led the study. "We tried to produce a fatigue crack by applying the maximum calculated load, but we gave up after three million cycles. For a sixty-year-old, it's in really great shape."

Teracom is pleased to note that the welds are in very good condition, which has a direct impact on regularly scheduled maintenance.

Teracom Samhällsnät delivers secure communications services over a robust and broad ranging infrastructure for vital functions in Sweden, in both the public and private sectors.

First photo: Tåsjömasten – 330 metres tall, prior to demolition in 2020.