MEL Health and Safety Consultants

Safety Alert on Tower Crane Masts

Collapses Linked to Manufacturing Defects

The Health and Safety Executive (HSE) has published a safety alert on the subject of tower crane mast collapses, following concerns regarding manufacturing defects.

The safety alert says the HSE has become aware of two crane mast failures in which faulty mast section “spigots” (essentially stopping pegs) were implicated. The first of these incidents was in Chicago in February 2009. The most recent incident involved a crane in London in April 2010.

The manufacturing defect has been identified in spigots used on K600 and K800 mast sections used in certain types of tower cranes.

The safety alert is urging the construction industry to take action immediately to identify potentially affected mast sections and ensure they are taken out of service and then quarantined for further investigation. The HSE has emphasised that if a tower crane mast fails and collapses, there is potential for multiple fatalities.

Tower crane masts or towers are constructed from a number of individual sections which are located one on top of another to achieve the required height. For the type of cranes covered by the safety notice, spigots provide a means of connecting individual mast sections together. As a result, their condition is crucial to the integrity of the mast.

The HSE says that metallurgical tests undertaken on the London crane showed that the spigot failed catastrophically in brittle fracture from a small fatigue crack. It is believed that there was a flaw in the heat treatment process during the manufacture of the spigot.


While investigations continue to isolate the cause of the problem, as a precaution, all spigots manufactured between 1 November 2006 and 28 Feb 2007 are suspected of being substandard, and subject to the remedial action outlined in the HSE’s safety alert.

Info Bite 93
July 2010