Working safely on guyed towers

Issued: 5/11/2024
Last Updated: 13/11/2024

Purpose

The purpose of this safety alert is to highlight the risk of fatal injury when guyed lattice towers fail due to inadequate guy wire support. These towers are commonly used as radio towers or for the support of metrological equipment. The safety alert will detail the importance of risk assessment of the construction process and the need to design suitable risk control measures based on the hierarchy of control. For the purposes of this alert the term ‘guy’ will be used to describe a guy wire, also known as a ‘stay’ or ‘stay wire’.

Background

A worker suffered fatal injuries when the guyed mast tower section they had climbed fell due to a failure of one of three guys. The mast was at the first guyed level (i.e. only three separate wires at third points were supporting the tower). It appears one of the guys had not been appropriately terminated at the anchor. A thimble protecting the stay wire had slipped out of the loop at the top of the tower section and required adjustment. The mast was climbed by the worker and while adjustments were being made, one guy wire that was not adequately terminated released and the tower fell. It appears the worker added additional tension to the guy that failed.

Contributing factors

The reasons why the one guy wire was not adequately terminated are unclear. However, contributing factors for an incident of this type include the following:

• The correction of human error during a critical construction step is less than adequate.
• Work systems involving the cross checking of critical work being inadequate.
• Redundancy on the tower at the point when the first level of guys was installed did not exist (i.e. if any one of the guys failed with the worker on the tower there was no alternative for the tower to fall with fatal injuries occurring).

Action required – risk assessment

The mast was in the initial construction phase and the incident highlights the need for builders of guyed lattice masts to conduct a risk assessment of the complete life cycle¹ of the project, and have regard for and include, both process failures and component failures during the construction process—no matter how simple they may be considered.

Some of the issues in a construction stage risk assessment should include:

• Review the construction methodology and identify, evaluate, and propose methods to control specific hazards
• Identify construction/existing operation conflicts and management strategy
• Implement measures to ensure design intent and hazard controls are all complied with
• Ensure a process is in place for change management.

In this matter the decision to climb was significant. It was appropriate in this instance that a local risk assessment be conducted.

When risk assessing the ‘hierarchy of control’ principles should be front of mind

Human factors

The matter highlights how human factors can have a direct influence on safety. This is one occasion where the intention to carry out a particular sequence of actions or a process does not result in the desired outcome. The intention fails because the actions did not go as planned (a slip or lapse) or because the plan itself was inadequate (a mistake).

Slips typically occur when carrying out familiar tasks that do not require much conscious thought and usually result from a lack of attention. Stressful circumstances such as having too much to do, having to work too quickly or simply feeling unfairly judged by colleagues or line managers can result in a cognitive overload.

Lapses are similar to slips in that the intention is correct, but the error occurs because of a failure of memory. Lapses result in a failure to carry out actions at the appropriate time or lose a place when carrying out a procedure or task. Like slips, lapses can be exacerbated by stressful circumstances.

Slips and lapses are not usually the result of ineffective training but can lead to fatal errors. They can be minimised by designing procedures that are resistant to such errors. This is particularly important for safety critical procedures such as those used in erecting a guyed tower.

Some of the principles involved in reducing slips and lapses apply equally to procedures utilised when erecting structures. Some of the risk control measures that can be implemented to reduce the likelihood of serious incidents occurring include the following:

• The use of checklists to ensure correct actions have been carried out or are carried out in the correct sequence.
• Causing individuals to make some sort of positive acknowledgment at vital points in a procedure before proceeding further, for example signing off procedures.
• Procedures should be clearly and unambiguously named. Colour coding paperwork can help differentiate specific procedural systems that are regarded as being particularly prone to error or when the risk of such error would result in a serious consequence.

Redundancy

Redundancy in the form of a system or safety process should also be considered when relying on components where the probability of failure is unknown or untested. The use of redundancy would be at its peak or most critical at the initial stand of the mast section where the supporting guys are at the lowest number.

One example of an engineering solution that provides a level of redundancy is the use of a second set of temporary guys on the initial tower section to be erected (refer Figure 1). This decreases the chances of an adverse event should there be a failure. Once more guys are introduced this risk dissipates. Any additional engineering risk control measures need to be designed by a suitably qualified professional engineer with relevant experience.

Figure 1: Tower erected to first level of guy wires with redundant guys attached