In this toolbox we devote attention to the topic crane earthing.
If a crane, concrete pump or a piling rig, if it falls over, can touch the live parts of an overhead line, crane earthing must be installed. The crane earthing protects workers if a crane were to fall over and land on the overhead lines. In contrast to the home where a fuse blows, this is different for overhead lines. The overhead lines may continue to be live (1800 V or 25 kV).
Whether crane earthing is required must be established by an expert (person responsible for the installation and the work, on the basis of the RailAlert Safe Working on High Voltage Installations Regulations (VVW-HS)). Only this person is authorised to issue an exemption to this.
There are risks associated with working on or near high voltage electrical installations involving a return line and earthing. This can result in serious injury as a result of the passage of current through a person’s body or because of electric arcing. This why only an Adequately Qualified Person Return Line and Earthing (AQP-RLE), following instruction by the work supervisor (WS), can install the crane earthing.
This must be established well in advance of the start of the work. This way the necessary measures can be taken on a timely basis to work safely.
- When a crane is equipped with an earthing cable and is required to move, guide the cable so that it does not come loose or is broken by the driving crane.
- If the cable is loose from the rail, report this to your supervisor.
Check out the scheme below to determine when crane earthing and extra measures, if applicable, are required.
Lightning
The condition that applies to lightning is that when the thunder and lightning flash are less than 10 seconds apart, you must seek shelter, for example in the site office. This is because the chance of a lightning strike is too high. Moreover, near overhead lines, the chance of a strike increases!
An earthing electrode must be installed. The earthing electrode (a pin in the ground or a sheet pile wall) serves to protect the signalling systems and other installations. The earthing electrode protects the installations against a lightning strike hitting the implement. The earthing electrode must be installed with a transfer resistance of < 10 Ohm.
Machines
- A machine connected to a structure that is also earthed (sheet pile wall, earthing pin) does not have to be disconnected when there is an approaching thunderstorm.
- Never install a return link (crane earthing) without an earthing electrode. The costs of an earthing electrode (approx €500) are disproportionate to the risk of collateral damage to substations. And consequently the risk of irregularities affecting train services. These costs quickly add up to €150 - €200K.
If the thunderstorm is already close by, simply leave things as they are. In other words, personal safety comes first. When it is disconnected, the machine must be outside the falling range, however.
Example:
The implement is within the fall range of the high voltage installation (overhead lines). A connection must be made with the return line (negative rail). In addition, the implement must always be protected against lightning.
The protection for touching the overhead lines and against a lightning strike are combined. Always check the following:
- Is there a connection between the track and the surge arrester (Soulé CLS)?
- Is there a connection between the surge arrester and the earthing electrode (earthing pin adjacent to the Soulé or the sheet pile wall)?
- Is there a cable present from the earthing pin or sheet pile wall to the implement?
If the answer is: NO, immediately contact the foreman.
The cable may not be longer than 65 metres. The cable must be short-circuit proof and reliable. The connection established this way guarantees a short circuit when the implement falls over and touches the overhead lines and is protected against lightning.
IN CASE OF EMERGENCY:
If something should fall on the tracks or get stuck on a level crossing, warn the train operator by waving a red flag or in some other way. Wild arm movements or waving your vest also helps.
You must do this at least 1,000 meters from the incident by standing along the tracks and making these gestures. Send a colleague in the other direction to do the same. Always stay outside danger zone A and think about your own safety!
Always pay attention to your own safety and follow the steps on the alarm card!
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