Five ways trapped key interlocks protect tanker loading and unloading

Loading and unloading tankers carries significant risk. Procedures are often complicated, particularly when earth lines and valve systems are involved. Drivers have to consider variables such as load characteristics, the frequency of vehicle movement and the number of products to be loaded or unloaded.

Potential issues include:

• “Drive-aways” while tankers are connected to equipment or damage to extended gantries;
• The wrong substance being loaded or unloaded;
• Shortcuts being taken and steps in safe loading missed, such as earth line connections being made or hoses returned;
• The danger of loading or unloading hazardous or flammable substances;
• Product spillage;
• The environmental impact of product release.

Loading and unloading tankers carries significant risk

Trapped key interlocks (TKIs) provide specific protection and risk control in these types of application. TKIs encode procedures to ensure that systems can only operate one way: the safe way. Depending on the application, TKIs typically control five main risks:

1) They immobilise vehicles while loading and unloading is taking place by using an airline interlock or interlocking existing barriers. This prevents a “drive-away” while equipment is connected.

2) For multi-step processes, they force drivers to always follow the correct procedure and avoid shortcuts.

3) They ensure that valves can only be operated when it is safe to do so.

4) They make sure the correct substance can only be delivered or received by the appropriate tanker.

5) As primarily mechanical devices, they do not pose an ignition-source risk in hazardous areas.

Designing an effective TKI-controlled tanker loading system requires a clear understanding of the procedure involved and the equipment to be included in each stage of the process. This should be carried out in conjunction with a thorough risk assessment of the process itself.

By: David Hughes, Sales Director, Castell Safety International Ltd.

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