How Do You Calibrate Crane Scales?

Weighing scales deliver the best results when they are properly calibrated. Ensuring scales are correctly calibrated can be an involved job – and this is particularly true of crane scales. So how do you calibrate crane scales? In this blog post, we’ll find out.

What is a crane scale?

A crane scale is a weighing device that determines an item’s weight by suspending it. Crane scales are typically used to weigh large, heavy items, and will usually be hung from a crane to do so. This also means crane scales can be used to ensure a crane is not overloaded.

Crane scales are great for weighing items in locations where space is limited, because they do not require floor space, and can be out of the way when not in use.

Why does a weighing scale need to be calibrated?

Calibration is the process of ensuring a weighing scale is displaying an accurate weight for the item being weighed. Over time, particularly in demanding industrial settings, weighing scales can begin to fall ‘out of calibration’ – this means the weight readings may start to become slightly less reliable.

It’s generally recommended that weighing scales have a calibration check once every 12 months, but you may wish to make this more frequent if your scales are used very frequently with quite punishing tasks.

A regularly calibrated crane scale will mean more reliable weight readings for you and your business.

Does calibration need to be performed by a specialist?

We recommend that, ideally, your crane scales are fully serviced at least once year by a specialist, during which a calibration check is performed. A full service will mean other aspects of the scale can be checked over and repaired or adjusted if necessary, to prolong the life of the scale.

A specialist will also be able to issue you with a new calibration certificate – this is a dated document that will show that the scale was correct at the time of calibration, and is a document that may be required for compliance reasons.

However, it is possible to calibrate the sales yourself, and even if you do have a specialist checking and servicing your scales annually, you may still want to ensure your scales are accurate during the periods in-between.

In this blog post, we are going to use the SHS Crane Scale from Adam Equipment as our example.

What do I need to calibrate my scale?

To perform scale calibration, you simply need a set of calibration weights. You can find calibration weights on the Inscale website here, and we’d recommend purchasing a calibration weight set.

You’ll need enough weights to be able to test the crane scale up to its capacity – so, if you have the Adam SHS 300, you’ll need 300kg-worth of weights.

We recommend a 5-point calibration – that is, check the scale at five points through its range. For a 300kg scale that would be every 60kg – so, as well as at zero, you should check at 60kg, 120kg, 180kg, 240kg and 300kg.

Ensure the weight set you purchase provides enough weights to be able to check the scale like this – for example, for the SHS 300, you may want to ensure you have fifteen 20kg weights.

How do you calibrate crane scales?

• To begin, press the Zero key on the Adam SHS 300 and at the same time switch the scale on using the on/off button.
  
  
• Release the Zero key and the display will show ‘SPAN.’ Before proceeding ensure there is no weight on the hook of the scale - unless you intend to use any chains or slings to hold the calibration weights.
  Add any items such as these to the hook before continuing.
  
  
• Press the Zero key again and the display will show ‘SET’ and the ‘00000’ once the scale is stable. Congratulations! You have completed zero calibration.
  
  
• Next, enter the test weight value for the first weight test. In our case, this would be 60kg: use the Hold and Unit buttons to change the value of the display until it shows 60kg.
  
  
• Once 60kg is showing on the display, add the 60kg weight to the scale, and when the scale is stable press the Zero key. The display should then show ‘HOLD.’
  
  
• Repeat the process in 60kg increments until you have reached the scale’s capacity.

Make sure calibration is carried out safely

It’s also worth noting that high capacity crane scales may be harder to calibrate due to how heavy the test weights will be. For the lower capacity crane scales use test weights with hooks, like these M1 Class weights. Alternatively, chains and shackles can be used between the test weights and the crane scale.

However, for higher capacity scales, particularly those of 5 tonne capacity or higher, you may need to use a lifting platform so the weights can be safely placed on the platform for lifting with the crane scale. If a platform or chains are used during calibration, this will need to be added to the scale and the Tare button pressed before weights are added.

Of course, always adhere to Health & Safety guidelines - for example, ensuring chains and shackles are correctly and safely affixed, and that no one steps underneath a load whilst it is being lifted by the crane. When lifting test weights, ensure the safe limit is not exceeded.

If you are unsure, or need further help with how to calibrate crane scales, please speak to the Inscale team on 01908 972 660. Inscale offers a return-to-base calibration service should this be easier for you.

Further reading

Just how important is scale calibration – and what can affect accuracy? We take a look in this calibration blog post.