OH&S question: “Are there limits on what we’re allowed to lift?”

Which, is often followed by “I thought there was a 15kg limit”.

Long story, short (in Victoria Australia), there isn’t any.

But ….

However, the Regulations require the employer to identify any task which involves hazardous manual handling, and then take actions to either eliminate or reduce the hazard and/or the associated risks. The Regulations include any task requiring the ‘application of high force’ as hazardous manual handling.
OHS Reps @ Work: Weight limits – what are the legal limits for lifting?

The following references might also be useful:

A guide to Handling large, bulk or awkward items
Code of Proactive for Manual Handling, Part 3
Manual Order Picking  (talks about "safe" lift zones)
Moving and Lifting Objects
Children’s Services – OH&S Kit

Western Australia:
OHS in Commercial Laundries and Drycleaners