When describing a graph or chart, you almost never need to use the passive. However, you probably will use the passive when describing a process diagram.
Imagine we have a diagram that shows the process of recycling used glass. One step in the process is labelled "grinding machine" (to grind means to crush or reduce into small particles).
Do you know the past participle of the verb grind? If you don't, you won't be able to make a passive sentence. But don't worry; there are various ways to describe this step.
Using a different verb:
1. Next, the glass passes through a grinding machine. (active form of 'pass')
2. Next, the glass is passed through a grinding machine. (passive form of 'pass')
3. Next, a grinding machine is used to crush the glass. (passive form of 'use')
If you know the verb 'grind' and its past participle 'ground':
1. Next, a machine grinds the glass. (active)
2. Next, the glass is ground in a machine. (passive)
I would probably use the last sentence above in my report, but the others are all acceptable. I'm working on a video lesson about process diagrams, with more advice about passive sentences. It should be ready tomorrow.