Factorio Forums

There is one thing in oil production that I can't figure out and I don't see it explained in any tutorials. Why produce light oil (cracked) and petroleum gas in chemical plants when it's already produced in the oil refinery? What am I missing?

Thanks, A

Cracking is for getting rid of light and heavy oil as byproducts. If you don't consume all light and heavy oil, the refinery will get clogged with output full on the light and heavy oil outputs and stop producing anything until there's free space again.

It's about balance. You'll end up using more of some products and less of others, and cracking is a way to keep from running out of one while being backed up in another.

Circuits can help you manage this. For example, I usually set up a row of chemical plants to crack heavy oil to light oil. I put a pump in front, and only pump on the condition that my total heavy oil (in storage tanks) is more than my total light oil. Similarly for light oil to petroleum: I only pump when there's more light oil than petroleum.

So that covers heavy oil and light oil.

But what if there's too much petroleum?

Well, in my experience, that never happens.

Tertius wrote: ↑

Thu May 23, 2024 10:07 am

Cracking is for getting rid of light and heavy oil as byproducts. If you don't consume all light and heavy oil, the refinery will get clogged with output full on the light and heavy oil outputs and stop producing anything until there's free space again.

Ah OK, that makes sense to me now. Thanks.

The challenge the game gives us with advanced oil processing is to use whatever we need from light oil and heavy oil and crack the surplus to the next higher tier (heavy > light, light > petroleum). Since petroleum gas consumption is highest in any factory, this production strategy ensures the refinery will not clog.

As Kyralessa wrote, this is the first facility where the circuit network is really useful. A tiny amount of it, no need for combinators. If you output all oil products into separate fluid tanks, you can measure how much you have of each.

As heavy oil consumer there is lubricant and heavy oil cracking. Connect the lubricant plant directly to the tank but put a pump in front of your heavy oil cracking plant(s) and wire it to the heavy oil fluid tank. As activation condition set heavy oil > 20000 in the pump. This way the pump works like a valve and you run heavy oil cracking only if the heavy oil tank gets too full.

The same with light oil, a light oil tank and a pump in front of the light oil cracking plant(s). This way you're getting rid of oil surplus and even increase the petroleum gas output with the junk.

Kyralessa wrote: ↑

Thu May 23, 2024 10:49 am

It's about balance. You'll end up using more of some products and less of others, and cracking is a way to keep from running out of one while being backed up in another.

Circuits can help you manage this. For example, I usually set up a row of chemical plants to crack heavy oil to light oil. I put a pump in front, and only pump on the condition that my total heavy oil (in storage tanks) is more than my total light oil. Similarly for light oil to petroleum: I only pump when there's more light oil than petroleum.

So that covers heavy oil and light oil.

But what if there's too much petroleum?

Well, in my experience, that never happens.

Have you got any recommendations for an optimal setup? My problem is not the cracking itself, it's how to spend the byproducts and on what. I am good at building production chains but not so good at figuring out what balances it all out so that it automatically can adjust to varying production levels.

Cheers ...

BrickVoidFCT

You can always convert needed excess to solid fuel and then prioritize its burning in furnaces, boilers, trains, etc.

BrickVoidFCT wrote: ↑

Sat Jun 01, 2024 12:44 am

Have you got any recommendations for an optimal setup?

What Kyralessa described, or some variation of it, is pretty much as good as it gets. The only thing you can add is producing solid fuel from petroleum gas if you have too much of the latter (as FuryoftheStars mentioned) - I have a setup that does this to provide a priority source of solid fuel for rocket fuel production.

This will balance itself except if you are disproportionately producing express transport belts (which only need lubricant), underground belts (ditto), and/or splitters (which don't need enough petroleum gas). I have never had this be a problem in practice, but it is unsolvable except for express splitters (by using coal liquefaction). Even the need to produce solid fuel from petroleum gas can be considered an edge case.