I've got one of those big red 20-gallon parts washers. You know the one. I mostly clean bicyle parts, and most bicycle lubricants are not petroleum-based. They're usually plant or wax-based. The idea is that a water-based degreaser, like Simple Green, should have no problem cleaning the stuff. My experience is that Simple Green is much better at rusting my parts washer than it is at actually washing parts. It never really got my bike parts clean, and now I'm left with a very rusty old parts washer.
I plan on refurbishing this machine, which is a fair amount of effort, but that puts me right back at square one; An imperfect system, susceptible to rust, with a solvent that doesn't really clean anything.
I'm considering moving to a petroleum-based solvent of some kind, like diesel. Or getting five gallons of that Saf-T-Clean stuff, assuming it's still available.
My main concerns are:
Fire hazard.
The fumes shouldn't give me cancer or kill too many brain cells.
It actually cleans parts.
What solvent are you using in your parts washer?
Edit: I just checked the pump spec, and it's only rated for water-based cleaners. So that limits my options.
I use Zep purple degreaser. It's worked fantastic for all my machines. Anything you get you should avoid the fumes anyways.
You will want to pay attention to material safety data sheets. Zep in particular does not require protective equipment except for gloves( which I recommend anyways!). Also has a low rating on flammability (1)
I have no idea what a part washer is, but maybe consider using an ultrasonic cleaner.
You can then either load it with surfactants (e.g. SLS) in a water phase or with apolar solvents like cineol, terpentine or limonene, which have similar solving capabilities as diesel, but are bio based and not as flammable.
Using surfactants alone without ultrasound won't work, but using solvents alone won't keep the particles in phase, as they would just sink to the bottom.
If you tell me exactly how this washer looks like/ works and what exactly you wanna clean, I can help you more.
Great that you looked into the compatibility first. Many solvents can dissolve, or at least swell, parts of the machine.
The good thing is, solvent isn't solvent. There are different kinds (polarities, etc.), and maybe something like alcohol might work.
Problem is, grease is hard to dissolve with those.
In the industry, you have special "laundry washing machines" (sort of) that work with hot solvent, e.g. benzyl alcohol, since you need movement and heat preferably to clean everything decently.
Even with a good solvent, degreasing with your washer alone won't work as great.
I personally would go for an ultrasound bath. They tend to work more mechanically (phsically) instead of chemically, and with them, you can dissolve the dirt with soapy water pretty easily, without any volatile solvents or risks. You can get a decent one for 50 bucks starting price, or 100 if you want a bit better one.