Video of the system in action

Here's some video of the monster in action. I'm turning the loop valve on and off and you can see what happens to the pressure as I do that. Also added a switch on the pump housing, which is nicer than plugging in a cord.

Second Pass Filter Set-Up

So, with an exploded water filter (the housing says they're good to 125 psi) I think the system was working a bit too well. I needed a way to regulate the pressure being generated by the pump, and there were two ways to do it. First, I could reduce the RPMs on the pump by reducing the pulley size on the motor or changing out the motor. And second, I could re-route the plumbing to create some sort of pressure relief system.

I tackled the second problem first. With the filler hole in the reservoir acting as the intake on the pump, I was free to create a loop with the high and low pressure lines. With a tee in the loop going to the filter (with a newly added pressure gauge so I could monitor it) and a ball valve on the loop, I could throttle how much pressure was generated at the filter. This system worked well, but even with the ball valve wide open, the filter was still seeing close to 20 psi.

With the pressure relief set-up in place it was time to tackle the issue of the motor. The motor I'd been working with was a 2hp 3600 rpm pump that pulled something like 10 amps at start-up. After considerable thought and much sorting though of old motors on the shelves of Industrial Liquidators, I settled on a 1/4 hp 1800 rpm motor(coincidentally rated for hazardous environment). This new motor, along with a much smaller pulley, seems to have been a good choice for the system. Now, when the valve on the loop is wide open, the pump is generating about 2 psi, and when fully closed, about 60 psi.

Too Much Pressure

After a lengthy debate with friends regarding pumps and which would be most appropriate for pushing waste vegetable oil through tiny filters, I finally decided on a course of action. Browsing the internet late at night I stumbled across a picture of a set-up where a power steering pump was being used to filter oil through a centrifuge filter.

As far as I know centrifuge filters are barrels with a funnel on the bottom. Waste oil is pushed against the wall at high pressure and particles in the stream fall towards the bottom while clean oil is collected higher up on the wall of the apparatus. That's my current best guess on this type of filter. I'll do some more research about them when I've got my current filter set-up sorted out.

At any rate, the thought of using a power steering pump as a cheap (12$) substitute for some of the hydraulic pumps I'd seen for sale piqued my interest and with Matt's encouragement we were off to Pulpo Pull a Part to fetch one. We ended up settling on the pump out of a Chevy S-10, but a Volvo across the isle yielded an almost identical model. After getting the pump home and collecting an electric motor along the way, I was ready to begin construction. Set up was easy and I was able to use scrap plywood to mount both the pump and motor. Measuring the pulley on the pump and motor gave me a ratio of roughly 10:6 yielding a pump rotation of 1800 rpm (motor was rated at 3600 rpm or some such). The immediate problem was that the pump cavitated badly, greatly reducing flow, and making quite a bit of noise. Filling the pump reservoir did little to solve the problem, as it would drain immediately after being turned on. Matt suggested I use the pump reservoir as the intake, and after a few hacks and tweaks, I was able to make good on his suggestion. The newly configured set-up allowed the pump to operate without cavitation and I was ecstatic, until the bottom of the water filter I was using exploded from the pressure.

First filter design

Here's a photo of my original garage filtration and pump set up for processing waste vegetable oil for fuel. The top barrel contains the dirty wvo that I've collected from the restaurant and passed through a cone filter. There's a stand pipe in the bottom of the tank that allows for settling and a second stop-cock that will allow me to drain off the dirty oil on the bottom. I was expecting a lot out of this set up when I finished it. I thought that gravity would do most of my work for me and that the pump would practically be an afterthought, but I was wrong.


There were a couple of problems with this set up. First, gravity is no where near as effective as I'd thought it would be, at least near the bottom of the barrel. Second, the pump I used, an old aquarium pump I had lying around, was totally ineffective. I knew going into it that the pump wasn't the best fit for the application, but I wanted to see what would happen. At any rate, the magnetic drive impeller did little to move oil through the filter set up and my first batch of vegi was processed by the slow work of gravity. I think it took about a week to filter 10 gallons of oil.


So at this point, the system simply didn't work and I needed a new solution. My first attempt at a fix was a sump pump, also just lying around the garage, that rested at the bottom of the dirty barrel and pumped oil out. Initial results seemed good, but the flow quickly slowed to a trickle as the pump picked up all the settled particulates at the bottom of the barrel and pushed them into the filter. One nice side effect of using this pump was that it heated the waste oil quite nicely as it flailed along pushing out a few drops.