Installing a Venturi
By Rick Da Tech
Are you tired of tweaking the valves on your Appleseed Biodiesel Processor to get the methoxide to flow in just right? Try a venturi. In this article we upgrade a typical appleseed to include all steel plumbing, well mostly steel, and a venturi for methoxide injection. We installed a bypass on the venturi so that it does not slow down the flow or offer any restrictions when we're mixing. Now when we add the methoxide we just open the valve to the venturi and close the bypass valve and it sucks in the methoxide at just the right rate. When all the methoxide is injected, we turn off the pump, and let the biodiesel drain to below the venturi, then close the valve to the venturi and open the bypass and turn the pump back on. Draining the biodiesel out of the venturi helps keep the tubing above the venturi new longer and also prevents the biodiesel from draining back into the methoxide container if the check valve sticks open.
The tubing above the venturi is 1" ID braid reinforced PVC tubing. I've use the high flow hose barbs from B100 Supply to go from the 3/4" plumbing to the 1" tubing to prevent any restrictions after the venturi that could affect venturi performance. While we don't want any restrictions after the venturi, we do need some back pressure. The back pressure is achieved by mounting the venturi on the vertical with a foot of tubing above it. This keep voids or air bubbles from forming inside the venturi mixing zone that could affect performance without adding any significant restrictions. Below the venturi we installed a cross that gives us a place to connect the bypass and a future expansion connection into our plumbing. It may end up being a second output connection, or it may end up being a place to install a thermocouple. For now we will be installing a sight gauge. We could have installed a pipe plug and saved a few dollars.
- one 3/4" ball valve
- one 3/4" union
- one 3/4" cross
- one mazei 584 3/4" venturi - available from Amazon.com
- one 3/4" elbow
- two 3/4"x1" high flow hose barbs
- three feet of 1" ID Braid Reinforced PVC tubing
- four to six 3/4" couplings
- an assortment of 3/4" pipe nipples
- Remove the return hose and hose barbs
- Remove the ball valve above the pump leaving the aux output valve alone
- hand fit the plumbing from the top down to the cross
- using 3/4" x 2ft nipples, build the return pipe up from the pump to below the cross, tightening with a wrench to snug, but not tight. You will tighten this more later.
- mount the union on the return pipe extending up from the pump. Tighten to snug with a pipe wrench. You will tighten more later.
- disassemble and reassemble to snug the plumping from the top of the water heater to the cross. As you tighten position the cross over the top of the union.
- Measure the distance from the union to the cross and add one inch to the measurement.
- Go to the hardware store and have them make a nipple for you to the size in the previous step
- Insert the nipple between the union and the cross and tighten.
- Using the pipe wrench on the union, tighten both halves of the union until you can slip them together.
- Continue tightening until the two halves of the union are aligned. There is a gap between the two halves that you can use to judge the alignment
- Make sure the gap is even all the way around the union, then attach the outer ring of the union to finish the connection.
- Test for leaks and retighten as needed to eliminate all leaks.