I am stumped; hydraulic circuit create overflow situation

[mackconsult]

I collect and process WVO for use as a fuel in my sprinter van. During the filtration an effective way of cleaning the WVO is to heat it up and centrifuge it.

Previously this OC20 pressure driven centrifuge has worked for me. At that time my return was just hung over the collection bowl underneath the centrifuge. It would run like this no problem, but was a little messy because of some small splashing that would occur.

Then I sarted using electrical driven centrifuges and hard plumbed my return into the top of the water heater as shown in this diagram. Couple weeks back the electrically driven centrifuge died, so I tried to use the OC20 pressure driven centrifuge as my backup (never removed it). During steady state running the oil will back up in the funnel and overflow onto the ground. I lost 35 gallons the other night. I find this interesting and can't figure out why this is happening. Orignally flow 2 and flow 3 were both going into the collection bowl and it would work fine. Now its only Flow 2 that is going into the collection bowl and it backs up? Note that in the original scenario the port that Flow 3 now goes into was open to atmosphere, and might have been venting.

I have a new electrically driven centrifuge coming from WVO designs so I will be back and running soon. Just want an answer as to why .....

 

[LittleInch]

Mackconsult. I think you've answered your own question. Just add a vent to the "tank" and it will work ok. It won't take much heat to create a positive pressure in the tank and prevent flow in. The water heater won't take much pressure before rupturing so you've probably been a bit lucky it hasn't failed.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mackconsult]

Like I mentioned I am not going to do anything because I have a new electrical driven centrifuge showing up in a couple of days. I am just trying to figure out an explanation. The oil coming in the top of the water heater is pretty much at the same temperature as the oil that is drawn in from the bottom. I would think that the air at the top of the water heater would be a few degrees cooler than the oil ..... yes I can vent it but I am asking why does it need to be vented.

 

[LittleInch]

So that the oil can flow into the heater. There is so little head available to the oil to flow into the tank that almost any excess pressure above atmospheric will stop it flowing in. The return oil will be hotter as it has gone through the pump. Give it a go and let us know if it works.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mackconsult]

Okay I can buy that. Not only does the gear pump add mechanical energy, but I am sure the pressure and then centrifuge are also adding mechanical energy.

I will post a video with the new centrifuge soon just for others viewing pleasure. Having a electric motor driven centrifuge does wonders because it gets rid of the whole pressure thing. When I do the electric motor driven centrifuge there is a bypass from the T w/ pressure relief valve that provides a certain amount of flow to the centrifuge, the return for this setup goes to the plumbed return on the top of the water heater. The return for the centrifuge goes to the top heater port of the water heater so then the funnel at the top becomes the vent per say.

It works so good and stable that I am able to run it over night and have fresh ready to run oil in the morning. I am able to do 70 gallons a day if I have to.

 

[katmar]

I agree that the heat from the pump and centrifuge is probably the major cause of the problem, but a contributing cause could be air pulled in with the centrifuged oil flowing via the funnel. Especially at start-up the level in the funnel will be low, and if the flow of clean oil is high enough it will entrain air into the tank.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"