Introduction: Build a Better Harvey Oil Filter
The Harvey oil filter is mostly used on vacuum pumps servicing freeze driers. Its an economical way of reusing dirty oil that has been filtered.
Vac pumps used on freeze driers and AC units should have their oil changed after every use as recommended by the manufacturer.
My mods that make my version better are using vacuum to suck the oil through the filter faster as well as using a drilled plastic irrigation fitting to allow for more complete scavenging of the dirty oil in the top tub. The original version outlets on the threaded side of the filter(top) have been blocked off and a new outlet drilled on the bottom, means no more oil running down the sides of the filter can.
Credit for the idea of drilling an outlet on the bottom goes to YouTube user Joe Puffenbarger II.
Step 1: Parts Needed.
- Glass jar is used because a plastic one will crush and deform under mild vacuum possibly allowing the apparatus to fall over, dirty oil everywhere.
- Plastic tub is used for pouring in the dirty oil, PP5 can handle the higher temps of hot oil.
- Silicone washer cut from a baking sheet, goes between the top tub and glass jar lid.
- Plastic 1/2 inch BSP irrigation plug is used to connect the jar and tub as well as thread into the oil filter, so your oil filter needs a matching thread.
- GUD Z120 oil filter which has a 1/2" BSP thread, however the plug thread is a taper while the filter thread is a parallel, which means the plug wont screw in all the way to the bottom.
- The Check valve on the glass jar is optional, you can always hook up the vac hose to a plastic barb fitting siliconed to the jar.
Tools I used were a diamond core drill bit, 3mm HSS bit for the plug inlet holes, small shifting spanner, chassis punch for clean holes in the lids and a drill press.
I also used a 1/2" BSP tap to convert the 13/16 threaded GUD Z280 to 1/2" BSP.
Im using a food saver type vac sealer which produces mid range vacuum, about 60%, I've also used a laboratory style diaphragm pump which runs to about 85% vacuum.
The burst pressure of the oil filter is 265psi and according to conversion calc, 101kpa is 14psi so whether or not a vacuum can damage the filter element or not is unknown to me at this stage. That said, I wouldn't advise using a 3 CFM pump that runs down to 50 microns, usually used in the AC service industry.
Step 2: The Oil Filter.
First the back story, the Harvey application uses an oil filter in a reverse path and upside down mount compared to the intended automotive use.
In the first pic, the left illustration shows the original auto oil flows, dirty oil into the filter from the oil pump enters through the ring of holes around the rim and filtered oil exits the center hole. Theres a bypass valve internally that bypasses the filter element should it become clogged, reasoning being that dirty oil is better than no oil in a running engine.
Looking at the inlet holes, one can see a rubber flap underneath that stops oil from draining out the can due to gravity when the engine is off.
The center segment shows the mod done to the outer ring of holes, they are blocked of with bitumen flashing. In the event of dirty oil leaking through the washer, its possible that the vac will suck it through the can, bypassing the filter element, definitely not what we want.
Right hand segment shows the new modified path of oil flow, outlet via a newly drilled 5mm dia hole in the bottom. Theres about 15mm space between the bypass valve and can housing, be carefull not to drill though the bypass valve, it will render the oil filter useless.
If the clamping on the washer between jar and tub isn't enough one can add a collar to improve things, I didnt find a need to.
I downloaded an oil filter app from the GUD website which allows one to search by thread size amongst others. I discovered the only 1/2" BSP filter is the Z120, fitted to late 70's early 80's cars and fairly expensive. The outer can diameter was larger than available glass jars and I would have had to source an o ring between the glass and can sides to make a vacuum tight seal.
The smaller Z280 fitted to newer cars was also half the price of the Z120, but it was a 13/16" thread, problem solved with a 1/2" BSP tap.
Step 3: How Its Used.
Pour dirty oil in the top and wait patiently for gravity to do its thing, or attach a vacuum pump, in this case the Freshpak Pro from Red Fish and be done in 5 or less.
Second pic is my quick fix to the jar seal leaking air, PVC tape around the lid.
Its important to run the oil through a few times to get rid of any metal shavings left in the filter can due to drilling the outlet hole, before using the unit for the oil of a machine with more critical tolerances like a vacuum pump.
Standard practice is to freeze the water content of dirty oil before pouring it into the modded Harvey, just like with the original version, water will shorten the oil filter life considerably.
Step 4: Results
I drained the oil from a 10 year old compressor and ran that through the Harvey filter.
Im well pleased with how well it cleaned the oil, there was no sediment that settled out in the jar bottom and it sucked the 500ml of oil through in under 3 minutes.