Finished pressing my Chilean grapes yesterday. Pressed 360 lbs. and did not do a second pressing of the pumice this time. With the SG at 1.000, I still had a heavy cap on the must and carefully scooped off the cap into buckets and broke it down into 4 pressings. By limiting the amount of each pressing I was able to get good extraction without having to break-up the pumice and press again. I poured-off the rest of the must into another clean fermenter and left the heavy sediment that was on the bottom. Got about 35 gallons that will be going into carboys by tomorrow and expect to loose another gallon or two in that transfer.
The press held up just fine with heavy hydraulic jack pressure. I noted that when the jacking gets hard, if you leave it for a few minutes, it will become easy again for another couple of strokes. It did take awhile to get that “last drop” out of the must. The pressed juice tasted great for this early in the process. However, I can recommend a change to anyone building a similar press, or any press for that matter. I would increase the height of the press (currently 54.5 inches) by another 4 or 5 inches to allow for additional height over the basket. With the current height, I can barely get a 5 gallon bucket horizontal when loading the press and the additional height will give you more working room.
Some have asked about adding a pressure gauge to a hydraulic jack operated press to be able to monitor pressing pressure. The following link will take you to a hydraulic jack modification process that adds a pressure gauge to a jack:http://www.albroswift.com/jack.htm
Here are the instructions without the pictures (go to above link to get full article with pictures):
Adding a pressure gauge to a hydraulic jack
Messy shop project. Idea copied off one of my pyro mentor’s website.
Picked a 12 ton press off craigslist, first thing I had to do was add a pressure gauge.
First thing, drain the fluid and tear it down. Wearing latex gloves and getting hydraulic fluid everywhere is a good reason not to touch the digital camera for this phase of the operation, but just picture the mess and then triple it!
After thoroughly cleaning the base, the setup begins:
Drill a 3/16 hole about 1-1/2” in, centering in the meat of the base, on the side opposite the rest of the ports.
then open the hole up to 5/16 for the first ¾”. Then run a 1/8” pipe thread tap in.
Clamp the base flat, connect the dots:
Now clean ‘er again, and reassemble, (where did those little parts go?) making note of the diameter of the piston base.
I used a hydraulic “Z” fitting, only rated up to 6000 PSI, probably re-plumb at a later date for full pressure. Anyway, passed the pressure test (the second time around)
Reason for measuring the piston diameter, to make a conversion for hydraulic pressure to lbs of force. Piston dia = 1.75 inches, giving me an area of a bit over 2.40 sq inches. At 6000 PSI gauge the force would equal about 14,400 lbs. to test my math, at 10,000 psi it figures to 24,053 lbs, probably not a coincidence it’s a 12 ton jack. Now it's time to figure out how to get hydraulic fluid out of my hair.
Pressure conversion chart (see web site) for conversion chart. You must measure your jack piston while you have it apart to come up with a pressure conversion factor.
I plan on adding a pressure gauge to my 6 ton jack to prevent over-pressing and for repeatable press results.