Wednesday, September 18, 2019

Chapman Fermenter - Closed Transfer Modification

The plastic fermenters in my brew room are nearly ten years old and ready for replacement. They still produce a good quality beer but they're not likely to support closed transfer keg filling. Using Co2 to push beer into a keg under pressure without having to rely on gravity solves two problems. Not having to deadlift fermenters out of a fermentation chamber will eliminate back strain. And pushing beer into a keg using Co2 will keep the beer fresher by preventing oxygen absorption.

Low Pressure Co2 Closed Transfer To Keg 
The ported Chapman seven gallon UniVessel Tank with ball valve best fit my budget and needs for a stainless steel fermenter. They are well made and sturdy enough for use in low-pressure transfers. However, a few modifications will need to be made to their lids. The center hole needs to be blocked to seal the tank. Holes for a gas ballock and thermowell weldless bulkhead fittings need to be drilled.

Co2 Ballock and Thermowell Weldless Bulkhead Fittings
Tool List:

  • A spray can of no-stick cooking oil 
  • 3/16 inch drill bit 
  • 1/4 to 7/8 inch step bit
  • 3/8 inch electric drill
  • Ruler, center punch and hammer
  • Channel-lock pliers or adjustable wrenches

Mark Center Of Hole Location And Dimple With Center Punch and Hammer
Cooking oil is a food-safe lubricant and perfect for drilling holes in stainless steel. It is easy to wipe off with a paper towel and remove with OxiClean.

Before drilling the 3/16 inch pilot hole spray cooking oil on the lid at the location of the hole. Apply downward pressure on the drill while quickly turning the motor on and off. This will prevent the drill bit from overheating and dulling it.

Slowly Drill Pilot Hole In Lid
Next, coat the step bit with cooking oil. And slowly use it to enlarge the pilot hole to a 1/2 inch diameter. Wipe off any excess oil and drill shavings from the lid.

Increase Hole Size From 3/16 To 1/2 Inch Diameter
Then turn the lid over and carefully remove any sharp edges using the step bit. Using a slow drill speed and minimal downward pressure of the drill motor. Care should be taken to remove any sharp burrs without making the hole larger than 1/2 inch in diameter.

Fermenter Lid With Gas Post And Thermowell Installed
With the holes deburred and all cooking oil removed the weldless bulkhead fittings can be installed. By hand start the threaded fittings into the holes in the top of the lid. Use a wrench if needed to thread the fittings all the way into each hole. Screw the lock nuts with washers on from the lid bottom. Snug the lock nuts up to the fittings hand tight. Then use a pair of wrenches to firmly tighten the lock nuts and fittings. Avoid over-tightening the fittings at this point. Squeezing the washers too tight may cause the fittings to leak or damage the washers.

#10 Rubber Stopper With 5/16 Inch Bolt, Nut And Washers
Stainless Steel Hardware List:

  • 2 - 5/16 x 2 inch hex bolts
  • 2 - 5/16 inch fender washers
  • 2 - 5/15 inch flat washers
  • 2 - 5/16 inch hex head nuts

To seal the 1 3/4 inch hole in the center of the lid with a #10 rubber stopper. Drill a 1/4 inch hole down through the center of the stopper. Then thread a 5/16 x 2 inch bolt with a fender, flat and lock washer into the narrow end of the stopper. Push the stopper into the center hole from the top of the lid. Add a fender, flat, lock washer and nut to the bolt end and firmly tighten them together. This will compress and expand the stopper in the hole creating an airtight seal.

Modified 7 Gallon Fermenters In A G&E 7 Cubic Foot Chest Freezer
When fermenting a Kolsch style beer using 1/4 inch inside diameter blowoff tubes connected to the gas posts. The 5.25 gallons of wort inside the 7-gallon fermenters left plenty of headroom for fermentation without fear of clogging the blowoff tubes. When fermenting a heavily hopped beer using a larger diameter blowoff tube is a good idea. Just unscrew the gas posts and clamp 1/2 inch inside diameter silicone tubing to the threaded end of the bulkhead fittings. The larger diameter tubing will further reduce the chance of clogging. But as far as this batch of beer goes primary fermentation is nearly done and everything is working out perfectly.

The maximum pressure rating of the Chapman fermenters is 3 psi. Use care not to exceed 2-3 psi when leak testing or using the fermenter under pressure. Failure to do so can cause the fermenter lid to become disfigured. Other than that as per Steve Chapman "The fermenters hold up just fine for pressure transfers, and many other uses."

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