Installing 55 gallon drum as boiler vessel

If you can afford and acquire a properly certified steam vessel, by all means install one. However, don't underestimate the economical versatility of the 55 gallon food grade barrel. In all the years I've been using them, I've not seen a single one fail catastrophically. They will start to warp at around 8 psi, and shortly after that the curled seams at top and bottom will begin to unfold, releasing the pressure slowly. If this happens, the drum is ruined, so be ready to replace it. The obvious solution though is to have proper over-pressure controls in place to ensure this doesn't happen.

In this installation, two lengths of 1/4" walled(.250), 2" steel square tubing was placed just above the auxiliary air intakes to hold the drum. Once the concrete blocks were cut to fit so the square tubing would hold the drum perfectly level, the tubing was welded to the rebar system and mudded in with mortar, then allowed to cure 24 hours before continuing. Be sure to weld or otherwise attach the square tubing to the rebar to prevent it shifting after numerous heat up and cool down cycles.

Weld, silver solder or braze a 1" black iron nipple to the barrel about 1" to 1.5" above the bottom. Place the barrel on the square tubing and measure for location of a 3" chase through the boiler for this pipe to exit as shown. When you lay a few more layers of block, repeat the process for the top steam pipe, also 1" black iron, which will thread into the 2" NPT threaded opening on the top of the drum, using a 1" X 2" threaded bushing.

As you lay your blocks be sure to keep extending the rebar vertically, and every two rows place horizontal rebar around the whole boiler as shown. Weld or otherwise tie all the rebar together and fill all the voids with concrete. When you reach the top two rows of block, you'll need to install your chimney outlet.

Don't run it straight out the top of the boiler or you'll have no way to clean the chimney pipe. Instead, purchase a double wall insulated stainless steel Tee with a cleanout opening and install on the rear of the boiler with the cleanout facing down as shown. This way you can run a chimney cleaning brush up through the pipe from the bottom.

Cut a 1/4" or 3/8" steel plate to fit the top. 3/8" plate is better suited for this purpose, but if you expect to be able to lift it on and off by yourself, stick with 1/4" plate.

Bolt concrete anchors to holes you'll cut in the plate, matching the voids in the concrete blocks below.

Fill the voids in your top two rows of block with concrete and while still wet, place the lid on top so the anchors sink down into the wet concrete and then place several bags of cement or other heavy weight on top to keep the lid firmly in place while the concrete cures for 24 hours. Later, you'll remove the nuts from the concrete anchors and lift the top back off. To ensure a good seal which is extremely critical, place about 1" of fresh mortar mix on the top row of filled blocks, apply wax paper over the wet mortar mix, and then set the lid back in place and bolt it down. This will force the mortar mix to form a perfect seal between your boiler and lid.

The wax paper will make it easy to get the lid back off again. Remove the wax paper, and polish the mating surface of mortar mix with a broken piece of concrete block. Fill in any cracks or voids with fresh mortar mix. When dry, cut and install a firebox gasket around the top. Now, once your boiler tank is installed and the lid fastened in place, you have a fully airtight installation.

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