Written by Rickdatech

55 Gallon drums come in plastic and in steel. They come with and without removable lids. The drums that come without removable lids are called Closed Head Drums or Tight Head Drums. They have one 2″ opening and one 3/4″ opening in the top. Unmodified Closed Head Drums are not suitable for use as a biodiesel processor. They are not pressure vessels and will come apart at the seams if too much pressure is applied. The photos to the left show what is left of a closed head drum after being filled with compressed air to 75 psi. The drum launched into the air and landed 70 feet away after one bounce. The missing lid launched into the neighboring woods like a Frisbee and was never seen again. The same thing can happen to a drum with a removable lid if the lid is bolted to the drum.

55 Gallon drums come in plastic and in steel. They come with and without removable lids. The drums that come without removable lids are called Closed Head Drums or Tight Head Drums. They have one 2″ opening and one 3/4″ opening in the top. Unmodified Closed Head Drums are not suitable for use as a biodiesel processor. They are not pressure vessels and will come apart at the seams if too much pressure is applied. The photos to the left show what is left of a closed head drum after being filled with compressed air to 75 psi. The drum launched into the air and landed 70 feet away after one bounce. The missing lid launched into the neighboring woods like a Frisbee and was never seen again. The same thing can happen to a drum with a removable lid if the lid is bolted to the drum.

Dry firing is when the element burns out after being exposed to air while energized. It will get hot enough to melt the element. That’s more than hot enough to ignite any methanol vapors inside the drum. When those vapors ignite, the pressure inside the drum instantly rises to above 100psi, blowing the drum apart at the seams.

I’ve checked into a number of these bursting drums. They all have a common element. The lid is launched off the drum like a Frisbee. Several have cut right through wooden and steel roofs. They are not often found after launching. The one exception was the lid that went half way through a brick wall. Getting the picture? When drums explode they do so with potentially lethal results. Take a cutting torch to a drum that held flammable liquids and you will see the same thing. One welder lost both of his leg cutting open a drum that still had enough vapors in it to ignite. Many have died cutting open drums that contained explosive vapors. It’s the same explosion that occurs in a sealed drum when the heating element is uncovered.

Enough Doom and Gloom. The solution is really simple. Use a lightweight loosely fitted lid on an open head drum. If you uncover the element in a processor with a plywood lid, the expanding gasses will push the plywood up a few inches and let the burning gasses escape without catastrophic damages. There are plastic lids and wooden lids, it would even be OK to use a metal lid as long as it was loose fitting. Just cutting a hole in the top of the drum is not enough to prevent dangerous pressure build up. Remove the lid completely. Or if you want to flip your drum upside down to take advantage of bungs on the bottom, then cut out the bottom (now top) completely. Whatever you make your processor from, please consider what would happen if it suddenly became pressurized to 150 or 200 psi.