This article is the first in a series about the hard part of making concrete – “The Precast & Cast Stone Mold Shop Help”.
Today we will talk about one way we save a little time and money in the mold shop by making our own 55 gallon drum vent dryers out of parts sourced from Home Depot.
A vent dryer is something that dries out the air that gets into a 55 gallon drum. We need dry air in the drums because the moist air can interact with the contents of the drum and make it go bad. In our case, it is polyurethane rubber, which is notorious for reacting with any moisture.
The most convenient retail solution we found on the internet cost $75 for 2 vent dryers (including shipping). We would add 4 more cartridges to get 1 year’s coverage, at $64 for 4, so the total would be $139. What’s worse, it will take 5-7 days to get to us at low shipping cost (faster for way more money).
The solution we came up with for 2 drum vent dryers will cost $29.70 for hardware, and $17 for desiccant which is at least 1 years supply. The total is $46 for 2 vents & at least 1 year supply of desiccant (savings of $93 and 4 days).
Our DIY drum vent solution.
The premise of the dryer is to filter any incoming air through our cannister of desiccant. This will remove any moisture from the air that is entering the drum. The air really only enters the drum when the resin that is pouring out of the faucet on the drum causes a vacuum at the top of the drum.
The desiccant we are using is “Silica Gel”. Actually, we are using kitty litter that is made from silica gel. If you buy kitty litter, make sure the label says silica gel.
How to use our drum vent dryer (desiccant dried).
Just before we open the faucet to let our drum contents out, we remove the pipe cap on the vent dryer to allow air to flow freely through the canister of silica gel and into the drum. This happens because a vacuum is formed in the empty space of the drum when our resin exits thus sucking in air to fill the vacuum. When we are finished pouring from the drum, we just replace the cap on the vent dryer. After 3 months, or when we get a new drum, we will replace the silica gel.
Here is a list of the items needed to make this drum vent dryer for use with silica gel desiccant.
- 6 to 8 inches of 2″ pipe ($2.30 for 1 foot)
- 2″ pipe cap – ($1.78)
- 2 inch pipe coupler – ($1.14)
- 2 inch to 3/4 inch bushing – ($2.55)
- 2.5 inch metal niple (3/4 inch NPT) – ($2.12)
- 3/4 inch NPT elbow, one side male, one side female ($3.82)
- PVC glue, teflon tape and a small piece of screen (on hand)
- Silica gel crystals – I used 1lb of silica gel per vent cannister. In our case, “Dr Elsey long haired kitty litter” – ($16.99 8lb)
Instructions on making the drum vent dryer.
Step 1. Putting screen in the bushing.
We need to stop the silica gel crystals from falling into the drum. To do that we used a hot glue gun to glue a 1.5 inch square piece of screen door screen into the 2″ bushing to cover the 3/4″ hole. You could also cut up drywall sanding screen.
Step 2. Glueing stuff.
Now we glue the bushing to the coupler and the coupler to the 2″ pipe.
Step 3. Screwing stuff.
Apply teflon tape to all the threads. Now just screw the 2.5 inch nipple pipe into the bushing and the other end into the elbow. You may want to put the elbow into the drum first and then screw the rest of the assembly into the elbow once the drum is in place. Make sure to plug drum vent hole while moving the drum.
Step 4. Fill with Silica Gel Crystals.
If you forgot step 1, then all the crystals will fall out. Otherwise you are almost done.
Step 5. Cap it off.
The pipe cap is not glued, it is just pushed on to the 2 inch pipe. We only remove the cap when we are going to pour product from the drum. This ensures maximum life of the silica gel.