DIY hot wash tank

[dfarning]

The most important step in metal finishing is not the final coat, rather it is the cleaning and preparation necessary to enable that final coat to adhere to the underlining metal. Working on old car parts, I have found the cleaning and degreasing stage is critical yet tedious. The most important tool is a good hot washer.

Hot washers, like ovens for you powder coaters, seem pretty pricey for small shops. So, I thought I would make my own. After several hours reading and asking questions on the Caswell forum and looking through the local tool and home improvement stores, I have come up with a design worth sharing.

Parts List:
20 gallon washer from tool store 69.99 (on Sale)
3500W-240V screw-in water heater element 8.00
Single element thermostat 13.50
Universal adapter kit 5.50
4 x 5/16-18 stainless steel nuts 1.00
1 tub silicone sealant 3.00
10 feet of 3w/10ga Wire 7.50

Special Tools needed:
1 5/8 inch hole saw

Design decisions
Water heater parts are commonly available in both 120 and 240 volts. I saw elements ranging in power from 3000 to 5800 watts. In order to keep keep the current flow down to around 15 amps for a 3500 watt element, I went with 240 rather then 120 volts. 120 volts would have been more convenient because the tanks pump is already wired for 120, but the current draw would have climbed to around 30 Amps.

There are three types of water heater thermostats; upper, lower, and single. Most residential water heater have two elements. One at the top of the tank and one at the bottom. Hot water is drawn from the top of the tank and cold water is feed back into at the bottom. In there systems each element has its own thermostat. My wash tank is only about 8 inches deep. I didn't think I would worry about heating the top and bottom individually, so I got a single.

The thermostats are very straight forward. They attach to the outside of the tank. They measure the temperature of the tank skin so you don't need to drill a special hole for a thermocouple. Through the sheet metal temperature is accurate enough for parts washing.

If you are handy with a welder, you can skip the adapter kit and weld a nut on to the back of the tank for the element to screw into. The adapter is just a threaded plate, a gasket, and four bolt. This allow you to attach the element to the tank without welding. The adapter plate also has to fingers which hold the thermostat against the tank.


Attached is a picture. In a follow on post I will include information on insulation and cost of operation.

I'll add some pictures of the wiring as soon as I figure out how to take small enough pictures

David

[dfarning]

hmm thought I could just edit a post to add a picture. Here is the wiring photo (without protective case for clarity.)

Make sure that you have almost zero resistance between the ground and the tank. Scratch off a little paint on the outside of the tank where the ground wire touches the tank. Then measure the resistance between the pump's ground(the 120 volt plug) and the heater's ground (the 240 volt plug). If the element or pump go bad, you want to ground through the ground wire not your feet.

David

[jrow]

Dave,

I like your idea. The only problem I can see is that electricity and water (parts cleaner) don't mix! Especially at 220 Volts!

My thoughts would be to use a heating element from a dishwasher. It would be 120 volts and would heat the liquid to above 140 degrees which should be enough to clean grease off parts. I'd also use some kind of plastic container (ABS or PVC) it would have less electrical conductive properties than metal!
And by all means use a GFI in your circuit.

John

[LakeRacer99]

Very nice, i was thinking about doing the same thing this weekend. I looked at an element just lie that for HW heaters. I was unsure of the differnt element power ranges. I am thinking 3500 watts is plenty for a job like this, possibly overkill. I need to research the elements some more.
You job looks very nice and I plan to take the same approach.
Thanks,

[dfarning]

As long as every thing is grounded correctly there shouldn't be any danger. Heater elements are designed to last many years in water heaters with out fail. Is there any difference between a water heater element and a dishwasher element. I would be interested in learning abut what dishwashers use for thermostats. No mater what you try make sure the tank is well grounded. Good point a GFI is now on my shopping list.

3500Watts is plenty of heating capacity for 20 gallons. It can warm up my tank from 60F to 110F in less than 30 minutes. It could also hold the tank at 165F without insulation. The tank ran very quietly with farm and fleet cleaner but makes a weird bubbling noise when filled with 25% oil eater. I wonder if a different type of element would be better?

Does anyone have any thoughts on filtration systems? This tank has become my prewash/presoak tank, so it gets grimmy pretty quickly. The tank already has a nice pump, so I thought I would hook up a 25 or 50 micro water filter with replaceable cartridges to clean out the gunk.

Dave

[dfarning]

Just got back from the store, I took John's advice at started looking for a GFI. I seems to be a bit had to find 30A 240 Volt GFI.

15A 120V were between $5 and $10 bucks. that would give you 1800 watts with no room to spare. At the upper end, there were several 50A 240V GIF/circuit breakers for around $90. I didn't see and 30A 240V GFIs. I guess I need to get on the phone and start calling around.

It should be easy to add a filter system all of the major brands of water filters sell a standard 'whole house' system for around $10 that uses a cartridge. I am testing a five micron filter currently. It cost about $1.50. There is no noticable decrease in pressure at the sprayer.

1 micron filters are around $2 while .5 micron filters were a bit more at $24.

I am think two filters in series a 5u and a 1u should clean up the tank pretty well.

I like the idea of being able to drop a filter off at the local transfer station every month or so rather than run all my dirty water through the city system.

David

[LakeRacer99]

I am gonna look for an element out of a coffee maker or electric skillet (or other 110v immersable element) to try for my 110v heating needs. I will be intersted in your filtration experimentation as well, I currently have the chinese washer from HF. and its stock filtration system.
What are you using for a cleaning solvent and how often do you guy change it? I bought some parts washer solvent from a farm store and looked up the MSDS onthe net and found it to be 90% Naptha, so I returned it and looked for something more bio friendly. I bought the heavy duty parts washer degreaser from HF and have an issue with it. I left it in my washer for a couple weeks and mold started to grow on the surfaces in there. I understand this stuff is bio-friendy, but should I expect to grow organisms in my washer...hehe? By the way, it does a decent job of cleaning up greasy boat motor parts.

[dfarning]

Here are the ongoing results of my filter test.

Cost
2 X Basic water filter housing 2 X $9.89
2 X Hose barb ½ to ¾ threaded 2 X $1.50
2 X hose clamps 2 X $.50
1 X ¾ x 4 nipple $0.90
1 X 5 Micron string wound filter $1.60
1 X .5 Micron carbon filter $12.80
4 ft ½ hose

I have tried two tests. One with just the 5 Micron filter and a second with both filters in series. The results can be seen below. With both filters, I can not tell the difference between clean solvent and filtered solvent.

With just the 5u filter there is enough pressure to go straight to the sprayer. With both filters there is a steady flow of output fluid, but not enough to run the sproyer. I will have to set up some sort of bypass valve so that when the sprayer valve is shut off the flow is redirected to the filters.

All of the fitting on HF's pumps are ½ hose. It should be pretty straight forward drill two holes above the tanks water line to mount the filters externally and conect with hose.

The filter housings are standard 10 inch units. If these filters can't handle the solvents, there should be others available online.

In the three jely jars below going from left to right are unfilter, filtered to 5u and filtered to .5u.

The second picture are the two filter bodies before mounting.

Dave

[pickleboy]

the problem is the .5 micron filter for this kind of application that is way to fine. i work in the aviation fuel biz at my day job and that industry only goes as low as a 1 micron. i would suggest a 5 as second behind a 25 primary to pull the big sediment out. this should give you good fluid movement and still keep it clean.

[dfarning]

I am a computer programmer by day so my knowledge of filters and detergents is pretty limited I was pretty hopeful when the I could not tell the difference between the .5u stuff and the new stuff. It has only been running about 2 hours now and there is already about a 2% drop in flow rate. I wonder if the filter will be clogged in just a few days? I'll see how long the filter lasts and then bump up to 1u and report the results.

Dave