oxygen concentrators

[Ahmdo Molah]

I have given up on my attempts to fix the DeVilbiss 525. Maybe some day I will try to replace the sieves.
All the years of using a semi-working concentrator ...].

Since you already have a working alternative, hence nothing to lose by giving your "DeVi" one more chance, consider the following*;

* Excerpt from DeVilbiss 525 Service Manual (p.15, COMPRESSOR Note #1 )
https://www.manualslib.com/manual/12...page=15#manual

" NOTE – A built-in thermal cutoff switch will shut the compressor off if it becomes overheated. This protects the compressor from damage caused by heat build-up. (Some models have an auxiliary thermostat mounted within the compressor compartment.)"

1. The "semi-working" of the compressor maybe due to the 'thermal cutoff switch' mentioned above, and the noise dampening foam maybe causing overheating of the compressor. I'd try removing as much of the internal foam as possible.
* My DeVi (515 series) is OLD so it does not have such fancy thermal sensor controlled throttle for the compressor, and when I first opened the housing the internal foam & adhesive were falling/crumbling/cooking on the compressor (which gets as hot as around 70 deg.C / 158 deg.F, clogging the exhaust fan underneath/compounding the thermal stress, and looked like a fudge/brownie batch exploded in an oven!

[ DeVilbiss 515 Foam Meltdown ]

DeVilbiss 515 Foam Meltdown.jpg

This explains why my DeVi took a little 'crap' of foam out of its lower exhausts(causing a brief nervous breakdown of the seller) when I was testing it on the day of purchase. I was more interested in the O2 analyser reading of 94% by 20 minutes of operation at 2~3lpm.

[ DeVilbiss 515 Foam Removed ]

DeVilbiss 515 Foam Removed .jpg
*The marshmallow-shaped compressor exhaust filter is temporarily removed in this photo.

2. Removing the noise dampening foam (ALL in my case, with the help of alcohol & some sticker remover spray for tough spots) would increase the internal 'air volume' (possibly cool air intake as well) around the compressor and may reduce the throttling of the compressor by the thermal sensor, allowing more consistent O2 supply.

The 'older' DeVilbiss units are built tough, but lack a heat exchanger & dedicated fan which most others (like your Nidek Nuvo 8) have. Even the newer DeVilbiss units only have a small aluminum heatsink block (10lpm unit) or an extended silicone hose connection from the compressor to the sieves/valves (5lpm units), which really are not enough considering how HOT the compressed air gets between the compressor and sieves.

My DIY (1m aluminum HVAC pipe) heat exchanger's intake brass coupling hovers around 65 deg.C/ 149 deg.F and its exhaust coupling hovers around 55 deg.C/ 131 deg.F, without a dedicated fan (only the beefy main fan under the compressor). The added moisture separator made of aluminum, and added brass nipples likely drop the temperature a bit further as well.

The noise level is not too bad, even with ALL the foam removed, with the front & back housing(covers) both on.

[Ahmdo Molah]

My previous post's mention of 'removal of ALL the internal foam' from a DeVilbiss 515 O2 concentrator necessitates an additional note specifically related to the exhaust vents of the concentrator's base.

DeVilbiss 515 Base

DeVilbiss 515 Base.jpg
*Note: the grey colored parts are my epoxy(JB-Weld) reinforcements for cracks in the caster pole sockets.

The main exhaust fan is mounted centrally (above the black rubber lined area), and exhaust air is blown down and split toward the left & right vents.

The top of the M-shaped exhaust airway is partially covered by the upper internal structure and partially by the base's foam cover, but when the base's foam cover is removed, the top of the exhaust vent airways get partially exposed.

DeVilbiss 515 Base [Partially Exposed Airways]

DeVilbiss 515 Base [Partially Exposed Airways].jpg


The exposed areas should be covered so that the hot exhaust can fully be directed out the vents. I considered using various foam materials treated with flame-retardants but considering their tendency to out-gas nasty chemical fumes, I opted for felt(natural wool)* as it has flame-retardant properties, to make a cover.
* Thick felt sheets can be expensive, but felt(sheep's wool) ironing mats are inexpensive and easy to get online.

The original base foam is attached to an identically outlined black rubber sheet, which served as a reference for my felt base cover.

DeVilbiss 515 Base [Felt (Wool) Cover]

DeVilbiss 515 Base [Felt (Wool) Cover].jpg


DeVilbiss 515 Base [Felt (Wool) Cover & Original Foam Cover's Rubber Sheet]

DeVilbiss 515 Base [Felt (Wool) Cover & Original Foam Cover's Rubber Sheet].jpg


Cheers.

[Doug Fattic]

I have given up on my attempts to fix the DeVilbiss 525. Maybe some day I will try to replace the sieves.
All the years of using a semi-working concentrator made so frustrated that I bought a brand new Nuvo 8, which as the name suggests produces 8 lpm of oxygen.
Oh, the wonders! It has made fillet brazing enjoyable again. On the other hand, I have learned that I don't really need 8 liters of oxygen.
The flame is so much hotter with the new unit (probably due to better oxygen purity) that for most work 3lpm is enough and my torch definitely can't handle more than 5lpm.

Hmm, last week I sent Yuriy money raised by my cycling friends to replace the tools stolen by the Russians after they broke down the door of our workshop in Bucha. They took general tools like our vises and drills and metric wrenches but not the bike specific equipment (as far as I know from Yuriy's report). Fortunately Yuiry put the Anvil fixtures in the steel shed next door that the Russians couldn't mange to break into. In the other storage shed they did manage to break in but just left my road bike. It was still there with the door wide open several weeks later when college people returned.

What i'm wondering out load is if getting an oxygen concentrator would be a smart purchase and within our replacement tools budget. That huge Oxygen tank we use took 2 people to move when it needs to be refilled. I also wonder if the oxygen supplier is still in existence? I'm not sure where Yuiry went to get it refilled. Of course for all the reasons I promote I would like to switch over anyway so the oxygen supply is more in our control. That modest workshop is where I started using propane instead of acetylene. I've been going through old pictures making frames in Ukraine for presentations I have to give this week end at a cycling event.

[Arttu]

I don't have a heated (or insulated) shop at the moment and need to do a bit of brazing. DeVilbiss states that the lowest operating temperature is 5°C /41°F, will I risk damaging the concentrator if I run it close to, or below freezing? Or am I better off heating the workshop to above the recommended temperature limit with a space heater?

[Doug Fattic]

Arttu, I don't have enough knowledge to answer your question of how cold is okay to run a DeVilbiss concentrator (besides what they recommend). When I was in Ukraine during the winter, I found it uncomfortable to work in the workshop unless it was at least 10º and preferably 15º C. I would turn on 2 space heaters to take the chill out. So I would think that for your own comfort, you would want to have your workshop heated to above the working temperature required of your concentrator.

One alternative would be to put the concentrator in a smaller space (like a closet) and use the space heater to heat up that smaller area instead of the entire workshop. One caution for doing that is that an oxygen concentrator needs a certain amount of space around it to function properly. It shouldn't be placed too close to the corner of 2 walls for example. Of course I don't have any idea of what the limits of surrounding space is required to function properly. Where are you located?

[Mark Kelly]

DeVilbiss states that the lowest operating temperature is 5°C /41°F, will I risk damaging the concentrator if I run it close to, or below freezing?

As I understand it, the problem is that the compressor causes moisture in the incoming air to condense* and the condensate can freeze in the lines and damage the unit.

Pre-drying the air is the usual solution if the unit can't be kept warm.