Homefill Tank Fill System

Homefill Based Tank Filling System

Homefill-Based Oxygen Tank Filling System Overview

This documents a do-it-yourself oxygen tank filling system based on the Invacare Homefill (HF) medical oxygen compressor. If you decide to do this too, you are responsible for your own safety and making sure that you know what you are doing. The HF off the shelf is set up for filling small medical tanks using an invacare platinum concentrator.

The platinum oxycon has two O2 outlets, a standard one on the face of the machine and another at the bottom. The bottom outlet is a special medical connector that serves as a bypass outlet. The O2 inlet of the HF is a special medical connector and that connects with the bottom outlet connector on the platinum oxycon. When the HF compressor pump is not running but the concentrator is still on, O2 is released through the main outlet on the face to prevent the concentrator from backing up and sounding the alarm. Once the compressor starts, O2 flows to the HF from the bottom outlet.

The HF has an onboard computer that monitors the incoming O2 purity, and will not fill a tank unless the purity is at least 90%. Also, when the HF is turned on, there is a 3-minute lag before the compressor starts. Because of this, the O2 bleedoff mechnism of the platinum is important so that the concentrator doesn't malfunction. The company recommends not topping off a tank if the pressure is greater than 1500 psi.

In order to Mod the HF to accept O2 from any concentrator, I changed the inlet to a standard 1/4" barb. I also added a check valve between the HF inlet and the concentrator (5 psi cracking pressure) to bleed off O2 before the HF compressor starts up. The check valve will also release O2 when the tank is filled and the HF stops but the concentator remains on.

The only other Mod needed was to replace the O2 outlet connector (for medical tanks) with a standard high pressure hose. To do this, I had cannibalized the medical connector fitting that connects with the last stage of the compressor, and had a special fitting brazed up that had a male hose connection. Once the new adapter and hose was connected, I got the tank fittings, performed a seal test, and proceeded to fill a K tank from completely empty.

During the first fill I noticed that some O2 was still bleeding off the check valve, so I screwed a plug into the check valve to seal it, and the fill progess improved. The HF and platinum is a very quiet system, much quieter than my devilbiss machines.

All in all, the moded HF works nicely, although it is slow. The first fill took 38 hours to fill the tank to 1650 psi, which is approximately 187 cubic feet. I have since got another K tank but have not yet hooked them both up. As I make improvements to the system, I'll post additonal information and fill rates.

I think the moded HF system is the same as one of those EX2000 systems I've seen for sale, and if they really are getting K tank fills in 24 hours, they must have made some other mod to increase the fill rate. I also tried the system with a 10 lpm machine, and the fill rate did not improve, which tells me the filling rate is limited by the HF compressor rather than the capacity of the concentrator.

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Upgrades to 2 Homefill Compressors

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Just a little bit more info on filling a 2-K tank system with a single HF.

using one Homefill, it too 47.4 hours to fill 250 CF in 2 K tanks.

I modified the system to add another HF to the system, so now it is configured to have 2 HF pumps and 2 K tanks. I also upped the pressure on each oxycon to increase the compressors' fill rates, and ran a quick fill test starting at about 1260 psi and finishing at approximately 1340 psi in 1.29 hours. This translates into a fill rate of about 14 CFH, which is pretty good. I think the higher pressure on the oxycons helped a lot. I will be running another fill test with the 2-HF system once I work the tanks down to about 400 psi, and will fill to 1500 psi (this is equal to a K tank fill of 250 cf), and logging the fill time. If all goes well, I hope to get a full K tank fill at around the 20-hour mark.

6-16-2010 - HF System Status: Consistently getting full K-Tank fills in 19 hours.

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Parts List and Schematic of the System

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Here is the general parts list and simple schematic (the picture in the link corresponds to the list numbers):

1. Cross or Tee, 3000 psi on output side of the HF

2. Check Valve, 5 psi cracking (parker c400b)

3. Needle valve (Norgren)

4. CGA 540 connector with 1/4" NPT nipple

5. Western Enterprises B-50 (adapter to input side of std. regulator)

6. High pressure Teflon Hose (SS Braided), 3000 psi

7. Miscellaneous adapters/fittings/couplings at #s: 1,2,3,4,5,6

8. Homefill: Welded a hose fitting to the output connector.

9. Homefill: Changed the O2 input connector to a 1/4" barb. [4]

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System Costs

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The general cost breakdown follows. When I started, I went to an industrial hose place and they normally do hydraulic hoses and connections, which use a JIC connection. Since I went down that route the first time, it committed me to the JIC connections for the the second HF. Needless to say, adapters to convert NPT to JIC can be expensive. If I would do it again, I would avoid JIC connectors and go with NPT (assuming they make high presure hoses with 1/4 inch NPT connectors). You should research your connectors first and try to standardize them to keep costs down. Anyway, here is the breakdown with the capital cost of the system amortized over the life of the HF (assuming the HF compressors last 90% of the rated lifespan of 5000 hours) and operational costs summed.

HF1 $ 450 OxyCon1 $ 225 1/4 to 1/4 barb inlet fitting $ 20 Welded HF Output Port - JIC#4 $ 35 Needle Valve $ 10

HF2 $ 600 OxyCon2 $ 240 1/4 to 1/4 barb inlet fitting $ 20 Welded HF Output Port - JIC#4 $ 35 Needle Valve $ 10

Cross npt $ 22 npt-jic adapters $ 40 CGA540 w/nipple $ 10 Tees $ 36 jic-NPT adapter $ 10 B50 $ 20 Parker Check Valves $ 70 Hose 1, 3000 psi $ 65 Hose 2, 3000 psi $ 55 Hose 3, 3000 psi $ 45 Misc $ 40 Used K tanks $ 140

TOTAL $2,198

fill time (hours): 21 life span (hours): 4500 Number of Fills: 214 System Cost/fill: $ 10.26 KWH/fill: 26.88 KWH$: $ 0.10 Electricity Cost/Fill: $ 2.69 Total $ per Tank Fill: $ 12.95

So the savings over purchasing tanks are OK but not great when the system cost is included. But it sure saves time and gas over many trips to the air guy, plus it saves my back too...