Harry's Home Compressor Project Updated April 2008 All photos were intentionally reduced in quality for internet publishing 
The end result of my home compressor project. This is my Alkin W31 compressor, "Nitrox Stik" and storage bank. 
The control board. INTRODUCTION Getting compressed breathing air in my area was difficult. I had to drive four hours round-trip to get my tanks filled with air. Obtaining Nitrox was even more difficult; I had to drive two hours to drop off my tanks at a dive shop. They filled the tanks by the partial-pressure blending method, which meant I also had to have oxygen-clean tanks. A few days later my tanks would be ready and I’d have to drive another four hours round-trip to retrieve the tanks. The cost to fill my double tanks with Nitrox was fifty-four dollars! What could I do? COULD I JUST BUY MORE TANKS? I suppose one solution to this problem was to purchase multiple sets of twin tanks with manifolds, then clean everything to oxygen-clean standards. That way I could fill multiple tanks with each trip to the dive shop. However, I really didn’t savor the thought of driving a total of eight hours just to fill my tanks, no matter how many tanks I was filling at once. Besides, it would cost about $400 for each set of aluminum twins with a manifold, and about $600 for each set of steel twins. Buying 5 or 6 sets of twins would set me back $2,000 to $3,600, which is nearly the cost of a basic home compressor. THE BOOSTER OPTION Another option was to get air fills from local fire departments. They have air compressors for their SCBA (Self-Contained Breathing Apparatus) rescue units. But they all have commercial “drawer”-type compressors that will fill only single composite tanks or single aluminum 80 tanks. In order to fill my aluminum and steel doubles from single aluminum 80s, I would have to purchase a $5,000 booster. In essence, a booster merely transfers gas from one tank to another. If I wanted to transfer air from my donor tank (a single aluminum 80 tank at 3,000 pounds per square inch) to my receiver tank (twin steel tanks at 3,442 PSI), I would need to “boost” the air to affect the transfer. The other problem with the booster option was the cleanliness of the fire department’s air. I would not be able to mix my own Nitrox using the partial-pressure blending method because I had no control over the fire department’s filtering and air purification system. I wanted Nitrox, so the booster was not viable. THINKING ABOUT MY OWN HOME COMPRESSOR Obtaining my own home compressor started looking like a good idea. I spent a year researching what was involved in operating my own compressor in my garage. The more I read, the more I became confused. There are no “guides” to assembling your own compressor system, although there is a lot of information available on the Internet from other do-it-yourself compressor enthusiasts. Ready-to-use commercial compressor systems were available for $10,000 to $30,000, but clearly the costs greatly outweighed the benefits in a home situtation. The effort to put together a basic home compressor for air plain fills seemed relatively easy and straight forward. A small compressor with the minimum necessary fittings and whips cost about $3,000 and is capable of pumping about 3 to 4 cubic feet per minute. However, adding a bank of storage bottles, a Nitrox Stik, air purifiers, high-pressure hoses and various gas analyzer greatly complicated the simple home compressor project that I initially had in mind. The costs ballooned to $5,000 to $6,000. As I read more and more about back-pressure regulators, check valves, moisture indicators, high-pressure tubing, carbon monoxide detectors, purification towers, oxygen servicing, I asked myself, “Should I even bother? Is it worth it?” My fear was heightened when I started reading about the dangers of high-pressure oxygen. The thought of a conflagration in my garage fueled by 277 cubic feet of high-pressure oxygen gave me second thoughts. In fact, I had third thoughts, fourth thoughts and fifth thoughts, too. MIXING NITROX Nitrox can be mixed by a variety of methods. The most common methods in the home compressor setting are (1) partial-pressure blending and (2) continuous mixing. Partial-pressure blending involves measuring a precise amount of high-pressure oxygen into empty scuba tanks, then topping off with compressed air to produce a target Nitrox mix. All parts, valves, connections, hoses and tanks involved in the partial-pressure blending process must be specially cleaned to prevent oxygen fires. At high pressures, even miniscule specs of organic matter in an improperly-cleaned component can serve as the nidus to ignite a fire. Even stainless steel will catch fire and burn when oxygen is present at 2,500 pounds per square inch. Question: How do you put out a fire consisting of flaming stainless steel fueled by compressed oxygen? The answer: VERY QUICKLY. A safer and inexpensive alternative to partial-pressure blending is continuous mixing. This method is much safer because 100% oxygen is used at near-ambient pressure and compressed oxygen is used at lower concentrations such as 32%. The idea is to blend the air and oxygen to the target mix before the gas becomes compressed. It is much safer to pump a 40% oxygen mix to 3,443 PSI than to work with 100% oxygen compressed to 2,500 PSI. The idea of continuous mixing was much more attractive to me than partial-pressure blending. CONTINUOUS MIXING A continuous mixing system has a baffled mixing chamber known as a “Nitrox Stik.” Air and oxygen are mixed in the Nitrox Stik and then fed into the compressor inlet. Commercial Nitrox Sticks cost $2,000 to $3,000, but effective home built models cost as little as $100. Initially when the compressor is turned on, only air is sucked through the Nitrox Stik. Then 100% oxygen is slowly fed into the intake of the Nitrox Stik at low pressures like 2 to 5 PSI. The oxygen is thoroughly mixed with air in the baffles of the Nitrox Stik. An oxygen analyzer at the outlet of the Nitrox Stik displays the percentage of oxygen in the mix as it is discharged from the Nitrox Stik. The oxygen flow can be increased or decreased as needed to create the desired Nitrox mix. A typical Nitrox mix is 32% oxygen. This mix is then fed into the compressor inlet. 
A home-made "Nitrox Stik." Ambient air is sucked through the lawn mower filter on top. Oxygen will be fed into the nipple on the top right. The air and oxygen will mix and homogenize as they pass through the baffles in the body of the cylinder. An oxygen analyzer at the bottom monitors the richness of the mix in real time. The hose coming out of the bottom feeds directly into the compressor intake. BUILDING A NITROX SIK There are many plans for building your own Nitrox Stik such as those found in Vance Harlow's Oxygen Hacker's Companion. You can also review the designs of commercial Nitrox Stiks such as Ross Cowell's Nitrox Stik or the Koflo Static Mixer. A Nitrox Stik must be long enough and contain enough baffles to thoroughly mix incoming air and the oxygen feed. However, the Nitrox Stik cannot be too long or have too much resistance to air flow as this will damage the compressor by inducing too much of a work load. An ideal Nitrox Stik will thoroughly mix air and oxygen but have no resistance to air flow. THE OXYGEN ANALYZER It is easiest to start with the oxygen analyzer and build your Nitrox Stik around that. I began by chosing the Oxycheq Expedition-X oxygen analyzer with a remote sensor (MSRP $329). The oxygen analyzer can be mounted to the wall in its case. A short data cord connects the analyzer to the included R-17D oxygen sensor. The sensor has an estimated lifetime of one year (replacement R-17D sensors: MSRP $70). The Expedition-X comes with a blue sensor "Tee" that you can incorporate into the outlet of your Nitrox Stik to sample the outflow. I built my Nitrox Stik around this "Tee." 
The Oxycheq Expedition-X with the data cord attached. 
The Oxycheq Expedition-X oxygen analyzer mounted to the control board in its protective box. The biggest issue with the analyzer is how to capture gas outflow and get it to the sensor. The compressor will pull a slight vacuum so your sensor will not accurately register if it sits in the blind end of a "Tee." Your sensor must sit directly in the flow of gas or you must divert gas to the sensor. Some people use miniature battery-powered diaphragm pumps to push gas flow through the sensor. 
The Hargraves Advanced Fluidic Solutions CTS micro diaphragm pump. 
The Oxycheq R-17D sensor, showing the vanes and the blue "Tee" that I incorporated into my Nitrox Stick. There is a screen in the blue "Tee" to form resistance and backflow of gas into the sensor port. The vanes of the sensor protrude deep into the lumen of the "Tee" to direct gas into the sensor. The o-rings enable the sensor to sit snugly in the "Tee" and prevent gas leaks. THE NITROX STIK BODY Many people use 1-inch or 1½-inch PVC pipes for the body of the Nitrox Stik. Since air flow resistance is proportional to the length and diameter of the pipe, I chose to use larger 3-inch diameter PVC pipe for the body of the Nitrox Stik. The patented commercial Nitrox Stik proportions are calculated to maximize mixing and minimize resistance, but I just guessed. My 3-inch diameter Stik is about 2 feet long. I build my Nitrox Stik by going to Ace Hardware with my blue "Tee" and pieced PVC sections together. Using a series of reducers, bushings and PVC pipe, I connected the 3-inch body to the small blue "Tee." You can get the sections to snugly fit together without glue by running a piece of plastic tape around the sections. If you chose to use glue, as I did, you must ensure that the glue has thoroughly dried and off-gassed before using it. I placed my Nitrox Stik over my heater vents for several days to evaporate the volitile glue. 
The bottom of my Nitrox Stick, showing the reducers and bushings that connect the 3-inch diameter cylinder body to the blue "Tee." INLET FILTER I mounted a lawn mower engine filter to the top of my Nitrox Stik. It is cheap and easily replaced. 
The inlet filter. The oxygen input nipple is visible on the right. 
The filter is mounted to a PVC screen and just sits snugly on top of the Nitrox Stik body. 
The filter is screwed to the PVC screen with a bolt, washer, lock washer and wing nut for ease of replacement. OXYGEN FEED Oxygen is fed into top of the Nitrox Stik. Medical oxygen tubing is routed from your oxygen tank to the Nitrox Stik. 
The oxygen nipple at the top of my Nitrox Stik. I just drilled a hole of appropriate size and the nipple was self-tapping. BAFFLES There are an infinite number of ways of making baffles for the inside of the Nitrox Stik. Many people stack PVC end caps with holes drilled through them. The holes cause turbulence and a slight amount of back-pressure to thoroughly mix the air and oxygen. This is the route that I chose. The end caps must fit air-tight into the cylinder body or gas will divert around your baffles and not mix well. I ran some plastic tape around the end caps to enure they fit snugly in the cylinder body. 
Looking up into the body of my Nitrox Stik, showing the last baffle. The baffle is nothing more than a PVC end cap with 5 holes drilled through it. Too many holes and your gas will not mix. Too few holes and your baffles create too much resistance for your compressor. I put the holes on alternate sides of the cylinder to force the gas to mix side-to-side. You must throughly deburr, sand and clean your drill work or fine hairs of PVC will get sucked into your compressor inlet. Checking your work with a backlight helps you to idenitfy fine hairs of PVC that you missed in the cleaning process. OUTLET FILTER Drilling PVC pipe creates quite a mess that is difficult to throughly clean. As a result of my doubts, I added an outlet filter to prevent PVC hairs from dropping out of the Nitrox Stik and into my compressor inlet. 
I added an outlet filter at the bottom of the Nitrox Stik, just before the reducers and the oxygen analyzer. This filter prevents any debris from the baffles from dropping into the compressor inlet. It doesn't seem to add much additional resistance. MY COMPRESSOR I settled on a Turkish-made Alkin W31 compressor for $2,900. It uses a 15-amp, single-phase 220V electric motor to drive a low-speed 3.5 cubic-feet-per-minute compressor with steel cylinders. Working pressure is 4,500 pounds per square inch. This gave me lower operating temperatures and a longer compressor life than some of the other small home compressors that are available. 
The Alkin W31 compressor, weighing in at about 115 pounds. The vertical cylinder mounted to the left of the cylinders is a water separator. The vertical cylinder mounted to the right is a small air purifier. The hose coming in from the right is the air intake. 
The electric motor of the Alkin W-31. I had an electrician remove the 15-amp NEMA plug and replace it with a normal 50-amp dryer plug. That way I could use the standard dryer outlet in my house. The associated circuit breakers in my electric box in the basement were replaced with 15-amp breakers. 
I replaced the strange factory compressor outlet fitting with a brass, 5,000 PSI 1/4-inch National Pipe Taper (NPT) male Parker quick-disconnect plug fitting. OXYGEN REGULATORS A standard 277-cubic foot medical oxygen tank comes pressurized to 2,500 PSI. Using an oxygen regulator, oxygen is titrated into the Nitrox Stik at much lower (and much safer) pressures such as 10 to 20 PSI. The oxygen flow must be carefully watched for several reasons. First and most importantly, an unattended oxygen regulator could allow the amount of oxygen entering the Nitrox Stik to creep upwards. You must not allow the concentration of oxygen entering the compressor to exceed 40%. This could lead to a terrible high-pressure oxygen fire. Second, as the oxygen tank is drained, its output pressure will drop. This may cause an unattended oxygen regulator to allow the amount of oxygen entering the Nitrox Stik to creep downwards, resulting in a lower oxygen percentage than your target mix. You will notice this when you see the oxygen analyzer reading lower than desired. Therefore, one must be watchful of fluctuations in the oxygen regulator output pressure. Constant adjustments of the oxygen regulator will be necessary to maintain a constant oxygen % coming out of the Nitrox Stik. Watch the oxygen analyzer reading and adjust the oxygen regulator accordingly. There are a variety of oxygen regulators available to control output from your oxygen supply tank. Your basic choices are between medical and welding oxygen regulators. One-stage welding regulators are relatively cheap ($50 to $70) but must be monitored closely to prevent creep. Two-stage welding regulators are more expensive ($150) but the addition of a second stage minimizes creep. When a precise oxygen output pressure is desired in the face of fluctuating (i.e., dropping) input pressures, a 2-stage welding regulator is ideal. 
A Smith 2-stage oxygen welding regulator. A 2-stage regulator delivers a constant flow to the output port despite decreasing pressure in the oxygen tank. I recommend the more expensive 2-stage regulators over the single-stage regulators for this reason. The output pressure on the Smith is adjustable by the user from 0 to 125 PSI. The intake is a standard CGA-540 nipple-and-sheath connector (visible, right) that connects directly to the oxygen tank valve. 
The output port of the Smith 2-stage oxygen welding regular is a threaded male 9/16-inch fitting. I bought a female-to-male adapter from McMaster-Carr to convert the 9/16-inch output to my standard 1/4-inch NPT fitting. Then I attached a brass, 5,000 PSI 1/4-inch National Pipe Taper (NPT) female Parker quick-disconnect plug fitting. 
I use the Smith regulator for gross flow control (at 10 PSI) and a needle valve for precise flow control. This way I can dial in 32.0% very precisely. There is very little delay (2 to 3 seconds) between valve adjustments and corresponding changes in oxygen levels at the bottom of the Nitrox Stik (as read by the Oxycheq oxygen analyzer). FITTINGS Standard compressor fittings are 1/4-inch National Pipe Taper (NPT). The plumbing of your system is as easy as matching male fittings to female fittings. As your purchase your components, you just need to know the gender of the input and output in order to piece everything together. I found it easiest to buy my components and get them in my hands so I knew what I had. Then I purchased the associated hoses, fittings and adapters. I suppose an alternative is to just purchase a large number of adapters, such as female-to-female and male-to-male adapters. In order to make everything adaptable and readily removable for cleaning, I used Parker quick-disconnect fittings where ever necessary. Originally I thought quick-disconnects were a panacea. But then I discovered that all of my leaks were at quick-disconnects. I had to remove many quick-disconnects and screw components together directly. Now I use quick-disconnects only where absolutely necessary. There is also always the possibility of a fitting popping off under pressure if it was not properly seated. Frequent inspections of the security of fittings is mandatory, as is staying out of the line of fire. The primary advantages of the quick-disconnects are that they allow the fittings to swivel and a component can be easily removed from the line without getting out the wrench. For instance, I have my 2-micron filter on quick-disconnects so that I can easily remove it for cleaning. I use the straight-through, valveless, brass Parker BST-series quick disconnects. They are rated to 5,000 PSI. There are two basic Parker BST-series quick disconnects: the plug (male) and the socket (female). Both the plug and the socket come in male and female 1/4-inch NPT fittings. This means there are four Parker BST-series quick disconnects from which to choose. The valveless variety are safer in my opinion because offer no hot-spots (valves) that could serve as ignition points. You must always bleed off the pressure, though, before you try to disconnect the valveless variety. 
The four types of BST-series Parker quick disconnects. Left to right: Male Plug (male 1/4-inch NPT fitting with a male quick-disconnect plug) Female Plug (female 1/4-inch NPT fitting with a male quick-disconnect plug) Male Socket (male 1/4-inch NPT fitting with a female quick-disconnect socket) Female Socket (female 1/4-inch NPT fitting with a female quick-disconnect socket) 
Another view of the four types of BST-series Parker quick disconnects. Left to right: Male Socket (male 1/4-inch NPT fitting with a female quick-disconnect socket) Female Socket (female 1/4-inch NPT fitting with a female quick-disconnect socket) Male Plug (male 1/4-inch NPT fitting with a male quick-disconnect plug) Female Plug (female 1/4-inch NPT fitting with a male quick-disconnect plug) MOISTURE Moisture is your enemy. Not only does moisture lead to corrosion of tanks, but it also reduces the capacity of your filters. High moisture content can be dangerous as it deactivates the carbon monoxide scrubbers in your filters. Moisture is also costly; the more moisture in the air, the more frequently you have to change your filters. So how to avoid moisture? You can start by not running your compressor when it's hot and humid. Some people have also run their compressor inlet into their house so that they pump air-conditioned air. The design of your compressor also plays a role in how well moisture is eliminated in the pumping process. See those interstage coils on your compressor? They are mositure condensors. 
Close up of the water separator and the cooling coil between the first and second stage cylinders on the Alkin W31. The valves with short blue hoses are water drains. Filters are designed to trap, among other things, moisture. Most compressors come with a small (e.g., 14 inch) filter "tower" that filters the gas. Additional tall (e.g., 32 inch) filter "towers" can be added in sequence to reduce the frequency of filter changes. The chemicals in the filter (such as activated charcoal, molecular seive and desiccant) absorb residual water and other contaminants such as hydrocarbons. The longer that a gas is in contact with a filter, the more the gas is filtered. This contact time is called the "dwell time." The manufacturer of your filters should provide you with a table of estimated filter life dependent on ambient temperature. The hotter it is, the shorter the life of your filters. If you pack your own filters then you'll have figure out the life of your filters from trial and error. The manufacturer of your compressor should also provide you with a recommended schedule of opening the moisture traps in your lines. For manually-operated drains, this is usually every 5 to 10 minutes during operation. Opening the drains blows out the water traps at whatever pressure your compressor is running at the time. So stand back. Most people have a moisture indicator mounted downstream of their filters to ensure that their filters are operating properly. The air should be extremely dry after it passes through the final filter. A high moisture content indicates that either your filters need replacing or your filters have failed. Remember the moisture indicator is just an adjunct to determining when to change your filters. You should be changing your filters according to the manufacturer's hourly schedule. A most common moisture indicator is merely a small, color-coded circular card called a "humidity plug." The "plug" change color based on the gross relative humidity. Ten percent humidity is blue and 30% is pink. You want to see blue all of the time. 
A moisture indicator (MSRP $50). It is merely a 4-inch tall hollow cylindrical chamber through which compressed gas passes. There is a spring that pushes the humidity plug up to the window so that the card can be read. A typical humidity plug is in the plastic bag with dessicant. I removed the Parker quick disconnects because of persistent leaks and screwed the component directly into the high-pressure line. 
A close-up of the indicator window through which the humidity card is viewed. BACK-PRESSURE VALVE Downstream from the filters is a back-pressure valve. This valve will not open until a pre-set pressure builds up, usually 1,800 to 2,000 PSI. This "pressure head" increases the filter's efficiency by increasing the dwell time. A pressure gauge mounted immediately adjacent to, and upstream from the back-pressure valve enables the fill operator to monitor and adjust the back pressure. Back-pressure valves are adjusted either by turning a screw or a knob. 
A back-pressure valve (MSRP $130) and digital pressure gauge. The digital pressure gauge is upstream from the back-pressure valve. I use this gauge to set my back pressure. The back pressure is set by turning the adjustment screw on the right. I like this particular back-pressure valve because I can mount it to the wall. My back pressure is set to roughly 1,800 to 2,000 PSI. The back-pressure valve is mounted to the control board with spacers to set the unit away from the board. This makes room for the pressure gauge. MICRO FILTER ANDI oxygen-compatible air standards require particulates be filtered down to less than 2 microns. Therefore I have a 2 micron filter downstream from my filters. This also protects the rest of my system from contamination in the event of a catastrophic filter blowout. 
A stainless-steel Swagelok 2 micron filter (MSRP $75) that is rated to 5,000 PSI. It can be cleaned by reverse blowing. The quick disconnects allow me to easily remove the filter for cleaning. DISTRUBTION MANIFOLD A distribution manifold allows the fill operator to distibute gas from one place to another just by opening and closing valves. The need for connecting and disconnecting hoses becomes unncessary. A large manifold with many ports allows quite a bit of modular flexibility. Storage tanks can be filled simultaneously with the same gas or individually with different gasses. Scuba tanks can be easily filled from storage tanks via cascade filling. A manifold is central to the fill station. 
A seven-port 5,000 PSI manifold (MSRP $100). A single calibrated pressure gauge (MSRP $80) is all that is necessary to monitor the pressures of multiple tanks. Flow from the compressor comes in from the left through a one-way check valve (MSRP $65). The check valve prevents back flow losses through the compressor. Here, the three upper ports connect to the three storage tanks. Two-way ball valves connected at the manifold will regulate flow to and from these storage tanks. The ports on the bottom and far right are for fill whips. CHECK VALVE A one-way check valve prevents high-pressure gas in the manifold from leaking back through the compressor and eliminates the need for a manual valve here. 
A one-way check valve. STORAGE TANKS I decided to bank my gas in three 444 cubic-foot DOT steel tanks (MSRP $400 to $700 apiece). Working pressure is 4,500 PSI. This gives me ability to either bank three different gases or cascade fill my scuba tanks with a single gas. I decided not to mount a pressure gauge on each tank, but to network the tanks in parallel into a high-pressure manifold with a single pressure gauge. The gas flow will be controlled by three 2-way ball high-pressure valves at the manifold. 
My bank bottles. These things weigh almost 200 pounds apiece when full. To the standard CGA-347 valves I attached wrench-tight 1/4-inch NPT adapters and 5,000 PSI Parker quick-disconnects. I mounted the steel tanks to my garage wall with angle iron brackets. I had to use a titanium drill bit to make any progress in the iron. The brackets are attached to the wall studs with long screws. To the left is an empty mounting bracket and chains (under construction) to hold the oxygen tank. 
A CGA-347 valve (brass). I attached a stainless-steel adapter (wrench tight) that converts the CGA-347 valve to a male 1/4-inch NPT. Then I attached a brass Parker female quick-disconnect plug. A high-pressure line will connect this valve to the distribution manifold. CARBON MONOXIDE Since even minute quantities of carbon monoxide would be fatal if breathed at depth (2 to 3 atmospheres), I wanted to be sure of my gas. There was always the remote possibility of the compressor oil heating up too much and flashing carbon monoxide into my system. So I needed a way to analyze my breathing mix for the deadly gas. The two methods are (1) inline testing and (2) point-of-use testing. Inline testing means that a carbon monoxide analyzer is inline with the filters and moisture indicators in your system. You monitor real-time and maximum carbon dioxide levels during the compressor operation process. Point-of-use testing means that, just like Nitrox, you have to test each individual tank for carbon monoxide before the tank is used. After reviewing the costs, advantages and disadvantages I decided to go with point-of-use testing. This method was slightly more labor-intensive than inline testing. However, I felt that a portable carbon monoxide analyzer would allow me to test my breathing gas for carbon monoxide anywhere I traveled. I settled on the BW Technologies Gas Alert carbon monoxide analyzer (MSRP $295). It is a real-time carbon monoxide detector and analyzer. As a detector, it can worn on a belt to continuously monitor carbon monoxide levels and alarm when appropriate. Unlike other detectors that sample every 30 seconds, the Gas Alert monitors for carbon monoxide continuously. As an analyzer, the Gas Alert works much like a Nitrox oxygen analyzer, reading carbon monoxide levels in real time as gas is fed into its sensor. Another advantage of the Gas Alert is that it reads down to zero parts per million (ppm). Some of the other point-of-use detectors have no application for scuba because their minimum detection range is on the order of 30 ppm. 
BW Technologies Gas Alert portable carbon monoxide detector (MSRP $295). This analyzer will be useful for detecting carbon monoxide in the range of 2 ppm, which is the recommended limit for scuba gas. Like most other carbon monoxide analyzers and detectors, the BW Technologies Gas Alert has to be calibrated periodically. It is almost an unavoidable chore in regards to carbon monoxide analyzers. There are some disposable carbon monoxide analyzers that do not require calibration, but their lifetime is limited to about a year and their cost is comparable to other analyzers (e.g., $300). So what's the point of having a disposable analyzer? Thus I had to purchase a 17-liter carbon monoxide calibration gas cylinder (10 ppm, MSRP $55) and a carbon monoxide regulator (MSRP $155). The analyzer must be calibrated semi-annually, which requires 1 to 1.5 liters of gas each time. At that rate, the calgas should last at least 5 years! 
Calibrating the BW Technologies Gas Alert portable carbon monoxide detector using the calgas cylinder. OXYGEN CLEANING In the interest of safety, I decided to oxygen clean all parts. This tedious process involved completely disassembling all components into their individual machined parts. Once disassembled, the parts were thoroughly degreased in an ultrasonic cleaner with specialized industrial cleaning agents. These include Blue-Gold and Crystal Simple Green. All Nitrile o-rings were replaced with oxygen-compatible Viton o-rings. 
Disassembling dozens of fittings and valves, cleaning them, and then reassembling all of the washers, springs, bearing, o-rings, etc., was very tedious and time-consuming. Even sweat from your fingers would contaminate the parts, so clean procedures had to be utilized. throughout the process. Oxygen-compatible grease (Christo-Lube) was used throughout. Here are a few dozen clean Parker quick-disconnects ready for use. 
A Parker quick disconnect disassembled for oxygen cleaning. 
Reassembling a Parker quick disconnect after oxygen cleaning presents some challenges. I think it is easiest to replace all of the ball bearings by rotating the sleeve around at an oblique angle. The high end of the sleeve holds the ball bearings in place while you replace the ball bearings where the sleeve dips down. This way the spring also assists in holding the ball bearings in their holes. Remember to remove the Nitrile o-rings before cleaning, and replace them with Viton AS568A-110 o-rings during reassembly. O-RINGS Standard o-ring sizes are classified by an AS568A "dash" number. For instance, the correct o-ring for a Parker BST quick disconnect is "dash" 110 (part number AS568A-110). 
A good supply of Viton o-rings is quite handy. Knowing how to order specific o-rings without guessing is even handier. 
A good set of calipers is necessary to accurately measure your o-rings for reordering. You'll need to know the inside diameter (I.D.) and cross-section (C.S.) to order the proper o-ring. Once you know the inside diameter (I.D.) and cross-section (C.S.), then go to an O-Ring Sizing Chart to determine the correct "dash" number. LINKS Here is a list of useful links. ORGANIZATIONS Compressed Gas Association AIR ANALYSIS Analytical Chemists HELIUM ANALYZERS Atomix Heliumizer Oxycheq CARBON MONOXIDE ANALYZERS Canary Sense Bogert Aviation RAE Systems Sensidyne Aeromedix Analox AIR FILTERS Discount Filters Filter Techs Performance Filtration Texas Technologies Lawrence Factor HIGH-PRESSURE HOSES Trident Marine Systems FIRE EXTINGUISHERS Global Industrial INSTRUMENTS & GAUGES Dwyer INDUSTRIAL SUPPLY Valin McMaster-Carr Parker Swagelok NITROX STIKS Koflo Static Mixer LlewocSIS Nitrox Stik COMPRESSOR OIL UltraChem COMPRESSOR SUPPLY Stallion Air Compressed Air Scuba Engineer Compressed Air Specialties Golem Gear Global Manufacturing Corporation August Industries Airpower International American Airworks Reliable Air Breathing Air Scuba.com Northeast Scuba Supply O-RINGS All O-Rings Macro Rubber COMMUNITY Scuba Board The Deco Stop |