I've had my own gas mixing whip for about 5 years now, which I put together myself and upgraded over time to it's current configuration. Eric asked if I would help him and others in our local group, put one together for their use so they could set up their own mixing station. The goal was to put together a whip for mixing nitrox / trimix that could also be used as a crossover whip, if needed. The following is an example of how you can put your own whip together if you are so inclined. If you are more of an armchair observer it will give you an understanding of how these things are constructed and used.

This whip was designed as an "ultimate" with all the bells and whistles that could be all things for all people. The design allows you to hook any bottle to any bottle by way of quick disconnects and also allows you to utilize both the digital and analog gauges as tank pressure checkers. Cost is about $510 compared to $685 for the Halcyon digital gauge mix whip, and this unit has more functionality. If you are just getting into the mixing game you can eliminate a lot of the luxury items like the digital gauge ($200) and the quick disconnects ($$$) and drop the price dramatically, down to a low of about $135.

So let's get to it! It is always nice to have someone with whom you can speak before starting D-I-Y projects to cut down the design time, reduce on the number of mistakes and eliminate purchasing items you don't really need. In my case I didn't know anyone that had done this so I was on my own. I relied heavily on information obtained from The O2 Hacker's Companion as well as some ideas from JT Barker's web site, with whom I was acquainted as the result of diving with the VB Tech group in Virginia Beach VA. Eric, David & Rolf had the benefit of my past experience (and mistakes), which put them way ahead of the game.

The planning stage is very important if you want to avoid sitting on your hands while waiting for that one last part to arrive or realizing that you didn't need these parts that you purchased. After some discussion with Eric, David, and Rolf I had a pretty good idea of what they wanted. I drew up some pictures and further discussed it with them. They agreed so it was decided that Eric would order the gauges and DIN scuba fittings and I would order the NPT, Quick Disconnect fittings and the HP hose from a couple of suppliers I have used in the past.

The whip was made with brass "straight through quick disconnects" (QD's) from Swagelok rated at 4200 psi. Seems Swagelok makes brass parts with higher pressure ratings than most other manufacturers which helps to keep the cost down when compared to stainless steel. Swagelock now has an online store (see below) where you can view their entire catalog and purchase their items. They forward the order to their distributor that is closest to your location for filling and shipping. In my case that was Washington Valve & Fitting in Frederick MD located about 30 minutes from where I live. When I made my original whip, I visited WV&F and went over their catalog with one of their salespeople who was very helpful. This time I knew what we wanted so I decided to try the direct order approach and see how it worked. I received the parts about a week after I ordered them so I am pleased with the process.

Parts

The way we decided to assemble the parts was modified slightly. Rather than have the hose run horizontally from the mix gauge, we turned the mix gauge "T" so the hose would run toward the ground. I've found that since the tanks being filled are less than half the height of the storage tanks, this runs the hose where it needs to go and relieves stress on the whip.

Legend	Description	Part Number	Quantity	Price ea.	Total
Swagelock
B	? NPTM X Stem	B-QF-4-S-4PM	4	$5.70	$22.80
C	? NPTF X Body	B-QF-4-B-4PF	3	$12.30	$26.90
D	Tee's ? NPTF	B-4-T	2	$9.10	$18.20
E	? NPTM X Body	B-QF-4-B-4P	1		$10.80
F	? NPTF X Stem	B-QF-4-S-4PF	2	$6.70	$13.70
McMaster Carr
G	6' PTFE Hose W/Santoprene Covered SS Braid	5723K333	1		$33.65
From Roberts Oxygen (local gas supplier)
H	CGA 540 (oxygen) "Hand Tight" Nut & Stem X ? NPTM (CGA Hand Tight Nut W/ Plastic Grip) (CGA 540 Hand Tight Stem)		1		$32 (for both)
I	CGA 580 (inert gas) "Hand Tight" Nut & Stem X ? NPTM (CGA 580 Hand Tight Nut W/ Plastic Grip) (CGA 580 Hand Tight Stem)		1
North East Scuba Supply
A	? NPTF X DIN filler w/push button bleede	001 039 DIN	2	$39.99	$79.98
J	? NPTM X ? NPTM Needle Valve	693 (Whitey Needle Valve)	1		$54.99
K	031002	Analog Supply Gauge	1		$17.95
L	80	Dwyer Digital Mix Gauge	1		$199.99

Assembly

Eric, David, and Bill arrived at the house about 7:30 pm. Bill, a recent newcomer to the area was there for observation and fellowship. My son David Jr. was also there, on convalescent leave from the USN so we David's had the Eric's and Bill's beat hands down. After introductions my wife just shook her head and left saying, "Just what we need in this house, another David!" Sort of funny though, every time someone said "Dave" three of us said "Yes???"

Since this whip would be subjected to high PP of O2 the first step was to clean all parts for "O2 service" (rather than the misnomer of "oxygen cleaning"). Swagelock parts can be ordered ready for O2 service by adding "SC11" to the end of any part number. However, the charge for this will be anywhere from about $6 to $20 per part, depending on the part. I ordered the parts for my first whip this way and then quickly learned to clean my own. The cleaning process involves removing any hydrocarbons from the surface of the parts so there is no "fuel" to complete the fire triangle (heat+oxygen+fuel) and create a flash. The process is not very complicated. Basically, hydrocarbons are grease/oil, so you need a "degreaser" that will not leave any of it's own hydrocarbons behind or contaminate the surface in some other way. Avoid solvents and march down the "O2 service cleaning products" aisle of your local grocery store and pick up a small bottle of Ivory Liquid hand dishwashing detergent, cost of about $1.79. Some folks use "Simple Green" although I understand the manufacturer recently said it should not be used for this purpose. Funny how NOAA used it for years. I guess too many people asked and they were afraid of the liability issue. If enough of you ask Proctor & Gamble if it permissible to use Ivory Liquid for this purpose, I'm sure they will put a disclaimer on the bottle. Also get some automatic dishwasher powder for "pre-cleaning".

Put about a tablespoon of dishwasher powder in a "DO2SCD" (Dalton O2 Service Cleaning Device) which is sometimes mistaken for plastic peanut butter jars. If you do use a plastic peanut butter jar make sure it is 1) "O2 safe peanut butter" such as "Skippy" and 2) you eat all the peanut butter first and clean the jar well. Running it through the dishwasher is a good idea! Fill with very hot water and drop in a few of the parts, screw on the cap and shake violently for a while, 3-5 minutes should do.

Dump the water, fill with fresh hot water and shake again to rinse. Replace the water and add a squirt of Ivory Liquid and repeat the process. Repeat the rinse a couple of times and then place the parts in a shallow dish and run hot water into the dish to rinse. After about 3-4 minutes remove the parts and place on a paper towel on a plate to dry.

Note: the QD bodies have lubricated o-rings inside. You need to fish these out with a dental pick prior to cleaning the body. Then remove the silicone from the o-rings, degrease them like the rest of the parts, lube them with Christolube or other O2 service lube and re-insert them following the cleaning of the bodies.

Once the parts are more or less dry you can proceed to the assembly stage. NPT threads are tapered and make a thread to thread seal rather than sealing with an o-ring like your tank, neck to valve seals. Although you can get metal to metal seal without, it is advisable to use some teflon thread sealant tape to make a better seal. The tape can be found in the plumbing section of your hardware store or at your local gas supplier. Wrap the tape around the threads 3 times. The tape is annoyingly thin and working with it is a bit of a pain but keep at it. It is important to "hold back" the tape from the first 2 threads. The reason for this is to insure that you don't get any of the tape inside the hose where it could contaminate the gas stream.

Now start assembling the parts . All you will need for this is a number of open end wrenches of the appropriate size. I'd suggest not using adjustable wrenches since they are a bit sloppy and can scar the parts, and NEVER, EVER, use channel locks, vice grips or other pliers on the whip. Think about order in which the parts need to be assembled so you don't work yourself into a corner. If this happens, just take whatever apart and reassemble in proper order. It may be helpful to assemble finger tight without teflon tape so you can determine the proper order. I always put the hose on last. One note is to have the valve positioned horizontally rather than vertically because the space between the two gauges is rather small.

The assembly is quite easy. I demonstrated the process to Eric and David on parts of my whip (which I was putting back together) and they then put theirs together while Bill, David Jr. and I watched.

After assembly hook the hose up to a scuba tank and blow some air through it to blow out any remaining moisture. Then hook it up to a couple of scuba tanks and pressurize it and listen for leaks. This one had only one minor leak, which only required tightening the offending part. At worst you have to remove the part (bleed the hose first!) and put fresh teflon tape on it. The stuff is so thin you can't use it a second time.

That about does it. Now go out there and blend!

Any questions feel free to email me.

Project Notes

Hose

The hose we used has a teflon inner lining, which is in itself very weak. It gets its strength from being covered with stainless steel braid and a Santoprene cover over the braid. The cover provides even greater chafe and abrasion protection plus it offers excellent ultraviolet, ozone, acid, and alkali resistance. It's easier to keep clean. Hose assemblies are available in the following lengths: 12", 18", 24", 30", 36", 42", 48", 54", 60", 66", and 72". It is available with a variety of ends in either stainless steel or brass. We chose the brass due to pressure needs (adequate for our need) and cost (about half the cost of the SS). We chose the "male union" X "male union" ends to facilitate the repositioning of parts and hose without having to use teflon tape.

Gauges

This whip uses a supply side analog gauge followed by a needle valve for good gas control followed by a high accuracy digital gauge. The digital gauge is the most expensive part of the whip coming in at $200 for a gauge with accuracy of +/- 0.25%. If you are on a strict budget you can go with a digital gauge for about half of that which is good +/- 1.0%, or an analog gauge. My first gauge was a 4 & ?" analog gauge that cost all of $24.95. It had 20 psi graduations and a range of 0-3000. No doubt it wasn't +/-1 % accurate, but it was repeatable which is more important. In mixing you will find that you will need to add a "fudge factor" or "swag" as ideal gas laws and real gas laws have never been introduced to each other!

 

You can skip the supply side gauge and only use the mix gauge. Just make sure you pressurize the whip with the supply bottle, checking to see that it has more pressure than the recipient tank before you proceed.

Needle Valves

The valve used in this project cost $55 and works fine. You can find valves as cheap as $18 or up in the $1000's. I have a 30,000 psi valve by Autoclave that cost $600, that I use now. It was on the supply line of the used Haskel I bought, so I, in effect got it for free. It makes other needle valves seem like globe valves! Of course there is no way I would have bought this thing new!

Some folks skip the needle valve and use the supply tank valve, but I wouldn't recommend it. Tank supply valves are consistently inconsistent. Some operate so smoothly and allow such control that you wonder why you need a needle valve. The next one is so coarse it will go from full off to full on in a 1/16th of a turn.

The needle valve has a direction of flow that the gas is supposed to follow, that is an "in" port and an "out" port. The Swagelock valve used in this project has an arrow etched into the side to show this. Make sure you install it properly. Putting the valve in backwards will result in a loss of control.

 

Some mention should be made as to where the needle valve should be placed, at the supply end or at the receiving end. I read everything I could find when I built my first whip and thought about it for a while and ultimately came to the belief that is should go on the supply end. The best reason I could come up with was that when pressurizing the whip, the gas doesn't have the distance to get up speed before being stopped abruptly by the needle valve.

Supply Side Connections

We used Hand Tight nuts and stems in this project. They cost about 4 times as much ($16 vs. $4) as a wrench tight nut and stem but are worth it in my opinion. No tools are needed to switch from one supply tank to another. You can also get an He to O2 (CGA-580 to CGA-540) adapter for about $4. Then you only need the CGA-540 Hand Tight and can skip the quick disconnects on the supply side. However you will then need one of these for each HE tank you have or will need to use a wrench to switch tanks. Spend the $16 for the extra hand tight and the $25 for the supply side quick disconnects!