New to me fill station. Working through the issues.

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So I got a cootwo and it consistently tests the air at .3-.4 ppm CO.

I got the nitrox stick set up and used a 1" flexible pvc hose to plumb it to the Rix. The hose smells like pvc and I've searched high and low for a better hose with no smell but the best I found was 26$ a foot silbraid silicon tubing. I pumped some air through it and it tested and smelled fine. I finally got the bank tanks back form the shot blaster and hooked up the nitrox stick. The good news is the blending is super stable and once adjusted it will run for hours with only minor tweaks and I was getting 31.9% with a CO reading of .3 ppm.

The bad news is the pvc hose is imparting a bad plastic taste to the air. The filter was taking it out but after a while it must be overwhelmed. The odor coming off the coalescers is plastic. The air coming out of the scuba regulator is like rubber. There is no reason to have trace analytics test it. I'm not going to breathe it. I taste tested the air when I started pumping it and then banked 1400cf of 32% which is what I got out of a T of O2. At the end I filled a scuba tank and it tasted like rubber. The banked air wasn't as bad so I figure the filter gave up a few hours into the pumping. I wasn't too keen on counting on the filter to clean it up in the first place so this result was not surprising.

I dumped the banks out the window and resumed my search for a hose. I finally settled on ordering a flexible intake hose from nuvair that they say has no odor or taste. I'll replace the filter when it gets here and start all over. 2 steps forward, 1 back.
 
used a 1" flexible pvc hose to plumb it to the Rix. The hose smells like pvc and I've searched high and low for a better hose with no smell.

In Europe the Air Intake Hose Assembly on a Rix SA-6 Breathing Air Compressor is a clear, clean and simple affair consisting of 3 parts:
1. The intake hose: A 19mm ID x 25mm OD (3/4 x 1”) and No longer than 4.5 Mtrs (15 foot) in length.
2. Two Jubilee Clips (Worm Gear Clamps) in 316 stainless Steel
3. Air Intake Filter consisting of a 10Mu Polyester pleated type element in a stainless steel “Tin Can” housing with 19mm (3/4”” NPT male thread or Hose Barb and for indoor use a 2Mu paper pleated element alternative can be used.

The hose material is proprietary and does not off gas or smell.
In Europe the cost is an eye watering £10 for a 4.5 metre, 15 foot length (around $14)
Been used on the Rix SA-6 for breathing air over 20 years now. Maybe longer. Before that originally it was a clear unsupported tube but it was subject to crushing and kinking before the rayon braided version was offered.

Although you dont say where you bought your hose I dare say, DIY stores or garden centres and the like offer hose made in China that are more suited for slurry drainage, rain water storage tanks and the like and this stuff smells from the onset. Photo below shows the hose connection and “Tin Can” filter on the current range of compressors

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In Europe the Air Intake Hose Assembly on a Rix SA-6 Breathing Air Compressor is a clear, clean and simple affair consisting of 3 parts:
1. The intake hose: A 19mm ID x 25mm OD (3/4 x 1”) and No longer than 4.5 Mtrs (15 foot) in length.
2. Two Jubilee Clips (Worm Gear Clamps) in 316 stainless Steel
3. Air Intake Filter consisting of a 10Mu Polyester pleated type element in a stainless steel “Tin Can” housing with 19mm (3/4”” NPT male thread or Hose Barb and for indoor use a 2Mu paper pleated element alternative can be used.

The hose material is proprietary and does not off gas or smell.
In Europe the cost is an eye watering £10 for a 4.5 metre, 15 foot length (around $14)
Been used on the Rix SA-6 for breathing air over 20 years now. Maybe longer. Before that originally it was a clear unsupported tube but it was subject to crushing and kinking before the rayon braided version was offered.

Although you dont say where you bought your hose I dare say, DIY stores or garden centres and the like offer hose made in China that are more suited for slurry drainage, rain water storage tanks and the like and this stuff smells from the onset. Photo below shows the hose connection and “Tin Can” filter on the current range of compressors

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It's my desire to use 1" line to reduce the resistance because the nitrox stick has some resistance built in. Rix only sells 3/4". Eric said it was vinyl.
 
It's my desire to use 1" line to reduce the resistance because the nitrox stick has some resistance built in. Rix only sells 3/4". Eric said it was vinyl.

Tell Eric from me that he needs to have a wander around his own stores, on second thoughts he may get lost among all the stuff they have over there. Rix make HP air compressors up to 100CFM at 5000psi and they have bigger bore inlet tubing. Just not in the SA-6 spares price list I guess. Incidentally the SA3 at 3cfm uses 1/2” bore and 12 foot long.

All Rix tubing USA side is what is called food and beverage grade, that is no phthalate or silicone in the hose material. Europe built SA’s use similar but not identical tubing and also in metric LOL .

But if you look at this for a SA-6 (sorry for the metric) a 155 l/min flow at 20C down a 4 metre length of tube with say a 20 mmHg calculated maximum pressure drop you could do this with a 13.6mm bore tube and would get 17.78 m.sec (58ft/sec) velocity. With a 0.275 psi pressure loss. Hence the maximum suggested 4 mtr 15 foot hose length. Now if you dropped the hose length to say 2 metres length the pressure drop would be 0.689 psi (its late here need to re calculate this)

Conversely if you say went for your 1 inch bore tube at 4 mtr length you would halve the gas velocity to 28 ft/sec and the pressure drop would be 0.023 psi. Similarly if you halved the length of 1” tube also to 2 mtr length the pressure drop would be 0.118 psi

Candidly I’m not at all convinced a mixing stick is indeed needed with a SA-6, just hot weld a 1/4” ID Vinyl oxygen line into your 1 inch hose (facing up towards the intake filter) about 2 foot back from the air intake filter itself or use suitable fittings and knock the mixing stick idea off.

Most mixing sticks are pretty rubbish with recip compressors and the “chop” “chop” flow characteristics of a typical reciprocating compressor will mix pretty well without the need for a stick.
The only purpose of the stick is to reduce an oxygen oil fire, and they don’t even do that well enough not to “cook” the oil at inlet compression, but you don’t have that oil problem with the SA-6 .

The only item worth having is a low pressure solenoid NC valve (normally closed) in the oxygen line that would need to be wired in order to energize on start and shut closed NC on stop. Also a relief valve up stream of the solenoid valve in case your oxygen regulator leaked.

Further the regulator needs to be a two stage pressure reducer design (not single stage) or else as the oxygen cylinder supply pressure drops P1 the outlet pressure from the regulator will increase P2 and the oxygen percentage flow in the required mix will increase accordingly. Iain
 
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iain- I'm at 2 mtr length with the 1" hose. The one I'm getting now is going to be a bushed down 1 1/2" hose. That's an interesting view on mixing nitrox through a Rix without a stick. The chopped flow pattern would seem to be a way to mix the O2 into the airstream but would not allow me an easy way to monitor the O2 content or the stability of the mix like I can with the stick.

I was under the impression that you didn't think it was a good idea to pump enriched mix through the SA6. I'm glad to see I was mistaken about that.

I am using a regulator and a medical O2 flow control valve. I have a solenoid tied to the starter control of the motor to shut off the O2 in the event that the motor is stopped for any reason. It is located between the regulator and the flow control valve. I turn off the O2 tank valve when not in use.

What would you recommend I keep on hand to service the Rix besides a set of third stage rings? Reed valves?
 
https://www.shearwater.com/products/perdix-ai/

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