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Post by cablehack on Dec 9, 2020 2:20:44 GMT
I've also never had a proper working float valve CA. I have. You would never know a cap tube has been fitted by the way the fridge operates. From all practical aspects, it works the same. But that's only once the cap tube characteristics and charge level has been optimised. Nevertheless, the float valve does have the advantage of charge level being less critical, and it automatically takes into account compressor speed variation when used on a 50 or 60 cycle supply. |
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Post by turbokinetic on Dec 10, 2020 1:48:07 GMT
Today I had a spare moment to deconstruct the blocked float valve from the CK-1. It is no wonder that nothing seemed to unblock this while it was in the system! The orifice was solid rust. I've repaired CA floats before by re-grinding the orifice. Those were brass. This one is steel and rusted badly. This is the actual seat where the needle closes off.  This is the back side of the seat assembly, where the line attaches, leading to the evaporator.  This is the amount of rust I was able to dig out with the small screwdriver shown. Still the orifice is blocked.  Thought you would like to see the actual root cause of the issue! Sincerely, David |
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Post by ChrisJ on Dec 10, 2020 2:01:14 GMT
Hi David,
Interesting it was full of rust. Something unhealthy went on.
I'm surprised the design looks just like the CA only steel.
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Post by Travis on Dec 10, 2020 2:32:45 GMT
Does MF play well with steel? I’m wondering why they switched and then went back to steel. Maybe it’s so2 that doesn’t play well with brass.
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Post by coldspaces on Dec 10, 2020 4:58:27 GMT
That's crazy. All I have found is carboned up crud in the floats. No way to blow that out with nitrogen!
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Post by ChrisJ on Dec 10, 2020 6:10:08 GMT
Does MF play well with steel? I’m wondering why they switched and then went back to steel. Maybe it’s so2 that doesn’t play well with brass. The tube in the CK is Everdur bronze, I believe the entire seat and tube may be in the CA. Perhaps they went with that for ease of machining but the higher pressure difference of so2 would erode the valve so they went to steel? |
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Post by ckfan on Dec 10, 2020 13:43:47 GMT
Wow, I never would have suspected the seat to be made out of steel. I am also shocked that so much rust formed in that one. I wonder how so much moisture got into the system. Makes you wonder what all of the other steel parts look like.
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Post by turbokinetic on Dec 10, 2020 14:04:57 GMT
Does MF play well with steel? I’m wondering why they switched and then went back to steel. Maybe it’s so2 that doesn’t play well with brass. I don't think SO2 and brass (under normal dry conditions) are a problem together. Think of all the brass parts in the old belt-drive mechanical shaft seals. That's crazy. All I have found is carboned up crud in the floats. No way to blow that out with nitrogen! No doubt! I think the float chamber might get somewhat explodey before the N2 pressure was able to dislodge the rust. Paul and I deconstructed a DR1 float which had the same failure. Before removal of the float chanber from the unit, we drilled the tube stub out of the float tail piece, to get full access to the bottom of the orifice. Tried hard steel wire and other methods to clear the orifice and nothing could be forced through there. Once it was apparent that couldn't be fixed; the float chamber was removed and mounted in a vise, upside down, so that gravity had the float open. We tried every way to save that one and couldn't get it cleared. Does MF play well with steel? I’m wondering why they switched and then went back to steel. Maybe it’s so2 that doesn’t play well with brass. The tube in the CK is Everdur bronze, I believe the entire seat and tube may be in the CA. Perhaps they went with that for ease of machining but the higher pressure difference of so2 would erode the valve so they went to steel? You're probably onto something with the float valve seat erosion issue having to do with pressure and materials. The earlier DR has a cast steel base with the seat orifice machined into it. Then the CA has the brass seat (with the erode-o-matic feature enabled by default); and then the CK went with steel seat, inside the brass tube. They use brass seats for water valves as well, and those erode too. Wow, I never would have suspected the seat to be made out of steel. I am also shocked that so much rust formed in that one. I wonder how so much moisture got into the system. Makes you wonder what all of the other steel parts look like. Well; the inside of the float chamber looks like-new, as did the float ball before I cut into it with the plasma torch. The copper inside the lines was also bright and unoxidized, and the oil was clear and smelled like fresh machine oil. So I don't think there is a wide-spread corrosion issue. I thought I had shared this picture already but didn't. Sorry! It's the other parts of the float. Notice there is no rust on anything. Also go back to the first post, and look at the pictures of the underside of the unit without the evaporator installed. The inside of the float chamber is visible, and shows zero rust.  I have a feeling that one could create a tool to restore the seat from the bottom, without damaging the float mechanism. The basic idea is to first drill out the tube stub to get a full 1/4" port where the seat is accessible. Then make a special tool; basically a piece of 1/4" drill rod with a very small needle tip ground into it. The 1/4" section would pilot into the tube bore, keping the needle tip in line with the orifice. Charge the system's high-side with nitrogen via the factory service port, and then ream the orifice from the tube bore. The N2 would expel the debris out of the float chamber instead of allowing it to be driven into the system to cause another blockage. Just a thought! Sincerely, David |
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Post by ChrisJ on Dec 10, 2020 16:40:08 GMT
I've wondered many times if the CA machines with working valves were simply retired very early, or if the problem of the eroded valve was due to NCG build up.
NCG builds up, increases head pressure and perhaps the brass valve simply cannot handle it. Or if the claims that NCG "holds the float down" was true, the valve doesn't open fully causing wire drawing issues?
I don't know, but the fact they switched the same valve design from bronze to steel suggests they either knew there was an issue, or, the engineers felt the higher pressure differential of SO2 was an issue with it.
I suppose we'll never know.
Perhaps someone can check my math.
With Methyl Formate running at 28"HG on the evap and +5 PSI on the condenser I get 18.75PSI difference. What happens with NCG issues?
SO2 machines typically run about 50 PSI on the condenser and close to a vacuum on the evaporator, so that's at least a 50 PSI difference. More than double a properly working CA machine.
David, was most of the corrosion/ rust on the underside of the valve, where the refrigerant boils etc?
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Post by turbokinetic on Dec 11, 2020 14:32:58 GMT
I've wondered many times if the CA machines with working valves were simply retired very early, or if the problem of the eroded valve was due to NCG build up. NCG builds up, increases head pressure and perhaps the brass valve simply cannot handle it. Or if the claims that NCG "holds the float down" was true, the valve doesn't open fully causing wire drawing issues? I don't know, but the fact they switched the same valve design from bronze to steel suggests they either knew there was an issue, or, the engineers felt the higher pressure differential of SO2 was an issue with it. I suppose we'll never know. Perhaps someone can check my math. With Methyl Formate running at 28"HG on the evap and +5 PSI on the condenser I get 18.75PSI difference. What happens with NCG issues? SO2 machines typically run about 50 PSI on the condenser and close to a vacuum on the evaporator, so that's at least a 50 PSI difference. More than double a properly working CA machine. David, was most of the corrosion/ rust on the underside of the valve, where the refrigerant boils etc? Yep the corrosion was all underneath the seat area, in the low-side of the system. The high side where the float ball and needle are located, that was like-new except for a wear groove in the needle tip. With SO2, it may run in the 50 to 75 PSI range on the high, but the low isn't a complete vacuum. If I remember, it will run at about 5 to 10" vacuum. So 2.5 to 5 PSIA on the low side, and 65 to 90 PSIA on the high side. So a worst-case delta-p would be about 87.5 PSI. I'm still not convinced the brass wear issue with MF isn't due to some sort of chemical process. Brass develops a coating of oxide which passivates it from further oxidation. If there is something about the MF / oil / noncondensable gas mix which is able to re-form the passive layer on brass; while the high gas velocity is constantly removing it - the constant removal and reforming of the passive layer would lead to slow erosion. |
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Post by ChrisJ on Dec 11, 2020 15:13:13 GMT
I've wondered many times if the CA machines with working valves were simply retired very early, or if the problem of the eroded valve was due to NCG build up. NCG builds up, increases head pressure and perhaps the brass valve simply cannot handle it. Or if the claims that NCG "holds the float down" was true, the valve doesn't open fully causing wire drawing issues? I don't know, but the fact they switched the same valve design from bronze to steel suggests they either knew there was an issue, or, the engineers felt the higher pressure differential of SO2 was an issue with it. I suppose we'll never know. Perhaps someone can check my math. With Methyl Formate running at 28"HG on the evap and +5 PSI on the condenser I get 18.75PSI difference. What happens with NCG issues? SO2 machines typically run about 50 PSI on the condenser and close to a vacuum on the evaporator, so that's at least a 50 PSI difference. More than double a properly working CA machine. David, was most of the corrosion/ rust on the underside of the valve, where the refrigerant boils etc? Yep the corrosion was all underneath the seat area, in the low-side of the system. The high side where the float ball and needle are located, that was like-new except for a wear groove in the needle tip. With SO2, it may run in the 50 to 75 PSI range on the high, but the low isn't a complete vacuum. If I remember, it will run at about 5 to 10" vacuum. So 2.5 to 5 PSIA on the low side, and 65 to 90 PSIA on the high side. So a worst-case delta-p would be about 87.5 PSI. I'm still not convinced the brass wear issue with MF isn't due to some sort of chemical process. Brass develops a coating of oxide which passivates it from further oxidation. If there is something about the MF / oil / noncondensable gas mix which is able to re-form the passive layer on brass; while the high gas velocity is constantly removing it - the constant removal and reforming of the passive layer would lead to slow erosion. This was the reason I asked if the rust was on the bottom side of the valve. It's a snip from the book Gill posted about SO2 and R12 from 1935  |
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Post by turbokinetic on Dec 12, 2020 7:15:39 GMT
Yep the corrosion was all underneath the seat area, in the low-side of the system........ This was the reason I asked if the rust was on the bottom side of the valve. It's a snip from the book Gill posted about SO2 and R12 from 1935 View AttachmentThat makes sense. It would be in an area where this effect could be very pronounced. |
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