Need advice on CMEP-OL clean out.

[jswick93]

I looked into getting one to Vancouver, it'd cost about $300 to get it there with UPS. I don't think I can afford to do that right now, but I also don't know what to do about this thing. I would like to get it usable. The bearings I posted pictures of are 6908RS bearings like ripcity said.

Ripcity, have you operated the pump at all with those ceramic bearings?

 

[jswick93]

Okay, here's another interesting picture. I just noticed this now. One of the piston heads has two little knicks in it, causing direct wear on the piston head gasket. Could this be contributing to why my issue is so bad? I can't imagine this even happening anywhere other than the factory. What's everyone's opinion?

 

[Rickys bong]

That certainly would have made the problem worse. That type of seal needs to have the sharp corner of the seal to be in perfect condition to seal properly. Butane will leak past the nick very easily.

RB

 

[jswick93]

There's no way to order a new part that I know of. That little metal piece just needs replaced. Sounds like something the people I got it from should fix for me.

 

[Rickys bong]

The metal piece on top with the nicks is just a retainer for the seal. The problem is the nick in the seal. Take a fine file and smooth off the nicks in the retainer, and replace the seal. The retainer can be beat to shit, it just holds the seal in place for the downward stroke of the piston.

The ding in the retainer didn't cause the damage to the seal, the seal was damaged before assembly.

Likely cause was that the piston and seal was made as a sub-assembly and the knob doing the final assembly either didn't notice the damage or caused it.

The flat head bolt holding the seal retainer has a shallow socket in it, so use a new allen key to take it apart.

I wouldn't blame your supplier, selling Chinese stuff is a crapshoot most of the time. Initial units will be great, and then the quality drops off. AI is the only reliable supplier of Chinese equipment I've seen so far.

Should have one of these in my shop shortly to look at.

RB

 

[jswick93]

The metal piece on top with the nicks is just a retainer for the seal. The problem is the nick in the seal. Take a fine file and smooth off the nicks in the retainer, and replace the seal. The retainer can be beat to shit, it just holds the seal in place for the downward stroke of the piston.

The ding in the retainer didn't cause the damage to the seal, the seal was damaged before assembly.

Likely cause was that the piston and seal was made as a sub-assembly and the knob doing the final assembly either didn't notice the damage or caused it.

The flat head bolt holding the seal retainer has a shallow socket in it, so use a new allen key to take it apart.

I wouldn't blame your supplier, selling Chinese stuff is a crapshoot most of the time. Initial units will be great, and then the quality drops off. AI is the only reliable supplier of Chinese equipment I've seen so far.

Should have one of these in my shop shortly to look at.

RB

Okay, that makes sense. Because the damage was in the same spot, I was just assuming it was from the plate holding it down.

I have seen that there are full ceramic bearings with a ptfe cage with the same dimensions as the 6908RS in this pump. Could those be used in place of these you think? Or not?

 

[Rickys bong]

I have seen that there are full ceramic bearings with a ptfe cage with the same dimensions as the 6908RS in this pump. Could those be used in place of these you think? Or not?

I'd be careful putting ceramic bearings into one of these. All 4 bearings would need to be replaced, and full ceramic, good quality bearings are not cheap. The bearing fits are critical too, ceramic units won't be forgiving of improperly sized shafts or bores that they fit into.

RB

 

[jswick93]

I heard from someone working on these pumps that there are a dry ptfe lubricated bearing in progress right now which should be available soon for these.

 

[Kenzyme]

RB you pretty much nailed it! The cmep-ol is very poorly designed for our application. I have already replaced the bearings on mine and scrapped the instrument valves and heat exchanger and vented the crankcase as a bandaid until a more suitable pump gets here.

I feel like ignorance is bliss when it comes to operating these machines...that's why most people don't think they're having any issues. Fyi I use a 3x24" column as a multi-stage vapor filter as well as 24" high collection pots so ingesting oil is a non-issue here. I have two 3x24" columns for liquid phase filtration on either side of my solvent tank.

If you don't run your cmep-ol into vacuum whatsoever, chances are you will only have to deal with normal wear of the piston seals (looking closely they appear to be a ptfe and graphite or moly composite) causing small particulates to enter your solvent. But once your piston seals start to wear, solvent vapor will pressurize the crankcase, dissolve the rod bearing lube and centrifugal forces will sling lubricant out towards the pistons, and then everything goes downhill from there (keep reading). The bearing seals do nothing to hold in the lubricant. If you recover into a vacuum at all, whether it be to pour out, muffin tech, or to recover the solvent from your column...whatever. To varying degrees, you will be pulling the rod bearing lubricant into the crankcase, past the piston seals and into your solvent. The bulk of this lubricant will be deposited in your heads, through the exhaust plumbing and into the heat exchanger. But to a lesser extent it will also get into your hoses, aftercooler, and supply tank, requiring one heck of a clean out if you care about what you do. The cup seals on this piston design just aren't suited to our application. Once the cylinders are contaminated, wear of both the piston seals and cylinder walls can happen rather quickly. Interestingly enough, in the cold I took one of my heads outside and attempted to clean the contamination with a butane soaked rag. The black stuff didn't dissolve nearly as easily as it did with 99% iso, which didn't make me feel confident trusting the butane flush out method that others have used. I scrapped everything downstream of the heads and started over.

The rod bearings are 6908-RS, the inboard shaft bearing is 6004RZ and the outboard bearing is 6203RZ. I am experimenting with a set of full-complement ceramic bearings that are supposed to be able to be run dry without lubricant, which could eliminate that source of contamination. But with the piston seal design on this pump, I don't plan on running it any longer than I have to.

Good luck everybody. Obviously don't do anything I talk about unless you are willing to accept responsibility for your own actions.

Are these bearings standard size to their part number, or are there different sizes for each part number? and if so what are the appropriate sizes? Our CMEP-OL has been running like a champ damn near around the clock, and it is now beginning to generate a shrill high pitched noise on and off, which I assume is a bearing going out. Sounded like an issue with the aluminum motor fan, so we took it off, cleaned it and replaced it, but was soon assured that it was not the issue, and it is my assumption that a bearing going out is the culperit

 

[FishmanK]

Are these bearings standard size to their part number, or are there different sizes for each part number? and if so what are the appropriate sizes? Our CMEP-OL has been running like a champ damn near around the clock, and it is now beginning to generate a shrill high pitched noise on and off, which I assume is a bearing going out. Sounded like an issue with the aluminum motor fan, so we took it off, cleaned it and replaced it, but was soon assured that it was not the issue, and it is my assumption that a bearing going out is the culperit

Saw a post by BHOgart in last few days that they have new bearing assemblies for these pumps with PTFE components
Asking about that yesterday @ BHOgart Eureka, was told that the San Jose store was the spot for rebuilds and new bearings for CMEP-OL

 

[Rickys bong]

Are these bearings standard size to their part number, or are there different sizes for each part number? and if so what are the appropriate sizes?

The number is unique to each bearing size, and they are standard sizes. The letters at the end designate the type of seal they have.

RB

 

[Kenzyme]

Saw a post by BHOgart in last few days that they have new bearing assemblies for these pumps with PTFE components
Asking about that yesterday @ BHOgart Eureka, was told that the San Jose store was the spot for rebuilds and new bearings for CMEP-OL

Called them yesterday and ordered the bearing set. I will report an update when installed with pics if I have time.

 

[Pure777Extracts]

Called them yesterday and ordered the bearing set. I will report an update when installed with pics if I have time.

Im pretty sure it is the bearings, That sounds like the sound mine was making when I took it in. BHOgart cleaned and lubricated bearings and was good to go. Going to get the new PTFE coated bearings later in the week.

 

[Old Gold]

I'm waiting for a call back hopefully, that they can also machine a hole in the crankcase. I didn't get to speak with the pump tech like I was told I would lol, but Sean at the San Jose store is looking into it for me. He's always been pretty helpful and upfront about things.

$100 for labor ain't bad. What are they charging for the bearings themselves?

Ideally it should be plumbed to a line that can be vented outside or into an external tank.
Band aid solution would be to put a mol sieve between the compressor outlet and the heat exchanger or at lease on the heat exchanger / condenser outlet on the outside of the compressor.

How does molecular seive fix the issue? I don't follow.

 

[Rickys bong]

How does molecular seive fix the issue? I don't follow.

Mol sieve on the outlet side will catch any grease exiting the commpressor.

RB

 

[n8oler]

I second RB, on the outlet for inevitable grease expulsion into your solvent tank from the CMEP-OL bearings(once the piston rings fail).
In my experiences pump failure/leakage is contributed to liquid solvent/extracts making their way from the collection vessel into the inlet of the pump. Which, creates buildup and ultimate top-end failure which lets solvent into the crankcase and decomposes the bearings seals.

 

[Old Gold]

Mol sieve on the outlet side will catch any grease exiting the commpressor.

RB

Right, I guess I should've been more clear...do we know what will effectively catch all residues from the pump?
I wouldn't think molecular seive would remove the need to fix up the crankcase.

 

[n8oler]

I know I'm a noob, but let me introduce myself. I have a year of testing and CMEP-OL rebuilds under my belt with a background in pharmaceutical engineering/fabrication. Which, has led me here to try and help the industry, most specifically CMEP's and sanitary fabrication.

OG to answer you questions

2 expansion chambers filled with 4a desiccant beads with a bottom -> up flow orientation on intake and exhaust will effectively catch all residuals and safeguard the pump.

A molecular sieve will remove the need to fix up the crankcase. (Though a bleeder valve on the bottom of the crankcase is not a bad idea!)
1. Every bearing has a lifespan and will fail at some point. Much quicker with solvent flushing the grease away from the ball bearings.
2. Solvent should not enter your crankcase at anytime. If it does you have piston ring failure.
3. If you have piston ring failure, its because you have extracts entering the pump. Its like throwing sand in the intake of your car.


I have been talking with Andrew at Sanitary Steel to provide feedback to CM refrigeration for the next generation.

These are my recommendations;

All compression fittings(no JIC refrigerant or npt fittings) Swagelok preferred.

All stainless(no brass on gauges, p-switch).

No brazing.

Better valves Swagelok preferred.

Better gauges Swagelok preferred.

Bearings that will not contaminate(100% sealed or ceramic).

Leak down test for the cylinders(indestructive way to test piston rings).

No radiator style condenser, something like a coil or jacketed (everyone has ice/dry ice/chillers).

Molecular sieves on both sides(expansion desiccant bead chamber).

Valved, vented crankcase with an oil catch basin.

Electrical box with nitrogen purging.

A step on the shaft to set crank depth/piston alignment on the shaft.

LMK if you have more questions!

 

[Rickys bong]

A molecular sieve will remove the need to fix up the crankcase. (Though a bleeder valve on the bottom of the crankcase is not a bad idea!)
1. Every bearing has a lifespan and will fail at some point. Much quicker with solvent flushing the grease away from the ball bearings.
2. Solvent should not enter your crankcase at anytime. If it does you have piston ring failure.
3. If you have piston ring failure, its because you have extracts entering the pump. Its like throwing sand in the intake of your car.

The piston seal they used is going to let a small amount of gas into the crankcase even when they are new. That's why I suggested a vented crankcase is the only way to solve the issue with some degree of certainty. I've seen this issue with other pump designs as well. Some designs pressurize the crankcase to balance the pressure across the piston seal but that concept allows crankcase contaminants to get into the pump outlet circuit.

What I'm sure is happening is that gaseous butane is dissolving into the bearing grease which comes out of solution when the pump is off and the pressure drops. Depending on conditions, when the butane starts boiling out of the grease it can push the grease past the seals.
I've seen this happen with the various pumps I've tried over the years. Eventually enough gets out to splatter onto the cylinder walls where it will find its way back to the top of the piston and the fluid being compressed. Not good.

Especially with the CM pump, the piston seals do a poor job of sealing anything that wants to go from the bottom of the piston upwards. Horrible design and only a single seal.
If the crankcase is vented through a tube that can be vented outside butane can never dissolve into the grease. You can also monitor any flow from the crankcase vent to monitor the health of the seals.

It's a conceptual design issue that better bearing seals won't solve. Their larger compressor is the same design, just 4 pistons instead of 2.

Peace

RB