Help needed in Venezuela.

Greetings from a Brit in South America. I think your forum is great, and regularly look in to pick up some good tips. Thanks.
Most of the equipment in this neck of the woods is prehistoric, but it's fun to keep all that old junk running. However, I've got a problem with a real dinosaur.

Here's the story:
40-ton open compressor made by a Spanish company called Ramon Vizcaya some 35 years ago. Chills water that cools red hot metal in a tool factory. The system is simple - the only controls are an oil pressure switch and high/low pressure refrigerant pressure switches. No computers, just great big knobs to turn it on and off.
Changed the expansion valve last year, and had no real problems at that time.
Last week the mechanical seal on compressor side of the drive shaft between the electric motor and the compressor started leaking. Customer's own mechanics changed it after I removed the R22. They do all their own mechanical work, and only call me for refrigeration-related stuff.

I returned to recharge the chiller and top up the oil when they had finished. It seemed to take longer than I expected to pull a vacuum, but I didn´t think much of it at the time.
However, when I started to charge the R22 into the vacuum (with the compressor turned off) I was surprised that it wouldn't pull the refrigerant out of the cylinder in a 90F environment.
All valves open on the compressor, guages and cylinder, but the R22 was going in r-e-a-l-l-y slowly.
Checked cylinder pressure - OK for the temperature. Rechecked valves - OK. Checked hoses . OK. Rechecked system pressure - couple of PSI only. The only two service valves are on the compressor itself.
Started up the compressor to try to pull in the refrigerant faster and the oil seal started leaking oil again. I'm not sure if they fitted it wrongly, or if it was the wrong seal, however while they get a new seal, it's given me some breathing space to think about why the system won't suck in refrigerant, and why it took so long to pull a vacuum.
Any ideas?
Saludos
El Tel.

Hi. El Tel:)
did you pressure test the compressor before vacumning? You could of also did a vacumn test, isolate the pump to the system, then watch for the vacumn gauge to rise, if it rises you have either a leak or an amount of water vapour boiling off.
With regards to the refrigerant flowing in, if the vacumn had already been broken by the air entering into the system by the shaft seal there would be no great rush of refrigerant into the system.
With regards to the shaft seal was the comp thust taken by a dial gauge? An old compressor will have a large thust or crank movement in and out, off and on the shaft seal. If this thrust is significantly larger than the manufactures given tolerance you will eat shaft seal and leak when the compressor off cycles. When the oil pressure is present during machine running the shaft pushes the seal faces hard together, harder than normal due to the extra movement in the worn bearings/shaft. When the compressor off cycles the lack of oil pressure lets the seal faces part, these seal faces are now excessivly worn due to the high pressure exerted on them during running with the beyond normal thrust. Now the seal leaks gas. A seal leaking oil is usually due to worn/misplaced rubbers or dirt on the seal faces. Although after a long service life a seal will also show wear by leaking oil.
Moral of the story, check the thrust without the new seal in place and rectify the thrust issue before fittting a new seal.
Regards. Andy.:)

Hi Andy, thanks for your advice.
Did a vacuum check at the time, no rise in pressure. The vacuum wasn't broken - at least not according to the guages - so I did expect a strong inrush of refrigerant. I know there was a vacuum, at least in the compressor, because I sucked oil into the compressor via the oil top-up valve without causing a major rise in pressure.
However, the guages behave as if the service valves were both closed - which they are not. After a good 10 minutes with everything full open both guages show just above atmospheric pressure - and around 175 PSI in the R22 cylinder.
I have a suspicion there's something stupidly basic about this problem - but I'm damned if I know what.
Your advice about the shaft is good. There is some longitudinal movement. I'll check it against the manual. The seal is a spring-loaded mechanical seal with rubber rings at both ends which surround the shaft. The part is inserted by sliding it along the shaft until it is seated inside. I would have thought the spring-loading would compensate for any shaft movement, but I will check tolerances as you suggest.
Thanks again for your input. Any further thoughts would be welcome.
Saludos.
El. Tel.

Hi, El Tel:)
yes normally the spring/s in the shaft seal would take up the slack, that is if the shaft tolerance is about right. In the case of thrusts outside the normal you are in the land of the unknown, it may be alright, but from my experience it won't be.
Remember more thrust movement creates more pressure on the seal faces wearing them very quickly. The leak occurs when the prematurly worn seal moves back off the thrust position when the compressor off cycles.
The slow to charge thing may be just a slow/lazy check valve on the refrigerant cylinder. These are fitted nowadays just to frustrate engineers wanting to decant and to some extent charge systems.
Regards. Andy.

Thanks again, Andy.
I will be working on that chiller again tomorrow. I'll let you know how it all turns out.
Regards.
El Tel.

Hi Andy,
Sorry it's taken a while to get back to you.
Life is interesting down in this neck of the woods - we're in the process of getting a civil war started here in Venezuela, which slows everybody down a bit (more than usual). On top of that, I had my beloved Mitsubishi panel van nicked! The cops have found it, after it was used in a robbery - and now they are keeping it as physical evidence until I cough up a large monetary incentive to release it. I don't know who's worse, the cops or the robbers. Maybe I'll join all the others, and drive around in a 1960's pickup with 7 out of 8 cylinders firing, bits hanging off, and a bucket under the exhaust pipe to catch the oil.
Anyway, down to business...
You were absolutely right about the play in the crank movement. It did in a couple of seals quite quickly, so I got annoyed and took the whole damn thing apart. Found bits of crankshaft spacer hidden under the oil filter! No parts here, of course, so we had to make replacements.
Also replaced the cylinder liners and pistons (they've had them wrapped in oil paper in an old box in the back of the toolshop since 1979, and didn't know what they were for!!). Made gaskets for everything. Put it all back together, and crossed my fingers.
Works like a charm. Whisper quiet. Cools like a good'un.
Never did discover why it wouldn't pull refrigerant into the system - but it stopped doing it, anyway.
Thanks for your help. I'll be visiting the UK at Christmas. If you give me your mobile number, I'll buy you a beer. You'll easily recognise me in the pub - I'll be the bloke in Bermudas and a straw hat.
Saludos from Venezuela.
El Tel.

Ooooops!!
Just noticed you're from Northern Ireland. Long way to go to buy you a beer!
Never mind... if you're ever in Venezuela.....
Merry Christmas.
El Tel.

Hi, El Tel:)
nice to hear your problem is resolved. It's not all new plant over here we have or share of old stuff too. About 5 year ago I overhauled a Udec (re-badged Sabroe) plant this was installed in 1963, ten years before I was born. All mk1 Sabroes two twelve cylinders and three 6 cyl SMC100 compressors on a pumped NH3 plant with blackmere pumps, you can hear ever stroke of the NH3 pumps, thump, thump. These babies are as installed with only shaft seals changed from packed to machanical.
To the best of my knowledge the plant is still running much as it was after I overhauled it. Oh and the compressors are DOL. with 150hp motors.
As for that drink, I am in the UK now and then, the company I work for is Uk based. Drop us an email when you are over and we can take it from there.
Regards. Andy

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I returned to recharge the chiller and top up the oil when they had finished. It seemed to take longer than I expected to pull a vacuum, but I didn´t think much of it at the time.

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I thought Andy's advice was right on from the beginning. Good enough to belong in a manual, actually.

Glad to hear you fixed the problem, El Tel. But do you think you made an initial poor observation or were trying to move too quickly in the first place? If the seals were leaking, you should have seen that during the charging process, nevermind the lack of a pressure test.

Just curious. Looking back, what did you miss? It is a question I ask myslef all the time.:)

I had a hose problem similar to yours. It was on older hose and when it was opened to the vacuum the rubber lining in the hose collapsed and twisted restricting flow. First i disconnected the hose and blew some gas through it with no apparent restrictions. Reconnected it opened it to the vacuum again and opened the bottle and still had reduced flow. It was a 1/4'' hose so I switched to a 3/8'' new hose and it charged normally. I did not discover the loose liner until I tried to use it to pull a vacuum on a Small Copeland compressor and the lining came out in pieces. So I cut the end off and it makes a nice oil draining hose. I don't work on halocarbon systems very often so my hoses tend to be neglected and I have been known to run some ammonia through them through them once in a while in a pinch. I know it is not good for them, but i purge them with air till the stink is gone.