Mycom 8L

[lraja]

Hi

There is a Mycom (model 8L, reciprocating) compressor, only 2 to 3 years has done, with new piston rings and oil rings in place. This machine takes an unusual amount of oil (say 2 - 3 liter a week). Anybody experience with Mycom to give an idea as to why ?

thanks

[Grizzly]

If you have ran the machine for 2 to 3 yrs, since replacing the rings.
Then likely they need replacing.
As per recommended service intervals!


If you have just replaced them I would be asking what was the wear in the bores like?

I am surprised you need to ask Iraja.
Given your Qualifications listed!
Grizzly

[Sandro Baptista]

Hi

There is a Mycom (model 8L, reciprocating) compressor, only 2 to 3 years has done, with new piston rings and oil rings in place. This machine takes an unusual amount of oil (say 2 - 3 liter a week). Anybody experience with Mycom to give an idea as to why ?

thanks

Since the beginning the compressor always lost that amount of oil? The operating regimen has changed?

How many hours per day the compressor work? Always at full load and at high suction pressures?

The piston rings and oil scraper how many hours they have?

Maybe, if the piston rings and oil scraper are okay, if the compressor works a lot hours per day, at almost full load, if works at high suction pressure...maybe a oil separator with coalescent filter is needed.


Hmmm...or maybe the oil return is not done properly...due to a clogged filter at oil return line or something else and the oil separator have a high level of oil and the mesh is overfilled with oil.
Is the oil return hot or cold???

[RANGER1]

Iraja ,
Why do you think 2-3 litres a week is to much ?
Are you comparing it to something else ?

[Sandro Baptista]

Iraja ,
Why do you think 2-3 litres a week is to much ?
Are you comparing it to something else ?

Like the Ranger1 said, if the compressor works a lot and on a hard regimen 2-3 litres a week it could not be so much with a normal oil separator or else mount an oil separator with coalescent filter.

[lraja]

Dear Ranger 1 & Sandro Baptista

Many thanks for the replies,

The case I compare this Mycom is, another more or less similar plant (design/application and capacity) running Gram compressors, but 15 years old with good maintenance, which take only 1 -2 liter a month (the worst case)

I gathered today that the maintenance of this Mycom has not been the best interest of the plant owners, guess that tells a lot.

I believe Sandro's point on oil separator could be very valid..

thanks all

[Sandro Baptista]

Dear Ranger 1 & Sandro Baptista

Many thanks for the replies,

The case I compare this Mycom is, another more or less similar plant (design/application and capacity) running Gram compressors, but 15 years old with good maintenance, which take only 1 -2 liter a month (the worst case)

thanks all

Every manufacturer has is own concept / criterion on the design of a oil separator for the same mass flow and regimen. Since many time ago I got the idea that MYCOM is a little "short" on oil separator for reciprocating compressor.
Maybe if you put on the separator an used bigger oil separator above (from a bigger compressor) it would be okay (more diameter and leght » longer mesh » less velocity and more steady time of the oil/refrigerant will ensure almost oil would stay on the separator)...and so no coalescent oil filter would be needed. Or if your compressor is driven by pulleys increase the pulley of the compressor block so it could run slower (of course loss of capacity will happen but maybe you have another compressor on stand by or at part load)...or put the compressor at part load and other compressor that would be stand-by can work to compensate » but more power consumption and more costs on compressor service would be needed...All of this is a game that can be played on several ways.

[Sandro Baptista]

Iraja,

Please see if the manufacturer respect the xxx ppm of oil separation (15...25...30...40 ppm)

[RANGER1]

Usually an 8L would be used bacause its cheap & you can rev them at higher speeds to get capacity .
2-3 litres a week is still OK but the Grams are certainly doing a good job .

Mycom can offer other piston ring configerations , so it may be worth checking on next rebuild .

Other things that could be considered are oil & discharge temps , as maybe water jackets + oil cooler need cleaning etc .

[Sandro Baptista]

Yes, high discharge temperatures don't improve the oil separation...by the contrary.

[-33.3]

2-3L isn't bad for us. Most of our mycoms (4B and 8b) use around 8L a week, one 8WB uses 30L every week.

We just rebuilt it one year ago as well. Complete rebuild and clean. We use the proper filters as spec'd by mycom as well. We do run at rather high discharge temperatures. Overall our entire plant has oil problems though.

[Sandro Baptista]

What kind of problems? Excessive oil consumption?

[RANGER1]

2-3L isn't bad for us. Most of our mycoms (4B and 8b) use around 8L a week, one 8WB uses 30L every week.

We just rebuilt it one year ago as well. Complete rebuild and clean. We use the proper filters as spec'd by mycom as well. We do run at rather high discharge temperatures. Overall our entire plant has oil problems though.

When you say filters specified by mycom , what filters are you refering to ie coalescers ?

Mycom changed piston rings configeration 20 yrs ago on ammonia service , since then oil consumption issues arrise every now & then .
Can you advise what rings you use ( part numbers CSO...BF7 ).
You can instal a "T" piece in breather hole between crankcase & suction chamber as excessive blow by causes sump to pressurize and blow oil into chamber around cylinder liners .
Use a 3/8" nipple & tee as a type of baffle .Screw into equalizing hole previously mentioned .
Also advise on type of oil return float ie is it working properly , hot to touch ?


When you overhaul comps do you lap or surface grind valve seats & check piston ring grooves for excessive wear or clearance ?

Makes the 8L look pretty good .

[-33.3]

Yea we have excessive oil consumption. We also run 4 rotary boosters. Which can on some days take 3-4 liters a day. Were also not returning back a proper amount of oil for what we put in.

Yep, the filters are coalescent. As for the oil rings and piston rings there all BF. I believe oil is BF7 and piston BF4.

Oil return float I cant find any info on. Nor can I read off of it what it is. I can tell you we replaced it 3 months ago though. It runs slightly warm but not bad.

As for what we did when we rebuilt. We bore out the piston sleeves. Checked for scores or marks, were all ok. Replaced all gaskets. Cleaned out and remove scale from water jackets. All new discharge and suction valve plates and springs. Cleaned out all strainers, we did check for distance between pins on pistons. All new oil and piston rings. All new bearings for con rods. Cleaned out the oil cooler. And brand new oil return float. While doing so we checked all other parts for marks or scores/wear they were all fine.

Hopefully that answers everything, keep in mind im still a apprentice so bare with me.

[Sandro Baptista]

We are all apprentices. We always are learning until we dead...;)

[RANGER1]

We have installed a Temprite oil seperator on 8WB that was using 5 litres a day & now uses nothing .
Try closing oil return & see if any difference in oil consumption .

Also on mycoms they sometimes have an equalizing valve from suction to discharge .
This is for easier starting so not starting against full head pressure .
Oil pressure closes piston once it gets going .
Have seen worn out ones pressurizing
sump .
If it has any of these the line should be cold once running , If not close valve off discharge line & see what happens as well .

[GCAP CoolCast]

do you have an in-line separator? if so it may be oil logged, or the drain plugged. when oil sits in the separator, diameter is decreased and the velocity proportionally increases, reducing the holding time and allowing oil to pass through up to the condenser.

[That's too cold]

Oil seperator is mandatory for good oil return to piston compressor. The only time we lose oil from our 8A Mycom is from excessive floodback or loss of ***** and then it pumps the oil out.

[A.R.S ltd]

have all the bores been deglazed when the rings were replaced

what speed does it run at ?