marine engineer

[cees hendriksen]

Hi, I am an engineer on a ship and underway, last year at the Singapore drydokking they installed 3 REFCOMP TYPE 553 SR hermetic compressors. now 6000 rhr later we have problems with 2 compressors, as soon as they are started they go to 100 % load at 250Amps but do not want to unload as the load drops also activating the solenoids with 220 Volt will not get the compressor of the 100%. drained the oil, renewed internal oilfilter, cleand external cap tubing, removed the solenoids and bench tested them, all seems to be ok. any help to solve this problem is appriciated, thanks for your input.

[sedgy]

hi cees, so you are saying that the solenoids energise to load the comp.
so they are not liquid line valves then ? can you confirm this please

[GHAZ]

hi it could be the slide valve rod broken or the spring broken, and not bringing the slide valve back , you,ll have to take the compressor apart, take off the oil seperater and then the screw pack back plate ,and have a look, be careful the back plate is under pressure from the spring plates, so undo the bolts carefully

[cees hendriksen]

hi cees, so you are saying that the solenoids energise to load the comp.
so they are not liquid line valves then ? can you confirm this please

Hi sedgy, thanks for your replay, the solenoids on this type compressor are in the lube oil system and are NC. They direct oil to a piston that moves a sliding valve over the screws and once closed the effective work area of the screws is 100% and the compressor is on max load. if one of the solenoid vlvs is activated it will bypass the oil to the sump, the piston retracts one step and moves the sliding valve back and the load of the compressorwill go to 75% etc. etc. untill fully unloaded. The compressor is a Refcomp SRC-S-553

[cees hendriksen]

hi it could be the slide valve rod broken or the spring broken, and not bringing the slide valve back , you,ll have to take the compressor apart, take off the oil seperater and then the screw pack back plate ,and have a look, be careful the back plate is under pressure from the spring plates, so undo the bolts carefully

Hi GHAZ,
Thank you for your quick response and for your information, we were afraid that it could be something like that but hoped for an easier solution. This is probably the reason that one of the compressors starts up with a very loud clack after about 5 seconds after the oil pressure has build up and throws the piston over??. The other compressor starts up slower without any noise before it goes to 100% load. The last thing that I want to try if possible at all, is to check that the common drain from the solenoids to the suction is clear do you have any tips of what the best way is of doing this?
This type of compressor is new to us and we never had one apart and the book does not give us enough information about how to do this, what parts we will need, what the correct procedures are and if it is recommended to this job in the field so we want to try anything else possible before we start a job like this so any other checks, ideas or tricks are welcome. We also like to know why and how this can happen the compressors ran only about 6000 hrs, is this a common problem or do we have to run the compressors a certain way to prevent this from happening again in the future.
We are sailing from Honolulu to Canada for a 3 months lay-up, our job list is long so we hope that it will stay cold and that summertime will start late this year.

[RCassist]

Hi cees, please let me know if possible the serial-numbers of the compressors. Even if the rod is broken the piston should already be at 100% position, so the loud noise in start-up sounds strange to me. Inform please also about type of refrigerant, and whether your are running on S&T exchangers in the evaporator, or direct expansion. The slide valves are for a certain period have been sensitive to problematic oil managment, i.e. for frequent liquid returns.

I can feed you with videos, showing the procedure, integrative to the manuals, if needed.

Have you mesured the amps when energizing solenoid 14? What happens?

Regards.

[sedgy]

hi cees, thanks for explaining the job , but sorry not worked on this type of system , when I sailed with the nz shipping Co, they just had halls Co2 units, all the best chief

[winks]

hi every one, i need heat load calculation program