SAB 163 HF auto Vi - strange noise

[Josip]

Compressor is working on ammonia at -10*C/35*C

After general overhaul around 33000 working hours assembling of compressor was without any problem.

There is some wear on the bottom of the Vi slide (longitudinal scratches from iron supports within housing ... on capacity slide some small wear on the bottom and on the top ... other parts with some small scratches and in my opinion all like normal wear ...

There is a very loud noise like rattling coming out from compressor at capacitry around 45% til to 70% ... below and above this capacity range compressor sound is normal ...

Compressor is possible to rotate by hand very easy and smooth ...

Hope someone had similar experience and can help to solve this problem ...

Thanks for your time and effort ...


Best regards, Josip

[RANGER1]

Josip,
Luckily have not experienced this problem, but have also only worked on man Vi
models, following is just my thoughts.
On the ones I have worked on have encountered wear on guide ports in discharge end of main slide valve allowing slide rotation. This causing possible contact with rotors.
So not sure on alto Vi how it secures Vi slide from this.
Also if Vi is atincorrect setting have noises coming out of machine.
Oil injection is nonadjustable because of orifice plate, so can't do much there.

So how does Vi work on these ones?
Vi at low then main slide reaches 100%, then both slides move together for
correct Vi?
Could Vi slide be for whatever reason be in the wrong position, causing over compression?
Can you tell where Vi slide position is at all times.
Could you somehow isolate it so it's at low Vi to test?

[Roxhead]

you may also want to confirm that the slide stop is still attached to the actuator. We run qty. of 4 SAB 128 MKII's and have had issues with the two seperating as they are oddly enough only held together via an epoxy material.
Just a thought, Craig

[Josip]

Hi all,

thanks for your time and suggestions ... problem solved ...

... slide valve was wear on the top side where is in contact with the guide port to prevent rotation, place on female side guide port i.e. discharge wall (guide port was perfectly intact due to the new design -slide area is much bigger than on the old type and wear is negligible), but we did not notice that during dismantling and assembling ...

after, with measuring we found slide valve wear and gave it to work shop for cold metalization (bonding) and grinding ... final matching we did manually with sand paper ...

Reduced (acceptable) noise still present in the same capacity range, but client and we are satisfied with job done ... at least we found what was wrong ... hope this will be of some help to others too ...

Seems it is not very simple to revamp both capacity and Vi slide, but that is another story. We do not have workshop drawings to make "original" copy ...

New slides are too expensive ...

Thanks again to all.

Best regards, Josip :)

[RANGER1]

Josip,
Thanks for the update, always nice to find something instead of those mysteries that occur from time to time.