Attached 2 pictures of swollen copper tubes I got from a colleague of me.
Machine is a 2 stage system, Bitzer, R404a, 5 compressors, 1 always in standby.
TV= -40°C, TC= variable but now minimum 25°C (AKC25H5 is used)
Copper was swollen after and before the NRV from compressor 2 and 4.
Fact was that machines was overfilled with oil, SH on the moment one of the copperlines exploded (compressor 4) was 2 to 5 K. They also discovered that the DANFOSS AKC25H5 the short switchings (range 1 to 5 sec) of the pressure switches hasn’t recorded whereby it’s possible the compressor went out and on very shortly.
Discharge header dismantled and nothing strange found.
Thickness of the copper tubes is same as normal used (+/- 1,2 mm.)
After examining the setup, they found that the very low SH was only and due to an AKV on an ice machine. The SH dropped to 2K when ice machine was working.
After the collapsing of discharge 4, they repaired it temporarily with normal copper (grey tube) which is thineer then the factory discharge tube.
Also this tube has swollen again (see picture)
You can see that also the copper after the NRV is swollen (picture 1, the vertical section of teh discharge line), not only the soldering.
And also the tube between compressor discharge and the NRV, the cracks just after the shut off valve on the compressor comes from the expanded copper line.
On the suction accumulator was on the bottom a drain connection for the oil with an SV. This SV was apparently not connected.
They changed the HP switch (KP Danfoss) with automatic reset to a version with manual reset.
1 Oilfloat functioned not properly and was changed.
Because they measured on 1 compressor higher discharge temperatures, they changed the valveplate of that compressor.
No is everything working normal.
Oil was drained out of the oil cylinder.
