Carrier 19FA Betriebsanleitung PDF herunterladen (Seite 23)

HVAC Training

Page : 23 of 42

Title:

Chiller Maintenance

Lesson Plan

NMH30C000105

Additional lessons learned:

OE11587 documents the failure of the Control room ventilation syste m chiller at Oconee

Nuclear Site caused by refrigerant leaks.

On March 9, 2000, w ith all three Oconee Units at 100 percent power, both control room chillers

were declared inoperable after both had tripped. The station started to shutdown the units as

required by the plant technical specifications. Refrigerant leaks were found at tubing fittings on

both chillers. Refrigerant was added to both chillers and the chillers declared operable. One chiller

was declared operable within three hours and the units were returned to 100 percent power.

Degraded copper tubing flares at filter/dryer connections on the chillers caused refrigerant leaks.

The station indicated that the root cause was insufficient detail in the maintenance procedures to

evaluate the flares. A lack of effective monitoring for refrigerant loss contributed to the event. The

tubing has been replaced and enhancements are planned for leakage monitoring. As a result of a

previous similar event, a recommendation was made to revise operations daily rounds sheets to

monitor operating parameters that would indicate proper refrigerant charge. This recommendation

was not adequately communicated to operations, and therefore was not implemented.

CRDR # 2583691 documents High Lube Oil Tin C oncentration on chiller 2MWCNE01B

1) Description of the Occurrence:

Lube oil analysis identified a high concentration of the metal Tin (Sn) in 2MWCNE01B oil samples.

An increasing trend of the concentration of tin in the normal chiller oil samples has been identified.

This CRDR to document a degrading trend and our response plan.

2) Extent of Condition / Transportability / Safety Significance :

The condition of normal chiller 2MWCNE01B was discussed with the Lube Engineer. There is a

sharp rise in the tin concentrations on chiller 2MWCNE01B only. The other normal chiller tin

numbers are under the 2 sigma (10 PPM Tin) line.

CRDR #2707271 documents that (U-2) ENGINEERING NOTES ANOM ALIES IDENTIFIED

WHILE MONITORING BEARINGS ON CHILLER 2MWCNE01B.

CRDR 2583691 has been tracking tin numbers in the oil samples from chiller 2MWCNE01B.

Inspections of the bull and pinion gear bearings on normal chillers 1MWCNE01B and

2MWCNE01B found evidence of over heating. As-found clearance on the pinion gear bearing was

less than minimum gap. Carbon residue on bearing surfaces. There is some evidence of copper

plating out on bearing surfaces.

The bearings show ware but have not failed. However, concern has been raised about as to why

the clearances have closed up and the localized overheating of the bearings.

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Carrier 19FA Betriebsanleitung Seite 23