Seal failure index

2.0 Oil barrier seals

Oil barrier seal index

2.2 Failure due to copper sulphide deposits

Click on photograph to enlarge
	Figure 2.2a Black deposit of copper sulphide on white metal lining of seal ring
	Figure 2.2b Failure of seal ring through loss of clearance caused by build up of copper sulphide deposit
	Figure 2.2c Guidance chart for selection of white metal lining for floating-bush seal rings for use with sulphur containing hydrocarbon process gas - based on operating experience using shaft peripheral velocity as an index of temperature. In very severe conditions, high speeds and high sulphur contents, sulphur reacts with lead forming a deposit of lead sulphide on the seal ring and an alternative seal design is required. Zone A Tin-rich white metal acceptable Zone B Copper-free lead-rich white metal acceptable Zone C Alternative seal design required
	Figure 2.2d Failure of floating-bush seal ring caused by build up of copper sulphide on white metal lining caused by reaction with zddp additive in the oil
Main Characteristics	This reaction occurs between the active sulphur present in 'sour' hydrocarbon gases and copper in the tin-rich white metal lining of the seal. Some relief can be obtained by using a copper-free lead white metal.
Cause
Note
Possible Confusion with Other Types of Damage	Reaction can also occur with active sulphur additives in the oil. Figure 2.2d shows a failed seal ring caused by operating with a high duty hydraulic oil containing zinc dialkyldithiophosphate (zddp).
Comment

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